CROSS REFERENCE TO RELATED APPLICATION

[oooi] The present application claims the filing benefits of U.S. provisional application,

Ser. No. 62/327,018, filed Apr. 25, 2016, which is hereby incorporated by reference herein in its entirety.

[0002] The present invention is directed to radar systems, and more particularly to radar systems for vehicles.

BACKGROUND OF THE INVENTION

[0003] The use of radar to determine range and velocity of objects in an environment is important in a number of applications including automotive radar and gesture detection. A radar system typically transmits radio signals and listens for the reflection of the radio signals from objects in the environment. By comparing the transmitted radio signals with the received radio signals, a radar system can determine the distance to an object. Using Doppler processing, the velocity of an object can be determined. Using various transmitter and receiver combinations, the location (angle) of an object can also be determined.

SUMMARY OF THE INVENTION

[0004] Methods and systems of the present invention provide for a shaped antenna pattern to enable a single radar system to support long, medium, and short range applications with a single set of sensing elements. An exemplary radar system of the present invention provides for an antenna pattern with a narrow, high-gain mainlobe for long range coverage and lower gain, broad shoulders for wider field of view or sensing (FOV) medium range and/or short range coverage. This exemplary radar system with the shaped antenna pattern reduces the overall number of sensors, and related cost, for vehicular applications. Difficulties, and cost of, integrating a large number of sensors on the vehicle are also mitigated.

[0005] A radar sensing system for a vehicle in accordance with an embodiment of the present invention includes a transmitter and a receiver. The transmitter is operable to or configured to transmit a radio signal. The receiver is operable to or configured to receive the transmitted radio signal reflected from objects in the environment. The transmitter includes an antenna and is operable to or configured to transmit the radio signal via the antenna. The antenna includes a plurality of linear arrays of radiators. An arrangement of the linear arrays of radiators is selected to form a selected or desired shaped antenna pattern having a selected or desired mainlobe shape and selected or desired shoulder shapes to cover selected sensing zones without nulls or holes in the coverage.

[0006] In an aspect of the present invention, cost and size of an individual sensor is reduced as well when compared to the cost and size of a sensor with multiple sets of sensing elements assigned to different sensing zones.

[0007] In another aspect of the present invention, the shaped antenna pattern is tailored to the detection ranges required for the different sensing zones with a smooth pattern shape that avoids nulls or holes in the coverage pattern, thereby mitigating drawbacks inherent in the approach using antenna pattern sidelobes to cover selected sensing zones.

[0008] In another aspect of the present invention, compared to the phased array

solution, the exemplary embodiment reduces costs. Furthermore, the exemplary embodiment is compatible with MIMO radar techniques which provide phased array type flexibility on receive via digital beamforming. MIMO radar techniques also offer advantages compared to phased array radar, including a synthetically enhanced virtual receive antenna with improved angle resolution and accuracy. Another advantage of MIMO radar with digital beamforming is the entire field of view or sensing (FOV) can be covered in a single, long duration dwell with improved Doppler resolution. [0009] These and other objects, advantages, purposes and features of the present invention will become apparent upon review of the following specification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[ooio] FIG. 1 is a plan view of an automobile equipped with one or more radar systems

[ooii] FIG. 2A and FIG. 2B are block diagrams of radar systems in accordance with the present invention;

[0012] FIG. 3 is a block diagram illustrating a radar system with a plurality of receivers and a plurality of transmitters (MIMO radar) in accordance with the present invention;

[0013] FIG. 4 is a plan view of an automobile equipped with a radar system and

exemplary multiple sensing zones for vehicular applications;

[0014] FIG. 5A, FIG. 5B, and FIG. 5C are plan views illustrating sensing solutions for the sensing zones illustrated in FIG. 4;

[0015] FIG. 6A is a block diagram of an exemplary sensor and a corresponding shaped antenna pattern in accordance with the present invention;

