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US-12625277-B1 - Antenna systems for circularly polarized radio signals

US12625277B1US 12625277 B1US12625277 B1US 12625277B1US-12625277-B1

Abstract

Antenna systems for receiving right and left hand circularly polarized signals are disclosed. An antenna system embodiment includes a top printed circuit board (PCB), a ground plane, and an antenna array including four conductive antenna elements positioned at relative zero, 90, 180, and 270 degree increments radially about a shared center point on the PCB, with each antenna element sloping upward in a left-handed direction from the ground plane towards the top PCB and connected to the ground plane and top PCB.

Inventors

  • Stephanie M. Bench
  • Mark S. Olsson
  • Ray Merewether

Assignees

  • SeeScan, Inc.

Dates

Publication Date
20260512
Application Date
20240215

Claims (18)

  1. 1 . An antenna system, comprising: an antenna array having multiple antenna elements generating input signals successively 90 degrees out of phase such that the input signals have a relative phase of zero, 90, 180, and 270 degrees, wherein the antenna array comprises four conductive elongate antenna elements positioned at relative zero, 90, 180, and 270 degree increments radially about a shared center point on a printed circuit board (PCB), with each antenna element sloping upward in a left-handed direction from a ground plane towards the PCB and connected to the ground plane and the PCB.
  2. 2 . The antenna system of claim 1 , further comprising a transmission line connecting the antenna elements at zero degrees to the antenna element at 90 degrees wherein the length of the transmission line generates a 90 degree phase shift aligning the phase of the input signal at zero degrees to the phase of the input signal at 90 degrees; a transmission line connecting the antenna elements at 180 degrees to the antenna element at 270 degrees wherein the length of the transmission line generates a 90 degree phase shift aligning the phase of the input signal at 180 degrees to the phase of the input signal at 270 degrees; a first transformer to receive signal from the 90 degree antenna elements and output a signal having no phase adjustment; a second transformer to receive signal from the 270 degree antenna elements and output a signal having an 180 degree phase adjustment that aligns with the phase of the first transformer output; and a coupling of the first and second transformers such that their outputs generate a combined, phase aligned output signal.
  3. 3 . The antenna system of claim 2 , wherein the antenna array comprises four conductive elongate antenna elements positioned at relative zero, 90, 180, and 270 degree increments radially about a shared center point on the PCB, with each antenna element sloping upward in a left-handed direction from the ground plane towards the PCB and connected to the ground plane and PCB.
  4. 4 . The antenna system of claim 2 , wherein the turns ratio of the first and second transformers controls for a target resistance.
  5. 5 . A multi-band navigation signal system, comprising: a single antenna to receive satellite navigation signals; and two or more satellite navigation receiver modules to receive satellite signals of different bands wherein all receiver modules are coupled to the single antenna, wherein the antenna is the antenna system of claim 1 .
  6. 6 . The multi-band navigation signal system of claim 5 , wherein the ground plane is circular.
  7. 7 . The multi-band navigation signal system of claim 5 , wherein the satellite navigation receiver modules include the L1, L2, and L5 bands.
  8. 8 . An antenna system, comprising: an antenna array having multiple antenna elements generating input signals successively 90 degrees out of phase such that the input signals have a relative phase of zero, 90, 180, and 270 degrees; a pair of 90 degree phase shifting elements wherein each phase shifting element is coupled to a pair of antenna elements in the antenna array to receive their associate input signals, shift the phase on one signal 90 degree to match that of its paired antenna element's signal, and output a combined signal 180 degree out of phase to that of the output signal of the other 90 degree phase shifting element; and a pair of low noise amplifiers, each coupled to a corresponding 90 degree phase shifting element to amplify the combined output signal of the corresponding phase shifting element and to isolate impedance differences the two 180 degree out of phase combined output signals.
  9. 9 . The antenna system of claim 8 , comprising: a first transformer element comprising a first inductor coupled to both low noise amplifiers that outputs right-hand circularly polarized signals at a second inductor, and a second transformer element comprising a first inductor and a second transformer wherein the first inductor is center tapped off the first inductor of the first transformer element and takes common mode signals and outputs left-hand circularly polarized signals at the second inductor.
  10. 10 . The antenna system of claim 8 , wherein the antenna array comprises four conductive elongate antenna elements positioned at relative zero, 90, 180, and 270 degree increments radially about a shared center point on a PCB, with each antenna element sloping upward in a left-handed direction from a ground plane towards the PCB and connected to the ground plane and the PCB.
  11. 11 . The antenna system of claim 10 , further including a top connector element of conductive material connecting the antenna elements at zero and 180 degrees and the antenna elements at 90 and 270 degrees along the PCB.
  12. 12 . The antenna system of claim 10 , wherein beam width control, bandwidth, and left-hand and right-hand signal ratio are adjusted based on a predefined slope angles and lengths of the antenna elements and dimensions of the ground plane.
