Patent Description:
Antenna systems are used in wireless communication networks. For example, vehicles may include one or more antennas, such as AM/FM radio antennas, satellite digital audio radio service antennas, global positioning system antennas, cell phone antennas, vehicle-to-everything (V2X), and the like. The antennas are operable for transmitting and/or receiving signals to/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. As such, the antenna systems may provide different antennas for different types of communication. However, providing multiple antennas may increase the cost of the antenna system and/or occupy a large area. Typical omnidirectional circularly polarized antennas include normal mode helical antennas or cloverleaf antennas. However, such antennas typically have a high profile. Cloverleaf antennas are typically pole mounted and not feasible for panel mount applications. Other omnidirectional antennas include higher-order-mode patch antennas. However, such antennas are electrically large (for example, typically larger than one electrical wavelength).

<CIT> discloses a multidirectional antenna comprising three semicircular radial antennas. <CIT> discloses an antenna having a plurality of single antennas of the inverted-F type. <CIT> discloses an antenna having a ground plane and an array of radiating and/or receiving elements.

There is a need for antennas small in physical dimension; having relatively high efficiency; capable of being placed in close proximity to associated electronic circuits without adversely effecting performance; easy to manufacture using standard, low-cost components; and capable of having radiation patterns altered to support different applications.

In accordance with the invention, there is provided an antenna assembly as defined in the appended claim <NUM>. In one 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 is resonant at a frequency f. The antenna elements are positioned generally equidistant from each other around the periphery. The antenna elements are electrically connected to a single antenna feed port. The antenna elements may provide a right-hand circularly polarized (RHCP) generally omnidirectional radiation pattern in a first operation mode. The antenna elements provide a right-hand circularly polarized (RHCP) broadside radiation pattern in a second operation mode. The antenna elements provide a left-hand circularly polarized (LHCP) broadside radiation pattern in a third operation mode. The antenna assembly includes a reflector positioned below the antenna elements configured to tilt a maximum radiation of the antenna elements upward by a tilt angle to create a conical radiation pattern when operated in the first operation mode.

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 is resonant at a frequency f. The antenna elements are positioned generally equidistant from each other around the periphery. The antenna elements are electrically connected to a single antenna feed port to provide a right-hand circularly polarized (RHCP) generally omnidirectional radiation pattern. The antenna assembly includes a reflector positioned below the antenna elements. The reflector tilts a maximum radiation of the antenna elements upward by a tilt angle to create a conical radiation pattern.

In a further 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 is resonant at a frequency f. The antenna elements are positioned generally equidistant from each other 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) generally omnidirectional radiation pattern in a first operation mode. The antenna elements provide a right-hand circularly polarized (RHCP) broadside radiation pattern in a second operation mode, and the antenna elements provide a left-hand circularly polarized (LHCP) broadside radiation pattern in a third operation mode.

<FIG> illustrates an antenna assembly <NUM> of a device <NUM> in accordance with an exemplary embodiment. The antenna assembly <NUM> is used to communicate with various remote devices <NUM>, <NUM>, <NUM>. The first remote device <NUM> represents a mobile (movable) remote device (for example, a handheld device, a vehicle, and the like). The second remote device <NUM> represents a stationary device, such as a light pole or other traffic control or traffic monitoring device. The third remote device <NUM> represents a drone or satellite. Communication with the first remote device <NUM> is generally horizontal or in a low elevation angle. Communication with the second remote device <NUM> is generally at a tilt angle (for example, the second remote device is located at a height above the device <NUM>). Communication with the third remote device <NUM> is generally at the broad side of the antenna, such as generally in the vertical direction.

The device <NUM> may be a wireless communication device, such as a sensing device (for example, a parking meter used for traffic control). In other embodiments, the device <NUM> is a vehicle, such as an automobile, configured to communicate with the various remote devices <NUM>, <NUM>, <NUM>. In other various embodiments, the device <NUM> may be a stationary component, such as a device used in a traffic control or traffic monitoring system. The device may have other applications in alternative embodiments. The device <NUM> includes a housing <NUM> holding the antenna assembly <NUM>.

