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Title:
ROADWAY MARKINGS WITH RADAR ANTENNA
Document Type and Number:
WIPO Patent Application WO/2019/148000
Kind Code:
A1
Abstract:
The disclosure describes an article, such as a pavement marking tape, that includes a retroreflective layer, a backing layer, and a radar reflective layers disposed between the retroreflective layer and the backing layer. The radar reflective layer includes a radar reflective structure that includes a first antenna; a second antenna that partially surrounds the first antenna; and a third antenna that partially surrounds the first antenna and the second antenna.

Inventors:
DOERING, Marcel (Carl-Schurz-Strasse 1, Neuss, Neuss, DE)
LIERSE, Markus (Carl-Schurz-Strasse 1, Neuss, Neuss, DE)
WEINMANN, Christian (Carl-Schurz-Strasse 1, Neuss, Neuss, DE)
SALEHI, Mohsen (3M Center, Post Office Box 33427Saint Paul, Minnesota, 55133-3427, US)
BUETTNER, Joern (Carl-Schurz-Strasse 1, Neuss, Neuss, DE)
CLEAR, Susannah C. (3M Center, Post Office Box 33427Saint Paul, Minnesota, 55133-3427, US)
Application Number:
US2019/015242
Publication Date:
August 01, 2019
Filing Date:
January 25, 2019
Export Citation:
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Assignee:
3M INNOVATIVE PROPERTIES COMPANY (3M Center, Post Office Box 33427Saint Paul, Minnesota, 55133-3427, US)
International Classes:
E01F9/50; G01S5/02; G01S13/93; H01Q1/32; H01Q15/14
Attorney, Agent or Firm:
TÉLLEZ, Carlos M. et al. (3M Center, Office of Intellectual Property Counsel Post Office Box 33427Saint Paul, Minnesota, 55133-3427, US)
Download PDF:
Claims:
CLAIMS

We claim:

1. An article comprising: a radar reflective structure comprising a plurality of antennas, the plurality of antennas including:

a first antenna;

a second antenna that partially surrounds the first antenna; and

a third antenna that partially surrounds the first antenna and the second antenna.

2. The article of claim 1, wherein each antenna of the plurality of antennas are substantially u- shaped.

3. The article of claim 1, wherein each antenna of the plurality of antennas include:

a first lateral member;

a second lateral member substantially parallel to the first lateral member; and

a longitudinal member coupled to the first lateral member and second lateral member, wherein a first end of each longitudinal member is coupled to a respective first end of the respective first lateral member,

wherein a second end of each respective longitudinal member is coupled to a respective first end of the respective second lateral member.

4. The article of claim 3, wherein each longitudinal member is substantially perpendicular to the respective first lateral member or the respective second lateral member.

5. The article of claim 3, wherein each longitudinal member is curved.

6. The article of claim 3, wherein the second end of each respective first lateral member and the second end of each respective second lateral member define an opening of the radar reflective structure.

7. The article of claim 1, wherein the first antenna comprises a first set of lateral members and a first longitudinal member, the first longitudinal member comprising a first midpoint,

wherein the second antenna comprises a second set of lateral members and a second longitudinal member, the second longitudinal member comprising a second midpoint,

wherein the third antenna comprises a third set of lateral members and a third longitudinal member, the third longitudinal member comprising a third midpoint, and wherein the first midpoint, second midpoint, and third midpoint define a straight line that is approximately parallel to the first set of lateral members, second set of lateral members, and third set of lateral members.

8. The article of claim 7, wherein the first longitudinal member, second longitudinal member, and third longitudinal member are substantially parallel to one another.

9. An article comprising:

a retroreflective layer;

a backing layer;

a radar reflective layers disposed between the retroreflective layer and the backing layer, the radar reflective layer comprising:

a radar reflective structure comprising a plurality of antennas, the plurality of antennas including:

a first antenna;

a second antenna that partially surrounds the first antenna; and

a third antenna that partially surrounds the first antenna and the second antenna.

10. The article of claim 9, wherein each antenna of the plurality of antennas are substantially u- shaped.

11. A method comprising: constructing pavement marking tape by at least:

providing a continuous base sheet including an upper surface and a lower surface;

adding a radar reflecting structure to the upper surface of the continuous base sheet; and coupling an adhesive layer to the lower surface of the continuous base sheet.

12. An array comprising two or more radar reflective structures,

wherein each radar reflective structure comprises, independently from each other”:

a first antenna;

a second antenna that partially surrounds the first antenna; and

a third antenna that partially surrounds the first antenna and the second antenna.

13. An array according to any of the preceding claims directed to arrays, wherein the orientation of at least one radar reflective structure is different from the orientation of another radar reflective structure within the array.

14. An array according to any of the preceding claims directed to arrays, wherein the dimension of at least one radar reflective structure is different from the dimension of another radar reflective structure within the array.

15. An array according to any of the preceding claims directed to arrays, comprising two or more radar reflective structures,

wherein each radar reflective structure comprises, independently from each other:

a first antenna;

a second antenna that partially surrounds the first antenna; and

a third antenna that partially surrounds the first antenna and the second antenna, wherein the orientation of the first radar reflective structure is approximately 180 degrees different from the orientation of the second radar reflective structure,

wherein each antenna in each of the radar reflective structures comprises

a first lateral member;

a second lateral member substantially parallel to the first lateral member; and a longitudinal member coupled to the first lateral member and second lateral member, wherein a first end of each longitudinal member is coupled to a respective first end of the respective first lateral member,

wherein a second end of each respective longitudinal member is coupled to a respective first end of the respective second lateral member,

wherein at least one of the first lateral member or a second lateral member of an antenna of the second radar-reflecting structure is partially surrounded by an antenna of the first radar-reflecting structure,

and wherein at least one of the antennas of the first radar-reflecting structure and at least one of the second radar-reflecting structure have a U-shape, and wherein the array comprises more than one row of radar-reflecting structures (e.g., Figs. 26-28).

Description:
ROADWAY MARKINGS WITH RADAR ANTENNA

TECHNICAU FIEUD

[0001] The disclosure relates generally to roadway markings comprising at least one radar-reflecting layer, which in turn may comprise one or more radar-reflecting structures such as antenna structures.

BACKGROUND

[0002] Automotive radars in a narrowband range are widely implemented for applications such as adaptive cruise control and blind spot monitoring. There has been global activity toward automotive radar systems that may distinguish objects on a roadway with greater accuracy than narrowband systems. A larger bandwidth radar system may enable higher spatial resolution, compared to a narrow bandwidth system, which may limit resolution. Some vehicle radar system manufacturers have begun to develop and implement higher frequency and wider bandwidth radar systems.

SUMMARY

[0003] In general, this disclosure is directed to a pathway article that includes a radar reflective structure with a large radar cross section (RCS) in a compact planar structure. A pathway article may include a pathway marking tape, traffic cone or barrel, stop sign, and similar articles. The radar reflective structure may include a plurality of antennas that create a radar reflecting surface. Selecting the spacing between the antennae may cause constructive interference leading to reflection in the backscatter direction, substantially opposite the direction of the incident radar radiation. The radar reflecting structures may provide cues for radar equipped vehicles traveling along a pathway that includes a pathway article of this disclosure.

[0004] Pathway articles of this disclosure may also include at least one additional feature along with these radar reflective structures that may be detected by other sensors on a vehicle. Examples of other features include retroreflective features detectable by the human eye, visible camera, infrared camera, and similar sensors. This redundancy in the detectable features of the pathway article may enable use of sensor fusion to provide greater confidence of detection of the pathway article under a wider range of conditions and to enable distinction between marking and other radar-reflective objects, such as other vehicles, in the field of view of the radar system.

[0005] In one example, the disclosure is directed to an article that includes a radar reflective structure. In some embodiments, the radar reflective structure includes a plurality of antennas, including a first antenna, a second antenna that partially surrounds the first antenna, and a third antenna that partially surrounds the first antenna and the second antenna.

[0006] In another example, the disclosure is directed to an article that includes a retroreflective layer, a backing layer, and a radar reflective layers disposed between the retroreflective layer and the backing layer. The radar reflective layer includes a radar reflective structure that includes a first antenna; a second antenna that partially surrounds the first antenna; and a third antenna that partially surrounds the first antenna and the second antenna.

[0007] The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

[0008] FIG. 1 is a conceptual diagram illustrating an example system 100 including a pathway article with radar reflecting structures, according to one or more techniques of this disclosure.

[0009] FIGS. 2A-2D are conceptual diagrams illustrating top views of example arrangements of radar reflecting structures within pathway articles, according to one or more techniques of this disclosure.

[0010] FIGS. 3A-3B are conceptual diagrams illustrating top views of example radar reflecting structures, according to one or more techniques of this disclosure.

[0011] FIG. 4 is a conceptual diagram illustrating an example system including a vehicle equipped with radar devices and a marking tape, according to one or more techniques of this disclosure.

[0012] FIG. 5 is a conceptual diagram illustrating atop view of an example pathway article that includes a plurality of radar reflecting structures, according to one or more techniques of this disclosure.

[0013] FIGS. 6A-6D are conceptual diagram illustrating a top view of pathway articles that includes a plurality of radar reflecting structures, according to one or more techniques of this disclosure.

[0014] FIG. 7 is a diagram illustrating a side view of an example reflection and scattering of a radar beam with a radar reflective array of this disclosure.

[0015] FIG. 8 is a conceptual diagram illustrating a top view of an example radar reflecting structure, according to one or more techniques of this disclosure.

[0016] FIGS. 9A-9C are conceptual diagrams illustrating a side view of an example pathway article that includes a radar reflecting structure, according to one or more techniques of this disclosure.

[0017] FIG. 10 is a flow chart illustrating an example technique for making a pathway article, according to one or more techniques of this disclosure.

[0018] FIG. 11 illustrates the principle of current induction on a reflecting structure. The figure shows theoretical equations of the current flow in the metallic surface caused by the magnetic field from the radar. As can be seen in this figure, the current direction is different to the direction of the magnetic field.

[0019] FIG. 12 shows the concept with slots (also termed antennas in this disclosure) in two orientations. The direction of the current needs to be modified to get a radiation back to the source. Current redirection is achieved by extending the slots by using a 90° comer.

[0020] FIG. 13 is a vector representation of the current distribution for a configuration such as shown in Figure 12. Fig. 13 shows the current guided in different directions because of the bended antennas (having lateral elements).

[0021] FIG. 14 is an application view and shows the direction of an incident wave on the reflecting structure. [0022] FIG. 15 is a bistatic directional reflective pattern and shows the reflective response (y/z plane; elevation view) of the structure caused by an incident wave.

[0023] FIG. 16 is an application view of an array and shows the direction of an incident wave on reflecting structure with double number of elements.

[0024] FIG. 17A is a bistatic directional reflective pattern and shows the reflective response (y/z plane; elevation view and y/x plane; azimuth view) of the structure caused by incident wave with double number of elements located in series.

[0025] FIG. 17B shows the array being analyzed in Fig. 17A, having a double number of elements located in series.

[0026] FIG. 18A is an application view of an array and shows the direction of an incident wave on reflecting structure with double number of elements located in series.

[0027] FIG. 18B is a bistatic directional reflective pattern and shows the reflective response (y/z plane; elevation and y/x plane, azimuth view) of the structure caused by incident wave with double number of elements located in series (Fig. 18A).

[0028] FIG. 18C shows superimposed views of the application of an array and its corresponding bistatic directional reflective pattern.

[0029] FIG. 19 shows superimposed views of the application of an array and its corresponding bistatic directional reflective pattern with modified width. The Figure shows the reflective response and resulting beam width in azimuth plane when the width of structure is modified.

[0030] FIG. 20 shows superimposed views of the application of an array and its corresponding bistatic directional reflective pattern with modified width. The Figure shows the reflective response and resulting beam width in azimuth plane when the width of structure is modified.

[0031] FIG. 21A is a bistatic directional reflective pattern and shows the reflective response (y/z plane; elevation view and y/x plane; azimuth view) of the structure caused by an incident wave with double number of elements in series & in parallel.

[0032] FIG. 21B shows superimposed views of a bistatic directional reflective pattern. The figure shows the reflective response (y/z plane; elevation view and y/x plane; azimuth view) of the structure caused by an incident wave with double number of elements in series & in parallel.

[0033] FIG. 22 shows an array of a combination of five radar-reflecting structures are rotated with respect to each other and other radar-reflecting structures have different dimensions from the rest.

[0034] FIG. 23 shows examples of structures that can be placed in the center of other radar-reflecting structures, being partially surrounded by the innermost antenna.

[0035] FIG. 24 shows various antenna shapes that can be used to increase radar reflectivity by widening the azimuthal angle.

[0036] FIG. 25 shows another antenna shape that can be used to increase radar reflectivity by widening the azimuthal angle. [0037] FIG. 26 is a conceptual diagram illustrating a top view of example arrangements of radar reflecting structures within pathway articles, according to one or more techniques of this disclosure. The figure shows how the pattern of reflection elements contains more active reflectors than other patterns when the incoming radar beam is narrow.

[0038] FIG. 27 is a conceptual diagram illustrating a top view of example arrangements of radar reflecting structures within pathway articles, according to one or more techniques of this disclosure. The figure shows how the pattern of reflection elements contains more active reflectors even if a narrow radar beam is used and is not necessarily aligned with a given row of structures.

[0039] FIG. 28 shows potential cutting lines on a tape comprising shifted reflection elements. As a result, this type of pattern allows for a higher number of potential cutting lines because regardless of the location of the cutting line, the resulting tape will have a substantial number of intact structures.

DETAILED DESCRIPTION

[0040] Even with advances in autonomous driving technology, infrastructure, including vehicle roadways, may have a long transition period during which fully autonomous vehicles, vehicles with advanced Automated Driver Assist Systems (ADAS), and traditional fully human operated vehicles share the road. Some practical constraints may make this transition period decades long, such as the service life of vehicles currently on the road, the capital invested in current infrastructure and the cost of replacement, and the time to manufacture, distribute, and install fully autonomous vehicles and infrastructure.

[0041] Autonomous vehicles and ADAS, which may be referred to as semi-autonomous vehicles, may use various sensors to perceive the environment, infrastructure, and other objects around the vehicle. These various sensors combined with onboard computer processing may allow the automated system to perceive complex information and respond to it more quickly than a human driver. A vehicle with radar systems or other sensors that takes cues from the vehicle pathway may be called a pathway -article assisted vehicle (PAAV). Some examples of PAAVs may include the fully autonomous vehicles and ADAS equipped vehicles mentioned above, as well as unmanned aerial vehicles (UAVs) (aka drones), human flight transport devices, underground pit mining ore carrying vehicles, forklifts, factory part or tool transport vehicles, ships and other watercraft and similar vehicles. A vehicle pathway may be a road, highway, a warehouse aisle, factory floor or a pathway not connected to the earth’s surface. The vehicle pathway may include portions not limited to the pathway itself. In the example of a road, the pathway may include the road shoulder, physical structures near the pathway such as toll booths, railroad crossing equipment, traffic lights, the sides of a mountain, concrete barriers, guardrails, and generally

encompassing any other properties or characteristics of the pathway or objects/structures in proximity to the pathway.

