An assisted satellite positioning system based on detecting signals from a number of satellites includes: (a) a mobile receiver; and (b) a base station communicating with the receiver over a low-power wireless communication network, the base station providing ephemeris data of a selected number of the satellites, but not all, using a compressed data format. The ephemeris data may include data concerning doppler frequency variations or elevation variations of the selected satellites over a predetermined time interval. The doppler frequency variations and the elevation variations may be represented in the compressed format by coefficients of a polynomial function of time. The polynomial function may be weighted to have lesser relative errors in larger doppler frequencies than lesser doppler frequencies, or to have lesser relative errors in lesser elevations than larger elevations. In one implementation, the low-power wireless communication network—such as a LoRa network—that has a range of at least 10 miles.

An assisted satellite positioning system based on detecting signals from a number of satellites includes: (a) a mobile receiver; and (b) a base station communicating with the receiver over a low-power wireless communication network, the base station providing ephemeris data of a selected number of the satellites, but not all, using a compressed data format. The ephemeris data may include data concerning doppler frequency variations or elevation variations of the selected satellites over a predetermined time interval. The doppler frequency variations and the elevation variations may be represented in the compressed format by coefficients of a polynomial function of time. The polynomial function may be weighted to have lesser relative errors in larger doppler frequencies than lesser doppler frequencies, or to have lesser relative errors in lesser elevations than larger elevations. In one implementation, the low-power wireless communication network—such as a LoRa network—that has a range of at least 10 miles.

A GNSS antenna 26 and an inertial measurement unit 25 are placed at a longitudinal center of a unit base 55 mountable onto a work vehicle. A wireless communication unit 27 is placed at the longitudinal one end side of the unit base 55. A wireless communication antenna 28 of the wireless communication unit 27 is placed in a front part of the unit base 55, which is located on the front side of a vehicle body when the unit base 55 is mounted on the work vehicle. The GNSS antenna 26 is provided above the inertial measurement unit 25.

A GNSS antenna 26 and an inertial measurement unit 25 are placed at a longitudinal center of a unit base 55 mountable onto a work vehicle. A wireless communication unit 27 is placed at the longitudinal one end side of the unit base 55. A wireless communication antenna 28 of the wireless communication unit 27 is placed in a front part of the unit base 55, which is located on the front side of a vehicle body when the unit base 55 is mounted on the work vehicle. The GNSS antenna 26 is provided above the inertial measurement unit 25.

The invention pertains to a method for operating a GNSS receiver in the presence of spoofed signals, the GNSS receiver having a plurality of satellite signal receive chains with a low associated antenna envelope correlation coefficient, the method comprising: receiving signals from said plurality of satellite signal receive chains; obtaining (1010) relative amplitude and phase values of respective signals as provided by a pair of satellite signal receive chains from among said plurality of satellite signal receive chains; clustering (1020) said received signals on the basis of said monitored relative amplitude and phase values; and asserting (1040) a spoofing detection state when said clustering reveals a cluster of signals exhibiting similar relative amplitude and phase values over a predetermined time frame (1030). The invention also pertains to a GNSS receiver.

The invention pertains to a method for operating a GNSS receiver in the presence of spoofed signals, the GNSS receiver having a plurality of satellite signal receive chains with a low associated antenna envelope correlation coefficient, the method comprising: receiving signals from said plurality of satellite signal receive chains; obtaining (1010) relative amplitude and phase values of respective signals as provided by a pair of satellite signal receive chains from among said plurality of satellite signal receive chains; clustering (1020) said received signals on the basis of said monitored relative amplitude and phase values; and asserting (1040) a spoofing detection state when said clustering reveals a cluster of signals exhibiting similar relative amplitude and phase values over a predetermined time frame (1030). The invention also pertains to a GNSS receiver.

A demodulator comprises a first-stage carrier demodulator and a second-stage carrier demodulator. The first-stage carrier demodulator is configured to remove or compensate for the tracking error in the baseband signal, where the tracking error comprises aggregate, channel tracking error of carrier phase for the same received band, sub-band, (baseband) GNSS satellite channel, or set GNSS channels. The second stage carrier demodulator is configured to remove or strip a carrier signal component without any unwanted image or carrier-related frequency artifacts and to prepare for correlation-based decoding or demodulation of the encoded baseband signal by the correlators. First correlators are configured to determine correlations for code phase tracking loop, where the code phase tracking loop is configured to estimate a corresponding code error component of the tracking error for the code local oscillator for a respective channel. Secondary correlators are configured to determine correlations for a carrier phase tracking loop, where the carrier phase tracking loop configured to estimate a corresponding aggregate feedback error for multiple channels or a set of channels.

A system for identifying spoofed navigation signals includes a multi-element antenna configured to receive a plurality of navigation signals. The system also includes at least one processor configured to determine an angle of arrival for each of the navigation signals and analyze the angles of arrival for the navigation signals to determine whether one or more of the navigation signals are spoofed. To analyze the angles of arrival for the navigation signals, the at least one processor may be configured to (i) determine whether two or more of the navigation signals were received at substantially the same angle of arrival (which may be based on a difference of less than 5° between the angles of arrival) and/or (ii) compare the angles of arrival for the navigation signals to at least one expected angle of arrival (which may be based on information about expected or actual positions of multiple satellites).

A multibeam Radio Frequency (RF) lens antenna is designed as a receiver for Global Navigation Satellite System (GNSS) applications, such as GPS (Global Positioning System), Galileo, GLONASS, COMPASS, and others. The RF lens and plurality of associated feed elements and receiver circuits combine to form a plurality of resulting high-gain relatively narrow beams that, taken together, allow reception of signals from GNSS satellites over the entire upper hemisphere. Any kind of RF lens can be used, where the lens can be of homogeneous or inhomogeneous, dielectric or metamaterial/metasurface construction. The benefit of this approach to build a GNSS receiver over existing alternatives is increased gain and decreased noise at each receiver, which improves the signal to noise ratio (SNR) and improves the accuracy and reliability of the position and time measurements, while also reducing the impact of, and sensitivity to, interference, jamming, and spoofing signals. The approaches described in this patent can be combined with existing signal processing and accuracy improvement methods (such as Real-Time Kinematic (RTK), Precise-Point Positioning (PPP), and Differential GPS (DEPS)) for further benefits. This system has applications within the surveying, maritime, land mobility, aerospace, and government positioning market areas.

The present invention provides an autonomous traveling work machine that can accurately receive positioning signals from navigation satellites and autonomously travel without deviating from a traveling path, even in the case of an inclined slope. The autonomous traveling work machine includes a traveling machine body, a positioning receiver that receives positioning signals from navigation satellites, an autonomous traveling control device that performs control for autonomous traveling along traveling paths based on the positioning signals, an inclination detection unit that detects the inclination of the traveling machine body and outputs inclination angle information, an inclination angle determination unit that determines an inclination angle based on the inclination angle information, and a rotation control mechanism that rotates the positioning receiver with one or more degrees of freedom. The rotation control mechanism keeps the positioning receiver horizontal based on the inclination angle.