<FIG> is a perspective view of the antenna assembly <NUM> in accordance with an exemplary embodiment. The antenna assembly <NUM> includes a ground plane <NUM> and a plurality of antenna elements <NUM> coupled to the ground plane <NUM>. In an exemplary embodiment, the antenna elements <NUM> are circularly polarized antenna elements. The antenna elements <NUM> may be planar inverted F antennas (PIFA) in various embodiments. In the illustrated embodiment, three antenna elements <NUM> are provided; however, greater or fewer antenna elements <NUM> may be provided in alternative embodiments. The antenna elements <NUM> are spaced equidistant from each other, such as being positioned at <NUM>° apart from each other. The antenna elements <NUM> may be identical to each other in an exemplary embodiment.

The ground plane <NUM> includes an upper surface <NUM> and a lower surface <NUM>. The ground plane <NUM> has an edge <NUM> between the upper surface <NUM> and the lower surface <NUM>. The edge <NUM> defines a periphery <NUM> of the ground plane <NUM>. In the illustrated embodiment, the ground plane <NUM> is circular; however, the ground plane <NUM> may have other shapes in alternative embodiments. The ground plane <NUM> is electrically conductive. Optionally, the ground plane <NUM> may be a metal plate or disc. Alternatively, the ground plane <NUM> 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 the upper surface <NUM> and/or a lower layer at the lower surface <NUM> and/or may be an intermediate layer of the printed circuit board. The printed circuit board may include other circuits, such as feed circuits electrically connected to the antenna elements <NUM>. An antenna feed <NUM>, such as a coaxial cable, may be electrically connected to the feed circuits at an antenna feed port <NUM>. The antenna feed board may be provided at the center of the ground plane <NUM> in various embodiments. Optionally, a single antenna feed <NUM> is provided and is electrically connected to each of the antenna elements <NUM>. Alternatively, separate antenna feeds <NUM> may be provided and electrically connected to the corresponding antenna elements <NUM>.

<FIG> is a perspective view of a portion of the antenna assembly <NUM> in accordance with an exemplary embodiment. <FIG> illustrates one of the antenna elements <NUM> coupled to the ground plane <NUM>. The antenna element <NUM> is coupled to the ground plane <NUM> near the periphery <NUM> of the ground plane <NUM>. The antenna element <NUM> is offset from the center of the ground plane <NUM>. Other mounting locations are possible in alternative embodiments.

The antenna element <NUM> includes a dielectric base <NUM> and a resonator element <NUM> coupled to the dielectric base <NUM>. The dielectric base <NUM> provides mechanical support for the resonator element <NUM>. In the illustrated embodiment, the dielectric base <NUM> is cylindrical having a top <NUM>, a bottom <NUM>, and a side <NUM> between the top <NUM> and the bottom <NUM>. The bottom <NUM> is mounted to the ground plane <NUM>. The dielectric base <NUM> may have other shapes in alternative embodiments.

The resonator element <NUM> includes a loop <NUM> and a conductive leg <NUM> extending from the loop <NUM>. The loop <NUM> is provided at the top <NUM> in the illustrated embodiment. The conductive leg <NUM> extends along the side <NUM> between the top <NUM> and the bottom <NUM>. In the illustrated embodiment, the loop <NUM> is a partial loop extending only partially circumferentially around the dielectric base <NUM>. Optionally, the loop <NUM> may be provided at the outer periphery of the top <NUM>. Other locations are possible in alternative embodiments. The loop <NUM> includes a right-hand segment <NUM> extending to the right side of the conductive leg <NUM> and a left-hand segment <NUM> extending to the left side of the conductive leg <NUM>. In the illustrated embodiment, the right-hand segment <NUM> is longer than the left-hand segment <NUM>. In alternative embodiments, the right-hand segment <NUM> and the left-hand segment <NUM> may have equal lengths. In other alternative embodiments, the left-hand segment <NUM> may be longer than the right-hand segment <NUM>. Having the right-hand segment <NUM> are longer than the left-hand segment <NUM> makes the resonator element <NUM> generally right-hand circularly polarized (RHCP). The provision of the left-hand segment <NUM> provides some left-hand circularly polarized (LHCP) radiation.

