Circularly polarized antenna assembly

Abstract

An antenna assembly (100) includes a ground plane (120) having a periphery. The antenna assembly includes a plurality of antenna elements (200). Each antenna element resonates at a frequency f. The antenna elements are positioned approximately equidistant from one another around the periphery (128). The antenna elements are electrically connected to a single antenna feed port (132). The antenna elements provide a substantially omnidirectional radiation pattern in a first operating mode (500). The antenna elements provide a right-hand circularly polarized (RHCP) broadside radiation pattern in a second operating mode (502). The antenna elements provide a left-hand circularly polarized (LHCP) broadside radiation pattern in a third operating mode (504). The antenna assembly includes a reflector (150) positioned below the antenna elements. The reflector tilts the maximum radiation of the antenna elements upward at a tilt angle (170) in the first operating mode to form a conical radiation pattern.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Non-Provisional Application No. 17 / 337,480, filed on June 3, 2021, and U.S. Provisional Application No. 63 / 161,621, filed on March 16, 2021, both entitled “CIRCULARLY POLARIZED ANTENNA ASSEMBLY,” which are incorporated herein by reference in their entireties. Technical Field

[0003] The subject matter herein relates generally to antenna assemblies. Background Art

[0004] Antenna systems are used in wireless communication networks. For example, a vehicle may include one or more antennas, such as an AM / FM radio antenna, a satellite digital audio radio service antenna, a global positioning system antenna, a cellular telephone antenna, a vehicle-to-everything (V2X) network, and the like. The antenna is operable to send and / or receive signals to and from the vehicle. Other devices, such as handheld devices, computers, and the like, use antennas. Some antennas may be directional. Other antennas may be omnidirectional. Thus, an antenna system may provide different antennas for different types of communications. However, providing multiple antennas may increase the cost of the antenna system and / or occupy a larger area. Typical omnidirectional circularly polarized antennas include common mode helical antennas or trefoil antennas. However, such antennas typically have a higher profile. Trefoil antennas are typically pole mounted and are not suitable for panel mount applications. Other omnidirectional antennas include high order mode patch antennas. However, such antennas are electrically large (e.g., typically larger than one electrical wavelength).

[0005] There is a need for an antenna that is physically small; has relatively high efficiency; can be placed close to associated electronic circuitry without adversely affecting performance; is easy to manufacture using standard, low-cost components; and has the ability to modify the radiation pattern to support different applications. Summary of the Invention

[0006] In one embodiment, an antenna assembly is provided that includes a ground plane having a periphery. The antenna assembly includes a plurality of antenna elements. Each antenna element resonates at a frequency f. The antenna elements are positioned approximately equidistant from one another around the periphery. The antenna elements are electrically connected to a single antenna feed port. The antenna element provides a right-hand circularly polarized (RHCP) approximately omnidirectional radiation pattern in a first operating mode. The antenna element provides a right-hand circularly polarized (RHCP) broadside radiation pattern in a second operating mode. The antenna element provides a left-hand circularly polarized (LHCP) broadside radiation pattern in a third operating mode. The antenna assembly may include a reflector located below the antenna element that is configured to tilt the maximum radiation of the antenna element upward at a tilt angle to form a conical radiation pattern when operating in the first operating mode.

[0007] In another embodiment, an antenna assembly is provided and includes a ground plane having a periphery. The antenna assembly includes a plurality of antenna elements. Each antenna element resonates at a frequency f. The antenna elements are positioned approximately equidistant from one another around the periphery. The antenna elements are electrically connected to a single antenna feed port to provide a right-hand circularly polarized (RHCP) substantially omnidirectional radiation pattern. The antenna assembly may include a reflector positioned below the antenna element. The reflector tilts the maximum radiation of the antenna element upward at a tilt angle to form a conical radiation pattern.

