# US 7,466,775 B2 · Method and apparatus for accurately detecting validity of a received signal > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,466,775 B2 - Document ID: US7466775B2 - Status: Granted - Kind: B2 - Application number: 10/683,062 - Filed: 2003-10-10 - Published: 2005-04-14 - Granted: 2008-12-16 - Earliest claimed: 2002-03-21 - Assignees: ViXS Systems, Inc. - Inventors: Paul Morris Astrachan - Web page: https://patentgrep.com/patent/US7466775B2 ## CPC - H04L 7/042: {Detectors therefor, e.g. correlators, state machines (digital correlators in general G06F17/15)} - H03D 7/161: {all the frequency changers being connected in cascade} - H04L 7/0041: {Delay of data signal} - H04L 7/007: {detection of error based on maximum signal power, e.g. peak value, maximizing autocorrelation} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H03D: DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER (masers, lasers H01S; circuits capable of acting both as modulator and demodulator H03C; details applicable to both modulators and frequency-changers H03C; demodulating pulses H03K9/00; transforming types of pulse modulation H03K11/00; coding, decoding or code conversion, in general H03M; repeater stations H04B7/14; demodulators adapted for AC systems of digital information transmission H04L27/00; synchronous demodulators adapted for colour television H04N9/66) ## Abstract A method for detecting validity of a received signal begins by performing an auto-correlation on the received signal to produce an auto-correlation resultant. The process continues by performing a cross-correlation on the receive signal with a reference signal to produce a cross-correlation resultant. The process then continues by mathematically relating the auto-correlation resultant with the cross-correlation resultant to produce a mathematical correlation relationship. The process then proceeds by interpreting the mathematical correlation relationship to indicate whether the receive signal is valid or not. ## Claims ### Claim 1 A method for accurately detecting validity of a received signal, the method comprises: performing an autocorrelation on the received signal to produce an autocorrelation resultant; performing a cross correlation of the received signal with a reference signal to produce a cross correlation resultant; mathematically relating the autocorrelation resultant with the cross correlation resultant to produce a mathematical correlation relationship; and interpreting the mathematical correlation relationship to indicate whether the received signal is valid or invalid. ### Claim 2 (depends on 1) The method of claim 1, wherein the performing the autocorrelation on the received signal further comprises: delaying the received signal by period of a valid signal to produce a delayed signal; correlating the received signal with the delayed signal to produce a correlated signal; and determining a moving average that represents energy of the correlated signal. ### Claim 3 (depends on 1) The method of claim 1, wherein the mathematically relating the autocorrelation resultant further comprises: determining a reference autocorrelation level based on a fixed length of the autocorrelation of a known input; normalizing the autocorrelation resultant with reference to the reference autocorrelation to produce a normalized autocorrelation resultant; scaling a ratio of the cross correlation resultant and the autocorrelation resultant based on the normalized autocorrelation resultant to produce the mathematical correlation relationship. ### Claim 4 (depends on 3) The method of claim 3, wherein the interpreting the mathematical correlation relationship further comprises: comparing the mathematical correlation relationship with a difference threshold; when the comparison of the mathematical correlation relationship to the difference threshold is favorable, indicating that the received signal is valid; and when the comparison of the mathematical correlation relationship to the difference threshold is unfavorable, indicating that the received signal is not valid. ### Claim 5 (depends on 1) The method of claim 1, wherein the mathematically relating the autocorrelation resultant with the cross correlation resultant further comprises: autocorr refcorr ⁢ ( xcorr autocorr ) > K wherein the autocorr corresponds to the autocorrelation resultant, the refcorr corresponds to a reference autocorrelation, the xcorr corresponds to the cross correlation resultant, and the K corresponds to a valid signal threshold. ### Claim 6 (depends on 5) The method of claim 5 further comprises: determining the reference autocorrelation based on a fixed length of the autocorrelation of a known input. ### Claim 7 An apparatus for accurately detecting validity of a received signal, the apparatus comprises: processing module; and memory operably coupled to the processing module, wherein the memory includes operational instructions that cause the processing module to: perform an autocorrelation on the received signal to produce an autocorrelation resultant; perform a cross correlation of the received signal with a reference signal to produce a cross correlation resultant; mathematically relate the autocorrelation resultant with the cross correlation resultant to produce a mathematical correlation relationship; and interpret the mathematical correlation relationship to indicate whether the received signal is valid or invalid. