Cross-Reference to Related Applications

[0001] This application claims priority from application No. 62/870614, filed 3 July 2019. For purposes of the United States, this application claims the benefit under 35 U.S.C. §1 19 of application No. 62/870614, filed 3 July 2019, and entitled LOW- PROFILE VHF ANTENNA which is hereby incorporated herein by reference for all purposes.

Technical Field

[0002] The present disclosure relates to antennas. More particularly, the present disclosure is directed to low-profile, very high frequency (VHF) antennas and systems that include such antennas.

Background

[0003] There are many applications which require transmitting and receiving VHF signals. One example is transmitting and receiving electromagnetic signals to and from space based antennas, for example satellite antennas. Other examples may include transmitting and receiving electromagnetic signals to and from aerial or terrestrial antennas.

[0004] VHF signals may be transmitted and received for a variety of purposes, for example: to exchange signals encoding a location, to indicate the status of a mechanism or system, to indicate the nature of the local environment, for voice communications, and/or for data communications.

[0005] There are many applications of VHF antennas which require the antenna to fit within a compact enclosure. For example, mounting a VHF antenna on a

standardized intermodal container (also known as a shipping container) requires that the antenna fit within a limited clearance space around the container. Other examples include mounting a VHF antenna on a body of a vehicle, for example a tractor unit or a tractor trailer. Many of these applications also require a VHF antenna which can operate proximate a conductive surface, for example a metal panel of an intermodal container or a tractor unit.

[0006] There is a need for a compact VHF antenna capable of operating in close proximity to conductive surfaces.

[0007] The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.

Summary

[0008] The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above- described problems have been reduced or eliminated, while other embodiments are directed to other improvements.

[0009] One aspect of the invention provides a low-profile, very high frequency antenna comprising: a radiating structure having a terminal and lying substantially within a first plane; a cable comprising an inner conductor and a shield, wherein the inner conductor is electrically connected to the terminal; and a low-pass filter coupled to the cable at a distance along the cable from the terminal; wherein a length of the cable between the terminal and the low-pass filter lies substantially within the first plane.

[0010] In some embodiments, the antenna comprises an electrically conductive member spaced apart from the radiating structure and lying substantially within a second plane; the second plane is parallel with the first plane; the radiating structure lies within a first area within the first plane; the conductive member extends within a second area within the second plane; and the second area includes a projection of the first area onto the second plane.

[0011] In some embodiments, the radiating structure comprises a first radiating element extending along a first axis and a second radiating element extending along a second axis; the first radiating element and the second radiating element are electrically connected to the terminal; the second axis is parallel with the first axis; and the first axis and second axis extend within the first plane.

[0012] In some embodiments, the first radiating element comprises a first trace of a printed circuit board (PCB); and the second radiating element comprises a second trace of the PCB.

[0013] In some embodiments, the first trace forms a first path about the first axis along a surface of and through an interior of the PCB; the first path has a substantially rectangular cross-section perpendicular to the first axis; the second trace forms a second path about the second axis along the surface of and through the interior of the PCB; and the second path has a substantially rectangular cross-section perpendicular to the second axis.

[0014] In some embodiments, the first radiating element comprises a first electrical conductor wound helically about a first path about the first axis; and the second radiating element comprises a second electrical conductor wound helically about a second path about the second axis.

[0015] In some embodiments, the antenna is configured to transmit or receive electromagnetic signals with a wavelength; a length of the first radiating element along the first path is substantially equal to one half of the wavelength; and a length of the second radiating element along the second path is substantially equal to one half of the wavelength.

[0016] In some embodiments, the antenna operates over very high frequencies (VHF), ultra high frequencies (UHF), and/or super high frequencies (SHF), wherein VHF are between 20 MHz and 300 MHz, UHF are between 300 MHz and 5 GHz, and SHF are between 3 GHz and 30 GHz.

[0017] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions. Brief Description of the Drawings

[0018] Exemplary embodiments are illustrated in referenced figures of the drawings.

It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.

[0019] Figs. 1 A and 1 B are schematic diagrams of a top view of an antenna according to an example embodiment of the present invention.

[0020] Fig. 1 C is a schematic diagram of a side view of the antenna depicted in figure 1 A.

[0021] Figs. 1 D and 1 E are schematic diagrams of embodiments of radiating structures according to example embodiments of the present invention.