[0008] In another embodiment, an antenna assembly is provided and includes a ground plane having a periphery. The antenna assembly includes a plurality of antenna elements. Each antenna element resonates at a frequency f. The antenna elements are positioned approximately equidistant from one another around the periphery. The antenna elements are electrically connected to a single antenna feed port. The antenna elements provide a right-hand circularly polarized (RHCP) substantially omnidirectional radiation pattern in a first operating mode. The antenna elements provide a right-hand circularly polarized (RHCP) broadside radiation pattern in a second operating mode, and the antenna elements provide a left-hand circularly polarized (LHCP) broadside radiation pattern in a third operating mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 An antenna assembly of an apparatus according to an exemplary embodiment is illustrated.

[0010] Figure 2 is a perspective view of an antenna assembly according to an exemplary embodiment.

[0011] Figure 3 is a perspective view of a portion of an antenna assembly according to an exemplary embodiment.

[0012] Figure 4 is a graph illustrating operating frequencies of antenna elements according to an exemplary embodiment.

[0013] Figure 5 is a chart illustrating various operating modes of an antenna assembly according to an exemplary embodiment.

[0014] Figure 6 is a diagram showing antenna characteristics of the antenna assembly operating in the first operation mode.

[0015] Figure 7 is a diagram showing antenna characteristics of the antenna assembly operating in the second operating mode.

[0016] Figure 8 is a diagram showing antenna characteristics of the antenna assembly operating in the third operating mode.

[0017] Figure 9 An antenna assembly according to an exemplary embodiment is illustrated having a reflector.

[0018] Figure 10 is a diagram illustrating a radiation pattern of an antenna assembly using a reflector positioned below a ground plane and antenna elements according to an exemplary embodiment.

[0019] Figure 11 is a diagram illustrating various examples of antenna assemblies having reflectors at different spacings from a ground plane and antenna elements according to example embodiments. DETAILED DESCRIPTION

[0020] Figure 1 The antenna assembly 100 of the device 102 according to an exemplary embodiment is illustrated. The antenna assembly 100 is used to communicate with various remote devices 104, 106, and 108. The first remote device 104 represents a mobile (or movable) remote device (e.g., a handheld device, a vehicle, etc.). The second remote device 106 represents a fixed device, such as a light pole or other traffic control or traffic monitoring device. The third remote device 108 represents a drone or satellite. Communication with the first remote device 104 is typically horizontal or at a low elevation angle. Communication with the second remote device 106 is typically at an oblique angle (e.g., the second remote device is located at a height above the device 102). Communication with the third remote device 108 is typically on the broad side of the antenna, such as in a generally vertical orientation.

[0021] Device 102 may be a wireless communication device, such as a sensing device (e.g., a parking meter for traffic control). In other embodiments, device 102 is a vehicle, such as a motor vehicle, configured to communicate with various remote devices 104, 106, 108. In various other embodiments, device 102 may be a stationary component, such as a device used in a traffic control or traffic monitoring system. In alternative embodiments, the device may have other applications. Device 102 includes a housing 110 that holds antenna assembly 100.

[0022] Figure 2is a perspective view of an antenna assembly 100 according to an exemplary embodiment. The antenna assembly 100 includes a ground plane 120 and a plurality of antenna elements 200 coupled to the ground plane 120. In an exemplary embodiment, the antenna elements 200 are circularly polarized antenna elements. In various embodiments, the antenna elements 200 may be planar inverted-F antennas (PIFAs). In the illustrated embodiment, three antenna elements 200 are provided; however, in alternative embodiments, more or fewer antenna elements 200 may be provided. The antenna elements 200 are spaced equidistantly from one another, for example, 120° apart. In an exemplary embodiment, the antenna elements 200 may be identical to one another.

[0023] Ground plane 120 includes an upper surface 122 and a lower surface 124. Ground plane 120 has an edge 126 between upper surface 122 and lower surface 124. Edge 126 defines a periphery 128 of ground plane 120. In the illustrated embodiment, ground plane 120 is circular; however, in alternative embodiments, ground plane 120 may have other shapes. Ground plane 120 is conductive. Optionally, ground plane 120 may be a metal plate or disk. Alternatively, ground plane 120 may be formed by a ground layer or conductive circuit of a printed circuit board. For example, the ground layer may be an upper layer at upper surface 122 and / or a lower layer at lower surface 124 and / or may be a middle layer of the printed circuit board. The printed circuit board may include other circuitry, such as a feed circuit electrically connected to antenna element 200. Antenna feed 130 (e.g., a coaxial cable) may be electrically connected to the feed circuit at antenna feed port 132. In various embodiments, the antenna feed pad may be located in the center of ground plane 120. Optionally, a single antenna feed 130 is provided and electrically connected to each antenna element 200. Alternatively, separate antenna feeds 130 may be provided and electrically connected to corresponding antenna elements 200.