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein the memory further comprises operational instructions that cause the processing module to perform the autocorrelation on the received signal by: delaying the received signal by period of a valid signal to produce a delayed signal; correlating the received signal with the delayed signal to produce a correlated signal; and determining a moving average that represents energy of the correlated signal. ### Claim 9 (depends on 7) The apparatus of claim 7, wherein the memory further comprises operational instructions that cause the processing module to mathematically relate the autocorrelation resultant by: determining a reference autocorrelation level based on a fixed length of the autocorrelation of a known input; normalizing the autocorrelation resultant with reference to the reference autocorrelation to produce a normalized autocorrelation resultant; scaling a ratio of the cross correlation resultant and the autocorrelation resultant based on the normalized autocorrelation resultant to produce the mathematical correlation relationship. ### Claim 10 (depends on 9) The apparatus of claim 9, wherein the memory further comprises operational instructions that cause the processing module to interpret the mathematical correlation relationship by: comparing the mathematical correlation relationship with a difference threshold; when the comparison of the mathematical correlation relationship to the difference threshold is favorable, indicating that the received signal is valid; and when the comparison of the mathematical correlation relationship to the difference threshold is unfavorable, indicating that the received signal is not valid. ### Claim 11 (depends on 7) The apparatus of claim 7, wherein the memory further comprises operational instructions that cause the processing module to mathematically relate the autocorrelation resultant with the cross correlation resultant by: autocorr refcorr ⁢ ( xcorr autocorr ) > K wherein the autocorr corresponds to the autocorrelation resultant, the refcorr corresponds to a reference autocorrelation, the xcorr corresponds to the cross correlation resultant, and the K corresponds to a valid signal threshold. ### Claim 12 (depends on 11) The apparatus of claim 11, wherein the memory further comprises operational instructions that cause the processing module to: determine the reference autocorrelation based on a fixed length of the autocorrelation of a known input. ### Claim 13 A radio receiver comprises: low noise amplifier operably coupled to amplify a radio frequency (RF) signal to produce an amplified RF signal; down conversion module operably coupled to convert the amplified RF signal into a baseband signal; data recovery module operably coupled to recapture data from the baseband signal, wherein the data recovery module includes: data detection module operably coupled to detect validity of the baseband signal to produce a valid signal indication; and demodulation module operably coupled to demodulate the baseband signal to produce the data in accordance with the valid signal indication, wherein the data detection module includes: processing module; and memory operably coupled to the processing module, wherein the memory includes operational instructions that cause the processing module to: perform an autocorrelation on the received signal to produce an autocorrelation resultant; perform a cross correlation of the received signal with a reference signal to produce a cross correlation resultant; mathematically relate the autocorrelation resultant with the cross correlation resultant to produce a mathematical correlation relationship; and interpret the mathematical correlation relationship to indicate whether the received signal is valid or invalid. ### Claim 14 (depends on 13) The radio receiver of claim 13, wherein the memory further comprises operational instructions that cause the processing module to perform the autocorrelation on the received signal by: delaying the received signal by period of a valid signal to produce a delayed signal; correlating the received signal with the delayed signal to produce a correlated signal; and determining a moving average that represents energy of the correlated signal. ### Claim 15 (depends on 13) The radio receiver of claim 13, wherein the memory further comprises operational instructions that cause the processing module to mathematically relate the autocorrelation resultant by: determining a reference autocorrelation level based on a fixed length of the autocorrelation of a known input; normalizing the autocorrelation resultant with reference to the reference autocorrelation to produce a normalized autocorrelation resultant; scaling a ratio of the cross correlation resultant and the autocorrelation resultant based on the normalized autocorrelation resultant to produce the mathematical correlation relationship. ### Claim 16 (depends on 15) The radio receiver of claim 15, wherein the memory further comprises operational instructions that cause the processing module to interpret the mathematical correlation relationship by: comparing the mathematical correlation relationship with a difference threshold; when the comparison of the mathematical correlation relationship to the difference threshold is favorable, indicating that the received signal is valid; and when the comparison of the mathematical correlation relationship to the difference threshold is unfavorable, indicating that the received signal is not valid. ### Claim 17 (depends on 13) The radio receiver of claim 13, wherein the memory further comprises operational instructions that cause the processing module to mathematically relate the autocorrelation resultant with the cross correlation resultant by: autocorr refcorr ⁢ ( xcorr autocorr ) > K wherein the autocorr corresponds to the autocorrelation resultant, the refcorr corresponds to a reference autocorrelation, the xcorr corresponds to the cross correlation resultant, and the K corresponds to a valid signal threshold. ### Claim 18 (depends on 17) The radio receiver of claim 17, wherein the memory further comprises operational instructions that cause the processing module to: determine the reference autocorrelation based on a fixed length of the autocorrelation of a known input.