The conductive leg <NUM> includes a feed tab <NUM> and a ground tab <NUM> with a slot <NUM> between the feed tab <NUM> and the ground tab <NUM>. The slot <NUM> provides an air gap between the feed tab <NUM> and the ground tab <NUM>. In the illustrated embodiment, the slot <NUM> does not extend along the entire height of the conductive leg <NUM>; however, the slot <NUM> may have other heights in alternative embodiments. The conductive leg <NUM> includes an intermediate portion <NUM> between the loop <NUM> and the tabs <NUM>, <NUM>. Sizes and shapes of the feed tab <NUM>, the ground tab <NUM>, and the slot <NUM> affect the antenna characteristics of the antenna element <NUM>.

In an exemplary embodiment, the antenna element <NUM> is designed for operation at a Wi-Fi / Bluetooth frequency, such as <NUM>. The antenna element <NUM> may be designed for operation at other frequencies in alternative embodiments. The antenna element <NUM> may be designed for operation multiple frequencies in various embodiments. In an exemplary embodiment, the antenna element <NUM> is electrically small. For example, the dimensions of the antenna element <NUM> are less than <NUM> wavelength at the target frequency. The antenna element <NUM> has a height <NUM> and a width <NUM>. The antenna element <NUM> is puck-shaped having the width <NUM> defined by a diameter of the antenna element <NUM>, which is greater than the height <NUM>. In an exemplary embodiment, the width <NUM> may be less than <NUM> wavelength. In various embodiments, the width <NUM> may be less than <NUM> wavelength. In an exemplary embodiment, the width <NUM> is <NUM> wavelength. In an exemplary embodiment, the antenna element <NUM> has a low-profile. The height <NUM> is less than <NUM> wavelength. In various embodiments, the height <NUM> may be less than <NUM> wavelength. In an exemplary embodiment, the ground plane <NUM> is sized to fit a plurality of the antenna elements <NUM> in relatively close proximity to each other. The ground plane <NUM> has a width <NUM> less than <NUM> wavelength. The ground plane <NUM> may have a width <NUM> less than <NUM> wavelength. In an exemplary embodiment. The width <NUM> is <NUM> wavelength. In an exemplary embodiment, the height <NUM> of the antenna element <NUM> is <NUM>, the width <NUM> of the antenna element <NUM> is <NUM> and the width <NUM> of the ground plane <NUM> is <NUM>. The antenna element <NUM> and the ground plane <NUM> may have other dimensions in alternative embodiments.

<FIG> is a chart illustrating an operating frequency of the antenna element <NUM> in accordance with an exemplary embodiment. The antenna element <NUM> may be designed to operate at approximately <NUM>, such as for Wi-Fi / Bluetooth communication.

<FIG> is a chart illustrating various modes of operation of the antenna assembly <NUM> in accordance with an exemplary embodiment. In the illustrated embodiment, the antenna assembly <NUM> is operable in a first operation mode <NUM>, a second operation mode <NUM>, and a third operation mode <NUM>. The first operation mode <NUM> is an in-phase operation mode where each of the antenna elements <NUM> are combined in-phase with each other. The second operation mode <NUM> is a right-hand operation mode where the antenna elements <NUM> have a right-hand phase shift. The third operation mode <NUM> is a left-hand operation mode for the antenna elements <NUM> have a left-hand phase shift.

In an exemplary embodiment, the antenna assembly <NUM> includes three antenna elements <NUM> spaced equidistant blade around the periphery <NUM> of the ground plane <NUM> (For example, spaced <NUM>° apart). The antenna elements <NUM> are rotated relative to each other such that the antenna elements <NUM> face in directions that are <NUM>° offset from each other. As such, the main radiation direction of each antenna element <NUM> is in a direction that is <NUM>° offset from the other antenna elements <NUM>.