[0042] In accordance with techniques of this disclosure, a pathway article (e.g., a road or pavement marking tape, traffic cone or barrel, stop sign, vehicle license plate, etc.) includes a radar reflective structure in a compact planar structure, the radar reflective structure having a large radar cross section (RCS). The radar reflective structure includes a plurality of antennas spaced on a planar surface to receive incident radar waves and reflect radar waves in the direction from which they are received. The spacing of the antennas is a function of angle of incidence and the expected frequency of the radar. The spacing between the antennas causes constructive interference and reflection in the backscatter direction. The pathway article may reflect an incident radar signal in the direction in which the radar signal was received, such that a PAAV may receive the reflected signal. The PAAV may determine pathway information (e.g., information about the pathway) based on the reflected signal, and may control operation of the PAAV based on the pathway information. Including radar reflective structures in the pathway article may increase the ability of a PAAV to detect a pathway in various conditions (e.g., inclement weather conditions), reduce the cost and complexity of components utilized by the PAAV to detect the pathway (e.g., by eliminating the need for other more costly components such as Light Detection and Ranging (LIDAR) components), provide redundant techniques for the PAAV to detect the pathway, or a combination therein. A PAAV may more accurately detect the vehicle pathway based on a radar return signal received from the pathway article, which may increase vehicle and passenger safety.

[0043] The pathway article may include at least one additional feature that may be detected by other sensor systems mounted on the vehicle. Examples of other sensors include: a camera configured to detect light in the human-visible light spectrum, infrared camera, LIDAR, or magnetic detector. The radar reflective structures and the additional feature(s) may be located in the same region of the pathway article or adjacent to each other. In some examples, including radar reflective structures in addition to other sensors may enable the vehicle to detect a vehicle pathway with greater confidence under a wider range of conditions and to enable distinction between marking and other radar-reflective objects, such as other vehicles, in the field of view of the radar system.

[0044] FIG. 1 is a conceptual diagram illustrating an example system 100 including a pathway article with radar reflecting structures, according to one or more techniques of this disclosure. System 100 includes PAAV 110, vehicle pathway 130, and one or more pathway articles 132A-132C (collectively, “pathway articles 132”).

[0045] In some examples, pathway article 132 include a pavement marking tape, a traffic sign (e.g., a stop sign, yield sign, mile marker, etc.), a license plate, a decal or similar article attached to a vehicle, a temporary traffic sign (e.g., a traffic cone or barrel), or other infrastructure articles. For example, as illustrated in FIG. 1, pathway article 132A includes a pavement marking tape indicating an outer edge of vehicle pathway 130 (e.g., for traffic traveling right to left), pathway article 132B include a pavement marking indicating a center line of vehicle pathway 130 (e.g., dividing traffic that travels left to right from traffic traveling right to left), and pathway article 132C indicating another outer edge of vehicle pathway 130 (e.g., for traffic traveling left to right).

[0046] In accordance with techniques of this disclosure, each pathway article of pathway articles 132 includes one or more radar reflecting structures. For example, as illustrated in FIG. 1, pathway article 132A includes radar reflecting structures 134A I -134A N , pathway article 132B includes radar reflecting structures 134B I -134B N , and pathway article 132C includes radar reflecting structures 134C I - 134C N (collectively,“radar reflecting structures 134”). In some examples, each of radar reflecting structures 134 is configured to receive radar radiation and reflect the radar radiation in the direction from which the radar radiation was received. For example, radar reflecting structures 134 may be configured to reflect radar radiation of a particular wavelength, such as radiation with a frequency between approximately 24 GHz and approximately 28 GHz or a frequency between approximately 76GHz and approximately 8 lGHz. It is to be understood that the wavelengths are example wavelengths only and that other ranges of wavelengths are possible. In some examples, radar reflecting structures 134 may include a plurality of antennas, which may be linear slot antennas, u-shaped antennas, or other shapes of antennas.

[0047] In some examples, each of pathway articles 132 may include additional human or machine detectable features. For example, pathway articles 132 may include a colored (e.g., yellow, white, etc.) surface detectable by a human operating or located within PAAV 110. In other words, at least a portion of pathway articles 132 may be colored in the human-visible light spectrum, such that pathway articles 132 are perceptible by humans. As another example, at least a portion of pathway articles 132 may include text, images, or other visual information. Similarly, pathway articles 132 may include a machine- perceptible surface. For example, at least a portion of pathway articles 132 may detectable via an infrared camera (e.g., an infrared camera onboard PAAV 110).

[0048] System 100 includes PAAV 110 that may operate on vehicle pathway 130. As described herein, PAAV generally refers to a vehicle that may interpret the vehicle pathway and the vehicle’s environment, such as other vehicles or objects. A PAAV may interpret information from one or more sensors (e.g., cameras, radar devices, etc.), make decisions based on the information from the one or more sensors, and take actions to navigate the vehicle pathway.

[0049] PAAV 110 of system 100 may be an autonomous or semi -autonomous vehicle, such as an ADAS. In some examples PAAV 110 may include occupants that may take full or partial control of PAAV 110. PAAV 110 may be any type of vehicle designed to carry passengers or freight including small electric powered vehicles, large trucks or lorries with trailers, vehicles designed to carry crushed ore within an underground mine, or similar types of vehicles. PAAV 110 may include lighting, such as headlights that emit light in the visible light spectrum as well as light sources that emit light in other spectrums, such as infrared. PAAV 110 may include other sensors such as radar, sonar, LIDAR, GPS, and communication links for the purpose of sensing the vehicle pathway, other vehicles in the vicinity, environmental conditions around the vehicle, and for communicating with infrastructure.

[0050] As shown in FIG. 1, PAAV 110 of system 100 may include one or more image capture devices 150, one or more radar devices 152, and computing device 140. PAAV 110 may include additional components not shown in FIG. 1 such as engine temperature sensor, speed sensor, tire pressure sensor, air temperature sensors, an inclinometer, accelerometers, light sensor, and similar sensing components.

[0051] Image capture devices 150 may convert light or electromagnetic radiation sensed by one or more image capture sensors into information, such as digital image or bitmap comprising a set of pixels. Each pixel may have chrominance and/or luminance components that represent the intensity and/or color of light or electromagnetic radiation. Image capture devices 150 may include one or more image capture sensors and one or more light sources. In some examples, image capture devices 150 may include image capture sensors and light sources in a single integrated device. In other examples, image capture sensors or light sources may be separate from or otherwise not integrated in image capture devices 150.

Examples of image capture sensors within image capture devices 150 may include semiconductor charge- coupled devices (CCD) or active pixel sensors in complementary metal-oxide-semiconductor (CMOS) or N-type metal-oxide-semiconductor (NMOS, Live MOS) technologies. Digital sensors include flat panel detectors. In one example, image capture devices 150 includes at least two different sensors for detecting light in two different wavelength spectrums.

[0052] In general, image capture devices 150 may be used to gather information about a pathway. Image capture devices 150 may face forward in the direction of travel of the vehicle, to the rear, to the sides, or face other angles relative to the direction of travel. Image capture devices 150 may comprise a suite of devices that provide image data in 360 degrees around the vehicle. Image capture devices 150 may have a fixed field of view or may have an adjustable field of view. An image capture device with an adjustable field of view may be configured to pan left and right, up and down relative to PAAV 110 as well as be able to widen or narrow focus. Image capture devices 150 may capture images of vehicle pathway 130, which may include images of lane markings, centerline markings, edge of roadway or shoulder markings, as well as the general shape of the vehicle pathway 130. Responsive to capturing images of vehicle pathway 130, image capture devices 150 may generate information indicative of the images and send the image information to computing device 140.

[0053] PAAV 110 includes one or more radar devices 152. Each radar device of radar devices 152 include a radar transmitter configured to emit radar radiation (e.g., radio waves) and a radar receiver configured to detect radar radiation. In some examples, radar devices 152 emit radar radiation with a frequency between approximately 24 GHz and approximately 28 GHz (e.g., approximately 24GHz with about a 200MHz bandwidth) or a frequency between approximately 76GHz and approximately 8 lGHz. It is to be understood that the frequencies listed are merely example frequencies and that other radar frequencies may be used.

[0054] Radar devices 152 may be include stationary radar devices 152, such that the radar transmitter emits radar radiation in a single direction and the radar receiver receives or detects radar radiation from a single direction. In some examples, one or more of radar devices 152 are pivotable or rotatable, such that the radar transmitter emits radiation in a range of directions (e.g., 45 degrees in a horizontal direction and 45 degrees in a vertical direction) and the radar receiver receives radar radiation from a range of directions. In some examples, the radar device may be physically stationary, but the beam may be steered (e.g. via a phased array.) In some examples, radar devices 152 detect radar radiation and output radar information about the detected radar radiation to computing device 140. The region illuminated by the transmitted radar radiation and in which the radar receiver receives radar radiation may be referred to as a radar devices field of regard (FOR).

[0055] In the example of FIG. 1, computing device 140 includes an interpretation component 142 and a vehicle control component 144. Components 142 and 144 may perform operations described herein using hardware, hardware and software, hardware and firmware, or a mixture therein. Computing device 140 may execute components 142 and 144 with one or more processors. Computing device 140 may execute any of components 142 and 144 as or within a virtual machine executing on underlying hardware.

[0056] In some examples, interpretation component 142 may receive information from image capture devices 150, radar devices 152, or both, and determine one or more characteristics of vehicle pathway 130. For example, computing device 140 may receive image information from image capture devices 150. Responsive to receiving the image information, interpretation component 142 of computing device 140 may perform image processing (e.g., filtering, amplification, and the like) and image recognition on the received image information. For example, interpretation component 15 may determine (e.g., using image recognition techniques) that the image information includes information indicative of pathway articles 132 and that pathway articles 132 correspond to pavement lane markings, also referred to as a pavement marking tape. Responsive to determining that pathway articles 132 correspond to pavement marking tape, interpretation component 142 may determine a position of vehicle 110 within a lane of pathway 130.

[0057] Similarly, interpretation component 142 may determine a position of vehicle 110 based at least in part on radar information received from radar devices 152. For example, radar devices 152 may output radar information that indicates an object was detected, a distance to the object, a direction of the object relative to vehicle 110, or any combination therein. In some examples, interpretation component 142 determines the direction and distance to the object (e.g., pathway article 132) based on the received radar information. Interpretation component 142 may determine that the radar information indicates the radar radiation was received from (e.g., reflected off) a pathway article, such as a pavement marking tape. For example, interpretation component 142 may determine that the radar radiation was received from a pathway article in response to determining the radar radiation reflected off an article within a threshold distance (e.g., 2 meters, a standardized width of a pathway lane, etc.), in response to determining radar radiation was received from opposite sides (e.g., driver side and passenger side) of PAAV 110, or both. Responsive to determining the radar information indicates that the radar radiation was received from a pathway article, interpretation component 142 may determine a position of vehicle 110 with a lane of pathway 130. For example, interpretation component 142 may determine a distance to the pathway article based on the received radar information. Responsive to determining the position of vehicle 110 within vehicle pathway 130, interpretation component 142 may output information about the vehicle position to vehicle control component 144.

[0058] Vehicle control component 144 may control or adjust operation of PAAV 110 based on the information received from interpretation component. For example, vehicle control component 144 may receive, from interpretation component 142, information indicating that vehicle 110 is approaching a pavement marking tape and may output a command to an electronic control unit (ECU) of vehicle 110 to adjust an orientation of one or more wheels of the vehicle 110 (e.g., by apply a force to the steering to turn the wheels or tires) to keep vehicle 110 within its current lane.

[0059] In some examples, computing device 140 may use information from interpretation component 142 to generate notifications for a user of PAAV 110, e.g., notifications that indicate a characteristic or condition of vehicle pathway 130. For example, responsive to receiving information indicating that vehicle 110 is approaching a pathway article, vehicle control component 144 may output a notification (e.g., audible, graphical, or tactile) to warn an occupant of vehicle 110 that vehicle 110 is approaching the pathway article.

[0060] Pathway articles that include radar reflective structure of this disclosure may have advantages over other types of pathway articles. Including radar reflective structures in the pathway article may increase the ability of a PAAV to detect a pathway in various conditions (e.g., inclement weather conditions), reduce the cost and complexity of components utilized by the PAAV to detect the pathway (e.g., by eliminating the need for other more costly components such as LIDAR), provide redundant techniques for the PAAV to detect the pathway, or a combination therein. For example, computing device 140 of PAAV 110 may combined the input from visual, radar and other sensors to provide a more complete interpretation of the vehicle pathway. For example, a lane assistant system based on optical camera systems may detect and analyze the course of the lane mainly by detection of the contrast between road surface and pavement marking. In hazardous or extreme weather condition (e.g., heavy rain ) the detection rate may decrease significantly. A pavement marking tape that includes radar reflective structures according to this disclosure may provide a redundant and more precise lane detection method (e.g., under some of these hazardous or extreme weather conditions). A PAAV may more accurately detect the vehicle pathway based on a radar return signal received from the pathway article, which may increase vehicle and passenger safety.

[0061] Examples in which the radar reflective structures of this disclosure are combined with other sensable elements may provide additional advantages over other types of pathway articles. For example, pavement marking tapes comprising these radar reflective structures and at least one additional sensable feature that may be detected by other sensor systems mounted on the automobile, such as magnetic detectors, to provide additional redundancy in a compact planar structure. In some examples, the radar reflective structures and the additional sensable feature may be located in the same region of the marking tape or adjacent to each other. In other words, the redundancy in the detectable features of the marking tape may enable use of sensor fusion to provide greater confidence of detection of the pavement marking under a wider range of conditions and to enable distinction between pavement marking and other radar- reflective objects in the field of view.

[0062] To simplify the explanation, the description in this disclosure may focus on the example of a pathway article on a pathway with the radar transceiver on the vehicle. However, the radar reflecting structures of this disclosure may equally apply in examples in which the radar reflecting structure are in a compact planar structure affixed to a vehicle, such as a license plate, a decal, or similar article. In some examples a radar transceiver may be stationary along the vehicle pathway and transmit incident radar radiation toward a vehicle and receive reflected radar radiation from the radar reflecting structure on the vehicle. In other examples, a first vehicle may transmit radar radiation toward a second vehicle and receive reflected radar radiation from the radar reflecting structure on the second vehicle. [0063] The radar reflective structures in a compact planar structure according to the techniques of this disclosure differ from other types of radar-reflective pavement markers. For example, the radar reflective structures of this disclosure and the compact planar structure may have advantages over cat’s eye pavement markers, because of lower cost, ease of maintenance and pavement marking tape may be more applicable in areas subject to snowfall and the use of snowplows than cat’s eye type pavement markers. The radar reflective structures of this disclosure may also have advantages over frequency selective surfaces. For example, because the radar reflecting structures are non-resonant, the radar cross-section is a function of the antenna spacing (e.g., spacing between antennas) but is not a function of the antenna size (e.g., length of the antennas), the radar reflecting structures may be less sensitive to manufacturing tolerances and electromagnetic loading. Further, because the radar reflecting structures are non-resonant, the size of the antennas is not limited to the resonant length.

[0064] FIGS. 2A-2D are conceptual diagrams illustrating top views of example arrangements of radar reflecting structures within pathway articles, according to one or more techniques of this disclosure.

FIGS. 2A-2D illustrate example respective pathway articles 232A-232D (collectively, pathway articles 232”), which may correspond to any of pathway articles 132 of FIG. 1. Pathway articles 232 illustrated in FIGS. 2A-2D are only examples and other pathway articles 232 may exist.

[0065] Each pathway article of pathway articles 232 include a plurality of edges 240, 242, 244, and 246. In some examples, edges 240, 242 may be referred to as long edges or long axis and edges 244, 246 may be referred to as short edges or short axis. For example, pathway articles 232 may be relatively longer than they are wide. For instance, pathway articles 232 may be pavement marking tapes that indicate a boundary of one or more lanes of traffic, and may be defined by a width on the order of several inches (e.g., approximately 4 inches, or approximately 10 centimeters) and a length on the order of yards (or meters), tens or hundreds of yards (or meters), miles (or kilometers), or longer.

[0066] As illustrated in FIG. 2A, pathway article 232A includes a plurality of radar reflecting structures 234A I -234A N (collectively,“radar reflecting structures 234A”). Each of radar reflecting structures 234A include a plurality of antennas. For example, radar reflecting structure 234Ai includes antennas 236A l 236A 2 , and 236A 3 (collectively,“antennas 236A”).