[0024] Figure 3 is a perspective view of a portion of antenna assembly 100 according to an exemplary embodiment. Figure 3 One of the antenna elements 200 is shown coupled to the ground plane 120. The antenna element 200 is coupled to the ground plane 120 near the periphery 128 of the ground plane 120. The antenna element 200 is offset from the center of the ground plane 120. In alternative embodiments, other mounting positions are possible.

[0025] Antenna element 200 includes a dielectric base 210 and a resonator element 220 coupled to dielectric base 210. Dielectric base 210 provides mechanical support for resonator element 220. In the illustrated embodiment, dielectric base 210 is cylindrical and has a top 212, a bottom 214, and a side 216 between top 212 and bottom 214. Bottom 214 is mounted to ground plane 120. In alternative embodiments, dielectric base 210 may have other shapes.

[0026] Resonator element 220 includes a loop 222 and a conductive leg 230 extending from loop 222. In the illustrated embodiment, loop 222 is disposed on top 212. Conductive leg 230 extends along side 216 between top 212 and bottom 214. In the illustrated embodiment, loop 222 is a partial loop, extending only partially circumferentially around dielectric base 210. Alternatively, loop 222 may be disposed on the outer periphery of top 212. In alternative embodiments, other locations are possible. Loop 222 includes a right leg 224 extending to the right of conductive leg 230 and a left leg 226 extending to the left of conductive leg 230. In the illustrated embodiment, right leg 224 is longer than left leg 226. In alternative embodiments, right leg 224 and left leg 226 may be of equal length. In other alternative embodiments, left leg 226 may be longer than right leg 224. Making the right hand segment 224 longer than the left hand segment 226 renders the resonator element 220 substantially right-hand circularly polarized (RHCP).Providing the left hand segment 226 provides some left-hand circularly polarized (LHCP) radiation.

[0027] The conductive leg 230 includes a feed pad 232 and a ground pad 234, with a slot 236 between the feed pad 232 and the ground pad 234. The slot 236 provides an air gap between the feed pad 232 and the ground pad 234. In the illustrated embodiment, the slot 236 does not extend along the entire height of the conductive leg 230; however, in alternative embodiments, the slot 236 may have other heights. The conductive leg 230 includes a loop 222 and an intermediate portion 238 between the pads 232 and 234. The size and shape of the feed pad 232, the ground pad 234, and the slot 236 affect the antenna characteristics of the antenna element 200.

[0028] In an exemplary embodiment, antenna element 200 is designed to operate at Wi-Fi / Bluetooth frequencies, such as 2.4 GHz. In alternative embodiments, antenna element 200 may be designed to operate at other frequencies. In various embodiments, antenna element 200 may be designed to operate at multiple frequencies. In an exemplary embodiment, antenna element 200 is electrically small. For example, the dimensions of antenna element 200 are less than 0.5 wavelengths at the target frequency. Antenna element 200 has a height 250 and a width 252. Antenna element 200 is disc-shaped, with width 252 defined by the diameter of antenna element 200 and greater than height 250. In an exemplary embodiment, width 252 may be less than 0.2 wavelengths. In various embodiments, width 252 may be less than 0.15 wavelengths. In an exemplary embodiment, width 252 is 0.13 wavelengths. In an exemplary embodiment, antenna element 200 has a low profile. Height 250 is less than 0.1 wavelengths. In various embodiments, height 250 may be less than 0.05 wavelengths. In an exemplary embodiment, ground plane 120 is sized to accommodate multiple antenna elements 200 positioned relatively close to one another. Ground plane 120 has a width 254 that is less than 0.5 wavelengths. Ground plane 120 may have a width 254 that is less than 0.35 wavelengths. In an exemplary embodiment, width 254 is 0.32 wavelengths. In an exemplary embodiment, height 250 of antenna elements 200 is 6 mm, width 252 of antenna elements 200 is 16 mm, and width 254 of ground plane 120 is 40 mm. In alternative embodiments, antenna elements 200 and ground plane 120 may have other dimensions.