In the first operation mode <NUM>, the antenna signals of each of the antenna elements <NUM> 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, the single antenna feed port <NUM> is provided at the center of the ground plane <NUM>. The transmission paths between the antenna feed port <NUM> and each of the feed points (for example, feed tab <NUM> shown in <FIG>) for the resonator elements <NUM> of the antenna elements <NUM> may have identical path lengths to avoid skew or delay along the path between the antenna elements <NUM> and the antenna feed port <NUM>. As such, the antenna signals of each of the antenna elements <NUM> are combined in-phase with each other. Due to the longer right-hand segments <NUM> of the resonator elements <NUM>, the antenna elements <NUM> are right-hand circularly polarized (RHCP) dominated. Having the plurality of antenna elements <NUM>, which are offset from each other around the ground plane <NUM>, provides an omnidirectional radiation pattern for the antenna assembly <NUM>. In an exemplary embodiment, the radiation pattern is omnidirectional in the horizontal plane. In an exemplary embodiment, the antenna assembly <NUM> has a maximum gain of -<NUM>. 2dBi (RHCP), a 3dB beamwidth of <NUM>° (RHCP), and an axial ratio within the 3dB beamwidth of less than 8dB. Changing of the size and/or shape and/or orientation of the antenna elements <NUM> and/or the ground plane <NUM> may affect the maximum gain, the 3dB beamwidth, and the axial ratio.

In the second operation mode <NUM>, the antenna signals of each of the antenna elements <NUM> are combined with a right-hand phase shift. The antenna signals are combined with delay elements to cause the phase shift. For example, the transmission paths between the antenna feed port <NUM> and the feed points for the resonator elements <NUM> of the antenna elements <NUM> may have different path lengths to intentionally induce skew or delay along the paths between the antenna elements <NUM> and the antenna feed port <NUM>. For example, a first antenna element 200a may have a normal path length, a second antenna element 200b may have a longer path length corresponding to <NUM>° phase shift from the first antenna element 200a, and a third antenna element 200c may have an even longer path length corresponding to <NUM>° phase shift from the first antenna element 200a. As such, the antenna signals of each of the antenna elements <NUM> are combined with a right-hand phase shift. Due to the longer right-hand segments <NUM> of the resonator elements <NUM>, the antenna elements <NUM> are right-hand circularly polarized (RHCP) dominated. The right-hand phase shift causes the radiation pattern to be broadside directional in a generally vertical direction. In an exemplary embodiment, the antenna assembly <NUM> has a maximum gain of <NUM>. 3dBi (RHCP), a 3dB beamwidth of <NUM>° (RHCP), and an axial ratio within 3dB beamwidth of less than 6dB. Changing of the size and/or shape and/or orientation of the antenna elements <NUM> and/or the ground plane <NUM> may affect the maximum gain, the 3dB beamwidth, and the axial ratio.

In the third operation mode <NUM>, the antenna signals of each of the antenna elements <NUM> are combined with a left-hand phase shift. The antenna signals are combined with delay elements to cause the phase shift. For example, the transmission paths between the antenna feed port <NUM> and the feed points for the resonator elements <NUM> of the antenna elements <NUM> may have different path lengths to intentionally induce skew or delay along the paths between the antenna elements <NUM> and the antenna feed port <NUM>. For example, the third antenna element 200c may have a normal path length, the second antenna element 200b may have a longer path length corresponding to <NUM>° phase shift from the third antenna element 200c, and the first antenna element 200a may have an even longer path length corresponding to <NUM>° phase shift from the third antenna element 200c. As such, the antenna signals of each of the antenna elements <NUM> are combined with a left-hand phase shift. The phase shift causes the dominant circular polarization to be left-hand circularly polarized (LHCP) dominated. The left-hand phase shift causes the radiation pattern to be broadside directional in a generally vertical direction. In an exemplary embodiment, the antenna assembly <NUM> has a maximum gain of <NUM>. 9dBi (LHCP), a 3dB beamwidth of <NUM>° (LHCP), and an axial ratio within 3dB beamwidth of less than 5dB. Changing of the size and/or shape and/or orientation of the antenna elements <NUM> and/or the ground plane <NUM> may affect the maximum gain, the 3dB beamwidth, and the axial ratio. The phase shift may be controlled by the transmission lines, such as by controlling the lengths of the transmission lines or by adding electrical components to the transmission line to cause delay and affect the phase shift. Optionally, variable phase shift circuits can be used to change the phases of the antenna elements individually, so the operation mode can change or shift between the operation modes <NUM>, <NUM>, and <NUM>.