[0067] In some examples, antennas 236A are generally or substantially U-shaped. Each antenna of antennas 236A may include a longitudinal member and two lateral members that form a U-shape. For example, as illustrated in FIG. 2A, antenna 236A includes longitudinal member 237A and lateral members 238A, 239A. Lateral members 238A and 239A may be substantially parallel to one another (do not touch each other and corresponding points in each of the members are separated by a distance that does not vary more than 10% from the average distance between such corresponding points. Longitudinal member 237A may be substantially perpendicular to either or both of lateral members 238A, 239A.

[0068] In the example of FIG. 2A, antenna 236A 2 partially surrounds antenna 236A 3 and antenna 236Ai partially surrounds both of antenna 236A 2 and 236A 3 . For example, antennas 236 may form concentric, u-shaped structures. In other words, antenna 236A 2 may surround antenna 236A 3 on three sides and antenna 236Ai may surround antennas 236A 2 and 236A 3 on three sides. For instance, the lateral members of antenna 236A 2 may be disposed exterior to the lateral members of antenna 236A 3 , such that all or a portion of the lateral members of antenna 236A 3 are not visible from edges 244, 246 of pathway article 232A (e.g., when looking at a sideview of pathway article 232A from edge 244 or edge 246). Likewise, the longitudinal member of antenna 236A 2 may be disposed exterior to the longitudinal member of antenna 236A 3 such that all or a portion of the longitudinal member of antenna 236A 3 is not visible from edge 240 of pathway article 232A. Antenna 236A 2 may not surround antenna 236A 3 on a fourth side. For example, antenna 236A 2 may not be disposed exterior to a side of antenna 236A 3 that does not include a lateral or longitudinal member, which may be referred to as on open side 235A (also referred to as an opening 235 A) of the antennas 236. In some examples, the longitudinal member of antenna 236A 3 may be entirely visible from edge 242 of pathway article 232A and only a portion of the longitudinal member of antenna 236A 2 may be visible from edge 242.

[0069] Similarly, the lateral members of antenna 236Ai may be disposed exterior to the lateral members of antenna 236A 2 , such that all or a portion of the lateral members of antenna 236A 2 are not visible from edges 244, 246 of pathway article 232A (e.g., when looking at a sideview of pathway article 232A from edge 244 or edge 246). Likewise, the longitudinal member of antenna 236Ai may be disposed exterior to the longitudinal member of antenna 236A 2 such that all or a portion of the longitudinal member of antenna 236A 2 is not visible from edge 240 of pathway article 232A. Antenna 236Ai may not surround antenna 236A 2 on a fourth side. For example, antenna 236Ai may not be disposed exterior to an open side 235A of antenna 236Ai (e.g., a side that does not include a lateral or longitudinal member).

[0070] In some examples, each radar reflecting structure of radar reflecting structures 234A may be orientated in the same or similar direction. For examples, as illustrated in FIG. 2A, each of radar reflecting structures 234A are orientated such that the lateral members 238, 239 of antennas 236 are substantially parallel to edges 244, 246 of pathway article 232. Similarly, each of radar reflecting structures 234A may be orientated such that the lateral member 237 of each antenna 236 is substantially parallel to edges 240, 242 of pathway article 232. For instance, radar reflecting structures 234A may be squared with pathway article 232A. In some examples, orientating radar reflecting structures 234A square with pathway article 232A may enable a radar equipped vehicle (e.g., PAAV 110 of FIG. 1) to detect pathway articles adjacent (e.g., directly adjacent) to vehicle 110 using radar devices that are orthogonal to the direction of travel of vehicle 110.

[0071] As illustrated in FIG. 2B, pathway article 232B includes a plurality of radar reflecting structures 234B I -234B N (collectively,“radar reflecting structures 234B”). Each of radar reflecting structures 234B include a plurality of antennas similar to antennas 236A of FIG. 2A. For example, radar reflecting structure 234Bi includes antennas 236Bi, 236B 2 . and 236B 3 (collectively,“antennas 236B”).

[0072] As illustrated in FIG. 2B, each of radar reflecting structures 234B are orientated in a same or similar direction (e.g., within a threshold number of degrees, which may be defined by a manufacturing tolerance) as one another. As further illustrated in FIG. 2B, each radar reflecting structure of radar reflecting structures 234B is angled relative to pathway article 232B. In other words, of radar reflecting structures 234B are not squared to pathway article 232B. For example, longitudinal member 237B of antenna 236Bi is not parallel to edges 240, 242 of pathway article 232B and is not perpendicular to edges 244, 246 of pathway article 232B. Similarly, lateral members 238B, 239B or antenna 236B1 are not parallel to edges 244, 246 of pathway article 232B and are not perpendicular to edges 240, 242 of pathway article 232B. In some examples, an open side 235B of antennas 236B may be angled relative to edge 242 of pathway article 232B. Orientating radar reflecting structures 234B as shown in FIG. 2B may enable radar reflecting structures 234B to receive incident radar radiation from, and redirect the radar radiation back to, directions that are not orthogonal to edges 240, 242 of pathway article 232B. In this way, radar reflecting structures 234B may enable a radar equipped vehicle (e.g., PAAV 110 of FIG. 1) to detect pathway articles ahead of or behind vehicle 110 using radar devices that directed within a threshold number of degrees (e.g., between approximately 30 and approximately 60 degrees) relative to the direction of travel of vehicle 110.

[0073] As illustrated in FIG. 2C, pathway article 232C includes a plurality of radar reflecting structures 234C I -234C N (collectively,“radar reflecting structures 234C”). Each of radar reflecting structures 234C include a plurality of antennas similar to antennas 236A of FIG. 2A. For example, radar reflecting structure 234Ci includes antennas 236Ci, 236C 2 , and 236C 3 (collectively,“antennas 236C”).

[0074] Radar reflecting structures 234C may be orientated in different directions. For example, as illustrated in FIG. 2C, radar reflecting structure 234Ci is orientated in a first direction and radar reflecting structure 234C 2 is orientated in a different direction. In some examples, radar reflecting structures 234C may be orientated in alternating directions. For example, radar reflecting structure 234Ci may be orientated in a first direction and radar reflecting structure 234C 2 may be orientated approximately 180 degrees opposite the orientation of radar reflecting structure 234Ci. In some examples, orientating radar reflecting structures 234C as shown in FIG. 2C may enable radar reflecting structures 234C to receive incident radar radiation from different directions, and redirect the radar radiation back to the respective direction from which the radiation was received. For instance, pathway article 232C may include a pavement marking tape dividing traffic traveling in opposite directions (e.g., such as pathway article 132B of FIG. 1) and may enable a single pathway article to reflect radar radiation to vehicles on opposite sides of a road. In this way, radar reflecting structures 234C may enable different radar equipped vehicles (e.g., PAAV 110 of FIG. 1) that are traveling in opposite directions to detect the same pathway article 232C.

[0075] As illustrated in FIG. 2D, pathway article 232D includes a plurality of radar reflecting structures 234D I -234D N (collectively,“radar reflecting structures 234D”). Each of radar reflecting structures 234D include a plurality of antennas similar to antennas 236A of FIG. 2A. For example, radar reflecting structure 234Di includes antennas 236Di, 236D 2 , and 236D 3 (collectively,“antennas 236D”).

[0076] Radar reflecting structures 234D may be orientated in different directions. In some examples, radar reflecting structures 234D are orientated in a pattern. For example, as illustrated in FIG. 2D, radar reflecting structure 234Di is orientated in a first direction, radar reflecting structure 234D 2 is rotated approximately 45 degrees from radar reflecting structure 234Di, radar reflecting structure 234D 3 is rotated approximately 45 degrees from radar reflecting structure 234D 2 , and so on. In some examples, orientating radar reflecting structures 234D as shown in FIG. 2D may enable radar reflecting structures 234D to receive incident radar radiation from different directions, and redirect the radar radiation back to the respective direction from which the radiation was received.

[0077] In this way, radar reflecting structures 234B may enable radar equipped vehicles to detect a given pathway article at various locations from various distances, and detect the pathway article when traveling in different directions.

[0078] In some examples, pathway articles 232 of FIGS. 2A-2D include a conductive material (e.g., copper) and the radar reflecting structures may be etched or otherwise removed from the conductive material. In some examples, pathway articles 232 may include a substrate upon which the radar reflecting structures are disposed (e.g., via vapor deposition).

[0079] FIGS. 3A-3B are conceptual diagrams illustrating top views of example radar reflecting structures, according to one or more techniques of this disclosure. FIGS. 3A-3B illustrate respective example radar reflecting structures 300A and 300B (collectively,“radar reflecting structures 300”), which may be examples of any of radar reflecting structures 234A-234D illustrated in FIGS. 2A-2D. Radar reflecting structures 300 are only examples and other radar reflecting structures may exist.

[0080] As illustrated in FIG. 3 A, radar reflecting structure 300A includes a plurality of antennas 310A- 310C (collectively,“antennas 310”). While radar reflecting structure 300A is described with reference to FIG. 3 A as including three antennas 310, radar reflecting structure 300A may include any number of antennas 310 (e.g., one, two, four, ten, twenty-five, etc.). In some examples, each antenna of antennas 310 are generally u-shaped.

[0081] In the example of FIG. 3 A, each antenna of antennas 310 are generally or substantially U-shaped. Each antenna of antennas 310 includes a longitudinal member and two lateral members that form a U- shape. For example, as illustrated in FIG. 3A, antenna 310A includes longitudinal member 311A and lateral members 312A, 314A, antenna 310B includes longitudinal member 311B and lateral members 312B, 314B, and antenna 310C includes longitudinal member 311C and lateral members 312C, 314C. In some examples, longitudinal members 311A, 311B, and 311C (collectively,“longitudinal members 311”) are substantially straight lines, which may be substantially parallel to one another. In some examples, lateral members 312A, 312B, 312C (collectively,“lateral members 312”) and lateral members 314A,

314B, and 314C (collectively,“lateral members 314”) are substantially straight lines. Lateral members 312 and lateral members 314 may be referred to as lateral members 312, 314. Lateral members 312, 314 may be substantially parallel to one another. In some examples, each longitudinal member of longitudinal members 311 may be substantially perpendicular to one or more (e.g., each) of lateral members 312, 314.

[0082] Each of longitudinal members 311 may include a first end and a second end. For example, longitudinal member 311 A includes a first end coupled to a first end of lateral member 312A and a second end coupled to a first end of lateral member 314A. Similarly, longitudinal member 311B includes a first end coupled to a first end of lateral member 312B and a second end coupled to a first end of lateral member 314B. Further, longitudinal member 311C includes a first end coupled to a first end of lateral member 312C and a second end coupled to a first end of lateral member 314C.

[0083] Lateral member 312A includes a second end distal the first end of lateral member 312A (e.g., away from the end where lateral member 312A couples to longitudinal member 311 A) and lateral member 314A includes a second end distal the first end of lateral member 314A. Similarly, lateral members 312B, 312C, 314B, and 314C each include a second end that is distal the respective first ends of lateral members 312B, 312C, 314B, and 3 l4C.

[0084] In some examples, the second end of lateral member 312A and the second end of lateral member 314A defines an opening 335A of antenna 310A. That is, longitudinal member 311A, lateral member 312A, and lateral member 314A may partially enclose a space on three sides, the unenclosed space defining opening 335A. The second ends of lateral members 312B, 314B define an opening 335B of antenna 310B, and the second ends of lateral members 312C, 314C define an opening 335C of antenna 310C.

[0085] As illustrated in FIG. 3A, antennas 310A-310C form concentric u-shaped structures. As used throughout this disclosure, concentric structures include a first structure that partially surrounds a second structure. For example, as shown in FIG. 3A, antenna 310B partially surrounds antenna 310A. That is, longitudinal member 311B of antenna 310B may be disposed exterior to longitudinal member 311A of antenna 310A, lateral member 312B of antenna 310B may be disposed exterior to lateral member 312A of antenna 310A, and lateral member 314B of antenna 310B may be disposed exterior to lateral member 314A of antenna 310A. In this way, all or a portion of the lateral members 312A, 314A of antenna 310A located interior to antenna 310B (e.g., such that they are not visible when viewed from either the negative X direction (X-) or positive X direction (X+)). As described above, antenna 310B includes an opening 335B, such that antenna 310B does not completely enclose or surround antenna 310A.

[0086] As further illustrated in FIG. 3 A, antenna 310C partially surrounds antenna 310A and antenna 310B. That is, longitudinal member 311C, lateral member 312C, and lateral member 314C of antenna 310C may be disposed exterior to longitudinal member 311B, lateral member 312B, and lateral member 314B of antenna 310B, respectively. Thus, all or a portion of the lateral members 312B, 314B of antenna 310B are located interior to antenna 310C (e.g., such that they are not visible when viewed from either the negative X direction (X-) or positive X direction (X+)). As described above, antenna 310C includes an opening 335C, such that antenna 310C does not completely enclose or surround antenna 310B.

[0087] Longitudinal members 311A-311C each include a respective midpoint 316A, 316B, and 316C (collectively,“midpoints 316”). Midpoints 316 may be defined as a point that is halfway between the first end and the second end the respective longitudinal members 311. In other words, midpoint 316A is located halfway between the first end and second end of longitudinal member 311A, midpoint 316B is located halfway between the first end and second end of longitudinal member 311B, and midpoint 316C is located halfway between the first end and second end of longitudinal member 311C. In some examples, antennas 310 are mirrored about the respective midpoints. Midpoints 316 may define a straight line, which may be parallel to one or more (e.g., all) of lateral members 312, 314 and perpendicular to one or more (e.g., all) of longitudinal members 311.

[0088] Longitudinal members 311 may be defined by various widths. In the example of FIG. 3A, longitudinal member 311A is defined by a first width W A , longitudinal member 311B is defined by a second width W B that is greater than the first width W A , and longitudinal member 311C is defined by a third width Wc that is greater than each of the first width W A and second width W B . In some examples, the distance between longitudinal members may be defined by the distance D 1. In some examples, as further illustrated in FIG. 8, width W A may be approximately 4.50mm, width W B may be approximately 8.40mm, and width Wc may be approximately l2.29mm.

[0089] Lateral members 312, 314 may be defined by various lengths. In the example of FIG. 3A, lateral members 312A, 314B are defined by a first length L A , lateral members 312B, 314B are defined by a second length L B that is longer than the first length L A , and lateral members 312C, 314C are defined by a third length Lc that is longer than each of the first length L A and second length L B . In some examples, the distance between lateral members may be defined by a distance D2, which may be the same or different than the distance Dl. In some examples, as further illustrated in FIG. 8, length L A may be approximately l.lOmm, length L B may be approximately 3.05mm, and length Lc may be approximately 4.99mm.

[0090] Longitudinal members 311 and lateral members 312, 314 are defined by a thickness. In some examples, the thickness of longitudinal members 311 and lateral members 312, 314 may be equal. In some examples, (e.g., as illustrated in FIG. 8), the thickness of longitudinal members 311 and lateral members 312, 314 equal approximately 0.25mm.

[0091] The distance D 1 may be based on the expected wavelength or expected frequency of the radar radiation for which radar reflecting structure 300A is designed to reflect. In some examples, distance Dl equals approximately one half of the wavelength the radar radiation for which radar reflecting structure 300A is designed to reflect. For example, when radar reflecting structure 300 is designed to reflect radar radiation with a frequency of 77GHz, which has a wavelength of approximately 3.89 millimeters (or approximately 0.153 inches), the distance Dl may be equal to approximately 1.945 millimeters.