[0022] Figs. 2A-2D are schematic diagrams of antennas according to example embodiments of the present invention.

[0023] Fig. 3 is a schematic diagram of a cable according to an example embodiment of the present invention.

[0024] Fig. 4 is a circuit diagram of an antenna according to an example embodiment of the present invention.

[0025] Fig. 5A and 5B are schematic diagrams of an antenna according to an example embodiment of the present invention mounted upon a vehicle.

[0026] Fig. 5C is a schematic diagram of an antenna according to an example embodiment of the present invention mounted upon an intermodal container.

[0027] Fig. 6 is a schematic diagram of an electronics package according to an example embodiment of the present invention.

Description

[0028] Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid

unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense. [0029] One aspect of the present invention provides low-profile very high frequency (VHF) antennas. VHF signals may be signals having frequencies in the range of about 20 MHz to about 300 MHz. Some embodiments of the antennas may transmit and/or receive VHF signals across a wide bandwidth of frequencies while providing a high impedance to a transmitter or receiver.

[0030] Some embodiments of the present invention provide antennas which may operate within close proximity to a conductive member. Close proximity may mean within 20 centimeters or 10 centimeters of a conductive member. A conductive member may include a metal panel of a vehicle or an intermodal container.

[0031] In some embodiments, the antenna operates over one or more of very high frequencies (VHF), ultra high frequencies (UHF) and super high frequencies (SHF). VHF, UHF, and SHF frequencies may comprise frequencies between about 20 MHz and about 5 GHz.

[0032] In some embodiments, the antenna operating at a frequency means that the antenna is resonant at the frequency. The antenna is resonant at a frequency if the capacitive reactance at the frequency substantially equals the inductive reactance at the frequency. When the capacitive reactance of the antenna substantially equals the inductive reactance of the antenna, the antenna presents a substantially resistive load to the source.

[0033] In some embodiments, the antenna operating at a frequency means that the voltage standing wave ratio (VSWR) of the antenna for the frequency is below a ratio of 2.5:1 . The VSWR of an antenna represents the ratio of input power to reflected power of the antenna. A VSWR ratio of 2.5:1 represents a ratio of 2.5 times input power for 1 times the reflected power.

[0034] In some embodiments, the antenna operating at a frequency means that the power loss of the antenna at the frequency is near or below -10 decibels (db) for the frequency. The power loss of the antenna is the ratio of power delivered to the antenna to the power radiated from the antenna. A power loss is below -10 db if the power loss is less than -10 db, for example -15 db or -20 db.

[0035] In some embodiments, an antenna comprise a low-profile electromagnetic radiating structure, and a shielded cable extending from the radiating structure. An inner conductor of the cable is electrically coupled to the radiating structure. A shield of the cable may be electrically grounded and may be at the same electrical potential as a ground of a transmitter or receiver. At least one low-pass filter, for example at least one ferrite bead, is magnetically coupled and/or electrically connected to the cable at a distance along the cable from the radiating structure.

[0036] The low-pass filter may comprise one or more of a ferrite bead, a capacitor, an inductor, and/or any components which may be magnetically coupled or electrically connected to the cable to attenuate high-frequency signals within the cable. In some embodiments, the low-pass filter attenuates signals with frequencies above 20 MHz, or signals with frequencies above 100 MHz.

[0037] As VHF signals are transmitted to the radiating structure, a portion of the signals is radiated by the radiating structure, and a portion of the signals is reflected back along the radiating structure. The reflected signals combine with the transmitted signals and may form standing waves along the radiating structure. The standing waves comprise voltage standing waves and current standing waves. In some embodiments, the voltage standing waves are out of phase with the current standing waves by 90 degrees.

[0038] The inner conductor of the cable may be coupled to the radiating structure at a point along the radiating structure where the voltage standing wave is at or near a maximum, and the current standing wave is at or near a minimum. The point at which the inner conductor of the cable is coupled to the radiating structure may be referred to as the driving point of the antenna. When the voltage standing wave is at a peak, the current standing wave is at a minimum and the input impedance is at or near a maximum. When the voltage standing wave is at a minimum, the current standing wave is at a peak and the input impedance is at or near a minimum. In some embodiments, the driving point is located at or near a peak of the voltage standing wave to provide a high input impedance.