  13. 13 . The antenna system of claim 10 , wherein the ground plane is circular in shape.
  14. 14 . The antenna system of claim 10 , wherein the PCB is circular in shape.
  15. 15 . The antenna system of claim 10 , further including an output terminal disposed on the ground plane.
  16. 16 . The antenna system of claim 8 , further comprising an impedance matching network coupled to the antenna array such that the impedance of the input signals at each antenna element matches that of the other antenna elements.
  17. 17 . The antenna system of claim 8 , wherein the antenna elements are elongate conductors each having a length of 40 approximately 38.62 mm and a slope angle of approximately 117 degrees.
  18. 18 . The antenna system of claim 8 , wherein the antenna is tuned for a frequency range spanning the lower L-band and upper L-band Global Navigation Satellite System (GNSS) navigational frequencies.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority under 35 U.S.C. § 119 (e) to U.S. Provisional Patent Application Ser. No. 62/899,296, entitled ANTENNA SYSTEMS FOR CIRCULARLY POLARIZED RADIO SIGNALS, filed on Sep. 12, 2019, the content of which is hereby incorporated by reference herein in its entirety for all purposes. This application is a continuation of U.S. patent application Ser. No. 17/020,487, filed Sep. 14, 2020, now U.S. Pat. No. 11,921,225. FIELD This disclosure relates generally to antennas and antenna systems for receiving circularly polarized signals. More specifically, but not exclusively, this disclosure relates to antennas and antenna systems for receiving circularly polarized signals for satellite navigation systems. BACKGROUND In wireless telecommunications, an unobstructed clear path between a transmitter and receiver is generally favorable to ensure communication of radio signals. In many instances, an unobstructed clear path is not possible or practical, thus causing transmitted signals to either fail to reach the receiver due to attenuation or, in some cases, reflect or refract off surfaces prior to reaching the receiver. Multipath signals resulting from such reflecting or refracting may introduce undesirable errors at the receiver due to changes in the signal's phase, amplitude, timing delays, and the like. Wherein the transmitted signal is circularly polarized, a multipath circularly polarized signal may be identified by a change in handedness. For instance, global positioning systems (GPS) as well as other global navigation satellite systems (GNSS) may include a network of satellites configured to all transmit right-hand circularly polarized (RHCP) signals. In instances where the RHCP signals reflect or refract off surfaces, a change in handedness may occur, resulting in left-hand circularly polarized (LHCP) signals which may be subject to various multipath errors. These multipath errors may dramatically impact performance and accuracy. There are various antennas and associated systems known in the art that attempt to correct for such multipath errors. For example, antennas and associated systems configured to receive and process circularly polarized signals may generally address multipath errors by attempting to cancel or otherwise reduce LHCP signals. However, existing antennas and systems result in suboptimal performance of associated GNSS or other devices. Accordingly, there is a need in the art to address these and other problems in the field of reception of GNSS and other circularly polarized radio signals, as well as other radio transmission and reception problems. SUMMARY This disclosure relates generally to antennas and antenna systems for receiving circularly polarized signals. More specifically, but not exclusively, this disclosure relates to antennas and antenna systems for receiving circularly polarized signals from navigation satellites. In one aspect, the present disclosure includes an antenna system having a top printed circuit board (PCB) and a ground plane with an antenna array comprising a series of conductive antenna elements disposed in between the top PCB and ground plane. The antenna elements may be positioned at relative zero, 90, 180, and 270 degree increments radially about a shared center point. Each antenna element may slope upward in a left-handed direction connecting from the ground plane and further slope toward the top PCB. In another aspect, the present disclosure includes an antenna system comprising an antenna array having multiple antenna elements generating input signals successively 90 degrees out of phase such that the input signals have a relative phase of zero, 90, 180, and 270 degrees. The antenna system further comprises an impedance matching network coupled to the antenna array such that the impedance of the input signals at each antenna element matches that of the other antenna elements. The antenna system further comprises a pair of 90 degree phase shifting elements wherein each phase shifting element is coupled to a pair of antenna elements in the antenna array to receive their associated input signals, shift the phase on one signal 90 degrees to match that of its paired antenna element's signal, and output a combined signal 180 degrees out of phase to that of the output signal of the other 90 degree phase shifting element. A low noise amplifier may be coupled to each 90 degree phase shifting element to amplify the combined output signal and isolate impedance differences in the 180 degree out of phase output signals. The antenna system further comprises a first transformer element and second transformer element. The first transformer element comprising a first inductor coupled to both low noise amplifiers that outputs right-hand circularly polarized signals at a second inductor. The second transformer element comprising a first inductor and second inductor. The first inductor of the second transformer element ma