[0092] In operation, radar reflecting structure 300A may receive radar radiation (e.g., emitted by vehicle 110 of FIG. 1). Radar reflecting structure 300A may scatter or reflect the incident radar radiation according to Equation 1 : n = 0, +1, 2 ... (Equation 1) where 0i is the angle of incidence, l is the wavelength, and On is the scatter angle (e.g., where the angle of incidence and scatter angle are measured from a direction normal to a surface of a pathway article). Constructive interference occurs when (Equation 2).

In other words, when the distance D 1 between longitudinal members 311 is equal to one half the wavelength l of incident radar radiation 302, radar reflecting structure 300A causes the reflecting radar radiation to constructively interfere, which may maximize the radar radiation reflected back to the source of the incident (also referred to as“incoming”) radar radiation (e.g., vehicle 110 of FIG. 1). Stated another way, radar reflecting structure 300A may maximize the reflected radar radiation 304 when the distance Dl equals one half the wavelength l of incident radar radiation 302.

[0093] In operation, radar reflecting structure 300A may receive radar radiation (e.g., emitted by vehicle 110 of FIG. 1) and may generate a current in the lateral members 312, 314 in response to receiving the radar radiation. In other words, the received radar radiation may induce a current in the y-direction. Longitudinal members 311 may interrupt currents in the y-direction, such that longitudinal members 311 generate a secondary current in the x-direction (e.g., normal to the current induced by the received radar radiation). The secondary current generated by longitudinal members 311 may generate a backscattering, or reflected radar radiation 304. Lateral members 312, 314 may direct or funnel the current in the y- direction towards longitudinal members 311, which may increase the current in the x-direction, thus potentially increasing backscattering of the reflected radar radiation 304. In other words, lateral members 312, 314 may increase the current in the x-direction (e.g., relative to examples that include longitudinal members 311 but do not include lateral members 312, 314) to increase the amount of radar radiation reflected by radar reflecting structure 300A. In other words, because the field intensity may be higher around lateral members compared to the surrounding area, the current density increases in these members, such that the flow of high density currents is directed to the longitudinal members (e.g., which are responsible for creating backscattered energy).

[0094] In some examples, increasing the widths WA, WB, WC of the respective longitudinal members 311A, 311B, and 311C may focus the beamwidth of reflected radar radiation 304. In other words, as the width of increases, the reflected radar radiation beam gets smaller and reflects more radar radiation.

Thus, increasing the width of longitudinal members 311 may increase the power of the reflected radar radiation in a particular region of space, while decreasing the region is space in which the vehicle is likely to detect the reflected radar radiation. In contrast, as the widths WA, WB, WC of the respective longitudinal members decreases, the beamwidth of reflected radar radiation 304 increases and the power in a given direction decreases (e.g., power density decreases), which may increase the region in space in which a vehicle may detect the reflected radar radiation, while decreasing the power of the reflected radar radiation in the given region of space.

[0095] In some examples, pathway articles that include one or more generally u-shaped radar reflecting antennas, as described according to one or more techniques of this disclosure, may help overcome the challenge for vehicle based radar systems to detect pavement markings that are caused by the shallow angle of incidence formed by the incident radar radiation from the radar transmitter. The techniques of this disclosure may increase radar-reflectivity of a pathway article by including radar reflective structures that cause the reflected radar radiation to send the energy back toward the radar transceiver. In other words, the techniques of this disclosure may increase the radar cross section of radar reflecting structures that are in a compact planar structure such as a pavement marking tape.

[0096] In other words, in the example where pathway article includes a pavement marking tape, the angle of incidence, or entrance angle, of the incident radar radiation may be low, compared to the surface of the pavement marking tape. The antennas may be configured to create a large radar cross section for radar reflecting structures 300 based on a low entrance angle. In other examples, such as when pathway article includes a barrier (e.g., a concrete barrier) or a license plate on a vehicle, the expected angle of incidence for the incident radar radiation may be high, i.e. have a high entrance angle. The dimensions and spacing for the radar reflecting structures 300 may be configured to create a large radar cross section based on a high entrance angle.

[0097] FIG. 3B illustrates an example radar reflecting structure 300B that includes a plurality of antennas 350A-350C (collectively,“antennas 310”). While radar reflecting structure 300B is described with reference to FIG. 3B as including three antennas 350, radar reflecting structure 300B may include any number of antennas 350 (e.g., one, two, four, ten, twenty-five, etc.). As illustrated in FIG. 3B, antennas 350A-350C form concentric u-shaped structures. For example, as shown in FIG. 3B, antenna 350B partially surrounds antenna 350A and antenna 350C partially surrounds antenna 350A and antenna 350B.

[0098] Antennas 350 may be similar to antennas 310 illustrated in FIG. 3A. For example, each antenna of antennas 350 are generally u-shaped. Each antenna of antennas 350 includes a plurality of lateral members and a longitudinal member. For example, as illustrated in FIG. 3B, antenna 350A includes longitudinal member 351 A and lateral members 352A, 354A, antenna 350B includes longitudinal member 351B and lateral members 352B, 354B, and antenna 350C includes longitudinal member 351C and lateral members 352C, 354C. Lateral members 352A, 352B, 352C (collectively,“lateral members 352”) and lateral members 354A, 354B, and 354C (collectively,“lateral members 354”) may be similar to lateral members 312, 314 of FIG. 3A. For example, lateral members 352, 354 may form substantially straight lines which may be substantially parallel to one another.

[0099] Longitudinal members 351 and lateral members 352, 354 may be arranged in a manner similar to longitudinal members 311 and lateral members 312, 314 of FIG. 3A. For example, lateral members 352, 354 may be substantially parallel to one another. Each of longitudinal members 351 may include a first end and a second end. For example, longitudinal member 351 A includes a first end coupled to a first end of lateral member 352A and a second end coupled to a first end of lateral member 354A. Similarly, longitudinal member 351B includes a first end coupled to a first end of lateral member 352B and a second end coupled to a first end of lateral member 354B. Further, longitudinal member 351C includes a first end coupled to a first end of lateral member 352C and a second end coupled to a first end of lateral member 354C.

[0100] In some examples, the second end of lateral member 352A and the second end of lateral member 354A defines an opening 365A of antenna 350A. That is, longitudinal member 351A, lateral member 352A, and lateral member 354A may partially enclose a space on three sides, the unenclosed space defining opening 365A. The second ends of lateral members 352B, 354B define an opening 365B of antenna 350B, and the second ends of lateral members 352C, 354C define an opening 365C of antenna 350C. [0101] Longitudinal members 351A-351C each include a respective midpoint 356A, 356B, and 356C (collectively,“midpoints 356”). Midpoints 356 may be defined as a point that is halfway between the first end and the second end the respective longitudinal members 351. In other words, midpoint 356A is located halfway between the first end and second end of longitudinal member 351A, midpoint 356B is located halfway between the first end and second end of longitudinal member 351B, and midpoint 356C is located halfway between the first end and second end of longitudinal member 351C. In some examples, antennas 350 are mirrored about the respective midpoints. Midpoints 356 may define a straight line, which may be parallel to one or more (e.g., all) of lateral members 352, 354.

[0102] In some examples, longitudinal members 351A, 351B, and 351C (collectively,“longitudinal members 351”) are curved. For example, longitudinal members 351 may be an arc (e.g., rather than a substantially straight line). As one example, longitudinal members 351A-351C may be concave relative to openings 365A-365C of the respective antennas 350A-350C.

[0103] In operation, radar reflecting structure 300B may operate in a manner similar to radar reflecting structure 300A. In some examples, when longitudinal members 351 are curved, radar reflecting structure 300B may increase the beamwidth of reflected radar radiation 304. In other words, curved longitudinal members 351 may reflect radar radiation 304 in more directions and may decrease the power of reflected radar radiation 304 in any given direction. Said another way, increasing the beamwidth of reflected radar radiation 304 may increase the region in space in which a vehicle may detect the reflected radar radiation, while decreasing the power of the reflected radar radiation in a given direction within that region of space.

[0104] FIG. 4 is a conceptual diagram illustrating an example system including a vehicle equipped with radar devices and a marking tape, according to one or more techniques of this disclosure. In the example of FIG. 4, system 400 includes pathway article 410 and PAAV 401. PAAV 401 may be equipped with one or more sensors including longer range radars (LRR) 402A and 402B, medium range radars (MRR) 404A and 404B and short range radars (SRR) 406A and 406B. PAAV 401 may also include other sensors, such as cameras, as described above in relation to FIG. 1. The radar system configuration of PAAV 401 depicted in FIG. 4 is just one example for illustration. In other examples, PAAV 401 may be equipped with additional, or fewer, radar systems and arranged in other configurations. To simplify the description of FIG. 4, PAAV 401 will be described as a roadway vehicle, such as an automobile, traveling along a roadway. However, in other examples, PAAV 401 may be other types of vehicles traveling on other types of pathways, as described above in relation to FIG. 1.

[0105] LRR 402A and LRR402B may be radar systems with a field of regard (FOR) in the direction of travel of PAAV 401 and used to detect and/or track objects ahead of and behind PAAV 401. In the example of FIG. 4, the FOR of LRR 402A is the region facing forward of PAAV 401 and LRR 402B is the region facing behind PAAV 401. In some examples, LRR 402A and LRR 402B are narrowband systems in the 24 GHz or 76 GHz bands. In other examples, LRR 402A and LRR 402B may be broadband systems in the 77 GHz band.

[0106] Narrowband systems in the 24 GHz and 76 GHz bands may be used for applications such as adaptive cruise control and blind spot monitoring. A broadband radar system, for example with a bandwidth of 4 GHz, may be also used for adaptive cruise control, blind spot monitoring and obstacle or pathway detection. A broader bandwidth may enable higher spatial resolution of the radar system, relative to a unit based on 24 GHz, for example, with a 200 MHz bandwidth, which limits resolution to one meter (1 m). Higher frequency devices, such as in the 79 GHz range, may enable miniaturization of the radar unit due to physical requirements on antenna size, and also produce a lower emission power, which has the added benefit of mitigating the risk of mutual interference from units on the same roadway. Examples of units in the range of 79 GHz may be useful for short-range and medium-range applications where distinguishing potential obstacles on a vehicle pathway may be valuable.

[0107] MRR 404A and MRR 404B may have a wider azimuth FOR toward the front and rear of PAAV 401, when compared to LRR 402A and LRR 402B. In some examples, the only overlap between the MRR and LRR systems is facing forward between 76-77 GHz. To account for that overlap, one concept may be to have the LRR 402A - 402B at 77 GHz unit have two polarizations, so that it could be distinguished from a signal generated by a MRR unit at 79 GHz. To account for that overlap, in some examples LRR 202A - 202B may have a different polarization, so that the LRR may be distinguished from a signal generated by a MRR unit. For example, a radar transmitter may transmit radar signals with transverse magnetic (TM) polarization or with transverse electric (TE) polarization. TE modes have the electric field transverse to the direction of propagation. TM modes have the magnetic field transverse to the direction of propagation.

[0108] SRR 406A and 406B may include an FOR to the right and left of the vehicle. Some applications for SRR 406A and SRR 406B may include imminent collision warning, for example to trigger air bags, as well as blind spot monitoring.

[0109] Pathway article 410, in the example of FIG. 4 may be a pavement marking tape or a tape attached to a barrier, such as a concrete barrier. Pathway article 410 includes radar reflective structure 420, radar reflective structure 422 and radar reflective structure 424. Each radar reflective structure 420-424 is at a different angle relative to the long axis 411 of pathway article 410. In contrast to radar-reflective pavement markers based on cat’s eye pavement markers and frequency selective surfaces, the radar reflective structures according to the techniques of this disclosure are in a compact planar structure. The compact planar structure may provide advantages over other types of roadway, for example that radar reflective structures of this disclosure may be included in marking tape that may be applied to pavement or other pathway structures.

[0110] As described above in relation to FIGS. 1 - 3B, the reflected radar radiation from the radar reflective structure 420-424 may be at a maximum when the lateral member or lateral portion of the radar reflective structure of the radar reflective structure is substantially orthogonal to the incident radar radiation. For example, radar reflective structure 420 is at an angle 412 that is parallel to long axis 411 of pathway article 410. In this orientation, radar reflective structure 420 is approximately orthogonal to the incident radar radiation from SRR 406B when PAAV 401 is approximately adjacent to radar reflective structure 420. [0111] In another example, when PAAV 401 moves to be adjacent to radar reflective structure 424, which is at angle 416 relative to long axis 404, radar reflective structure 424 would not be orthogonal to the incident radar radiation from SRR 406B. Therefore, SRR 406B may receive less reflected radiation from radar reflective structure 424 when PAAV 401 is adjacent to radar reflective structure 424.

Similarly, SRR 406B may receive less reflected radar radiation when adjacent to radar reflective structure 422 at angle 414 relative to long axis 411. In contrast, the incident radar radiation from MRR 404A and LRR 402A may be orthogonal to radar reflective structure 422 or radar reflective structure 424 when PAAV 401 is at some distance from radar reflective structure 422 or radar reflective structure 424.

Therefore, MRR 404A and LRR 402A may receive a more reflected radiation from radar reflective structure 422 or radar reflective structure 424 when PAAV 401 is at some distance from radar reflective structure 422 or radar reflective structure 424.

[0112] In this manner, by selecting the angle of a radar reflective structure relative to the long axis of pathway article 410, and therefore relative to the position of PAAV 401, the radar reflective structure of this disclosure may be adapted to a variety of functions. As one example, radar reflective structure 420 at angle 412 may be used in a lane guidance function, in addition to any lane guidance function from a visual or other type of camera. The lane guidance function from multiple sources may be used as a cross check by computing device 140 depicted in FIG. 1. In other examples, such as if the lane markings are visibly obscured (e.g., by dirt, snow, rain, or other material), radar reflective structure 420 may provide a more accurate lane guidance function than can be provided by a visual camera under these conditions. Similarly, radar reflective structure 424 may be used to provide forewarning of an upcoming curve or lane shift based on the reflected radiation from MRR 404A and LRR.

[0113] FIG. 5 is a conceptual diagram illustrating atop view of an example pathway article that includes a plurality of radar reflecting structures, according to one or more techniques of this disclosure. In some examples, pathway article 500 represents a marking tape (e.g., a pavement marking tape), however, other examples of pathway article 500 may exist.

[0114] Pathway article 500 is defined by a length LPA and a width WPA. In some examples, pathway article is relatively short in a first direction compared to a second direction. For example, pathway article 500 may be defined by a width WPA on the order of inches or centimeters (e.g., approximately 4 inches or approximately 10 centimeters) and a length LPA of several meters, feet, or yards. For example, pathway article 500 may include a continuous sheeting (e.g., manufactured in a roll) that is approximately 4 inches wide and approximately 50 feet long. FIG. 5 illustrates a portion of the length LPA of pathway article 500.

[0115] Pathway article 500 includes a first long edge 502A and a second long edge 502B that each span the length LPA of pathway article 500. First long edge 502A and second long edge 502B (collectively, “long edges 502”) may be substantially parallel to one another. Pathway article 500 includes a first short edge and a second short edge (not shown).

[0116] In some examples, pathway article 500 includes a radar reflecting array 505 that includes a plurality of radar reflecting structures 510A-510N (collectively,“radar reflecting structures 510”). Radar reflecting array 505 may include any number of radar reflecting structures 510. [0117] Each of radar reflecting structures 510 may correspond to radar reflecting structures 300A, 300B of FIGS. 3A and 3B, respectively. Radar reflecting structures 510 each include a plurality of antennas. For example, radar reflecting structure 510A includes antennas 512A I -512A N (collectively,“antennas 512A”) and radar reflecting structure 510N includes antennas 512N I -512N N (collectively,“antennas 512N”). Antennas 512A - 512N (collectively,“antennas 512”) may be generally u-shaped.

