Abstract: Signals L1CA, L1P, L2P and L2C transmitted by a GPS satellite are received and the carrier phases ?LCA and ?L2C are estimated from L1CA and L2C. The cross-correlation P between the downconverted signals L1P and L2P is determined, taking into account the delay between signals. The sign of P is used to enable direct determination of the half-cycle ambiguity AL1CA of the L1CA signal. In some examples, this is done by downconverting the L2P signal by a replica having a phase derived from ?L2C, instead of determining the phase of the L2P replica by a tracking loop, enabling determination of AL1CA directly from the sign of P. In some examples, the phase ?L2P of the L2P replica is determined by a tracking loop, and the half-cycle ambiguity AL1CA is determined based on the sign of P and on the difference between the carrier phases ?L2P and ?L2C.

Abstract: A method is disclosed for detecting a disturbance in a signal of a GNSS satellite. The method includes receiving from the GNSS satellite a first signal and a second signal having a carrier frequency different from a carrier frequency of the first signal; measuring a carrier phase difference between the first signal and the second signal and between different epochs; determining an ionosphere delay rate; determining a first indicator; and detecting the disturbance based on the first indicator meeting a predetermined requirement. The first indicator is determined by a first Kalman filter. A quadratic expression given by ½(??12+??r?t)2, wherein ??12 represents the measured carrier phase difference and ?r represents the ionosphere delay rate, is used in the first Kalman filter as an observable.

Abstract: The application pertains to a method for determining a phase of a target data carrier in a GNSS system, the method comprising: in an initialization phase: determining, at a first point in time, a bias term of a synthetic carrier phase function constructed to mimic a phase of the target data carrier; and in an operational phase: using said bias term determined in said initialization phase, obtaining a value of the synthetic carrier phase function, said value corresponding to a second point in time; and comparing a measured phase of the target data carrier at the second point in time to said value to assess the presence or absence of a half-cycle phase discrepancy; wherein said synthetic carrier phase function is constructed to mimic said phase of said target data carrier at points in time subsequent to said first point in time without requiring readjustment of said determined bias term.

Abstract: The invention pertains to a method for recreating unavailable measurements in a GNSS system by producing at least one GNSS parameter estimate Formula (I) at a target carrier frequency (fk), the method comprising at least one of: deriving (1030), from one or more available pseudorange measurements (Pi) at respective other carrier frequencies (fi), a pseudorange estimate Formula (II) at said target carrier frequency (fk) and deriving (1040), from said one or more available pseudorange measurements (Pi) and one or more available carrier phase measurements (?i) at said respective other carrier frequencies (fi), a carrier phase estimate Formula (III) at said target carrier frequency (fk).

Abstract: The application pertains to a method for determining a phase of a target data carrier in a GNSS system, the method comprising: in an initialization phase: determining, at a first point in time, a bias term of a synthetic carrier phase function constructed to mimic a phase of the target data carrier; and in an operational phase: using said bias term determined in said initialization phase, obtaining a value of the synthetic carrier phase function, said value corresponding to a second point in time; and comparing a measured phase of the target data carrier at the second point in time to said value to assess the presence or absence of a half-cycle phase discrepancy; wherein said synthetic carrier phase function is constructed to mimic said phase of said target data carrier at points in time subsequent to said first point in time without requiring readjustment of said determined bias term.

Abstract: 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.

Abstract: 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.

Abstract: The invention pertains to a method for recreating unavailable measurements in a GNSS system by producing at least one GNSS parameter estimate Formula (I) at a target carrier frequency (fk), the method comprising at least one of: deriving (1030), from one or more available pseudorange measurements (Pi) at respective other carrier frequencies (fi), a pseudorange estimate Formula (II) at said target carrier frequency (fk) and deriving (1040), from said one or more available pseudorange measurements (Pi) and one or more available carrier phase measurements (?i) at said respective other carrier frequencies (fi), a carrier phase estimate Formula (III) at said target carrier frequency (fk).

Abstract: A receiver for satellite navigation includes a signal processor for deriving from a satellite signal a pseudorandom sequence of code chips, a converter for producing a digitized version of the received PRN sequence, a first and second shift register (3, 7), a code generator (4), a set of correlators, circuitry for summing correlation values and circuitry for determining a maximum of the summed correlation, and a scheduler (20). The receiver includes at least one multiplexer (6, 24), configured to transform multiple PRN sequences into an interleaved sequence and to enter the interleaved sequence into the first or second shift register (3, 7). The summing circuitry has multiple summing circuits (11) for separately summing correlation values related to the multiple PRN sequences. The circuitry for determining a maximum is configured to determine the maximum in one or more subgroups of sums determined by the multiple summing circuits (11).

Abstract: The present invention is related to a method and apparatus for processing a signal sent by a transmitter to a receiver, in particular for ranging applications. The signal is typically sent by a satellite, and comprises a carrier signal, modulated by at least one pseudo random noise code and a navigation signal. The method of the invention comprises a step of estimating the multipath error at each calculation of the range. The estimation is done by a multipath estimator module (23) on the basis of a predefined formula, said formula being a linear combination of said correlation values. Said formula is based on the calculation of at least four correlation values between at least four different versions of the PRN code and the PRN encoded signal sent by the transmitter. All except two of the coefficients used in the linear combination may be set to zero.

Abstract: The present invention is related to a method and apparatus for processing a signal sent by a transmitter to a receiver, in particular for ranging applications. The signal is typically sent by a satellite, and comprises a carrier signal, modulated by at least one pseudo random noise code and a navigation signal. The method of the invention comprises a step of estimating the multipath error at each calculation of the range. The estimation is done by a multipath estimator module (23) on the basis of a predefined formula, said formula being a linear combination of said correlation values. Said formula is based on the calculation of at least four correlation values between at least four different versions of the PRN code and the PRN encoded signal sent by the transmitter. All except two of the coefficients used in the linear combination may be set to zero.