[0016] FIG. 6B is a graph illustrating relative gain and angle extent of an exemplary shaped antenna pattern in accordance with the present invention;

[0017] FIG. 7A is a block diagram illustrating an exemplary antenna in accordance with the present invention;

[0018] FIG. 7B is a block diagram illustrating exemplary phase and amplitude

distribution implemented in a 3-way combiner of the antenna illustrated in FIG. 7A, in accordance with the present invention;

[0019] FIG. 7C is a graph illustrating an exemplary shaped antenna pattern for the

phase and amplitude distribution of FIG. 7B, in accordance with the present invention;

[0020] FIG. 8A is a block diagram illustrated an exemplary antenna in accordance with the present invention;

[0021] FIG. 8B is a block diagram illustrating exemplary phase and amplitude

distribution implemented in a 6-way combiner of the antenna illustrated in FIG. 8A, in accordance with the present invention; [0022] FIG. 8C is a graph illustrating an exemplary shaped antenna pattern for the phase and amplitude distribution of FIG. 8B, in accordance with the present invention;

[0023] FIG. 9 is a graph illustrating exemplary MIMO radar antenna patterns, in

accordance with the present invention;

[0024] FIG. 10A is a block diagram illustrating an exemplary antenna for shaping an antenna pattern in the vertical dimension, in accordance with the present invention;

[0025] FIG. 10B is a diagram illustrating vertical sensing zones relative to a road

surface;

[0026] FIG. 1 1 is a block diagram illustrating an exemplary antenna with patch radiators of varying dimensions for shaping an antenna pattern in both the horizontal and vertical dimensions, in accordance with the present invention;

[0027] FIG. 12 is a block diagram illustrating an exemplary antenna with patch radiators of varying dimensions for shaping an antenna pattern in the both the horizontal and vertical dimensions, in accordance with the present invention; and

[0028] FIG. 13 is a block diagram illustrating an exemplary single-layer microstrip

corporate feed network used to connect a two-dimensional array of patch radiators for shaping an antenna pattern in both the horizontal and vertical dimensions, in

accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] The present invention will now be described with reference to the accompanying figures, wherein numbered elements in the following written description correspond to like-numbered elements in the figures. The shaped antenna pattern of the present invention enables a single radar system with a single set of sensing elements to mitigate the number of sensors, as well as the number of sets of sensing elements per sensor, needed to cover multiple sensing zones. Multiple sensing zones are required for many current and future sensing applications, including those for vehicular active safety and autonomous driving. The present invention reduces the overall number and cost of the sensors per vehicle for these applications, as well as the cost and size of an individual sensor. Challenges and cost related to integration of a large number of sensors on a vehicle are also mitigated. [0030] FIG. 1 illustrates an exemplary radar system 100 configured for use in a vehicle

150. In an aspect of the present invention, a vehicle 150 may be an automobile, truck, or bus, etc. As illustrated in FIG. 1 , the radar system 100 may comprise one or more transmitters and one or more receivers 104a-104d for a plurality of virtual radars. Other configurations are also possible. As illustrated in FIG. 1 , the radar system 100 may comprise one or more receivers/transmitters 104a-104d, control and processing module 102 and indicator 106. Other configurations are also possible. FIG. 1 illustrates the receivers/transmitters 104a-104d placed to acquire and provide data for object detection and adaptive cruise control. The radar system 100 (providing such object detection and adaptive cruise control or the like) may be part of an Advanced Driver Assistance System (ADAS) for the automobile 150.

[0031] FIG. 2A illustrates an exemplary radar system 200 with an antenna 202 that is time-shared between a transmitter 206 and a receiver 208 via a duplexer 204. As also illustrated in FIG. 2A, output from the receiver 208 is received by a control and processing module 210 that processes the output from the receiver 208 to produce display data for the display 212. The control and processing module 210 is also operable to produce a radar data output that is provided to other control units. The control and processing module 210 is also operable to control the transmitter 206.