[0118] In some examples, each radar reflecting structure 510 of radar reflecting array 505 is oriented in substantially the same direction, such that each radar reflecting structure 510 in array 505 is configured to receive incident radar radiation 532 from a particular location 530 and maximize the reflected radiation 534 returned to the particular location 530. For example, radar reflecting structure 510A includes an opening 518A that defines a line 520A that intersects edge 502B at an angle 522A. Similarly, radar reflecting structure 510N includes an opening 518N that defines a line 520N that intersects edge 502B at an angle 522N, where angle 522A and angle 522N are substantially the same angle (e.g., within a threshold number of degrees, such as 0.1 degrees) when radar reflecting structures 512A and 512N are orientated in substantially the same direction. In this way, when each radar reflecting structure 510 of a given radar reflecting array 505 are orientated in substantially the same direction, each radar reflecting structure 510 may receive incident radar radiation 532 from a particular location 530 and may maximize the reflected radar radiation 534 directed to the particular location 530.

[0119] Pathway article 500 includes a conductive material used to form radar reflecting structures 510.

In some examples, pathway article 500 includes a conductive layer that includes a conductive material, such as a layer of bulk metal, foils, and conductive coatings. In such examples, radar reflecting structures 510 may be formed by etching, or otherwise removing, portions of the conductive layer. In other words, pathway article 500 may include a conductive layer where a portion of the conductive layer has been removed in the shape of radar reflecting structures 510, such that radar reflecting structures 510 form an open or empty region in the conductive material.

[0120] In some examples, radar reflecting structures 510 of radar reflecting structures 510 may include a conductive material that is placed on, or embedded in, a non-conductive dielectric layer or sheet. The conductive material may be copper or other metal material etched on non-conducting substrate. In another example, the conductive material may include any metal or conductive material deposited via masked vapor deposition, microcontact printing, conductive ink or other suitable processes onto a non conducting substrate. In other words, radar reflecting structures 510 may formed by depositing conductive material on another layer, rather than removing conductive material from a conductive layer.

[0121] In some examples, pathway article 500 may include a grounded film. Radar reflecting structure 510 may be disposed on top of the grounded film, which may reductive or remove transmission and image components of a reflected radar. Adding a ground plane on the opposite side of the radar reflecting structure from the incident radar radiation (e.g., beneath radar reflecting structures 510) may increase the amount of radiation reflected to the radar transceiver (e.g., a larger backscattering level). In some examples, such as where radar reflecting structures are etched from a conductive material, incident radar radiation may travel through the open region that forms radar reflecting structures 510 and bounce back from the ground plane resulting in the larger backscattering level.

[0122] FIGS. 6A-6D are conceptual diagram illustrating a top view of pathway articles that includes a plurality of radar reflecting structures, according to one or more techniques of this disclosure. In some examples, pathway articles 600A-600D (collectively,“pathway articles 600”) of FIGS. 6A-6D represent a marking tape (e.g., a pavement marking tape), however, other examples of pathway articles 600 may exist.

[0123] Pathway articles 600 are defined by a length LPA and a width WPA. In some examples, pathway articles 600 are relatively short in a first direction compared to a second direction. For example, pathway articles 600 may be defined by a width WPA on the order of inches or centimeters (e.g., approximately 4 inches or approximately 10 centimeters) and a length LPA of several meters, feet, or yards. For example, pathway articles 600 may include a continuous sheeting (e.g., manufactured in a roll) that is

approximately 4 inches wide and approximately 50 feet long. FIGS. 6A-6D illustrate various portions of the length LPA of pathway articles 600.

[0124] Pathway articles 600 includes a first long edge 602A and a second long edge 602B that each span the length LPA of pathway articles 600. First long edge 602A and second long edge 602B (collectively, “long edges 602”) may be substantially parallel to one another. Pathway articles 600 includes a first short edge and a second short edge (not shown).

[0125] Pathway articles 600 may each include one or more radar reflecting arrays. As illustrated in FIG. 6A, pathway article 600A includes radar reflecting arrays 605, 610, and 615 that each include one or more radar reflecting structures. While radar reflecting arrays 605, 610, and 615 are shown as including five radar reflecting structures each, radar reflecting arrays 605, 610, and 615 may include any number of radar reflecting structures (e.g., one, two, twenty, etc.). The number of radar reflecting structures in one radar reflecting array may be different than the number of radar reflecting structures in another radar reflecting array.

[0126] As illustrated in FIG. 6A, radar reflecting arrays 605, 610, and 615 are orientated in different directions. In some examples, radar reflecting array 605 may be orientated to receive incident radar radiation and maximize the amount of reflected radar radiation 606 that is reflected back to location 607. As shown in FIG. 6A, radar reflecting array 610 may be orientated to receive incident radar radiation and maximize the amount of reflected radar radiation 611 that is reflected back to location 612. Similarly, radar reflecting array 615 may be orientated to receive incident radar radiation and maximize the amount of reflected radar radiation 616 that is reflected back to location 617. While radar reflecting arrays 605, 610, and 615 are illustrated as being orientated in different directions, in some examples, one or more of radar reflecting arrays 605, 610, and 615 may be orientated in a same or similar direction.

[0127] By orientating radar reflecting arrays 605, 610, and 615 in different directions on the same pathway article 600A, a single pathway article 600A may receive radar radiation from multiple radar devices on a single vehicle, and reflect radar radiation to the multiple radar devices on the single vehicle, such that the vehicle may more accurately determine its location or position within a vehicle pathway. For instance, radar reflecting array 605 may be orientated to reflect radar radiation to vehicles traveling towards radar reflecting array 605 (e.g., when radar reflecting array 605 is 100 meters away from a current position of the vehicle), such that a vehicle may determine the upcoming course of the vehicle pathway. Radar reflecting array 610 may be oriented to reflect radar radiation to vehicles when the vehicle is adjacent to radar reflecting array (e.g., when radar reflecting array 610 is at a same location of the vehicle pathway as the vehicle), such that the vehicle may determine its current position within a lane of the vehicle pathway (e.g., how far the vehicle is from a left or right lane marking). Radar reflecting array 615 may be oriented to reflect radar radiation to a first vehicle traveling in a first direction after the vehicle has passed radar reflecting array 615, which may enable a vehicle to determine its yaw to better, or to reflect radar radiation, or to reflect radar radiation to a second vehicle traveling in the opposite (e.g., wrong) direction as the second vehicle travels towards radar reflecting array 615.

[0128] As illustrated in FIG. 6B, pathway article 600B includes radar reflecting arrays 620, 625, 630, and 635 that each include one or more radar reflecting structures. While radar reflecting arrays 620, 625, 630, and 635 are shown as including three radar reflecting structures each, radar reflecting arrays 620,

625, 630, and 635 may include any number of radar reflecting structures (e.g., one, two, twenty, etc.).

The number of radar reflecting structures in one radar reflecting array may be different than the number of radar reflecting structures in another radar reflecting array.

[0129] As illustrated in FIG. 6B, radar reflecting arrays 605, 610, and 615 are orientated in the same or similar directions. In some examples, radar reflecting arrays 620, 625 may be orientated to receive incident radar radiation and maximize the amount of reflected radar radiation 622, 623 that is reflected back to location 621. Similarly, radar reflecting arrays 630, 635 may be orientated to receive incident radar radiation and maximize the amount of reflected radar radiation 622, 623 that is reflected back to location 631.

[0130] In some examples, pathway article 600B may include a plurality of radar reflecting arrays disposed approximately adjacent to one another to reflect radar radiation to substantially the same location. For example, a first group of radar reflecting arrays may include radar reflecting arrays 620, 625 separated by a distance DARRAY. In other words, a first group of radar reflecting arrays may include two or more radar reflecting arrays in a cluster. In some examples, the distance DARRAY may be less than the width of the radar reflecting arrays. For example, the distance DARRAY may be approximately equal to the width of the smallest or innermost antenna (e.g., width WA of antenna 310A of FIG. 3A). Similarly, a second group of radar reflecting arrays may include radar reflecting arrays 630, 635 separated by a distance DARRAY. In some examples, clustering radar reflective arrays may increase the amount of radar radiation reflected back to a particular location (e.g., location 621 or location 631).

[0131] In some examples, a distance between each antenna of a particular radar reflecting structure may be a first distance, and the distance between each antenna of a different radar reflecting structure may be different. For example, the distance between the antennas of radar reflecting structure 624A of radar reflecting array 620 may be a first distance and the distance between the antennas of radar reflecting structure 624B of radar reflecting array 625 may be a different distance. In this way, radar reflecting array 620 may maximize the amount of radar radiation returned to location 621 for a first frequency band and radar reflecting array 625 may maximize the amount of radar radiation returned to location 621 for a second, different frequency band. In other words, in examples where the distance between antennas is different in different arrays, the arrays may increase the overall bandwidth of radar radiation.

[0132] In some examples, the first group of radar reflecting arrays 620, 625 are separated from the second group of radar reflecting arrays 630, 635 by a distance DSPACE. In some examples, distance DSPACE may be larger than distance DARRAY. In other words, the distance DSPACE between two different clusters or groups of radar reflective arrays may be greater than the distance DARRAY between the individual radar reflective arrays in the group. For example, the distance DSPACE may be on the order of meters whereas the distance DARRAY may be on the order of millimeters. In this way, pathway article 600B may maximize the amount of radar radiation reflected to discrete locations and reduce manufacturing costs by spacing the groups or clusters of radar reflecting arrays relatively far apart (e.g., compared to the size of the groups of radar reflecting arrays themselves).

[0133] As illustrated in FIG. 6C, pathway article 600C includes radar reflecting arrays 640, 645, 650, and 655 that each include one or more radar reflecting structures. While radar reflecting arrays 640, 645, 650, and 655 are shown as including five radar reflecting structures each, radar reflecting arrays 640, 645, 650, and 655 may include any number of radar reflecting structures (e.g., one, two, twenty, etc.). The number of radar reflecting structures in one radar reflecting array may be different than the number of radar reflecting structures in another radar reflecting array.

[0134] As illustrated in FIG. 6C, pathway article 600C may include a plurality of radar reflecting arrays disposed approximately adjacent to one another. For example, a first group of radar reflecting arrays may include radar reflecting arrays 640, 645 separated by a distance DARRAY, as described with reference to FIG. 6B. Similarly, a second group of radar reflecting arrays may include radar reflecting arrays 650, 655 separated by a distance DARRAY- In some examples, the first group of radar reflecting arrays 640, 645 are separated from the second group of radar reflecting arrays 650, 655 by a distance DSPACE as described with reference to FIG. 6B.

[0135] In some examples, the radar reflecting arrays within a group or cluster of radar reflecting arrays may be orientated in directions. In the example of FIG. 6C, radar reflecting array 640 is orientated in a first direction and radar reflecting array 645 is orientated in a second direction (e.g., approximately 180 degrees opposite the orientation of radar reflecting array 640). In this way, pathway article 600C may reflect radar radiation to vehicle traveling in the opposite directions on a vehicle pathway.

[0136] As illustrated in FIG. 6D, pathway article 600D includes radar reflecting arrays 660, 665, 670, 675, and 680 that each include one or more radar reflecting structures. While radar reflecting arrays 660, 665, 670, 675, and 680 are shown as including three radar reflecting structures each, radar reflecting arrays 660, 665, 670, 675, and 680 may include any number of radar reflecting structures (e.g., one, two, twenty, etc.). The number of radar reflecting structures in one radar reflecting array may be different than the number of radar reflecting structures in another radar reflecting array. [0137] As illustrated in FIG. 6D, pathway article 600D may include groups of radar reflecting arrays orientated in a first direction separated by one or more radar reflecting arrays orientated in a second direction, where the number of radar reflecting arrays orientated in the second direction is less than the number of radar reflecting arrays orientated in the first direction.

[0138] In the example of FIG. 6D, pathway article 600D includes a first group of radar reflecting arrays that includes radar reflecting arrays 660, 665 and a second group of radar reflecting arrays that includes radar reflecting arrays 675, 680. The first and second group of radar reflecting arrays may be orientated in a first direction. The first group of radar reflecting arrays 660, 665 may be separated from the second group of radar reflecting arrays 675, 680 by radar reflecting array 670 that is orientated in a second, different direction (e.g., approximately 180 degrees opposite the first direction). For example, when a vehicle pathway includes a one-way road, the first and second groups of radar reflecting arrays may be orientated to maximize the amount of radar radiation reflected to vehicles traveling the intended direction of the vehicle pathway. Radar reflecting array 670 may be orientated to maximize the amount of radar radiation reflected in the opposite direction to provide lane marking information to vehicles traveling in the wrong direction. By orientating more radar reflective arrays in a particular (e.g., correct) direction while still orientating some radar reflective arrays in a different (e.g., incorrect) direction, pathway article 600D may reflect radar radiation to vehicles traveling in different directions while providing relatively more radar reflective arrays for PAAVs traveling in the intended direction of the vehicle pathway.

[0139] FIG. 7 is a diagram illustrating a side view of an example reflection and scattering of a radar beam with a radar reflective array of this disclosure. FIG. 7 illustrates a cross sectional view of a radar reflective structure 700A with 0 = 0 (theta = 0) indicating the angle orthogonal to the radar reflective structure of the radar reflective array. To simplify the description, the radar reflective array will be described in terms of a radar reflective array that is part of a pavement marking tape. Therefore, 0 = 0 indicates a direction straight up and + 90 and - 90 indicating directions along the pavement surface.

[0140] Incident radar radiation 701 strikes radar reflective structure 700A resulting in a reflected radar radiation 704 with 3 dB vertical beamwidth 706 as well as backscatter 702. Radar reflective structure 700A may include any one or more radar reflective structures, such as described above in relation to FIGS. 5A-6D.

[0141] In some examples, the type of radar reflective structure, as well as the length, number of structures, material, spacing and other properties of radar reflective structure 700A may determine the beamwidth of reflected radar radiation 704, the amount of energy that is reflected and in the backscatter 702 and the direction of reflected radar radiation 704. In some examples, increasing the lateral length of each radar reflective structure of radar reflective structure 700Amay have little impact on 3dB vertical beamwidth 706, i.e. the angular position of the 3dB boundary of reflected radar radiation 704 as well as little impact on the energy lost to backscatter 702 and side lobes. However, increasing the lateral length may increase the energy in reflected radar radiation 704. Increasing the number of radar reflective structures in radar reflective structure 700A may increase the magnitude of the main lobe of reflected radar radiation 704 as well as decrease the 3dB vertical beamwidth 706. The number of radar reflective structures in an array may be limited by the angle of the radar reflective array relative to the long axis of the pathway article, as well as the dimensions of the pathway article and spacing between radar reflective structures as needed for the expected frequency of the incident radar radiation.

[0142] In some examples, radar reflecting structure 700A may include a conducting ground plane below the reflective elements. The ground plane may be separated from the reflective elements by a dielectric substrate. The addition of a ground plane at a predetermined distance below the reflective elements of radar reflecting structure 700A may increase reflected energy in reflected radar radiation 704 by hindering incident radar radiation from passing into the ground. The added ground plane may also de-couples radar reflecting structure 700A electromagnetically from the ground materials.

[0143] FIG. 8 is a conceptual diagram illustrating a top view of an example radar reflecting structure, according to one or more techniques of this disclosure. Radar reflecting structure 800 includes a plurality of antennas. Each antenna of radar reflecting structure 800 includes a longitudinal member and two lateral members. FIG. 8 illustrates the example widths and example lengths of the antennas of radar reflecting structure 800. For example, the antennas of radar reflecting structure 800 may be defined by respective lengths of approximately l. lOmm, approximately 3.05mm, approximately 4.99mm, approximately 6.94mm, approximately 10.84mm, approximately 12.79mm, approximately 14.73mm, approximately 16.68mm, and approximately 18.63mm. Similarly, the antennas of radar reflecting structure 800 may be defined by respective widths of approximately 4.50mm, approximately 8.40mm, approximately l2.29mm, approximately l6T6mm, approximately 20.08mm, approximately 23.98mm, approximately 27.88mm, approximately 31.77mm, and approximately 35.67mm. In some examples, the antennas of radar reflecting structure 800 are defined by a thickness approximately 0.25mm.

