# US 10,484,029 B2 · Receiver of signals, in particular of GNSS signals, comprising an interference rejection filter, and associated method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,484,029 B2 - Document ID: US10484029B2 - Status: Granted - Kind: B2 - Application number: 16/222,998 - Filed: 2018-12-17 - Published: 2019-06-27 - Granted: 2019-11-19 - Earliest claimed: 2017-12-21 - Assignees: Thales - Applicants: Thales - Inventors: Nicolas Martin; Jean-Michel Perre; Nicolas Bastien - Web page: https://patentgrep.com/patent/US10484029B2 ## CPC - H04B 1/1036: {with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters (H04B1/123 takes precedence; filter circuits H03H)} - G01S 19/21: Interference related issues {; Issues related to cross-correlation, spoofing or other methods of denial of service} - G01S 19/37: Hardware or software details of the signal processing chain - H04B 2001/1063: {using a notch filter} - H04B: TRANSMISSION - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES ## Abstract A receiver of signals likely to be disturbed by an interfering signal, the receiver includes an interference rejection filter comprising a multiplying gain applied respectively to an in-phase channel and an in-quadrature channel of a signal received by the receiver, the value of the multiplying gain being determined by a nonlinear function Ki(ρ) of the modulus ρ of the received signal, the function Ki(ρ) being determined so as to maximize the signal-to-noise ratio after application of the multiplying gain and demodulation of the received signal. ## Claims ### Claim 1 A receiver of signals likely to be disturbed by an interfering signal, the receiver comprising an interference rejection filter comprising a multiplying gain applied respectively to an in-phase channel and to an in-quadrature channel of a signal received and digitized by the receiver, the value of the multiplying gain being determined by a nonlinear function Ki(ρ) of the modulus ρ of the received signal, the function Ki(ρ) being determined so as to maximize the signal-to-noise ratio after application of the multiplying gain and demodulation of the received signal. ### Claim 2 (depends on 1) The receiver of signals according to claim 1, wherein the nonlinear function Ki(ρ) depends on the probability density f(ρ) of the received signal, a function of the modulus ρ of the signal. ### Claim 3 (depends on 2) The receiver of signals according to claim 2, wherein the interference rejection filter comprises a unit for computing the modulus of the received signal from the in-phase channel and from the in-quadrature channel of the received signal, the multiplying gain being implemented by a memory in which are saved a plurality of values of the nonlinear function Ki(ρ), the memory having a first input linked to the output of the modulus computation unit. ### Claim 4 (depends on 2) The receiver of signals according to claim 2, wherein the multiplying gain is implemented by a memory in which are saved a plurality of values of the nonlinear function Ki(ρ), the memory having a first input intended to receive the absolute value of the in-phase channel of the signal, a second input intended to receive the absolute value of the in-quadrature channel of the signal. ### Claim 5 (depends on 2) The receiver of signals according to claim 2, further comprising an estimator of a ratio J/N between the power of an interfering signal and the power of a thermal noise, the nonlinear function Ki(ρ) depending on said ratio J/N. ### Claim 6 (depends on 5) The receiver of signals according to claim 5, wherein the estimator of a ratio between the power of an interfering signal and the power of a thermal noise comprises a unit for computing the fourth order moment of the modulus of the signal. ### Claim 7 (depends on 6) The receiver of signals according to claim 6, wherein the unit for computing the fourth order moment comprises an adder for summing the in-phase channel of the signal, raised to the power of 2, and the in-quadrature channel of the signal, raised to the power of 2, a multiplier for raising to the power of 2 the output of the adder and an averaging filter. ### Claim 8 (depends on 6) The receiver of signals according to claim 6, wherein the estimator of a ratio between the power of an interfering signal and the power of a thermal noise further comprises a member for computing the ratio between the fourth order moment of the signal and the second order moment of the signal raised to the power of 2. ### Claim 9 (depends on 8) The receiver of signals according to claim 8, comprising at least one automatic gain control device configured to control the amplitude of the received signal in accordance with a power setpoint, the second order moment of the signal being taken to be equal to the power setpoint of the automatic gain control. ### Claim 10 (depends on 5) The receiver of signals according to claim 5, wherein the probability density f(ρ) of the modulus of the received signal is determined, for a plurality of values of the ratio J/N between the power of an interfering signal and the power of a thermal noise, from the value of the amplitude of the interfering signal and from the standard deviation of the thermal noise. ### Claim 11 (depends on 5) The receiver of signals according to claim 5, wherein the interference rejection filter comprises a unit for computing the modulus of the received signal from the in-phase channel and from the in-quadrature channel of the received signal, the multiplying gain being implemented by a memory in which are saved a plurality of values of the nonlinear function Ki(ρ), the memory having a first input linked to the output of the modulus computation unit, and wherein the memory has an additional input linked to the output of the estimator of the ratio J/N. ### Claim 12 (depends on 1) The receiver of signals according to claim 1, wherein the nonlinear function Ki(ρ) depends on the ratio between the derivative f′(ρ) of the probability density of the received signal as a function of the modulus and the probability density f(ρ) of the received signal, divided by the modulus ρ of the received signal. ### Claim 13 (depends on 1) The receiver of signals according to claim 1, wherein the nonlinear function Ki(ρ) depends on an a priori estimate of a ratio J/N between the power of an interfering signal and the power of a thermal noise. ### Claim 14 (depends on 1) The receiver of signals according to claim 1, wherein the interfering signal has a constant envelope. ### Claim 15 (depends on 1) The receiver of signals according to claim 1, wherein the received signals are satellite radionavigation signals. ### Claim 16 A method for receiving signals likely to be disturbed by an interfering signal, comprising the steps of: receiving respectively an in-phase channel and an in-quadrature channel of a signal, computing a multiplying gain from a nonlinear function Ki(ρ) of the modulus ρ of the received signal, the nonlinear function Ki(ρ) being determined so as to maximize the signal-to-noise ratio after application of the multiplying gain and demodulation of the received signal, applying the multiplying gain respectively to the in-phase channel and to the in-quadrature channel of the digitized signal. ### Claim 17 (depends on 16) The method for receiving signals according to claim 16, wherein the nonlinear function Ki(ρ) depends on the probability density f(ρ) of the received signal, a function of the modulus ρ of the signal. ### Claim 18 (depends on 16) The method for receiving signals according to claim 16, wherein the nonlinear function Ki(ρ) depends on the ratio between the derivative f′(ρ) of the probability density of the received signal and the probability density f(ρ) of the received signal, divided by the modulus ρ of the received signal. ### Claim 19 (depends on 16) The method for receiving signals according to claim 16, further comprising a step of estimation of a ratio J/N between the power of an interfering signal and the power of a thermal noise, the nonlinear function Ki(ρ) depending on said ratio J/N.