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US-20260126555-A1 - NON-COOPERATIVE POSITION, NAVIGATION, AND TIMING EXTRACTION FROM VSAT COMMUNICATIONS SIGNALS USING MULTI-BEAM PHASED ARRAY ANTENNA

US20260126555A1US 20260126555 A1US20260126555 A1US 20260126555A1US-20260126555-A1

Abstract

A ground antenna determines the current time and its own position from received signals that were transmitted by artificial earth satellites for communication. A high-gain multi-beam electrically-steered antenna is combined with a processing system to measure the angles between two or more satellites and determine the present distance to each satellite by the information broadcast on the TT&C channel. The knowledge of the angles and distances, as well as the trajectory of the satellites, can be combined with their locations as predicted by the satellite ephemeris data to triangulate the location of the receiver. This system is different from conventional GPS antennas because it does not require the cooperation of active communication with the satellites to derive a location estimate. The location is computed by the ground terminal, not by the satellite. This system can be used in cases where other locating services are offline, jammed, or otherwise unavailable to maintain location and time synchronization.

Inventors

  • Jeremiah P. Turpin
  • Brian Murphy BILLMAN
  • John Finney

Assignees

  • ALL.SPACE NETWORKS LIMITED

Dates

Publication Date
20260507
Application Date
20250430

Claims (20)

