Distortion suppression using thresholding techniques

Details Distortion suppression using thresholding techniques Distortion suppression using thresholding techniques

1990-09-10

1993-12-14

Safourek, Benedict V.

Pulse or digital communications

Repeaters

Testing

307555, 328116, 375102, 375104, H04B 110

Patent

active

052710386

ABSTRACT:
A distortion suppressor and method for suppressing distortion that performs processing in the time domain to suppress partial time distortion of received signals, and/or the frequency domain to suppress partial band distortion of the received signals. For time domain suppression, the received signals are sampled and sample amplitudes are sorted. Based on the sorted samples, the receiver searches for two levels, S.sub.L and S.sub.M, representing clipping and removal thresholds. Any samples having amplitudes above S.sub.L are removed (zeroed), samples having amplitudes below S.sub.L are left alone, and samples having amplitudes between S.sub.L and S.sub.M are clipped to S.sub.L. The processor searches for optimum S.sub.L and S.sub.M values to maximize the signal to noise ratio of the received signals. For frequency domain suppression, the received signals are processed by a Fourier transform (FFT) processor. The spectrum of output signals from the FFT processor is sampled in a manner similar to the time domain suppression. The sample amplitudes are sorted, and the clipping and removal thresholds, S.sub.L and S.sub.M, are determined such that the output signal to noise ratio is maximized. Samples having amplitudes above S.sub.M are zeroed, and samples having amplitudes between S.sub.L and S.sub.M are clipped to S.sub.L. The resulting signal has a maximum signal to noise ratio, that maximizes receiver performance. Clipping and removal thresholds S.sub.L, S.sub.M are set with reference to the sorted amplitude profile, which determines two optimum clipping and removal threshold levels for the frequency distribution. Finally, the signals levels are clipped as stated above to maximize the suppression of interference and noise while achieving minimum distortion of the signals.

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patent: 3760282 (1973-09-01), Arnold et al.
patent: 3963983 (1976-06-01), Hogg
patent: 4458206 (1984-07-01), Dellande et al.
patent: 4630290 (1986-12-01), Kage
patent: 4815108 (1989-03-01), Oda
patent: 4965757 (1990-10-01), Grassart
patent: 4970605 (1990-11-01), Fogaroli et al.

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