[0144] FIGS. 9A-9C are conceptual diagrams illustrating a side view of an example pathway article that includes radar reflecting structures, according to one or more techniques of this disclosure. FIG. 9A illustrates an example pathway article 900. In some examples, pathway article 900 includes a compact planar structure, such as a marking tape (e.g., a pavement marking tape).

[0145] Pathway article 900 includes radar reflective layer 908. Pathway article may include sensable layer 902, backing layer 910, and one or more other layers, which may not be shown in FIG. 9A.

[0146] In some examples, pathway article 900 includes a pavement marking tape which may be used for marking lanes, centerlines, edges or other features of a vehicle pathway. In such examples, the dimensions of pathway article 900 may conform to a standard as prescribed by the region of use. For example of a pavement marking for marking lanes, the material may be between about 7.5 and 30 centimeters (3 and 12 inches) wide and 30 centimeters (12 inches) long or longer. In the United States, pavement marking tapes are about 4, about 6, or about 8 inches wide (approximately 10 cm - approximately 20 cm). In Europe, pavement marking tapes are typically about 15 or about 30 centimeters wide.

[0147] In some examples, pathway article 900 may be used as a decal, or similar structure for use indoors, such as a warehouse or factory vehicle pathway. For an indoor application, pathway article 900 may not include for example, a protective layer or a conformance layer. In other examples, such as a decal or license plate used on a vehicle, pathway article 900 may include a protective layer, which may help prevent moisture, oil, dirt or other contaminants from affecting the sensible layer and/or radar reflective layer. In such examples, pathway article 900 may not include protection from tires nor anti-skid features. In some examples, such as when pathway article 900 is constructed for a rough surface, such as a concrete barrier, pathway article 900 may include a conformance layer. In some examples, pathway article 900 may not include a conformance layer (e.g., when pathway article 900 is constructed to be applied to a smooth surface). In other words, the construction of pathway article 900 may be specific for the particular application to which a pathway article 900 is intended to be used, such that pathway article 900 may not include all layers described in this disclosure and may include additional layers not described.

[0148] Sensable layer 902, in the example of FIG. 9A may include a retroreflective layer 906 and one or more protective layers 904. Retroreflective layer 906 may include reflective elements, such as visible light reflective elements, LIDAR reflective elements, UV and IR reflective elements, magnetic elements, and other similar elements that may be detectable by one or more sensors on a PAAV (not shown in FIG. 9A). Examples of retroreflective layer 906 may include an exposed-lens system, an enclosed lens retroreflective sheet, encapsulated-lens, embedded lens, cube-comer type, microsphere-based

retroreflective sheetings that comprise a monolayer of transparent microspheres partially embedded in a binder layer, and other types of retroreflective sheeting as well as combinations of any of the above. Retroreflective layer 906 may also include a texture to provide high retroreflectivity at both high and low light entrance angles. Sensable layer 902 is configured to allow radar signals to pass through sensable layer 902, where sensable layer 902 is placed over radar reflecting structures in radar reflective layer 908. In examples in which sensable layer 902 includes magnetic or metallic elements, the magnetic or metallic elements may be in a separate location (e.g., displaced horizontally) from the radar reflecting structures of radar reflective layer 908.

[0149] Sensable layer 902 may also be colored in the visible spectrum to provide additional cues to vehicle operators or a computing device, such as computing device 40 described above in relation to FIG. 1. Some example colors may include red, yellow, white or blue. In some examples, a combination of opaque and light transmissive colorants may be used. In this way, pathway article 900 would have effective day and night time colors (e.g., pathway article 900 may be detectable in day and night).

Materials used in sensable layer 902, such as colorants, may be selected to avoid interference with the functions of the radar reflective arrays in radar reflective layer 908.

[0150] Protective layer 904 may comprise a thin, high abrasion resistance and/or dirt resistant coating applied to the top surface of retroreflective layer 906 to protect retroreflective layer 906 from traffic wear and dirt accumulation. In some examples, protective layer 904 may be radar and light transmissive. In some examples, skid control particles may be partially embedded in protective layer 904, or in a layer on top of protective layer 904 (not shown in FIG. 9A). Skid control particles, may be referred to as anti -skid particles, and may be included in the upper surface of a pavement marking tape to improve the traction of vehicles. In some examples, protective layer 904 may include a release liner or apply a release treatment, e.g., silicone, to the top surface. In some examples, pathway article may include a pavement marking tape may be wound into a roll form and the release liner may make it easier to dispense the marking tape.

[0151] Protective layer 904 may be single layer or multilayer, e.g., further comprising a top film overlying underlying layers. In some examples, aliphatic polyurethanes may be used for top films because aliphatic polyurethanes properties may include clear, resistant to dirt build-up, flexible enough to conform to the road surface, bond to inorganic anti-skid particles, and resist discoloration with exposure to ultraviolet radiation.

[0152] Some other examples of protective layer 904 may include, but are not limited to, ceramer coatings or crosslinked water-based polyurethane coatings. As used herein, "ceramer" refers to a fluid comprising surface-modified colloidal silica particles dispersed in a free-radically polymerizable organic liquid. Advantages of a ceramer coating may include the ability to withstand outdoor conditions with resistance to moisture, light and heat, resistance to abrasion, chemical attack and coloration by automobile engine oil. In some examples, a ceramer precursor coating composition may be applied to the surface of retroreflective layer 906, preferably including the top surface of any refracting elements and portions of base layer 910 and radar reflective layer 908 not covered by refracting elements. The ceramer precursor composition may be cured to form sensable layer 902 with an abrasion resistant, light transmissive ceramer coating.

[0153] Backing layer 910 may include a conformance layer 912 and/or a scrim layer (not shown in FIG. 9A) and adhesive layer 914. In some examples, backing layer 910 may also a scrim material to impart increased tear resistance, which allows a temporary pavement marking to be removable. Conformance layer 912 may include material such as aluminum. Conformance layer 912 may enable radar reflective layer 908 to remain substantially planar when pathway article 900 is attached to a rough surface, for example, by conforming to uneven surfaces in a vehicle pathway or other material to which pathway article 900 may be applied. In other words, conformance layer 912 may allow a pathway article 900 applied to a rough surface to conform and adhere to the surface, while ensuring that the rough surface does not substantially distort radar reflective layer 908, thereby enabling radar reflective layer 908 to retain radar reflective properties.

[0154] In some examples, one or more layers included in backing layer 910 may be referred to as a carrier fdm, or a continuous base sheet. Some examples of materials that may be included in one or more layers may include polyethylene terephthalate (abbreviated as PET or PETE), polyesters, acrylics, rubbers, thermoplastics, polyoefms and similar materials.

[0155] Radar reflective layer 908 may include a plurality of radar reflective structures as described above in relation to FIGS. 1 - 6D. For example, radar reflective layer may include one or more radar reflective structures (e.g., a plurality of radar reflective arrays) described with reference to FIGS. 1-6D. For example, the one or more radar reflective structures of radar reflective layer 908 may be configured to receive incident radar radiation and maximize the amount of radar radiation reflected back to a particular location. The plurality of radar reflective arrays may be arranged on radar reflective layer 908 with any combination of angles with respect to a long axis of pathway article 900, as well as combinations of groupings, and spacing. The combinations may also include combinations of straight and/or curved radar reflective restructures described above.

[0156] In some examples, radar reflecting layer 908 includes a conductive layer that includes a conductive material, such as a layer of bulk metal, foils, and conductive coatings. In such examples, the radar reflecting structures of radar reflecting layer 908 may be formed by etching, or otherwise removing, portions of the conductive layer. In other words, radar reflecting layer 908 may include a conductive layer where a portion of the conductive layer has been removed in the shape of radar reflecting structures, such that the radar reflecting structures form an open or empty region in the conductive material.

[0157] In some examples, the radar reflecting structures of radar reflecting layer 908 may include a conductive material that is placed on, or embedded in, a non-conductive dielectric layer or sheet. The conductive material may be copper or other metal material etched on non-conducting substrate. In another example, the conductive material may include any metal or conductive material deposited via masked vapor deposition, microcontact printing, conductive ink or other suitable processes onto a non conducting substrate. In other words, the radar reflecting structures of radar reflecting layer 908 may formed by depositing conductive material on another layer, rather than removing conductive material from a conductive layer.

[0158] In some examples, radar reflecting layer 908 includes a conducting ground plane below the radar reflecting structures. The ground plane may be separated from the radar reflecting structures by a dielectric substrate. The addition of a ground plane at a predetermined distance below the radar reflecting structures of radar reflecting layer 908 may increase reflected energy in reflected radar radiation by hindering incident radar radiation from passing through the radar reflecting structure into the ground. The added ground plane may also de-couple the radar reflecting structures in radar reflective layer 908 electromagnetically from the ground materials.

[0159] In some examples, radar reflective layer 908 exhibits high retroreflectivity at both high and low entrance angles. In some examples of pathway article 900, the spacing, or other dimensions of radar reflective structures of radar reflective arrays in radar reflective layer 908 may be adjusted to account for the expected entrance angle, i.e. the radar signal angle of incidence. As described above, the spacing and other dimensions of radar reflective structures may be a function of the expected radar frequency and incident radar radiation. As one example, pathway article 900 may include a marking tape in an application such as a stripe on a guard rail, Jersey barrier, or wall that is parallel a first vehicle pathway and perpendicular to a second pathway that intersects the first pathway on the opposite side of the first pathway from the second pathway. In this parallel/perpendicular application, a marking tape may include radar reflective arrays configured for a low entrance angle and other radar reflective arrays configured for a high entrance angle.

[0160] In some examples, pathway articles with radar reflective structures according to this disclosure will be resistant to corrosion in installed environments, and to retain dimensional stability. In examples that include a metal layer on the surface of the radar reflective structure, such as stamped foil, vapor deposited layer, or conductive ink, may be corrosion-protected by fully encapsulating with a protective layer comprising a weatherable, abrasion-resistant, low dielectric material to prevent the ingress of chlorides and water. Some examples may include an anti-corrosion surface treatment. Both metallic and non-metallic examples may be encapsulated with a weatherable, abrasion-resistant, low dielectric layer to prevent collection of debris that may interfere with the reflectivity. Some examples of pavement marking tapes with dimensionally stable arrays may be formed on filled rubber premix compositions that are not substantially deformed in operation.

[0161] Pathway article 900 may be assembled by providing a sensable layer 902, which may comprise retroreflective layer 906 and protective layer 904, and applying, such as by laminating, conformance layer 912 to the bottom surface of sensable layer 902. In some examples, a layer of adhesive or primer may be applied to the surface of one or more layers prior to laminating. The criteria for suitable adhesive materials and primers will be dependent in part upon the nature of the sheeting and the intended application. In some examples, either conformance layer 912 or a configuration member (not shown in FIG. 9A) could be first applied to retroreflective layer 906. For instance, in one example, a retroreflective sheet may be applied to an aluminum conformance layer 912 followed by lamination of a configuration member, e.g., a mesh (not shown in FIG. 9A). Adhesive layer 914 may be applied to the pathway article 900 before application to a desired substrate, such as a roadway. In some examples, pathway article 900 includes a marking tape comprising a compact planar structure that can withstand repeated traffic impact and shear stresses in combination with other effects of sunlight, rain, road oil, road sand, road salt, and vehicle emissions.

[0162] FIG. 9B illustrates an example pathway article 920, according to one or more techniques of this disclosure. Pathway article 920 may include a compact planar structure, such as a marking tape (e.g.. a pavement marking tape). In the example of FIG. 9B, pathway article 920 includes sensable layer 921, radar reflective layer 940 and backing layer 934. Backing layer 934 comprises conformance layer 936, configuration member 932, and adhesive layer 938. As described above, backing layer 934 may also include a scrim material (not shown in FIG. 9B). In some examples, radar reflective layer 940 may be included in backing layer 934. Radar reflective layer 940 may be similar to radar reflective layer 908 described with reference to FIG. 9A. For example, radar reflective layer may include one or more radar reflective structures (e.g., a plurality of radar reflective arrays) described with reference to FIGS. 1-6D. For example, the one or more radar reflective structures of radar reflective layer 940 may be configured to receive incident radar radiation and maximize the amount of radar radiation reflected back to a particular location.

[0163] Sensable layer 921 includes a protective layer 929 and retroreflective sheet 922. Protective sheet 929 is similar to protective layer 904 described above in relation to FIG. 9A.

[0164] Enclosed-lens retroreflective sheet 922 comprises a monolayer of retroreflective elements 924 formed into first portions of the monolayer arranged in an upwardly contoured profile 926A and second portions 928 of the monolayer are arranged a lower, sometimes substantially planar profile. First portions 926A are elevated above second portions 928 by configuration member 932. These upwardly contoured portions 926A, with their relatively vertical profiles may provide enhanced retroreflective performance. First, when the pathway article is oriented as a pavement marking or guard rail marking, the incidence angle or entrance angle of light to the upwardly contoured portions 926A may be lower than the incidence angle to the second lower portions 928. This may achieve and effective retroreflective result. Second, the higher elevation of upwardly contoured portions 926A may facilitate the run off of water that might degrade retroreflective performance. Third, in the example of pavement markings, upwardly contoured portions 926A have been observed to result in improved adhesion to the road surface.

[0165] Upwardly contoured portions 926A may be implemented in any way that will elevate portions of the retroreflective sheet. In the example of FIGS. 9B and 9C, such means is use of a configuration member. Configuration members may be of any shape so long as they elevate some portions of the retroreflective sheet. In some examples, the configuration member is a mesh or netting of strands or even simply an assembled array of unconnected strands. When the article is assembled the strands define the first upwardly contoured portions 926A and the openings between the strands define the second lower portions 928. Some examples of shapes may include rectangles, diamonds, hexagons, curves, circles, sinusoidal ridges (e.g., nested in parallel or intersecting), etc. Each second lower portion 928 may be essentially separated from neighboring lower portions or they may intersect, depending upon the shape of the first upwardly contoured portions 926A.

[0166] In the example of FIG. 9B, configuration member 932 may be directly attached to retroreflective sheet 922. In some examples, pathway article 920 may include a tie layer (not shown in FIG. 9B) between one or more layers. The tie layer may be a layer that adheres well to the surfaces of mating layers. For example, ethylene methacrylic acid will adhere to both aluminum and nitrile rubber layers. In other examples, conformance layer 936 may be directly attached to the bottom of the radar reflective layer 940, followed by a configuration member and adhesive layer 938. In some examples, the retroreflective sheet and configuration members may be substantially coextensive, while in other examples may be not co-extensive. In the example of FIG. 9B, backing layer 934 comprises

configuration member 932 bonded to optional conformance layer 936.

[0167] FIG. 9C illustrates another example pathway article 950, according to one or more techniques of this disclosure. Pathway article 950 is similar to pathway articles 900 and 920 of FIGS. 9A and 9B, with a different example of conformance members 9xx. Features among the figures with the same reference numbers have the same function and description.

[0168] As illustrated in FIG. 9C, pathway article 950 includes sensable layer 951, radar reflective layer 940 and backing layer 954. Backing layer 934 comprises optional conformance layer 936, and adhesive layer 938. As described above backing layer 934 may also include a scrim material (not shown in FIG. 9B). In some examples, radar reflective layer 940 may be included in backing layer 934 or may be considered a separate layer.

