# US 2014/0153617 A1 · Communications device and related method that detects radio frequency (rf) interferer on a communications channel > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0153617 A1 - Document ID: US20140153617A1 - Status: Published application - Kind: A1 - Application number: 13/705,251 - Filed: 2012-12-05 - Published: 2014-06-05 - Earliest claimed: 2012-12-05 - Assignees: Harris Corporation - Applicants: Harris Corporation - Inventors: James A. NORRIS; Brian J. Taylor; William L. Tyler - Web page: https://patentgrep.com/patent/US20140153617A1 ## CPC - H04L 27/14: Demodulator circuits; Receiver circuits - H04L 27/0006: {Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio (for spectrum sharing between different networks H04W16/14)} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A communications device includes a demodulator configured to demodulate a received communications signal into complex time domain samples. A processor is coupled to the demodulator and configured to determine the variance over time domain magnitude samples, perform a complex Fast Fourier Transform (cFFT) on the complex time domain samples as magnitude and phase to obtain frequency domain samples and determine the variance over the frequency domain samples. A comparator compares a variance ratio of the time domain magnitude samples and the frequency domain samples with a threshold to determine if a RF interferer is present, indicative that the communications channel is busy. ## Claims ### Claim 1 A communications device, comprising: an input configured to receive a communications signal over a communications channel; a demodulator coupled to the input and configured to demodulate the received communications signal into complex time domain samples; a processor coupled to the demodulator and configured to: determine the variance over time domain magnitude samples, perform a complex Fast Fourier Transform (CFFT) on the complex time domain samples as magnitude and phase to obtain frequency domain samples, and determine the variance over the frequency domain samples; and a comparator configured to compare a variance ratio of the variance in the time domain magnitude samples and the variance in the frequency domain samples with a threshold to determine if a RF interferer is present, indicative that the communications channel is busy. ### Claim 2 (depends on 1) The communications device according to claim 1, wherein the demodulator is configured to demodulate the received communications signal into in-phase (I) and quadrature (Q) signal components. ### Claim 3 (depends on 2) The communications device according to claim 2, and further comprising a vector magnitude determinator configured to receive I and Q signal components and determine complex time domain samples as magnitude and phase. ### Claim 4 (depends on 1) The communications device according to claim 1, and further comprising a normalizing circuit configured to normalize time domain magnitude samples to a fractional amplitude value. ### Claim 5 (depends on 1) The communications device according to claim 1, wherein the processor is configured to determine the mean over the time domain magnitude samples before determining the variance over time domain samples. ### Claim 6 (depends on 1) The communications device according to claim 1, wherein a variance ratio below the threshold is indicative that the RF interferer signal is present. ### Claim 7 (depends on 1) The communications device according to claim 1, wherein a variance ratio above a threshold is indicative of noise on the communications channel without an RF interferer signal. ### Claim 8 A communications device, comprising: a transceiver configured to transmit and receive communications signals over a communications channel and comprising: a demodulator configured to demodulate a received communications signal into complex time domain samples; a processor coupled to the demodulator and configured to: determine the variance over time domain magnitude samples, perform a complex Fast Fourier Transform (CFFT) on the complex time domain samples as magnitude and phase to obtain frequency domain samples, and determine the variance over the frequency domain samples; and a comparator configured to compare variance ratio of the variance in the time domain magnitude samples and the variance in the frequency domain samples with a threshold to determine if a RF interferer is present, indicative that the communications channel is busy, wherein in response to the indication that the communications channel is busy, the transceiver will not transmit a communications signal over the communications channel. ### Claim 9 (depends on 8) The communications device according to claim 8, wherein a variance ratio below the threshold is indicative that the RF interferer signal is present. ### Claim 10 (depends on 8) The communications device according to claim 8, wherein a variance ratio above a threshold is indicative of noise on the communications channel without an RF interferer signal. ### Claim 11 A method of detecting a radio frequency (RF) interferer signal on a communications channel, comprising: receiving a communications signal within a receiver; demodulating the communications signal within a demodulator and obtaining a plurality of complex time domain samples; determining the variance over time domain magnitude samples; performing a complex Fast Fourier Transform (CFFT) on the complex time domain samples as magnitude and phase to obtain frequency domain samples; determining the variance over the frequency domain samples; and comparing a variance ratio of the variance in the time domain magnitude samples and the variance in the frequency domain samples with a threshold to determine if a RF interferer is present, indicative that the communications channel is busy. ### Claim 12 (depends on 11) The method according to claim 11, further comprising demodulating the communications signal to obtain in-phase (I) and quadrature (Q) signal components; and processing the I and Q signal components to obtain the plurality of complex time domain samples as magnitude and phase. ### Claim 13 (depends on 11) The method according to claim 11, wherein a variance ratio below the threshold is indicative that the RF interferer signal is present. ### Claim 14 (depends on 11) The method according to claim 11, wherein a variance ratio above a threshold is indicative of noise on the communications channel without an RF interferer signal. ### Claim 15 (depends on 11) The method according to claim 11, further comprising determining the mean over the time domain magnitude samples before determining the variance over time domain samples. ### Claim 16 (depends on 11) The method according to claim 11, further comprising determining the mean over the frequency domain samples before determining the variance over the frequency domain samples. ### Claim 17 (depends on 11) The method according to claim 11, further comprising normalizing time domain magnitude samples to a fractional amplitude value. ### Claim 18 (depends on 11) The method according to claim 11, wherein the RF interferer comprises a communications signal transmitted from a second wireless communications device.