[0029] Figure 4 2 is a diagram illustrating an operating frequency of the antenna element 200 according to an exemplary embodiment. The antenna element 200 may be designed for operation at approximately 2.4 GHz, for example, for Wi-Fi / Bluetooth communications.

[0030] Figure 5 1 illustrates various operating modes of the antenna assembly 100 according to an exemplary embodiment. In the illustrated embodiment, the antenna assembly 100 can operate in a first operating mode 500, a second operating mode 502, and a third operating mode 504. The first operating mode 500 is an in-phase operating mode, in which each antenna element 200 combines in phase with each other. The second operating mode 502 is a right-handed operating mode, in which the antenna elements 200 have a right-handed phase shift. The third operating mode 504 is a left-handed operating mode, in which the antenna elements 200 have a left-handed phase shift.

[0031] In the exemplary embodiment, the antenna assembly 100 includes three antenna elements 200 that are equally spaced (e.g., spaced 120° apart) around the periphery 128 of the ground plane 120. The antenna elements 200 are rotated relative to each other so that the antenna elements 200 face in directions that are 120° offset from each other. Thus, the primary radiation direction of each antenna element 200 is in a direction that is 120° offset from the other antenna elements 200.

[0032] In the first operating mode 500, the antenna signals of each antenna element 200 are combined in phase with each other. The antenna signals are combined without any phase shift or delay in any of the antenna signals. For example, a single antenna feed port 132 is provided at the center of the ground plane 120. The antenna feed port 132 is connected to each feed point (e.g., Figure 2 The transmission paths between the feed patch 232 shown can have the same path length to avoid skew or delay along the path between the antenna element 200 and the antenna feed port 132. As a result, the antenna signals of each antenna element 200 are combined in phase with each other. Due to the longer right-hand side 224 of the resonator element 220, the antenna element 200 is predominantly right-hand circularly polarized (RHCP). Having multiple antenna elements 200 offset from each other around the ground plane 120 provides an omnidirectional radiation pattern for the antenna assembly 100. In an exemplary embodiment, the radiation pattern is omnidirectional in the horizontal plane. In an exemplary embodiment, the antenna assembly 100 has a maximum gain (RHCP) of -0.2 dBi, a 3 dB beamwidth (RHCP) of 95°, and an axial ratio within the 3 dB beamwidth of less than 8 dB. Changing the size and / or shape and / or orientation of the antenna element 200 and / or the ground plane 120 can affect the maximum gain, 3 dB beamwidth, and axial ratio.

[0033] In the second operating mode 502, the antenna signals of each antenna element 200 are combined with a right-hand phase shift. The antenna signals are combined with a delay element to induce a phase shift. For example, the transmission paths between the antenna feed port 132 and the feed point of the resonator element 220 of the antenna element 200 can have different path lengths to intentionally induce a skew or delay along the path between the antenna element 200 and the antenna feed port 132. For example, the first antenna element 200a can have a normal path length, the second antenna element 200b can have a longer path length corresponding to a 120° phase shift from the first antenna element 200a, and the third antenna element 200c can have an even longer path length corresponding to a 240° phase shift from the first antenna element 200a. Thus, the antenna signals of each antenna element 200 can be combined with a right-hand phase shift. Due to the longer right-hand side 224 of the resonator element 220, the antenna element 200 is predominantly right-hand circularly polarized (RHCP). The right-hand phase shift causes the radiation pattern to be broadside oriented in a generally vertical direction. In an exemplary embodiment, the antenna assembly 100 has a maximum gain (RHCP) of 3.3 dBi, a 3 dB beamwidth (RHCP) of 133°, and an axial ratio within the 3 dB beamwidth of less than 6 dB. Changing the size, shape, and / or orientation of the antenna element 200 and / or the ground plane 120 can affect the maximum gain, 3 dB beamwidth, and axial ratio.