The antenna assembly <NUM> may be periodically switched between the various operation modes, such as at intervals, such as with variable phase shift circuits. The first operation mode <NUM> may be for communication (for example, transmit and/or receive) with corresponding remote devices, such as the first and second remote devices <NUM>, <NUM> for vehicle communication, keyless entry, access control, remote control, tracking, tolling, other IoT applications, and the like. The second and third operation modes <NUM>, <NUM> may be for communication with the third remote devices <NUM>, such as satellite communication global navigation, RFID, and the like, due to the generally broadside directional radiation patterns. In various embodiments, the second operation mode <NUM> is for receiving communication signals and the third operation mode <NUM> is for transmitting communication signals, or vice versa. As such, the antenna assembly <NUM> is capable of beam steering and polarization switching for enhanced wireless communication from a single antenna assembly <NUM>. The antenna assembly <NUM> is electrically small and has a low profile and can be panel mounted to a generally flat surface without occupying considerable space above the panel. The antenna assembly <NUM> is a broad beam, circularly polarized antenna assembly. The antenna assembly <NUM> is reconfigurable, being operable as an omnidirectional antenna assembly and as an axial directional antenna assembly by switching between the various operation modes. The radiation beam direction and polarization of the antenna assembly <NUM> can be changed for different applications. The antenna assembly <NUM> is low cost compared to conventional antennas providing such advantages.

<FIG> is a chart showing antenna characteristics of the antenna assembly <NUM> operated in the first operation mode showing in-phase combination of the antenna elements <NUM>. <FIG> shows the gain radiation pattern and the axial ratio of the antenna assembly <NUM>. <FIG> shows the generally omni-directional radiation patterns in the generally horizontal direction, including the total gain radiation pattern, the RHCP gain radiation pattern, and the LHCP gain radiation pattern.

<FIG> is a chart showing antenna characteristics of the antenna assembly <NUM> operated in the second operation mode showing right-hand phase shifts of the antenna elements <NUM>. <FIG> shows the gain radiation pattern and the axial ratio of the antenna assembly <NUM>. <FIG> shows the generally broadside directional radiation patterns in the generally vertical direction, including the total gain radiation pattern, the RHCP gain radiation pattern, and the LHCP gain radiation pattern.

<FIG> is a chart showing antenna characteristics of the antenna assembly <NUM> operated in the third operation mode showing left-hand phase shifts of the antenna elements <NUM>. <FIG> shows the gain radiation pattern and the axial ratio of the antenna assembly <NUM>. <FIG> shows the generally broadside directional radiation patterns in the generally vertical direction, including the total gain radiation pattern, the RHCP gain radiation pattern, and the LHCP gain radiation pattern.

<FIG> illustrates the antenna assembly <NUM> in accordance with an exemplary embodiment. The antenna assembly <NUM> includes a reflector <NUM> below the ground plane <NUM> and the antenna elements <NUM>. The reflector <NUM> is used to tilt the maximum radiation of the antenna elements <NUM> upward by a tilt angle to change the radiation pattern from the horizontal plane to a higher azimuth angle when the antenna assembly <NUM> is operated in the first operation mode. For example, the reflector <NUM> changes the radiation pattern from an omnidirectional radiation pattern to a conical radiation pattern.

The reflector <NUM> is manufactured from a metal material. The reflector <NUM> is electrically conductive. The reflector <NUM> has an upper surface <NUM> facing the ground plane <NUM> and the antenna elements <NUM> and a lower surface <NUM> opposite the upper surface <NUM>. The reflector <NUM> has an edge <NUM> between the upper surface <NUM> and the lower surface <NUM> defining a periphery <NUM> of the reflector <NUM>. In the illustrated embodiment, the reflector <NUM> is circular; however, the reflector <NUM> may have other shapes in alternative embodiments. In an exemplary embodiment, the reflector <NUM> is a larger surface area than the ground plane <NUM>. For example, the periphery <NUM> of the reflector <NUM> is located beyond the periphery <NUM> of the ground plane <NUM>. In an exemplary embodiment, the reflector <NUM> is planar and oriented parallel to the ground plane <NUM>. However, in alternative embodiments, the reflector <NUM> may be angled relative to the ground plane <NUM>. In other alternative embodiments, the reflector <NUM> may be nonplanar, such as being dish shaped or concave. The shape of the reflector <NUM> is used to focus the antenna radiation. The reflector <NUM> is spaced apart from the ground plane <NUM> by a spacing <NUM>. The spacing <NUM> controls the tilt angle of the maximum radiation direction of the antenna elements <NUM>. Additionally, the size and/or shape of the reflector <NUM> controls the tilt angle. The reflector <NUM> has a width <NUM> greater than the width of the ground plane <NUM>. Optionally, the ground plane <NUM> may be centered over the reflector <NUM>. Alternatively, the ground plane <NUM> may be offset from the center of the reflector <NUM>, which may affect the directionality of the antenna radiation pattern.