[0169] Sensable layer 951 includes a protective layer 929 and retroreflective sheet 922. Protective sheet 929 is similar to protective layer 904 described above in relation to FIG. 9A. In the example of FIG. 9C configuration member 952 is applied to retroreflective sheet 922 followed by lamination of radar reflective layer 940, conformance layer 936 and adhesive layer 938. [0170] As with configuration member 932 of FIG. 9B, configuration members 952 may be polymeric. Some examples of polymeric materials may include polyurethanes and polyolefin copolymers such as polyethylene acid copolymer consisting of ethylene methacrylic acid 35 (EMAA), ethylene acrylic acid (EAA), ionically crosslinked EMAA or EAA.

[0171] Upward contoured portions 926B may be achieved by laminating configuration members 952 to any region beneath the retroreflective sheet 922. In other words, configuration members 952 may be placed between retroreflective sheet 922 and adhesive layer 938, which bonds the marking tape to a desired substrate, e.g., a roadway. Optional adhesive layer 938 may be applied before application to the desired substrate, Thus, the configuration member can be placed in any layer beneath the retroreflective sheet insofar as it results in the desired configuration. Because the purpose of the configuration member is to impart an upward profile to the retroreflective sheet, its placement can vary for processing

convenience.

[0172] In other examples, pathway article 900, 920 and 950 may be assembled by providing a sensable layer and backfilling upwardly contoured profiles with a filling material. The upwardly contoured profiles may be formed by variety of techniques. In one example, retroreflective sheet 922 may be gathered together in portions and any voids backfilled. In other examples, retroreflective sheet 922 may be fed into an embossing roll to form the upwardly contoured profiles of a variety of shapes, as described above. An embossing roll may have an advantage in causing less disruption of the sensable layer, when compared to laminating the sensable layer to a preformed configuration layer, such as in the example of Fig 9B.

Disruption may lead to reduction of retroreflective brightness or reduce physical integrity of the sheeting.

[0173] Forming the profiles may create voids or depressions in the back of the retroreflective sheet (i.e., the non-reflective side). It may be desirable to fill the voids with some material that provides sufficient dimensional stability to retain the described profiles. Backfill material may be conformable so the resultant marking tape is flexible and conformable while retaining the contoured profile described herein. For example, a polymeric film may be used as backfill material. The polymeric film may be heated to flow into the voids in the structured regions. Radar reflective layer 940 may be laminated or otherwise assembled to the sensable layer after the formation and backfill of the upwardly contoured profiles. As described above, a tie layer may be included between any of the layers.

[0174] Pathway articles 900, 920 and 952 may be configured to be sufficiently conformable so that the desired upwardly contoured profiles 926A and 926B of retroreflective sheet 922 can be achieved. In some examples, configuration member, such as configuration members 932 and 952 may self-adhere to conformance layer 936, if present, which may have an advantage of improved durability when compared to other configurations. In addition to providing the functions disclosed herein, the configuration layer may impart improved mechanical properties to a pavement marking material in similar manner as the scrim layer described above in relation to FIG. 9B.

[0175] As described above, a variety of techniques may be used to add colorants to some portion the pathway articles of this disclosures. Some examples may include a light and radar transmissive colored top film. In other examples, a colorless top film could be applied to a colored retroreflective sheet. [0176] FIG. 10 is a flow chart illustrating an example technique for making a pathway article, according to one or more techniques of this disclosure. The technique of FIG. 10 will be described in terms of FIGS. 9A - 9C, unless otherwise noted. The techniques in the description of FIG. 10 is just one example. In other examples, the techniques of FIG. 10 may be performed in a different order, and may include a subset of steps described or additional steps not described with reference to FIG. 10.

[0177] One technique for making a pathway article, such as a pavement marking tape, may include providing a continuous base sheet including an upper surface and a lower surface (1002). The base sheet may include any one or more of the layers included in backing layer 934, such as configuration member 932 and conformance layer 936. The base sheet may be one continuous length along the long axis, such as long axis 411 depicted in FIG. 4. In other examples, the base sheet may be a shorter length such as approximately 15 cm, approximately 1 meter, or other lengths. The base sheet may be any width, as appropriate for the intended application, such as approximately 10 cm wide.

[0178] In some examples, the techniques of this disclosure may include applying a sensable layer to the upper surface of the continuous base sheet, such as by laminating a surface of the sensable layer to the base sheet upper surface (1004). The sensable layer may include features that are visible to the human eye or camera that detects light in the human-visible spectrum or infrared spectrum, such as

retroreflective layer 922. The sensable may also include features such as magnetic elements that may be detectable by other sensors on a PAAV. In some examples, retroreflective layer 922 includes an embedded-lens retroreflective sheet, which may include a layer of transparent microspheres having front and back surfaces, a cover layer in which the front surface of the microspheres are embedded, and an associated reflective means behind the back surface of the microspheres. In other examples,

retroreflective layer 922 may include a retroreflective sheet comprisng a monolayer of cube-comer elements. In other examples, retroreflective layer 922 may include one or more first upwardly contoured profile 926A and 926B, which may be arranged in an interconnected network.

[0179] In some examples, a pathway article that includes a compact planar structure, such as pathway article 950, may be further assembled by applying a continuous conformance layer, such as conformance layer 936 to the lower surface of the continuous base sheet (1006). Conformance layer 936 may comprise a variety of materials, including aluminum, and may be applied along with a tie layer and a scrim layer. Some examples of marking tape may also include adhesive layer 938.

[0180] The method of manufacturing a pathway article may include adding one or more radar reflective structures disposed between sensable layer 902 and the continuous base sheet (1008). In some examples, the method includes adding radar reflective structures in the plane of the continuous base sheet. The radar reflective structures may be one of a plurality of radar reflective structures (e.g., such as radar reflective structures depicted in FIGS. 1-6D). The radar reflective structures may be arranged at a variety of angles and spacings to perform various functions as described above in relation to FIGS. 1 - 3B. In some examples, the method includes adding one or more radar reflective arrays, such as the radar reflective arrays illustrated in FIGS. 6A-6D. Radar reflective structures and arrays may comprise a conductive material and have dimensions and spacing configured to reflect incident radar radiation from one or more radar transceivers in a PAAV.

[0181] In some examples, adding one or more radar reflecting structures includes disposing a conducting layer between sensable layer 902 and the continuous base sheet and removing portions of the conductive layer to form radar reflecting structures. For example, theconductive layer may include a conductive material, such as a layer of bulk metal, foils, and conductive coatings. Removing portions of the conductive layer to form the radar reflecting structures may include etching portions of the conductive layer. In such examples, the radar reflecting structures may form an open or empty region in the conductive material.

[0182] In some examples, adding one or more radar reflecting structures includes adding a conductive material to a non-conductive dielectric layer or sheet. For example, adding one or more radar reflecting structures may include depositing a conductive material via masked vapor deposition, microcontact printing, conductive ink or other suitable processes onto a non-conducting substrate, to form radar reflecting structures (e.g., generally u-shaped radar reflecting structures).

[0183] In some examples, adding one or more radar reflecting structures includes adding a conducting ground plane below the radar reflecting structures. For example, the method may include disposing a ground plane, a dielectric substrate on top of the ground plane, and one or more radar reflecting structures on top of the dielectric substrate.

[0184] In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over, as one or more instructions or code, a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, computer-readable media generally may correspond to (1) tangible computer-readable storage media, which is non-transitory or (2) a

communication medium such as a signal or carrier wave. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and/or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0185] By way of example, and not limitation, such computer-readable storage media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It should be understood, however, that computer- readable storage media and data storage media do not include connections, carrier waves, signals, or other transient media, but are instead directed to non-transient, tangible storage media. Disk and disc, as used, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0186] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry.

Accordingly, the term“processor”, as used may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described. In addition, in some aspects, the functionality described may be provided within dedicated hardware and/or software modules. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0187] The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC) or a set of ICs (e.g., a chip set).

Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as described above, various units may be combined in a hardware unit or provided by a collection of interoperative hardware units, including one or more processors as described above, in conjunction with suitable software and/or firmware.

[0188] It is to be recognized that depending on the example, certain acts or events of any of the methods described herein can be performed in a different sequence, may be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the method). Moreover, in certain examples, acts or events may be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors, rather than sequentially.

[0189] In some examples, a computer-readable storage medium includes a non-transitory medium. The term“non-transitory” indicates, in some examples, that the storage medium is not embodied in a carrier wave or a propagated signal. In certain examples, a non-transitory storage medium stores data that can, over time, change (e.g., in RAM or cache).

[0190] In some embodiments, in order to increase the spatial reflectivity, multiple radar-reflecting structures are located on one strip either in series, parallel or both, creating an array. In some

embodiments, some of the radar-reflecting structures are rotated with respect to other FIG. 22 shows an array of a combination of five radar-reflecting structures are rotated with respect to other radar-reflecting structures in the same array.

[0191] In those embodiments, each of the radar-reflecting structures will generate a reflection with a directional pattern. However, because of the rotation, the directional patterns will also be rotated. All directional patterns will sum up to a resulting directional pattern with a broader opening angle compared to an array in which all of the radar-reflecting structures are not rotated with respect to each other (i.e., have the same orientation).

[0192] In some embodiments, the rotation angle can be small or large. In some embodiments, the rotation angle is from 0.5 to 30 degrees, In other embodiments, rotation angle is from 0.5 to 20 degrees, or from 0.5 to 15 degrees, or from 0.5 to 10 degrees, or from 0.5 to 5 degrees, or from 0.5 to 3 degrees, or about 1 degree, or about 2 degrees, or about 3 degrees, or about 4 degrees, or about 5 degrees, or about 6 degrees, or about 7 degrees, or about 8 degrees, or about 9 degrees, or about 10 degrees, or about 11 degrees, or about 12 degrees, or about 13 degrees, or about 14 degrees, or about 15 degrees, or about 16 degrees, or about 17 degrees, or about 18 degrees, or about 19 degrees, or about 20 degrees, or about 25 degrees, or about 30 degrees.

[0193] In some embodiments, in order to increase the frequency bandwidth of reflectivity and with it the elevation opening angle, multiple radar-reflecting structures are located on one strip either in series, parallel or both - as before, but the radar-reflecting structures are scaled up or down with respect to each other.

[0194] In those embodiments, each of the radar-reflecting structures generates a small-band frequency response and elevation opening angle. However, because of the up- or down-scaling, the frequency response and the main elevation reflective beam will be shifted down- or upwards. By proper design, all frequency responses and elevation opening angles add up to a resulting broader-band frequency response and broader elevation opening angle.

[0195] In some embodiments, both methods can also be combined on one stripe or multiple stripes as shown in FIG 22, in which the radar-reflecting structures are rotated and scaled.

[0196] FIG. 22 shows an array of a combination of five radar-reflecting structures are rotated with respect to each other (having a different orientation) and other radar-reflecting structures have different dimensions from the rest (are scaled up or down). This type of array generates a resulting reflect array with a broader frequency response and increased spatial coverage (azimuth AND elevation) for the reflection.

[0197] As the antennas in the middle of the radar-reflecting structures get smaller, the efficiency of those antennas will decrease. As a consequence, the smaller antennas towards the innermost portion of the radar-reflecting structures can be left out without a significant loss in performance. The resulting empty space might be too small for U-Shaped reflectors.

[0198] Other embodiments of the present disclosure utilize the empty space at the center of the innermost antenna by adding reflectors of other types which are small enough to fit into that space. The space being utilized in these embodiments can be seen, for example, as the space encompassed by elements 312A, 316A, and 314A in Figure 3A, or by elements 352A, 356A, and 354A in Figure 3B.

[0199] In the frequency range around 77GHz, the wavelength is around 3,9mm. This means that the size of resonating reflective structures is also in that range or a fraction of those dimensions. [0200] Resonating reflective structures that can be used in these embodiments include, but are not limited to, for example YAGI-Reflectors, planar dipole-resonators a, patch resonators or bow-tie resonators.

[0201] A possible implementation of the resonating reflectors in the free area of, for example, the U- Shaped reflectors, is shown below in Fig. 23. It should be noted that only the innermost antenna of the, for example, U-Shaped radar-reflecting structures is shown.

[0202] In this embodiment, the previous unusable space in the middle of radar-reflecting structures can be used to generate additional reflections, which can add up to the reflection of the radar-reflecting structures generating an overall increased reflection for the entire structure.

[0203] For the type of radar-reflecting structures shown, for examples, in Fig. 3A, the current induced by the radar-planewave is flowing perpendicular to the field components of the plain wave, as depicted in Fig. 11.

[0204] This means that if the conductive channels, defined by the antennas (y-direction), are perpendicular to the plane-wave (x-direction), then the surface currents on the boundary between air and conductor will be at a maximum.

[0205] That is, when the currents are forced in the x-direction by the transversal component of the u- shaped slot, the direction of the E-Fields will be normal to the incident plane wave E-Field component, comparable to a dipole antenna, leading to good radar reflectivity and detectability. Because the wavelength is around 3.9mm at 77GHz, the length of the“dipole” is high compared to the wavelength leading to the narrow main-lobe in the reflecting directional pattern.

[0206] In some embodiments, to widen the main-lobe, we propose two approaches: (a) make sure that the current can be induced efficiently from a wider amount of degrees around the previous main lobe.

This can be done by, for example, bending the straight line of the longitudinal elongated (y-) portion of the antenna, and (b) widen the azimuth angle for the backscattering transversal (x-) elongated portion by bending the straight line in this direction.

[0207] Some possible variations of an implementation can be seen in Figure 24. One of ordinary skill in the art understands that there are other shapes no depicted that can suit this solution in which at least a portion of the antenna is curved.

[0208] In other embodiments, one extreme version would be to not use straight portions in the antenna and end up in a round version of the U-Shape design as shown in Figure 25.

[0209] This version has the widest opening angle. However, as the opening angle increases, the smaller the peak backscattering will be as the energy will be less focused. Nonetheless, this solution or a combination of any of the designs in Figures 24 and 25, could be beneficial depending on the requirements of the application.

[0210] Another embodiment is directed to an array of radar-reflecting structures in which the pattern which distributes the reflection elements more evenly across the area of the array. This leads to a better utilization of the available space and a decreased spatial dependency. In one embodiment, this goal is accomplished by shifting each column by approximately one half of the width of one reflector element or antenna. See, for example, Figure 26. With this pattern, the likelihood that complete reflector elements (antennas) are illuminated by a beam and are able to reflect the signal is higher and is relatively independent of the direction from which the radar signal is coming from, especially for radar sources with narrow directional scope.

[0211] The new pattern also maintains a minimum length for each of the antennas (e.g., u-shape structures) by shifting the slots partly inside each other, so that one set of radar-reflecting structures are not only facing a second set of radar-reflecting structures but are also partially surrounding at least one of the lateral portions of the second set of antennas. See Figures 26 and 27, where the active reflectors are shown encompassed by black rectangles. This type of pattern increases the use of the available area within the array.

[0212] Another advantage of the patterns described in the preceding paragraph is that, if it becomes necessary to cut the tape during the production process, the patterns provide more flexibility. Because every element that is cut-through will have decreased performance or not work properly, the new structure has a larger number of intact structures if cutting is done as shown in, for example, Figure 28.

[0213] Various examples of the disclosure have been described. These and other examples are within the scope of the following claims.

EXAMPLARY EMBODIMENTS

1. An article comprising: a radar reflective structure comprising a plurality of antennas, the plurality of antennas including:

a first antenna;

a second antenna that partially surrounds the first antenna; and

a third antenna that partially surrounds the first antenna and the second antenna.

2. The article of embodiment 1, wherein each antenna of the plurality of antennas are substantially u-shaped.

3. The article of any of the preceding embodiments, wherein each antenna of the plurality of

antennas include:

a first lateral member;

a second lateral member substantially parallel to the first lateral member; and

a longitudinal member coupled to the first lateral member and second lateral member, wherein a first end of each longitudinal member is coupled to a respective first end of the respective first lateral member,

wherein a second end of each respective longitudinal member is coupled to a respective first end of the respective second lateral member.