[0039] The grounded shield of the cable provides a grounded conductor proximate to the radiating structure, known as a counterpoise. The size of the counterpoise provided by the shield is set by coupling a low-pass filter to the cable. The length of the shield between the radiating structure and the low-pass filter operates as the counterpoise.

[0040] In some embodiments, the counterpoise may act as a ground plane.

[0041] In some embodiments, the antenna may be configured to transmit and/or receive VHF signals with a certain carrier frequency. In these embodiments, the length of the counterpoise may be selected to be a function of a wavelength corresponding to the carrier frequency; for example, one half of the wavelength, or one quarter of the wavelength.

[0042] The size of the radiating structure may also be based on a function of a wavelength corresponding to a carrier frequency of the transmitted or received signal, for example a length of one or more elements forming the radiating structure may be one half or one quarter of a wavelength corresponding to a carrier frequency.

[0043] Fig. 1 A is a schematic diagram of an antenna 100 according to an example embodiment. Antenna 100 comprises radiating structure 10, cable 12 and low-pass filter 14. Antenna 100 is a low profile antenna, wherein a height of antenna 100 in distance D3 is substantially less than a length of antenna 100 in distance D1 and substantially less than a width of antenna 100 in distance D2. In some embodiments, the length of antenna 100 is at least ten times the height of antenna 100 and the width of antenna 100 is at least four times the height of antenna 100.

[0044] Antenna 100 may be electrically connected to source 16. Source 16 may be configured to generate signal Si with frequency h corresponding to wavelength l _{1 ;} and antenna 100 may be configured to radiate signal Si generated by source 16.

[0045] Radiating structure 10 has length / in direction D1 , width w in direction D2, and height h in direction D3. In some embodiments, at least one of length / and width w are substantially greater than height h. For example, width w may be at least four times height h, and/or length / may be at least ten times height h. Accordingly, radiating structure 10 may lie substantially within plane P1 .

[0046] In some embodiments, length / of radiating structure 10 is approximately 10 centimeters, width w of radiating structure 10 is approximately 5 centimeters, and height h of radiating structure 10 is approximately 1 .25 centimeters. [0047] A first end of cable 12 is electrically connected to terminal 18 of radiating structure 10 and a second end of cable 12 is electrically connected to source 16. Low-pass filter 14 is coupled to cable 12 at a first distance along cable 12 from terminal 18, forming a length 12’ of cable 12 between low-pass filter 14 and terminal 18. Length 12’ of cable 12 lies substantially within plane P1 . Length 12’ of cable 12 may be substantially within plane P1 when length 12’ of cable 12 is within 5 centimetres of plane P1 .

[0048] In some embodiments, length 12’ of cable 12 is substantially equal to one half or one quarter of wavelength A In some embodiments, length 12’ of cable 12 is within 5% of one half or one quarter of wavelength Ai .

[0049] Antenna 100 may comprise an electrically conductive member 22. Conductive member 22 may lie substantially within plane P2, wherein plane P2 is parallel with plane P1 .

[0050] As shown in figure 1 B, radiating structure 10 may lie within area 10’ of plane P1. Conductive member 22 may extend within area 22’ of plane P2. Area 22’ may include a projection of area 10’ onto plane P2.

[0051] A portion or all of length 12’ of cable 12 may lie within area 12” of plane P1 . Area 22’ may include a projection of area 12” onto plane P2.

[0052] Figure 1 C depicts a schematic side view of antenna 100 showing plane P1 and plane P2.

[0053] In some embodiments, radiating structure 10 comprises terminal 18, and one or more radiating elements 20A, 20B, 20C and 20D (collectively radiating elements 20) are electrically connected to terminal 18. Radiating elements 20A and 20C extend from terminal 18 in opposing directions along axis A1 , and radiating elements 20B and 20D extend from terminal 18 in opposing directions along axis A2. Axis A1 is parallel with axis A2. Axes A1 and A2 may be parallel with plane P1 .

[0054] In some embodiments, A1 and A2 are spaced apart by a distance of between 2 centimeters and 10 centimeters.

[0055] Each of radiating elements 20 comprises an electrical conductor. Radiating elements 20 are electrically connected in parallel to terminal 18. [0056] The respective length of the conductors forming radiating elements 20 may be substantially equal. Substantially equal means that the length of the conductors forming each of radiating elements 20 is within +/- 5% of the length of the conductors forming the other radiating elements 20.