<FIG> is a schematic illustration showing the radiation pattern of the antenna assembly <NUM> using the reflector <NUM> positioned below the ground plane <NUM> and the antenna elements <NUM>. The reflector <NUM> is used to tilt the maximum radiation of the antenna elements <NUM> upward by a tilt angle <NUM> to change the radiation pattern from the horizontal plane to a higher azimuth angle. In the illustrated embodiment, the reflector <NUM> causes the radiation pattern to be a conical radiation pattern where the maximum radiation is located a distance above the horizontal plane.

<FIG> is a chart showing various examples of the antenna assembly <NUM> with the reflector <NUM> at different spacings <NUM> from the ground plane <NUM> and the antenna elements <NUM>.

In a first example <NUM>, the reflector <NUM> is positioned a distance of <NUM> from the antenna elements <NUM>. The antenna assembly <NUM> has a maximum gain of <NUM> dBi. The maximum gain elevation angle is <NUM>°.

In a second example <NUM>, the reflector <NUM> is positioned a distance of <NUM> from the antenna elements <NUM>. The antenna assembly <NUM> has a maximum gain of <NUM> dBi. The maximum gain elevation angle is <NUM>°.

In a third example <NUM>, the reflector <NUM> is positioned a distance of <NUM> from the antenna elements <NUM>. The antenna assembly <NUM> has a maximum gain of <NUM> dBi. The maximum gain elevation angle is <NUM>°.

In a fourth example <NUM>, the reflector <NUM> is positioned a distance of <NUM> from the antenna elements <NUM>. The antenna assembly <NUM> has a maximum gain of <NUM> dBi. The maximum gain elevation angle is <NUM>°.

The antenna characteristics, such as the radiation pattern, are affected by the spacing <NUM> between the reflector <NUM> and the antenna elements <NUM>. If a higher elevation angle is desirable, the reflector <NUM> may be positioned closer to the antenna elements <NUM>. If a lower elevation angle is desirable, the reflector <NUM> may be positioned further from the antenna elements <NUM>. Other changes are possible to change the radiation pattern, such as changes in the size and/or shape of the reflector <NUM>.

Claim 1:
An antenna assembly (<NUM>) comprising:
a ground plane (<NUM>) having a periphery (<NUM>);
a plurality of antenna elements (<NUM>), each antenna element resonant at a frequency f, the antenna elements positioned generally equidistant from each other around the periphery, the plurality of antenna elements being electrically connected to a single antenna feed port (<NUM>), the antenna elements providing a generally omnidirectional radiation pattern in a first operation mode (<NUM>) in which the antenna elements (<NUM>) are connected to the antenna feed port (<NUM>) without phase shift, the antenna elements providing a right-hand circularly polarized, RHCP, broadside radiation pattern in a second operation mode (<NUM>) in which the antenna elements are connected to the antenna feed port with right-hand phase shifts, and the antenna elements providing a left-hand circularly polarized, LHCP, broadside radiation pattern in a third operation mode (<NUM>) in which the antenna elements are connected to the antenna feed port with left-hand phase shifts; and
a reflector (<NUM>) positioned below the ground plane (<NUM>) and the antenna elements (<NUM>), the reflector tilting a maximum radiation of the antenna elements upward by a tilt angle (<NUM>) in the first operation mode (<NUM>) to create a conical radiation pattern.