[0032] FIG. 2B illustrates an alternative exemplary radar system 250 with a pair of

antennas 202a, 202b: an antenna 202a for the transmitter 206 and another antenna 202b for the receiver 208.

[0033] An exemplary MIMO radar system is illustrated in FIG. 3. With MIMO radar systems, each transmitter signal is rendered distinguishable from every other transmitter by using appropriate differences in the modulation, for example, different digital code sequences. Each receiver correlates with each transmitter signal, producing a number of correlated outputs equal to the product of the number of receivers with the number of transmitters. The outputs are deemed to have been produced by a number of virtual receivers, which can exceed the number of physical receivers. [0034] The radar sensing system of the present invention may utilize aspects of the radar systems described in U.S. Pat. Nos. 9,575,160 and/or 9,599,702, and/or U.S. patent applications, Ser. No. 15/481 ,648, filed Apr. 7, 2017, Ser. No. 15/416,219, filed Jan. 26, 2017, and/or Ser. No. 15/292,755, filed Oct. 13, 2016, and/or U.S. provisional applications, Ser. No. 62/382,857, filed Sep. 2, 2016, Ser. No. 62/381 ,808, filed Aug. 31 , 2016, Ser. No. 62/327,003, filed Apr. 25, 2016, Ser. No. 62/327,004, filed Apr. 25, 2016, Ser. No. 62/327,005, filed Apr. 25, 2016, Ser. No. 62/327,006, filed Apr. 25, 2016, Ser. No. 62/327,015, filed Apr. 25, 2016, Ser. No. 62/327,016, filed Apr. 25, 2016, Ser. No. 62/327,017, filed Apr. 25, 2016, which are all hereby incorporated by reference herein in their entireties.

SHAPED ANTENNA PATTERNS:

[0035] FIG. 3 illustrates a radar system 300 with multiple antennas 302, 304,

transmitters 306 and receivers 308. Using multiple antennas allows a radar system 300 to determine the angle of objects/targets in the environment. Depending on the geometry of the antenna system 300, different angles (e.g., with respect to the horizontal or vertical) can be determined. The radar system 300 may be connected to a network via an Ethernet connection or other types of network connections 314. The radar system 300 includes memory 310, 312 to store software used for processing the received radio signals to determine range, velocity, and location of objects/targets in the environment. Memory may also be used to store information about objects/targets in the environment.

[0036] Current and future vehicular applications related to active safety and autonomous driving envision long, medium, and short range sensing zones with unique requirements in terms of detection range and horizontal field of view (FOV). Current sensing solutions include separate long range, medium range, and/or short range sensors, resulting in high cost and challenges in vehicle integration. Other solutions including providing different sets of sensing elements within a single sensor, with the different sets of sensing elements covering different sensing zones. Multiple sensing elements increase the size and cost of the individual sensor. [0037] Other current solutions for a single sensor with multiple sensing zones include the use of the radar antenna pattern main lobe to cover a long range, narrow FOV sensing zone and antenna pattern sidelobes to cover medium range and/or short range sensing zones with wider FOV. The use of antenna pattern sidelobes can often be insufficient in terms of detection range for the medium range sensing zone. Further, the nulls inherent in the antenna sidelobe structure may lead to unacceptable holes in the coverage pattern.

[0038] Still another solution for a single sensor includes the use of a phased array

antenna with flexible gain, beamwidth, and scan angle. This solution provides the most flexibility, but is typically too expensive for vehicular radar.

[0039] The shaped antenna pattern of the present invention enables a single radar system with a single set of sensing elements to mitigate the number of sensors, as well as the number of sets of sensing elements per sensor, needed to cover multiple sensing zones. FIG. 4 illustrates multiple exemplary sensing zones generally specified for vehicular applications. Three different sensing zones are often specified, for example, a long range zone 410, a medium range zone 420, and a short range zone 430. Each sensing zone may be specified with a different range and horizontal angle field of view (FOV). Different angle resolutions, angle accuracies, and update rates for each sensing zone may be specified as well. In FIG. 4, the exemplary sensing zones are illustrated for the region forward of a host vehicle 400.