[0057] Figure 1 D depicts an embodiment of radiating elements 20 wherein radiating elements 20 comprise traces of one or more Printed Circuit Boards (PCBs). Each of radiating elements 20 may comprise a trace which forms a path along the surface of and through an interior of the PCB. For example, radiating element 20A may comprise trace 21 A, radiating element 20B may comprise trace 21 B, radiating element 20C may comprise trace 21 C, and radiating element 20D may comprise trace 21 D. Traces 21 A, 21 B, 21 C and 21 D may be collectively referred to as traces 21 .

[0058] The path formed by traces 21 A and 21 C may form substantially rectangular cross-sections perpendicular to axis A1 when projected onto a plane perpendicular to axis A1 . The path formed by traces 21 B and 21 D may form substantially rectangular cross-sections perpendicular to axis A2 when projected onto a plane perpendicular to axis A2.

[0059] Traces 21 may comprise any electrically conductive material affixed to or formed by the PCB, for example copper, solder, or metal wire. As further examples, traces 21 may comprise copper tracks along a surface of the PCB, and/or holes through the PCB filled with copper.

[0060] Traces 21 each form a number of turns. A turn of traces 21 is a complete path of either of traces 21 A or 21 C about axis A1 , or a complete path of traces 21 B or 21 D about axis A2. In the embodiment depicted in figure 1 D, each of traces 21 form nine turns, however each of traces 21 may form any number of turns, for example 50 turns.

[0061] Figure 1 E depicts an embodiment of radiating elements 20 wherein radiating elements 20 each comprise a helically wound electrical conductor, for example a helically wound copper or steel wire. Radiating element 20A may comprise electrical conductor 23A, radiating element 20B may comprise electrical conductor 23B, radiating element 20C may comprise electrical conductor 23C, and radiating element 20D may comprise electrical conductor 23D. Electrical conductors 23A, 23B, 23C and 23D may be collectively referred to as electrical conductors 23.

[0062] Electrical conductors 23A and 23C may form substantially circular cross- sections perpendicular to axis A1 . Electrical conductors 23B and 23D may form substantially circular cross-sections perpendicular to axis A2.

[0063] Electrical conductors 23 each form a number of turns. A turn of electrical conductors 23 is a complete path of either of electrical conductors 23A or 23C about axis A1 , or a complete path of electrical conductors 23B or 23D about axis A2. In the embodiment depicted in figure 1 E, each of electrical conductors 23 form five turns. However, each of electrical conductors 23 may form any number of turns, for example 50 turns.

[0064] Each turn of electrical conductors 23A and 23C have a substantially circular cross-section perpendicular to axis A1 when projected onto a plane perpendicular to axis A1 , and each turn of electrical conductors 23B and 23D have a substantially circular cross-section perpendicular to axis A2 when projected onto a plane perpendicular to axis A2. The cross-sectional area and/or shape of the turns of electrical conductors 23 may be substantially equal to one another.

[0065] In some other embodiments of radiating structure 10:

• the cross-section of the turns of electrical conductors 23 may be rectangular, oval, or polygonal;

• the cross-section of the turns of electrical conductors 23 may increase or decrease respectively along axes A1 and A2; and/or

• electrical conductors 23 may extend substantially straight and along axes A1 or A2.

[0066] The length along each respective path of radiating elements 20 may be selected to be a function of a carrier frequency h of signal Si generated by source 16. Carrier frequency h corresponds to a wavelength K . In some embodiments, the length along each respective path of radiating elements 20 is substantially equal to one half of K . In some embodiments, the length along each respective path of radiating elements 20 is substantially equal to one quarter of K . The length along each respective path of radiating elements 20 may be substantially equal to either one half of A ₁ or one quarter of A ₁ when the length of each of radiating elements 20 is within +/- 5% of either one half of Ai or one quarter of Ai .

[0067] Radiating elements 20 may be substantially rigid and maintain their shape without any supporting structure.

[0068] In some embodiments, each of radiating elements 20 are supported by a low dielectric material, for example fiberglass, plastic or foam.

[0069] In some embodiments, length 12’ of cable 12 extends along axis A3, wherein axis A3 is substantially parallel with axes A1 and A2. Substantially parallel may mean axis A3 is within three degrees of each of axes A1 and A2. Axis A3 may be parallel with plane P1 .

