Tektronix, Inc.

William J Cooper

Daniel G Baker

Bruce J Penney

A recursive noise reduction filter for video components reduces the noise bandwidth of a signal without degrading the signal spectrum. Demodulated chrominance or peak detected chrominance from a video signal output by a video system in reponse to a video test signal is input to the recursive noise reduction filter which acts as a comb filter to suppress noise significantly at frequencies other than harmonics of the horizontal line rate. The signal is scaled by a first attenuator having a scaling factor of (1-a), where (a) is less than one, and input to a summing circuit. Also input to the summing circuit is a delayed signal from a prior horizontal line scaled by the scaling factor (a). The output of the summing circuit is a filtered output signal. The signal is sampled only during horizontal lines that have the video test signal and is stored for subsequent accumulation with other horizontal lines also having the video test signal. The fitler serves to add the vertically correlated part of the signal corresponding to the video test signal while averaging out the noise, thus improving the overall signal to noise ratio without degrading the signal spectrum and, hence, enhancing differential gain and phase measurements.

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Aloha, OR, United States of America

William J Cooper