4. The article of any of the preceding embodiments, wherein each longitudinal member is

substantially perpendicular to the respective first lateral member or the respective second lateral member.

5. The article of any of the preceding embodiments, wherein each longitudinal member is curved.

6. The article of any of the preceding embodiments, wherein the second end of each respective first lateral member and the second end of each respective second lateral member define an opening of the radar reflective structure.

7. The article of any of the preceding embodiments, wherein the first antenna comprises a first set of lateral members and a first longitudinal member, the first longitudinal member comprising a first midpoint,

wherein the second antenna comprises a second set of lateral members and a second longitudinal member, the second longitudinal member comprising a second midpoint,

wherein the third antenna comprises a third set of lateral members and a third longitudinal member, the third longitudinal member comprising a third midpoint, and

wherein the first midpoint, second midpoint, and third midpoint define a straight line that is approximately parallel to the first set of lateral members, second set of lateral members, and third set of lateral members.

8. The article of any of the preceding embodiments, wherein the first longitudinal member, second longitudinal member, and third longitudinal member are substantially parallel to one another.

9. The article of any of the preceding embodiments, wherein the radar reflective structure is a first radar reflective structure, wherein the plurality of antennas is a first plurality of antennas, the article further comprising: a second radar reflective structure comprising a second plurality of antennas,

wherein an orientation of the first radar reflective is different from an orientation of the second radar reflective structure.

10. The article of any of the preceding embodiments, wherein the orientation of the first radar

reflective structure approximately 180 degrees different from the orientation of the second radar reflective structure.

11. An article comprising:

a retroreflective layer;

a backing layer;

a radar reflective layers disposed between the retroreflective layer and the backing layer, the radar reflective layer comprising:

a radar reflective structure comprising a plurality of antennas, the plurality of antennas including:

a first antenna;

a second antenna that partially surrounds the first antenna; and

a third antenna that partially surrounds the first antenna and the second antenna.

12. The article of any of the preceding embodiments directed to articles, wherein each antenna of the plurality of antennas are substantially u-shaped.

13. The article of any of the preceding embodiments directed to articles, wherein each antenna of the plurality of antennas include:

a first lateral member;

a second lateral member substantially parallel to the first lateral member; and a longitudinal member coupled to the first lateral member and second lateral member, wherein a first end of each longitudinal member is coupled to a respective first end of the respective first lateral member,

wherein a second end of each respective longitudinal member is coupled to a respective first end of the respective second lateral member.

14. The article of any of the preceding embodiments directed to articles, wherein each longitudinal member is substantially perpendicular to the respective first lateral member or the respective second lateral member.

15. The article of any of the preceding embodiments directed to articles, wherein each longitudinal member is curved.

16. The article of any of the preceding embodiments directed to articles, wherein the second end of each respective first lateral member and the second end of each respective second lateral member define an opening of the radar reflective structure. 17. The article of any of the preceding embodiments directed to articles, wherein the first antenna comprises a first set of lateral members and a first longitudinal member, the first longitudinal member comprising a first midpoint,

wherein the second antenna comprises a second set of lateral members and a second longitudinal member, the second longitudinal member comprising a second midpoint,

wherein the third antenna comprises a third set of lateral members and a third longitudinal member, the third longitudinal member comprising a third midpoint, and

wherein the first midpoint, second midpoint, and third midpoint define a straight line that is approximately parallel to the first set of lateral members, second set of lateral members, and third set of lateral members.

18. The article of any of the preceding embodiments directed to articles, wherein the first longitudinal member, second longitudinal member, and third longitudinal member are substantially parallel to one another.

19. The article of any of the preceding embodiments directed to articles, wherein the radar reflective structure is a first radar reflective structure, wherein the plurality of antennas is a first plurality of antennas, the article further comprising:

a second radar reflective structure comprising a second plurality of antennas,

wherein an orientation of the first radar reflective is different from an orientation of the second radar reflective structure.

20. The article of any of the preceding embodiments directed to articles, wherein the orientation of the first radar reflective structure approximately 180 degrees different from the orientation of the second radar reflective structure.

21. A method comprising: constructing pavement marking tape by at least:

providing a continuous base sheet including an upper surface and a lower surface;

adding a radar reflecting structure to the upper surface of the continuous base sheet; and coupling an adhesive layer to the lower surface of the continuous base sheet.

22. The method of any of the preceding embodiments directed to methods, wherein adding the

reflective structure comprises creating a plurality of substantially u-shaped antennas by at least: creating a first antenna;

creating a second antenna that partially surrounds the first antenna; and

creating a third antenna that partially surrounds the first antenna and the second antenna.

23. The method of any of the preceding embodiments directed to methods, wherein each antenna of the plurality of antennas include:

a first lateral member;

a second lateral member substantially parallel to the first lateral member; and

a longitudinal member coupled to the first lateral member and second lateral member, wherein a first end of each longitudinal member is coupled to a respective first end of the respective first lateral member, wherein a second end of each respective longitudinal member is coupled to a respective first end of the respective second lateral member.

The method of any of the preceding embodiments directed to methods, wherein each longitudinal member is substantially perpendicular to the respective first lateral member or the respective second lateral member.

The method of any of the preceding embodiments directed to methods, wherein each longitudinal member is curved.

The method of any of the preceding embodiments directed to methods,

wherein the first antenna comprises a first set of lateral members and a first longitudinal member, the first longitudinal member comprising a first midpoint,

wherein the second antenna comprises a second set of lateral members and a second longitudinal member, the second longitudinal member comprising a second midpoint,

wherein the third antenna comprises a third set of lateral members and a third longitudinal member, the third longitudinal member comprising a third midpoint, and

wherein the first midpoint, second midpoint, and third midpoint define a straight line that is approximately parallel to the first set of lateral members, second set of lateral members, and third set of lateral members.

The method of any of the preceding embodiments directed to methods, wherein the first longitudinal member, second longitudinal member, and third longitudinal member are substantially parallel to one another.

The method of any of the preceding embodiments directed to methods, further comprising coupling a retroreflective layer to the radar reflective structure, such that the radar reflective structures is disposed between the continuous base sheet and the retroreflective layer.

The method of any of the preceding embodiments directed to methods, wherein adding the radar reflective structure to the continuous base sheet comprises:

removing, from a layer of conductive material, at least a portion of the conductive material to form a plurality of antennas; and

coupling the layer of conductive material to the upper surface of the continuous base sheet. The method of any of the preceding embodiments directed to methods, wherein adding the radar reflective structure comprises:

depositing a conductive material on the continuous base sheet to form a plurality of antennas. A process comprising: receiving, by a computing device of a vehicle and from a radar transceiver of the vehicle, a radar signal;

determining, by the computing device and based at least in part on the radar signal, information about a vehicle pathway;

adjusting, by the computing device, operation of the vehicle based on the information. 32. The process according to any of the preceding embodiments directed to processes, wherein determining the information about the vehicle pathway comprises determining a boundary of the vehicle pathway.

33. The process according to any of the preceding embodiments directed to processes, wherein

determining the information about the vehicle pathway comprises determining a direction of intended vehicle travel for the vehicle pathway.

34. The process according to any of the preceding embodiments directed to processes, further

comprising:

receiving, by the computing device, sensor data generated by a sensor of the vehicle, wherein determining the information about the vehicle pathway is further based on the sensor data.

35. The process according to any of the preceding embodiments directed to processes, wherein the sensor comprises an image sensor, a global positioning system (GPS) sensor, or a light imaging detection and ranging (LIDAR) sensor.

36. The process according to any of the preceding embodiments directed to processes, wherein

adjusting the operation of the vehicle comprises adjusting an orientation of one or more wheels of the vehicle.

37. A computer-readable storage medium comprising instructions that, when executed by at least one processor, cause the at least one processor to perform the method of any of claims 31-36.

38. A computing device comprising at least one processor; and

a memory comprising instructions that, when executed by the at least one processor, cause the at least one processor to perform the method of any of claims 31-36.

39. The computing device of embodiment 38, further comprising the radar transceiver.

40. The article according to any of the preceding embodiments directed to articles, wherein the radar reflective structure is a first radar reflective structure, wherein the plurality of antennas is a first plurality of antennas, the article further comprising: at least a second radar reflective structure comprising a second plurality of antennas.

41. An article according to any of the preceding claims directed to articles, wherein each radar

reflective structure is chosen, independently from each other, from any of the radar reflective structures presented in any of the drawings in this application.

42. An array comprising two or more radar reflective structures,

wherein each radar reflective structure comprises, independently from each other”:

a first antenna;

a second antenna that partially surrounds the first antenna; and

a third antenna that partially surrounds the first antenna and the second antenna.

43. An array according to any of the preceding claims directed to arrays, wherein the orientation of at least one radar reflective structure is different from the orientation of another radar reflective structure within the array. 44. An array according to any of the preceding claims directed to arrays, wherein the orientation of each of the radar reflective structure within the array is the same.

45. An array according to any of the preceding claims directed to arrays, wherein the dimension of at least one radar reflective structure is different from the dimension of another radar reflective structure within the array.

46. An array according to any of the preceding claims directed to arrays, wherein the orientation of each of the radar reflective structure within the array is the same.

wherein each antenna of the plurality of antennas include:

a first lateral member;

a second lateral member substantially parallel to the first lateral member; and

a longitudinal member coupled to the first lateral member and second lateral member, wherein a first end of each longitudinal member is coupled to a respective first end of the respective first lateral member,

wherein a second end of each respective longitudinal member is coupled to a respective first end of the respective second lateral member.

47. An array according to any of the preceding claims directed to arrays, wherein the length of the outermost longitudinal member of at least one radar reflective structure is different from the length of the outermost longitudinal member of another radar reflective structure within the array.

48. An array according to any of the preceding claims directed to arrays, wherein the length of the outermost longitudinal member of at least one radar reflective structure is different from the length of the outermost longitudinal member of another radar reflective structure within the array, and wherein the difference in length is greater than 2% of the length of the smaller outermost longitudinal member of the two.

49. An array according to any of the preceding claims directed to arrays,

wherein the length of the outermost longitudinal member of at least one radar reflective structure (first) is different from the length of the outermost longitudinal member of another radar reflective structure (second) within the array,

wherein the difference in length is greater than 2% of the length of the smaller outermost longitudinal member of the two, and

wherein the orientation of the first radar reflective structure is different from the orientation of the second radar reflective structure within the array.

50. An array according to any of the preceding claims directed to arrays, wherein each radar

reflective structure is chosen, independently from each other, from any of the radar reflective structures presented in any of the drawings in this application.

51. An article according to any of the preceding claims directed to articles, wherein the radar

reflective structure further comprises a set of resonating reflecting structures, wherein the set of resonating reflecting structures is being partially surrounded by the first antenna. 52. An article according to any of the preceding claims directed to articles, wherein the radar reflective structure further comprises a set of resonating reflecting structures, wherein the set of resonating reflecting structures is being partially surrounded by the first antenna, and wherein the shape of the antennas is chosen, independently from each other, from any of the antenna shapes presented in any of the drawings in this application.

53. An article according to any of the preceding claims directed to articles, wherein the radar

reflective structure further comprises a set of resonating reflecting structures, wherein the set of resonating reflecting structures is being partially surrounded by the first antenna, and wherein the antennas are u-shaped.

54. An article according to any of the preceding claims directed to articles, wherein the radar

reflective structure further comprises a set of resonating reflecting structures, wherein the set of resonating reflecting structures is being partially surrounded by the first antenna, wherein the shape of each of the resonating reflecting structures within the set is chosen, independently from each other, from any of the radar reflective structures presented in any of the drawings in this application, including, but not limited to, those in Fig. 23.

55. An array according to any of the preceding claims directed to arrays, wherein each of the radar reflective structures within the array are chosen, independently from each other, from any of the radar reflective structures described in any of the preceding claims.

56. An article according to any of the preceding claims directed to articles, wherein each antenna of the plurality of antennas include:

a first lateral member;

a second lateral member substantially parallel to the first lateral member; and

a longitudinal member coupled to the first lateral member and second lateral member, wherein a first end of each longitudinal member is coupled to a respective first end of the respective first lateral member,

wherein a second end of each respective longitudinal member is coupled to a respective first end of the respective second lateral member, and

wherein at least one of the first lateral member, second lateral member, or longitudinal member of at least one antenna is curved.

57. An article according to any of the preceding claims directed to articles, wherein each antenna of the plurality of antennas include:

a first lateral member;

a second lateral member substantially parallel to the first lateral member; and

a longitudinal member coupled to the first lateral member and second lateral member, wherein a first end of each longitudinal member is coupled to a respective first end of the respective first lateral member,

wherein a second end of each respective longitudinal member is coupled to a respective first end of the respective second lateral member, and wherein all three, the first lateral member, the second lateral member, and the longitudinal member of at least one antenna are curved.

58. An article according to any of the preceding claims directed to articles, wherein each antenna of the plurality of antennas include:

a first lateral member;

a second lateral member substantially parallel to the first lateral member; and

a longitudinal member coupled to the first lateral member and second lateral member, wherein a first end of each longitudinal member is coupled to a respective first end of the respective first lateral member,

wherein a second end of each respective longitudinal member is coupled to a respective first end of the respective second lateral member,

wherein all three, the first lateral member, the second lateral member, and the longitudinal member of at least one antenna are curved, and

wherein the curvature of each of the first lateral member, the second lateral member, and the longitudinal member is determined independently from each other and can be a convex or concave curvature.

59. An article according to any of the preceding claims directed to articles, wherein each antenna of the plurality of antennas have a shape, selected independently from each other, that is a partial circle (a circle that is not complete).

60. An array according to any of the preceding claims directed to arrays, comprising two or more radar reflective structures,

wherein each radar reflective structure comprises, independently from each other:

a first antenna;

a second antenna that partially surrounds the first antenna; and

a third antenna that partially surrounds the first antenna and the second antenna, wherein the orientation of the first radar reflective structure is approximately 180 degrees different from the orientation of the second radar reflective structure,

wherein each antenna in each of the radar reflective structures comprises

a first lateral member;

a second lateral member substantially parallel to the first lateral member; and a longitudinal member coupled to the first lateral member and second lateral member, wherein a first end of each longitudinal member is coupled to a respective first end of the respective first lateral member,

wherein a second end of each respective longitudinal member is coupled to a respective first end of the respective second lateral member,

wherein at least one of the first lateral member or a second lateral member of an antenna of the second radar-reflecting structure is partially surrounded by an antenna of the first radar-reflecting structure. An array according to any of the preceding claims directed to arrays, comprising two or more radar reflective structures,

wherein each radar reflective structure comprises, independently from each other:

a first antenna;

a second antenna that partially surrounds the first antenna; and

a third antenna that partially surrounds the first antenna and the second antenna, wherein the orientation of the first radar reflective structure is approximately 180 degrees different from the orientation of the second radar reflective structure,

wherein each antenna in each of the radar reflective structures comprises

a first lateral member;

a second lateral member substantially parallel to the first lateral member; and a longitudinal member coupled to the first lateral member and second lateral member, wherein a first end of each longitudinal member is coupled to a respective first end of the respective first lateral member,

wherein a second end of each respective longitudinal member is coupled to a respective first end of the respective second lateral member,

wherein at least one of the first lateral member or a second lateral member of an antenna of the second radar-reflecting structure is partially surrounded by an antenna of the first radar-reflecting structure,

and wherein at least one of the antennas of the first radar-reflecting structure and at least one of the second radar-reflecting structure have a U-shape, and wherein the array comprises more than one row of radar-reflecting structures (e.g., Figs. 26-28).