[0034] In the third operating mode 504, the antenna signal of each antenna element 200 is combined with a left-handed phase shift. The antenna signal is combined with a delay element to induce a phase shift. For example, the transmission path between the antenna feed port 132 and the feed point of the resonator element 220 of the antenna element 200 can have different path lengths to intentionally induce a skew or delay along the path between the antenna element 200 and the antenna feed port 130. For example, the third antenna element 200c can have a normal path length, the second antenna element 200b can have a longer path length corresponding to a 120° phase shift from the third antenna element 200c, and the first antenna element 200a can have an even longer path length corresponding to a 240° phase shift from the third antenna element 200c. Thus, the antenna signal of each antenna element 200 is combined with a left-handed phase shift. The phase shift causes the primary circular polarization to be predominantly left-handed circular polarization (LHCP). The left-handed phase shift causes the radiation pattern to be broadside oriented in a generally vertical direction. In an exemplary embodiment, the antenna assembly 100 has a maximum gain (LHCP) of 3.9 dBi, a 3 dB beamwidth (LHCP) of 112°, and an axial ratio within the 3 dB beamwidth of less than 5 dB. Changing the size and / or shape and / or orientation of the antenna element 200 and / or the ground plane 120 can affect the maximum gain, 3 dB beamwidth, and axial ratio. The phase shift can be controlled by the transmission line, for example by controlling the length of the transmission line, or by adding electrical components to the transmission line to create a delay and affect the phase shift. Optionally, a variable phase shift circuit can be used to individually change the phase of the antenna elements so that the operating mode can be changed or switched between operating modes 500, 502, and 504.

[0035] The antenna assembly 100 can periodically switch between various operating modes, for example at regular intervals, such as by utilizing a variable phase shift circuit. The first operating mode 500 can be used to communicate (e.g., transmit and / or receive) with corresponding remote devices, such as the first and second remote devices 104 and 106, for vehicle communications, keyless entry, access control, remote control, tracking, toll collection, other IoT applications, and the like. Due to the generally broadside directional radiation pattern, the second and third operating modes 502 and 504 can be used to communicate with the third remote device 108, such as for satellite communications, global navigation, RFID, and the like. In various embodiments, the second operating mode 502 is used to receive communication signals, and the third operating mode 504 is used to transmit communication signals, or vice versa. Thus, the antenna assembly 100 enables beam steering and polarization switching to enhance wireless communications from a single antenna assembly 100. The antenna assembly 100 is electrically small and has a low profile, and can be board-mounted to a generally flat surface without occupying significant space above the panel. The antenna assembly 100 is a wide-beam, circularly polarized antenna assembly. The antenna assembly 100 is reconfigurable and can be operated as an omnidirectional antenna assembly and as an axial antenna assembly by switching between various operating modes. The radiation beam direction and polarization of the antenna assembly 100 can be changed for different applications. Compared to conventional antennas, the antenna assembly 100 provides these advantages at a low cost.

[0036] Figure 6 is a graph illustrating antenna characteristics of the antenna assembly 100 operating in the first operating mode, showing an in-phase combination of the antenna elements 200 . Figure 6 The gain radiation pattern and axial ratio of the antenna assembly 100 are shown. Figure 6 A generally omnidirectional radiation pattern in a generally horizontal direction is shown, including a total gain radiation pattern, a RHCP gain radiation pattern, and a LHCP gain radiation pattern.

[0037] Figure 7 is an illustration of the antenna characteristics of the antenna assembly 100 operating in the second operating mode, showing the right-hand phase shift of the antenna element 200 . Figure 7 The gain radiation pattern and axial ratio of the antenna assembly 100 are shown. Figure 7 Radiation patterns that are generally broadside oriented in a generally vertical direction are shown, including a total gain radiation pattern, a RHCP gain radiation pattern, and a LHCP gain radiation pattern.