  1. 1 - 27 . (canceled)
  2. 28 . A satellite communication system, comprising: an electrically-steered antenna configured to receive satellite transmissions from a plurality of directions via a plurality of beams; and one or more processors configured to: direct the electrically-steered antenna to track, and receive signals from, a plurality of non-global navigation satellite system (GNSS) satellites; and determine a location of the electrically-steered antenna based on data comprising: location information of the plurality of non-GNSS satellites determined from the signals; and timing information of the signals.
  3. 29 . The satellite communication system of claim 28 , wherein the data further comprises: ephemeris information indicating a trajectory of at least one non-GNSS satellite of the plurality of non-GNSS satellites.
  4. 30 . The satellite communication system of claim 29 , wherein the one or more processors are configured to obtain the ephemeris information via terrestrial communication.
  5. 31 . The satellite communication system of claim 28 , further comprising an inertial measurement unit configured to locally track relative motion and position of the electrically-steered antenna.
  6. 32 . The satellite communication system of claim 31 , wherein the data further comprises position information of the electrically-steered antenna obtained from the inertial measurement unit.
  7. 33 . The satellite communication system of claim 28 , wherein the data further comprises: doppler information of the signals.
  8. 34 . The satellite communication system of claim 28 , wherein the timing information comprises both: a time of arrival of the signals at the electrically-steered antenna; and a transmission time of the signals from the plurality of non-GNSS satellites.
  9. 35 . The satellite communication system of claim 28 , wherein the electrically-steered antenna is a passive receiver.
  10. 36 . The satellite communication system of claim 35 , wherein the electrically-steered antenna is configured to receive the satellite transmissions from the plurality of directions simultaneously via the plurality of beams.
  11. 37 . The satellite communication system of claim 35 , wherein the electrically-steered antenna comprises a single aperture.
  12. 38 . The satellite communication system of claim 37 , wherein the electrically-steered antenna is a very small-aperture terminal antenna.
  13. 39 . The satellite communication system of claim 28 , wherein non-GNSS satellites of the plurality of non-GNSS satellites are disposed in different satellite constellations.
  14. 40 . The satellite communication system of claim 39 , wherein the non-GNSS satellites of the plurality of non-GNSS satellites are disposed in different orbits.
  15. 41 . The satellite communication system of claim 28 , wherein the signals are at least partially at a frequency above L-band.
  16. 42 . The satellite communication system of claim 28 , wherein the at least one processor is configured to determine the location of the electrically-steered antenna by: using the location information to determine: a first angle to a first non-GNSS satellite of the plurality of non-GNSS satellites; a second angle to a second non-GNSS satellite of the plurality of non-GNSS satellites; using the first angle, the second angle, and the timing information to determine: a first distance from the electrically-steered antenna to the first non-GNSS satellite; a second distance from the electrically-steered antenna to the second non-GNSS satellite; and using the first angle, the first distance, the second angle, and the second distance to calculate an estimated position of the electrically-steered antenna.
  17. 43 . A method for operating a satellite communication system including an electrically-steered antenna and one or more processors, the method comprising: directing, with the one or more processors, the electrically-steered antenna to track a plurality of non-global navigation satellite system (GNSS) satellites; receiving, with the electrically-steered antenna, signals from the plurality of non-GNSS satellites; determining, with the one or more processors, a location of the electrically-steered antenna based on data comprising: location information of the plurality of non-GNSS satellites; and timing information of the signals.
  18. 44 . The method of claim 43 , wherein determining the location of the electrically-steered antenna comprises: using the location information to determine: a first angle to a first non-GNSS satellite of the plurality of non-GNSS satellites; a second angle to a second non-GNSS satellite of the plurality of non-GNSS satellites; using the first angle, the second angle, and the timing information to determine: a first distance from the electrically-steered antenna to the first non-GNSS satellite; a second distance from the electrically-steered antenna to the second non-GNSS satellite; and using the first angle, the first distance, the second angle, and the second distance to calculate a first estimated position of the electrically-steered antenna.
  19. 45 . The method of claim 44 , wherein determining the location of the electrically-steered antenna further comprises: receiving doppler information of the signals; using the doppler information to determine at least one revised value of the first angle, the first distance, the second angle, and/or the second distance; and using the at least one revised value to calculate a second estimated position of the electrically-steered antenna.
  20. 46 . The method of claim 44 , wherein determining the location of the electrically-steered antenna further comprises: receiving ephemeris information of the plurality of non-GNSS satellites; and using the ephemeris information to determine at least one revised value of the first angle, the first distance, the second angle, and/or the second distance; and using the at least one revised value to calculate a second estimated position of the electrically-steered antenna.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a continuation claiming the benefit under 35 U.S.C. § 120 of U.S. patent application Ser. No. 18/135,520, filed Apr. 17, 2023, and entitled “NON-COPERATIVE POSITION, NAVIGATION, AND TIMING EXTRACTION FROM VSAT COMMUNICATIONS SIGNALS USING MULTI-BEAM PHASED ARRAY ANTENNA,” which is hereby incorporated by reference herein in its entirety. U.S. patent application Ser. No. 18/135,520 is a continuation claiming the benefit under 35 U.S.C. § 120 of U.S. patent application Ser. No. 16/854,442, filed Apr. 21, 2020, and entitled “NON-COOPERATIVE POSITION, NAVIGATION, AND TIMING EXTRACTION FROM VSAT COMMUNICATIONS SIGNALS USING MULTI-BEAM PHASED ARRAY ANTENNA,” which is hereby incorporated by reference herein in its entirety. U.S. patent application Ser. No. 16/854,442 claims the benefit of priority of U.S. Provisional Application No. 62/958,043, filed on Jan. 7, 2020, which is hereby incorporated by reference herein in its entirety. FIELD OF THE INVENTION The present invention relates to determining the location and time of a receiver based on signals transmitted from a satellite. BACKGROUND The Global Positioning System (GPS) and more generally Global Navigation Satellite Systems (GNSS) are in common use for civil and defence purposes worldwide. These systems use constellations of specially designed satellites, generally referred to here as GNSS satellites, to broadcast high precision dedicated GNSS signals. Those dedicated GNSS signals are structured to allow the receiver to obtain straightforward time synchronization, determine distance measurements to the receiver from each satellite in the constellation, and therefore determine the receiver's position on Earth. Such multiple GNSS satellite systems are in operation or planned for operation, including GPS (USA), Galileo (EU), GLONASS (Russia), BeiDou (China), and others. Most of these systems operate in the same or closely separated frequencies of around 1-2 GHz and are intended to interoperate to allow receivers to access multiple networks for greater accuracy and reliability. If one constellation is unavailable, another may still be accessible. GNSS systems operate in the same fundamental way. Receivers interpret signals transmitted from the satellites to determine the current time based on the GPS system epoch. That time and the structure of the signals are used to determine the distance from each satellite, which is then used to estimate a position. Dedicated GNSS signals transmit signals using CDMA (Code Division Multiple Access) techniques that allows multiple satellites to transmit at the same frequency without interfering with each other. This approach also has a benefit for very low signal-to-noise (SNR) environments, where a very long code can help to improve the SNR through signal correlation, as well as provide positive identification of the signal. The coded signals from the dedicated GNSS satellites are designed to provide precise time calibration as well as include information on the health and status of the satellite and the rest of the constellation (including orbital parameters). A conventional GNSS receiver is shown in FIG. 1, where the antenna 102 of the receiver 101 receives signals simultaneously from a number of GNSS satellites 103, 105 in one or more constellations. The signals 107, 109 from the satellites in each constellation are received by the antenna 102 and are separated and interpreted by the receiver 101 to produce the calculation of time and location of the receiver. To determine a location, a high accuracy estimate of the current time and the time of flight for the radio signals from three or more satellite locations are necessary to fix a position of the receiver in three dimensions, assuming the current time is already known to high precision. The minimum number of satellites needed to simultaneously determine the current time and the unknown position is four; four measurements (each resulting in an equation) are required to allow solving for the four unknowns—the three position variables x, y, z, and time t. Once the distances and times of the transmission start are determined for each transmitting satellite, the positions of the satellites are then computed based on their known ephemeris and the current time, and the position of the receiver can be computed by trilateration. Like all wireless communications systems, GNSS transmissions are susceptible to jamming or can even be intentionally disabled by their operators. By operating at similar bands, a jamming signal can affect all the networks simultaneously. By sharing a common architecture and frequency band, the benefits of interoperability come with the disadvantages of multiple networks potentially becoming unavailable at the same time from the same cause. For this reason, alternate Position, Navigation, and Timing (PNT) systems are desirable as backups to the GNSS systems. Alternates can include the use o