# US 12,007,472 B2 · Adaptive hybrid tracking algorithms for radio signal parameters estimations > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,007,472 B2 - Document ID: US12007472B2 - Status: Granted - Kind: B2 - Application number: 18/338,662 - Filed: 2023-06-21 - Published: 2023-10-19 - Granted: 2024-06-11 - Earliest claimed: 2020-01-21 - Assignees: The Regents of the University of Colorado - Applicants: The Regents of the University of Colorado - Inventors: Yang Wang; Yu T. Morton - Web page: https://patentgrep.com/patent/US12007472B2 ## CPC - G01S 13/89: for mapping or imaging - G01S 19/39: the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO - G01S 7/354: {Extracting wanted echo-signals (Doppler systems G01S13/50)} - G01S 13/003: {Bistatic radar systems; Multistatic radar systems} - G01S 19/22: Multipath-related issues - 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 digital direct line-of-sight (DLOS) intermediate frequency (IF) signal of a DLOS component of an RF carrier signal transmitted by a transmitter located above the surface of the earth and a digital reflected IF signal of a reflected component of the carrier signal that is reflected from a specular point (SP) on the surface of the earth are received. Modeled reference signal parameters are generated using the digital DLOS IF signal and known locations of one or more receiving antennas, the transmitter, and the SP. A reference signal is generated based on the modeled reference signal parameters and feedback of a previously estimated Δϕ. The reference signal is correlated with the digital reflected IF signal to produce in-phase (I) and quadrature-phase (Q) correlation results. An estimated C/N0 and an estimated Δϕ for the digital reflected IF signal are calculated from the correlation results. ## Claims ### Claim 1 A system for tracking a carrier-to-noise ratio (C/N0) and a phase correction (Δϕ) of a reflected radio frequency (RF) carrier signal, comprising: one or more processors that receive a digital direct line-of-sight (DLOS) intermediate frequency (IF) signal of a DLOS component of an RF carrier signal transmitted by a transmitter located above the surface of the earth and a digital reflected IF signal of a reflected component of the carrier signal that is reflected from a specular point (SP) on the surface of the earth, generate modeled reference signal parameters using the digital DLOS IF signal and known locations of one or more receiving antennas, the transmitter, and the SP, generate a reference signal based on the modeled reference signal parameters and feedback of a previously estimated Δϕ, correlate the reference signal with the digital reflected IF signal to produce in-phase (I) and quadrature-phase (Q) correlation results, and calculate an estimated C/N0 and an estimated Δϕ for the digital reflected IF signal from the correlation results. ### Claim 2 (depends on 1) The system of claim 1, wherein the one or more receiving antennas comprise a first antenna to receive the DLOS component and a second antenna to receive the reflected component. ### Claim 3 (depends on 1) The system of claim 1, wherein the one or more processors further calculate a centimetric height at the SP from the estimated Δϕ. ### Claim 4 (depends on 1) The system of claim 1, wherein the carrier signal comprises a global navigation satellite system (GNSS) carrier signal and the locations of the one or more receiving antennas, the transmitter, and the SP are determined from information carried by the GNSS carrier signal. ### Claim 5 (depends on 1) The system of claim 1, wherein the carrier signal comprises a carrier signal of a communications system and the locations of the one or more receiving antennas, the transmitter, and the SP are determined from information transmitted separately from ground stations of the communications system. ### Claim 6 (depends on 1) The system of claim 1, wherein the feedback of a previously estimated Δϕ comprises a state vector and the reference signal is generated based on the modeled reference signal parameters and the state vector. ### Claim 7 (depends on 6) The system of claim 6, wherein the state vector is estimated using a filter. ### Claim 8 (depends on 7) The system of claim 7, wherein the filter comprises a Kalman filter. ### Claim 9 (depends on 7) The system of claim 7, wherein the filter comprises a proportional integral filter. ### Claim 10 (depends on 7) The system of claim 7, wherein the filter comprises a Weiner filter. ### Claim 11 (depends on 8) The system of claim 8, wherein the one or more processors further eliminate noise in the estimated Δϕ by adjusting parameters of the filter based on the estimated C/N0 and the estimated Δϕ. ### Claim 12 (depends on 11) The system of claim 11, wherein the one or more processors further adjust the parameters of the filter based on an empirical phase noise model. ### Claim 13 (depends on 1) The system of claim 1, wherein the one or more processors calculate the estimated C/N0 and the estimated Δϕ in real-time. ### Claim 14 A method for tracking carrier-to-noise ratio (C/N0) and a phase correction (Δϕ) of a reflected radio frequency (RF) carrier signal, comprising: receiving a digital direct line-of-sight (DLOS) intermediate frequency (IF) signal of a DLOS component of an RF carrier signal transmitted by a transmitter located above the surface of the earth and a digital reflected IF signal of a reflected component of the carrier signal that is reflected from a specular point (SP) on the surface of the earth; generating modeled reference signal parameters using the digital DLOS IF signal and known locations of one or more receiving antennas, the transmitter, and the SP; generating a reference signal based on the modeled reference signal parameters and feedback of a previously estimated Δϕ; correlating the reference signal with the digital reflected IF signal to produce in-phase (I) and quadrature-phase (Q) correlation results; and calculating an estimated C/N0 and an estimated Δϕ for the digital reflected IF signal from the correlation results. ### Claim 15 (depends on 14) The method of claim 14, wherein the one or more receiving antennas comprise a first antenna to receive the DLOS component and a second antenna to receive the reflected component. ### Claim 16 (depends on 14) The method of claim 14, further comprising calculating a centimetric height at the SP from the estimated Δϕ. ### Claim 17 (depends on 14) The method of claim 14, wherein the carrier signal comprises a global navigation satellite system (GNSS) carrier signal and the locations of the one or more receiving antennas, the transmitter, and the SP are determined from information carried by the GNSS carrier signal. ### Claim 18 (depends on 14) The method of claim 14, wherein the carrier signal comprises a carrier signal of a communications system and the locations of the one or more receiving antennas, the transmitter, and the SP are determined from information transmitted separately from ground stations of the communications system. ### Claim 19 (depends on 14) The method of claim 14, wherein the feedback of a previously estimated Δϕ comprises a state vector and the reference signal is generated based on the modeled reference signal parameters and the state vector. ### Claim 20 A computer program product, comprising a non-transitory and tangible computer-readable storage medium whose contents include a program with instructions being executed on a processor to perform a method for tracking a carrier-to-noise ratio (C/N0) and a phase correction (Δϕ) of a reflected radio frequency (RF) carrier signal, the method comprising: providing a system, wherein the system comprises one or more distinct software modules, and wherein the distinct software modules comprise a signal parameter modeling module, a reference generator, a correlator, and an estimator; receiving a digital direct line-of-sight (DLOS) intermediate frequency (IF) signal of a DLOS component of an RF carrier signal transmitted by a transmitter located above the surface of the earth and a digital reflected IF signal of a reflected component of the carrier signal that is reflected from a specular point (SP) on the surface of the earth using the signal parameter modeling module; generating modeled reference signal parameters using the digital DLOS IF signal and known locations of one or more receiving antennas, the transmitter, and the SP using the signal parameter modeling module; generating a reference signal based on the modeled reference signal parameters and feedback of a previously estimated Δϕ using the reference generator; correlating the reference signal with the digital reflected IF signal to produce in-phase (I) and quadrature-phase (Q) correlation results using the correlator; and calculating an estimated C/N0 and an estimated Δϕ for the digital reflected IF signal from the correlation results using the estimator.