[0038] Figure 8 is an illustration of the antenna characteristics of the antenna assembly 100 operating in the third operating mode, showing the left-hand phase shift of the antenna element 200 . Figure 8 The gain radiation pattern and axial ratio of the antenna assembly 100 are shown. Figure 8Radiation patterns that are generally broadside oriented in a generally vertical direction are shown, including a total gain radiation pattern, a RHCP gain radiation pattern, and a LHCP gain radiation pattern.

[0039] Figure 9 An antenna assembly 100 according to an exemplary embodiment is shown. Antenna assembly 100 includes a ground plane 120 and a reflector 150 below antenna element 200. When antenna assembly 100 operates in a first operating mode, reflector 150 is configured to tilt the maximum radiation of antenna element 200 upward at a tilt angle to change the radiation pattern from a horizontal plane to a higher azimuth angle. For example, reflector 150 changes the radiation pattern from an omnidirectional radiation pattern to a conical radiation pattern.

[0040] Reflector 150 is made of a metallic material. Reflector 150 is electrically conductive. Reflector 150 has an upper surface 152 facing ground plane 120 and antenna element 200, and a lower surface 154 opposite upper surface 152. Reflector 150 has an edge 156 between upper surface 152 and lower surface 154, defining a periphery 158 of reflector 150. In the illustrated embodiment, reflector 150 is circular; however, in alternative embodiments, reflector 150 may have other shapes. In the exemplary embodiment, the surface area of ​​reflector 150 is greater than that of ground plane 120. For example, periphery 158 of reflector 150 is located outside periphery 128 of ground plane 120. In the exemplary embodiment, reflector 150 is planar and oriented parallel to ground plane 120. However, in alternative embodiments, reflector 150 may be angled relative to ground plane 120. In other alternative embodiments, reflector 150 may be non-planar, such as dished or concave. The shape of reflector 150 serves to focus antenna radiation. Reflector 150 is separated from ground plane 120 by spacer 160. Spacer 160 controls the tilt angle of the direction of maximum radiation of antenna element 200. Furthermore, the size and / or shape of reflector 150 controls the tilt angle. Width 162 of reflector 150 is greater than the width of ground plane 120. Optionally, ground plane 120 can be centered above reflector 150. Alternatively, ground plane 120 can be offset from the center of reflector 150, which can affect the directionality of the antenna radiation pattern.

[0041] Figure 10 FIG1 is a schematic diagram illustrating the radiation pattern of antenna assembly 100 using reflector 150 positioned below ground plane 120 and antenna element 200. Reflector 150 is used to tilt the maximum radiation of antenna element 200 upward at a tilt angle 170 to change the radiation pattern from the horizontal plane to a higher azimuth angle. In the illustrated embodiment, reflector 150 causes the radiation pattern to be a conical radiation pattern, with the maximum radiation located a certain distance above the horizontal plane.

[0042] Figure 11 is a diagram illustrating various examples of antenna assemblies 100 having reflectors 150 located at different spacings 160 from the ground plane 120 and the antenna element 200 .

[0043] In the first example 800, the reflector 150 is located at a distance of 5 mm from the antenna element 200. The antenna assembly 100 has a maximum gain of 0.2 dBi. The maximum gain elevation angle is 50°.

[0044] In the second example 802, the reflector 150 is located at a distance of 30 mm from the antenna element 200. The antenna assembly 100 has a maximum gain of 0.3 dBi. The maximum gain elevation angle is 60°.

[0045] In the third example 804, the reflector 150 is located at a distance of 40 mm from the antenna element 200. The antenna assembly 100 has a maximum gain of 0.4 dBi. The maximum gain elevation angle is 70°.

[0046] In the fourth example 806, the reflector 150 is located at a distance of 60 mm from the antenna element 200. The antenna assembly 100 has a maximum gain of 0.7 dBi. The maximum gain elevation angle is 80°.

[0047] Antenna characteristics, such as the radiation pattern, are affected by the spacing 160 between the reflector 150 and the antenna element 200. If a higher elevation angle is desired, the reflector 150 can be positioned closer to the antenna element 200. If a lower elevation angle is desired, the reflector 150 can be positioned further away from the antenna element 200. Other variations are possible to alter the radiation pattern, such as variations in the size and / or shape of the reflector 150.