[0040] FIGs. 5A, 5B, and 5C illustrate exemplary sensing solutions for the sensing

zones illustrated in FIG. 4. FIG. 5A illustrates three sensors mounted on the front of the host vehicle 400. As illustrated in FIG. 5A, a long range sensor 510, a medium range sensor 520, and a short range sensor 530 are provided, such that a sensor is provided for each sensing zone. The respective regions covered by each sensor are illustrated as well, with a long range sensor coverage 512 for the long range sensor 510, a medium range sensor coverage 522 for the medium range sensor 520, and a short range sensor coverage 532 for the short range sensor 530. [0041] FIG. 5B illustrates a single sensor 500B with three sets of sensing elements: (i) long range antennas 540, (ii) medium range antennas 550, and (iii) short range antennas 560, each set assigned to a different sensing zone. The respective regions covered by each set of antennas are shown as well, with a long range antennas coverage 542 for the long range antennas 540, a medium range antennas coverage 552 for the medium range antennas 550, and a short range antennas coverage 562 for the short range antennas 560.

[0042] FIG. 5C illustrates a single sensor 500C with antenna 570 consisting of a single set of antenna elements 572. The antenna 570 forms an antenna pattern 580 with a mainlobe 582 and sidelobes 584 used to cover the three sensing zones. Note the presence of "nulls" in the sidelobe structure, as illustrated by the exemplary sidelobe null 586. Sidelobe nulls are characterized by substantially reduced antenna gain compared to the nominal antenna gain in the sidelobe region. These sidelobe nulls result in substantially reduced detection range compared to the nominal detection range over the sidelobe region.

[0043] FIGs. 6A and 6B illustrate a single sensor embodiment of the present invention, where a single sensor 600 is illustrated with an antenna 610 consisting of a single set of antenna elements 612. The antenna 610 forms a shaped antenna pattern 620 with a mainlobe 622 and "shoulders" 624 to cover the sensing zones illustrated in Fig. 4 without nulls or holes in the coverage. FIG. 6B is a graph illustrating the relative gain and angle extent of the shaped antenna pattern 630 for the mainlobe 632 and

"shoulders" 634 portions of the pattern. The antenna gain and horizontal FOV (angle extent) of the mainlobe 632 and "shoulders" 634 are tailored to the antenna gain and horizontal FOVs (angle extents) required for the different sensing zones (636, 638, 642). The resulting antenna pattern is smooth without nulls or holes in the pattern.

[0044] FIGs. 7A, 7B, and 7C illustrate an exemplary embodiment of the present

invention that uses a transmit and/or receive antenna 700 consisting of three linear arrays of radiators 710 that are arranged as vertical columns of radiators 710, as shown in FIG. 7A. The radiators may also be referred to as elements. The three vertical columns of radiators are combined into a single antenna port using a three-way power combiner 740. The transmit and/or receive antennas with linear arrays of radiators or elements can be implemented using well known antenna structures and fabrication techniques, including multi-layer printed circuit board antennas with, for example, microstrip feed lines and patch radiators, substrate integrated waveguide (SIW) feed lines, and SIW slotted radiators, coplanar waveguide feed lines with SIW slotted radiators, or suitable combinations thereof. Other common types of feed and radiator structures can be used as well. The antenna illustrated in FIG. 7A would typically be recognized to represent patch radiators 720 connected by microstrip feed lines 730.