[0070] Cable 12 may comprise inner conductor 30 and shield 32 (see figure 3). A first end of inner conductor 30 is connected to terminal 18 of radiating structure 10 and a second end of inner conductor 30 may be connected to a terminal of source 16.

Shield 32 may be connected to a second terminal of source 16. The second terminal of source 16 may be a ground terminal of source 16.

[0071] Low-pass filter 14 may attenuate high-frequency signals transmitted by the shield of cable 12. In some embodiments, antenna 100 is configured to transmit and/or receive signals within a frequency band, and low-pass filter 14 attenuates signal within the frequency band of antenna 100.

[0072] Antenna 100 may comprise electrically conductive member 22, wherein conductive member 22 is an electrical conductor lying substantially within plane P2. In some embodiments conductive member 22 is substantially longer than antenna 100 in distance D1 and substantially wider than antenna 100 in distance D2. Conductive member 22 may be a metal panel of an intermodal container or a metal panel of a vehicle, for example.

[0073] In some embodiments, radiating structure 10 is spaced apart from conductive member 22, for example between 1 centimeter and 5 centimeters. Radiating structure 10 may be spaced above conductive member 22 by any low dielectric or electrically insulating material, for example by air, plastic screws or a foam board, such as an extruded polystyrene foam board. [0074] Antenna 100 may provide a high input impedance to source 16. A high input impedance may be an input impedance of at least 50W at frequencies within a frequency band of the transmitted and/or received signals of antenna 100.

[0075] Radiating structure 10, cable 12 and low-pass filter 14 are connected in series. Antenna 100 and source 16 may have common antenna ground 24. Antenna ground 24 may be at a different electrical potential than conductive member 22. Accordingly, antenna ground 24 and conductive member 22 may be electrically insulated from one another. In some embodiments, antenna ground 24 and conductive member 22 are at an equal electrical potential. Antenna ground 24 and conductive member 22 may be electrically connected.

[0076] Low pass filter 14 may be any component magnetically coupled and/or electrically connected to cable 12 and configured to attenuate high-frequency signals transmitted by the shield of cable 12. In some embodiments, high-frequency signals are signals having a frequency within the band of radio frequencies, for example signals between 20 MHz and 300 GHz. In other embodiments, high-frequency signals are signals with a frequency within the band of very high frequency (VHF) signals, for example signals between 20 MHz and 300 MHz.

[0077] Some embodiments of radiating structure 10 comprise only two of radiating elements 20. Figure 2A depicts an embodiment of radiating structure comprising radiating element 20A and 20B. Figure 2B depicts an embodiment of radiating structure comprising radiating element 20A and 20C.

[0078] Where radiating structure 10 comprises two or more radiating elements 20, radiating elements 20 may be arranged in parallel side-by-side, end-to-end, or a combination of side-by-side and end-to-end.

[0079] Some embodiments of antenna 100 comprise length 12’ of cable 12 extending along an axis perpendicular to axes A1 and A2, as depicted in figure 2C. Some embodiment of antenna 100 comprise length 12’ of cable 12 extending along a periphery of radiating structure 10, for example along two sides of radiating structure 10, as depicted in figure 2D.

[0080] Figure 3 depicts an embodiment of cable 12 comprising a co-axial cable 300. Co-axial cable 300 comprises inner conductor 30, insulating core 34, and shield 32. Insulating core 34 electrically insulates inner conductor 30 from shield 32. In some embodiments, insulating core 24 comprises a dielectric material.

[0081] Figure 4 is a circuit diagram of antenna 100 connected to source 16. The electrical properties of antenna 100 may be represented by impedance 42 in series with radiating element 44. The electrical properties of length 12’ of cable 12 may be represented by capacitance 46 in series with impedance 48 and inductance 50.

[0082] Signal generator 16 is configured to generate carrier signal Si . Carrier signal Si has carrier frequency h corresponding to carrier wavelength A Signal generator 16 may be further configured to encode carrier signal Si with input signal s ₂ by modulating carrier signal Si with input signal s ₂ to generate encoded signal s ₃ . Input signal s ₂ has input frequency f ₂ corresponding to input wavelength l ₂ . Encoded signal s ₃ has encoded frequency f ₃ corresponding to encoded wavelength l ₃ and bandwidth b·

[0083] In some embodiments, a receiver may be connected to antenna 100 in the place of signal generator 16. In such embodiments, the receiver is configured to receive signals having a carrier frequency h corresponding to carrier wavelength K .