[0048] It should be understood that the above description is intended to be illustrative rather than restrictive. For example, the above embodiments (and / or aspects thereof) may be used in combination with one another. In addition, many modifications may be made to adapt specific circumstances or materials to the teachings of the present invention without departing from its scope. The dimensions, material types, orientations of various parts, and the number and position of various parts described herein are intended to define the parameters of certain embodiments and are by no means restrictive and are merely exemplary embodiments. After reading the above description, many other embodiment modifications within the scope of the claims will be apparent to one of ordinary skill in the art. Therefore, the scope of the present invention should be determined with reference to the appended claims and the full scope of equivalents to these claims. In the appended claims, the terms "including" and "wherein" are used as the plain English equivalents of the respective terms "comprising" and "wherein." In addition, in the appended claims, the terms "first," "second," "third," etc. are used merely as labels and are not intended to impose numerical requirements on their objects.

Claims

1. An antenna assembly (100), comprising: a ground plane (120) having a periphery (128); a plurality of antenna elements (200), each resonating at a frequency f, the antenna elements being positioned equidistant from one another around the periphery, the plurality of antenna elements being electrically connected to a single antenna feed port (132), the antenna elements providing an omnidirectional radiation pattern in a first operating mode (500), wherein the antenna elements (200) are connected to the antenna feed port (132) without phase shift in the first operating mode (500); the antenna elements providing a right-hand circularly polarized (RHCP) broadside radiation pattern in a second operating mode (502), wherein the antenna elements are connected to the antenna feed port with a right-hand phase shift in the second operating mode (502); and the antenna elements providing a left-hand circularly polarized (LHCP) broadside radiation pattern in a third operating mode (504), wherein the antenna elements are connected to the antenna feed port with a left-hand phase shift in the third operating mode (504); and A reflector (150) is located below the antenna element, and in the first operating mode (500), the reflector tilts the maximum radiation of the antenna element upward at a tilt angle (170) to form a conical radiation pattern.

2. The antenna assembly (100) of claim 1, wherein: The antenna element (200) is connected to the antenna feed port (132) out of phase in the second and third operating modes (502, 504).

3. The antenna assembly (100) of claim 1, wherein: The transmission feed length between the antenna element (200) and the antenna feed port (132) is variable to control phase shift.

4. The antenna assembly (100) of claim 1, wherein: The plurality of antenna elements (200) include a first antenna element (200a), a second antenna element (200b), and a third antenna element (200c), wherein the second antenna element has a phase shift of -120° compared to the first antenna element in the second operating mode (502) and a phase shift of +120° compared to the first antenna element in the third operating mode (504), and the third antenna element has a phase shift of -240° compared to the first antenna element in the second operating mode and a phase shift of +240° compared to the first antenna element in the third operating mode.

5. The antenna assembly (100) of claim 4, wherein: The second antenna element (200b) has a 0° phase shift compared to the first antenna element (200a) in the first operating mode (500), and the third antenna element (200c) has a 0° phase shift compared to the first antenna element in the first operating mode.

6. The antenna assembly (100) of claim 1, wherein: The reflector (150) is spaced apart from the ground plane (120) by a spacer (160) selected to control the tilt angle (170).

7. The antenna assembly (100) of claim 1, wherein: The reflector (150) has a surface area selected to control the tilt angle (170).

8. The antenna assembly (100) of claim 1, wherein: The reflector (150) is planar and oriented parallel to the ground plane (120), with the periphery (158) of the reflector being outside the periphery (128) of the ground plane.

9. The antenna assembly (100) of claim 1, wherein: Each antenna element (200) includes a dielectric base having a top (212), a bottom (214), and a side (216) between the top and the bottom, the antenna element including a resonator element (220) coupled to the dielectric base (210), the resonator element including a loop (222) and a conductive leg (230) extending from the loop, the conductive leg including a feed patch (232) and a ground patch (234) separated by a slot (236), the ground patch being electrically connected to the ground plane (120), the feed patch being electrically connected to the antenna feed port (132), the loop being disposed on the top of the dielectric body, and the conductive leg extending along the side of the dielectric body.

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