[0045] The shaped antenna pattern of the present invention is realized in the horizontal dimension by an appropriate phase and amplitude distribution in the power combiner 740. FIG. 7B illustrates an example phase and amplitude distribution 750 implemented in the 3-way power combiner 740 that produces the exemplary shaped antenna pattern 760 illustrated in FIG. 7C. When using three linear arrays of radiators arranged as vertical columns of radiators 710 with a three-way power combiner 740, the shaped horizontal pattern is limited to two shoulders 764, as illustrated in FIG. 7C. FIG. 7C illustrates that the higher gain mainlobe region 762 of the shaped pattern typically covers long and/or medium range sensing zones. The relative gain and width of the shoulder region can be adjusted by the phase and amplitude distribution in the power combiner to cover medium and/or short range sensing zones. The horizontal profile of the shaped antenna pattern of the present invention can be further optimized to the specified sensing zones if greater than three vertical columns of radiators are used for an individual transmit or receive antenna. When using more than three vertical columns of radiators, the number of branches in the power combiner is correspondingly increased resulting in more degrees of freedom to adjust the phase and amplitude distribution for additional control of the horizontal antenna pattern profile.

[0046] FIGs. 8A, 8B and 8C illustrate an exemplary embodiment of the present invention using a transmit and/or receive antenna 800 composed of six linear arrays of radiators arranged as vertical columns of radiators 810 and a six-way power combiner 840, as illustrated in FIG. 8A. FIG. 8A also illustrates that each column of radiators 810 comprises a series of individual radiators 820 interconnected by feedline connections 830. The exemplary amplitude and phase distribution 850, illustrated in FIG. 8B, produces the shaped antenna pattern 860 illustrated in FIG. 8C. As illustrated in FIG. 8C, the particular amplitude and phase distribution 850 produces an exemplary antenna pattern shape 860 with a shaped antenna pattern mainlobe 862 and shaped antenna pattern shoulders 864. Note that there are a pair of shoulders 864 for each side of the antenna pattern.

[0047] MIMO radar systems generally use a set of multiple transmit and receive

antennas, as illustrated in FIG. 3. In a preferred embodiment using the present invention with MIMO radar, each transmit and receive antenna incorporates the same or common shaped pattern, for example, the shaped antenna pattern illustrated in FIG. 7C. In another embodiment, the individual antennas may use different shaped antenna patterns. For example, a transmit antenna may use a first shaped antenna pattern (such as shown in FIG. 7C) and a receive antenna may use a second shaped antenna pattern (such as shown in FIG. 8C) that is different from the first shaped antenna pattern.

[0048] FIG. 9 illustrates MIMO radar antenna patterns 900 when using the present

invention within a MIMO radar structure incorporating digital beamforming on receive. MIMO radar digital beamforming is implemented in the signal processing software to combine signals associated with selected groups of transmit and receive antennas. The digital beamforming process produces multiple narrow beams 900 spread across angle with a peak gain that follows the envelope of the two-way (transmit x receive) shaped antenna pattern 920, where the x-axis of the graph is the angle in degrees and the y- axis of the graph is relative gain (dB). Each individual lobe in FIG. 9 represents the antenna pattern of an individual MIMO beam. As an example, the boresight beam 910 and a two-way shaped antenna pattern (shaped transmit antenna pattern x shaped receive antenna pattern) are indicated in FIG. 9.

[0049] The exemplary embodiments of the present invention are not constrained to

shaping of the horizontal antenna pattern tailored to specified horizontal sensing zones. For example, the present invention can be applied to shape the antenna pattern in the vertical dimension tailored to specified vertical sensing zones by using transmit and/or receive antennas composed of multiple horizontal rows of radiators combined into a single antenna port using a power combiner. As an example, FIG. 10A illustrates an exemplary antenna 1000 arranged to shape the antenna pattern in the vertical dimension using three linear arrays of radiators arranged as horizontal rows of radiators 1010 and a 3-way power combiner 1040. In a manner analogous to shaping the horizontal antenna pattern, illustrated in FIGs. 7B and 7C, a vertical antenna pattern is shaped by an appropriate amplitude and phase distribution implemented in the 3-way power combiner 1040.