[0084] In some embodiments, a transceiver configured to receive and transmit signals with carrier frequency T corresponding to carrier wavelength is connected to antenna 100 in the place of signal generator 16.

[0085] In some embodiments of antenna 100:

• low pass filter 14 comprises one or more ferrite beads;

• the ferrite beads comprise one or more ferrite collars surrounding cable 12;

• each of radiating elements 20 comprise a trace of a PCB;

• the PCB on which radiating elements 20 are printed is 5 centimeters long, 5 centimeters wide, and 1 .5 millimeters high;

• each trace is 100 centimeters long;

• each trace forms 50 turns;

• axes A1 and A2 are spaced apart by 2.5 centimeters;

• the turns of each trace are 1 millimeter apart;

• the traces are spaced apart by 2 centimeters; • the PCB is affixed to a mounting base and spaced apart from the mounting base by a low dielectric material, for example plastic screws or a foam block;

• cable 12 has an impedance of 50 W;

• cable 12 is an RG174, RG316, or RG58, or other 50 W coaxial cable;

• length 12’ of cable 12 is 24 centimeters long;

• length 12’ of cable 12 extends along three sides of the PCB, and extends from the PCB 9 centimeters before being coupled to low-pass filter 14;

• low-pass filter 14 comprises a 200 MHz low-pass filter;

• cable 12 is held to the mounting base by glue, epoxy, or non-conductive

screws; and/or

• inner conductor 30 is soldered to a trace of the PCB.

[0086] In some embodiments, antenna 100 is configured to transmit and receive frequencies in the range of about 137 MHz to about 150 MHz. Low-pass filter 14 may comprise a 100 MHz low-pass filter.

[0087] Figure 5A is a side view of antenna 100 according to an example embodiment mounted upon side panel 74 of container truck 70. Antenna 100 is electrically connected to electronics package 72. Antenna 100 transmits signals generated by electronics package 72 to one or more Low Earth orbiting satellites, and/or receives signals from one or more Low Earth orbiting satellites and transmits the received signals to electronics package 72.

[0088] During operation, truck 70 may pass within a clearance distance of other objects, for example objects along a roadway like other vehicles, tunnel walls, and undersides of overpasses. The clearance distance between side panel 74 of truck 70 and these other objects may be, for example, 20 centimeters or less. Therefore, any object mounted upon side panel 74 must be less than the clearance distance, otherwise the mounted object may contact another object during the operation of truck 70.

[0089] In some embodiments, antenna 100 projects from side panel 74 of truck 20 by less than a side clearance distance, for example less than 20 centimeters.

[0090] In some embodiments, the clearance distance is 10 centimeters. [0091] Figure 5B is a view of truck 70 where antenna 100 and electronics package 72 are mounted on front panel 76 of truck 70. Antenna 100 may project from front panel 76 of truck 20 by less than a front clearance distance, for example less than 20 centimeters.

[0092] Side panel 74 and front panel 76 of truck 70 may comprise an electrically conductive material, for example steel or aluminum. Antenna 100 may be configured to operate within the clearance distance of the electrically conductive material comprising truck 70. Side panel 74 and/or front panel 76 of truck 70 may form electrically conductive member 22 of antenna 100.

[0093] Antenna 100 and/or electronics package 72 may be mounted within the clearance distance on any panel of truck 70, for example top panel 77 of truck 70, as alternatively depicted in figure 5B.

[0094] Figure 5C is a perspective view of antenna 100 and electronics package 72 according to an example embodiment mounted upon an intermodal container 78. Container 78 may be configured to fit within a clearance distance of other objects, for example container carriers, cranes, or other intermodal containers. Antenna 100 may project from container 78 by less than the clearance distance of container 78, for example less than 20 centimeters, or less than 10 centimeters.

[0095] One or more panels of container 78 may comprise an electrically conductive material, for example steel or aluminum. Antenna 100 may be configured to operate within the clearance distance of the electrically conductive material comprising container 78. One or more panels of container 78 may form electrically conductive member 22 of antenna 100.

