Circuit for the adaptive suppression of narrow band interference
First Claim
1. A circuit for the adaptive suppression of narrow band interference comprisingmeans receiving analog signals,Fourier transform means performing an N point weighted Fourier transform on said received analog signals,squaring means for squaring the output of said Fourier transform means,recursive filter means for filtering the output of said squaring means to provide a smoothed power spectral density signal, andan interference signal cancelling circuit receiving said smoothed power spectral density signal and cancelling interference signals from said received analog input signals in response thereto.
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Abstract
Adaptive suppression of narrow band interference is realized by a filter that automatically makes estimates of interfering signals in the frequency domain and separates the interference from the desired signal. Received analog signals are Fourier transformed in accordance with a CHIRP Z algorithm, squared, and filtered by an N point serial structural CCD to provide a smoothed power spectral density signal. The smoothed power spectral density signal is utilized to cancel interfering signals by any one of three mechanizations. One mechanization comprehends a threshold circuit that generates binary signals in response to the CCD output. The binary signals control a gate that gates strong frequency components (the estimates of the interfering frequency coefficient) from the Fourier transformer through to an inverse Fourier transformer. The inverse Fourier transformed strong frequency components are then subtracted from the delayed received analog signal. A second mechanization transmits the full Fourier transformed spectrum to the inverse Fourier transformer and utilizes the gate to notch out the strong frequency components in response to the CCD output. The third mechanization weights the Fourier transformed frequency coefficients with the smoothed power spectral density signal, inverse transforms the weighted spectrum and subtracts it from the delayed analog signal.
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Citations
6 Claims
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1. A circuit for the adaptive suppression of narrow band interference comprising
means receiving analog signals, Fourier transform means performing an N point weighted Fourier transform on said received analog signals, squaring means for squaring the output of said Fourier transform means, recursive filter means for filtering the output of said squaring means to provide a smoothed power spectral density signal, and an interference signal cancelling circuit receiving said smoothed power spectral density signal and cancelling interference signals from said received analog input signals in response thereto.
Specification