[0050] Vertical shaping of the antenna pattern may be appropriate, for example, when the specified vertical FOV and detection range varies substantially for long range, medium range and/or short range objects/targets. This is often the case for vehicular radar, as illustrated in FIG. 10B. Without vertical pattern shaping, the vertical extent of the mainlobe may need to be broadened for acceptable coverage at short range resulting in reduced detection range for long range objects and increased susceptibility to unwanted detection of overhead and road surface objects.

[0051] The present invention is also not constrained to pattern shaping in only a single dimension. FIGs. 1 1 and 12 illustrate pattern shaping in two dimensions, horizontal and vertical, according to an embodiment of the present invention using transmit and/or receive antennas with multiple linear arrays of radiators arranged as either vertical columns of radiators 1 100 or horizontal rows of radiators 1200 connected using a power combiner 1 140, 1240, with an appropriate phase and amplitude distribution, to shape the antenna pattern in one dimension. In FIG. 1 1 , the power combiner 1 140 shapes the antenna pattern in the horizontal dimension, while in FIG. 12, the power combiner 1240 shapes the antenna in the vertical dimension.

To shape an antenna pattern in the orthogonal dimension, an appropriate phase and amplitude distribution is realized along each row or column of radiators. Phase and amplitude along individual linear arrays of radiators can be controlled with known techniques including, for example, selecting a particular width and/or length of microstrip used to interconnect individual patch radiators of a linear array of patch radiators and/or particular dimensions of the individual patch radiators. FIGs. 1 1 and 12 illustrate the amplitude distribution along a linear array of radiators controlled by the dimensions of the individual patch radiators 1 120, 1220 while the phase distribution along a linear array of radiators is controlled by the length of the microstrip connections 1 130, 1230. In FIG. 1 1 the distribution of amplitude and phase along the line/vertical column of radiators 1 1 10 shapes the antenna pattern in the vertical dimension, while in FIG. 12 the distribution of amplitude and phase along the line/horizontal row of radiators 1210 shapes the antenna pattern in the horizontal dimension.

[0053] In another aspect of the present invention, the amplitude and phase along a linear array of radiators may be controlled using SIW slotted radiators with the position and dimension of each slot used to control the amplitude and phase of each radiator.

[0054] In yet another aspect of the present invention, a two-dimensional array of

radiators may be implemented with both horizontal and vertical amplitude and phase distribution by use of a single or multi-layer corporate feed network to connect each individual radiator via power combiners.

[0055] FIG. 13 illustrates an exemplary single layer microstrip corporate feed network

1320 used to connect a two-dimensional array of patch radiators 1300. The horizontal and vertical antenna patterns are shaped by the two-dimensional amplitude and phase distribution over the array of radiators.

[0056] The two-dimensional amplitude distribution for an array of patch radiators may be controlled by the dimensions of the individual patch radiators 1310 and the two- dimensional phase distribution may be controlled by the length of the microstrip feed line routed to each radiator, as illustrated in FIG 13. The length of feed line routed to each radiator 1310 can be controlled, for example, by adding a loop 1330 of varying length to individual segments of the corporate feed network 1320. [0057] In yet another aspect of the present invention, the amplitude distribution may be controlled over a two-dimensional array of patch radiators by varying the width of individual segments of the microstrip corporate feed network.

[0058] A variety of embodiments have been presented herein that allow for the selection of a desired antenna pattern shape using only a single sensor. As discussed herein, using a variety of patch radiator shapes, microstrip feedline lengths and thicknesses, horizontal and vertical antenna pattern shapes may be created. As also discussed herein, a given antenna pattern shape may be utilized as either a transmit antenna or as a receive antenna, or in the alternative as both.

[0059] Changes and modifications in the specifically described embodiments can be carried out without departing from the principles of the present invention, which is intended to be limited only by the scope of the appended claims, as interpreted according to the principles of patent law including the doctrine of equivalents.