[0096] Electronics package 72 may comprise one or more of:

• source 16;

• a VHF signal receiver;

• a VHF signal transmitter;

• a positioning module, for example a global positioning system (GPS) module;

• a communications module, for example a WiFi transceiver and/or a radio transceiver;

• a clock; and • a power source, for example a battery.

[0097] Figure 6 depicts an embodiment of electronics package 72 comprising GPS module 82, controller 84, VHF signal encoder 86, and VHF transmitter 88. VHF transmitter 88 is electrically connected to antenna 100. For example, an output terminal of VHF transmitter 88 may be connected to cable 12 of antenna 100.

[0098] GPS module 82 is configured to receive one or more GPS signals and to determine a global position of GPS module 82. Controller 84 is configured to control VHF signal encoder 86 to encode the global position in a VHF signal, and to control VHF transmitter 88 to drive antenna 100 with the encoded VHF signal. The encoded VHF signal may be transmitted by antenna 100 to one or more low-earth orbit satellites. The VHF signal may be between about 137 MHz to about 150 MHz.

[0099] Controller 84 may be configured to periodically determine the global position, encode the global position, and drive antenna 100 with the encoded global position. The period may be between once every 15 minutes and once every hour.

[0100] Controller 84 may be configured to control VHF signal encoder 86 to encode additional data to the global position, for example one or more of: a unique identifier associated with electronics package 72, a time the global position was determined, and/or state information of controller 84. The unique identifier may identify a particular electronics package 72 among a plurality of electronics packages.

Interpretation of Terms

[0101] Unless the context clearly requires otherwise, throughout the description and the claims:

• “comprise”,“comprising”, and the like are to be construed in an inclusive

sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”;

• “connected”,“coupled”, or any variant thereof, means any connection or

coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements can be physical, logical, or a combination thereof; • “herein”,“above”,“below”, and words of similar import, when used to describe this specification, shall refer to this specification as a whole, and not to any particular portions of this specification;

• “or”, in reference to a list of two or more items, covers all of the following

interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list;

• the singular forms“a”,“an”, and“the” also include the meaning of any

appropriate plural forms.

[0102] Words that indicate directions such as“vertical”,“transverse”,“horizontal”, “upward”,“downward”,“forward”,“backward”,“ inward”,“outward”,“vertical”, “transverse”,“left”,“right”,“front”,“back� ��,“top”,“bottom”,“below”,“above”,“under� �, and the like, used in this description and any accompanying claims (where present), depend on the specific orientation of the apparatus described and illustrated. The subject matter described herein may assume various alternative orientations.

Accordingly, these directional terms are not strictly defined and should not be interpreted narrowly.

[0103] Where a component (e.g. a filter, signal generator, assembly, device, circuit, etc.) is referred to above, unless otherwise indicated, reference to that component (including a reference to a“means”) should be interpreted as including as equivalents of that component any component which performs the function of the described component (i.e., that is functionally equivalent), including components which are not structurally equivalent to the disclosed structure which performs the function in the illustrated exemplary embodiments of the invention.

[0104] Specific examples of systems, methods and apparatus have been described herein for purposes of illustration. These are only examples. The technology provided herein can be applied to systems other than the example systems described above. Many alterations, modifications, additions, omissions, and permutations are possible within the practice of this invention. This invention includes variations on described embodiments that would be apparent to the skilled addressee, including variations obtained by: replacing features, elements and/or acts with equivalent features, elements and/or acts; mixing and matching of features, elements and/or acts from different embodiments; combining features, elements and/or acts from embodiments as described herein with features, elements and/or acts of other technology; and/or omitting combining features, elements and/or acts from described embodiments.

[0105] Various features are described herein as being present in“some

embodiments”. Such features are not mandatory and may not be present in all embodiments. Embodiments of the invention may include zero, any one or any combination of two or more of such features. This is limited only to the extent that certain ones of such features are incompatible with other ones of such features in the sense that it would be impossible for a person of ordinary skill in the art to construct a practical embodiment that combines such incompatible features. Consequently, the description that“some embodiments” possess feature A and“some embodiments” possess feature B should be interpreted as an express indication that the inventors also contemplate embodiments which combine features A and B (unless the description states otherwise or features A and B are fundamentally incompatible).

[0106] It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions, omissions, and sub-combinations as may reasonably be inferred. The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.