Adaptive threshold suppression of impulse noise
First Claim
1. For use with a signal processing apparatus in which an input signal to be processed may contain signal anomalies having amplitudes which are significantly greater than that of said input signal, a method of controllably suppressing said signal anomalies comprising the steps of:
- (a) sampling said input signal to generate a plurality of input signal samples;
(b) storing successive ones of said plurality of input signal samples and producing a first signal representative of the stored samples;
(c) comparing said input signal with said first signal and generating a second signal in response to said input signal satisfying a predetermined relationship with said first signal; and
(d) selectively coupling said first signal to a prescribed signal processing operator in response to said second signal, said prescribed signal processing operator generating an output signal representative of said input signal with said signal anomalies suppressed.
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Abstract
Impulse noise suppression upstream of digital processing circuitry contains a sample and hold mechanism which samples the input signal and stores a plurality of sequential sample values respectively representative of the amplitude of the input signal at successive sample times. The contents of the sample and hold mechanism are compared with an input signal sample to determine whether or not the there are abnormal amplitude variations which potentially constitute impulse noise. In one embodiment the comparison is referenced to the average magnitude of the input signal. In another embodiment the input signal is coupled to a cascaded arrangement of sample and hold circuits which sample and store a plurality of sequential sample values. The time differentials between successive sampling times are such there is little likelihood of occurrences of impulse noise spikes during any two successive sample intervals. The contents of the last sample and hold circuit of the cascaded plurality are compared with the contents of each of selected other sample and hold circuits of the cascaded chain. If the (earliest in time) sampled value stored in the last sampled and hold circuit is determined to be larger (by a system thermal noise offset) than the sampled value of any of the selected samples, then this sample is identified as being a potential noise impulse sample and is prevented from being coupled to downstream processing circuitry. Otherwise it is coupled through a downstream lowpass filter for subsequenty signal analysis.
29 Citations
21 Claims
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1. For use with a signal processing apparatus in which an input signal to be processed may contain signal anomalies having amplitudes which are significantly greater than that of said input signal, a method of controllably suppressing said signal anomalies comprising the steps of:
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(a) sampling said input signal to generate a plurality of input signal samples; (b) storing successive ones of said plurality of input signal samples and producing a first signal representative of the stored samples; (c) comparing said input signal with said first signal and generating a second signal in response to said input signal satisfying a predetermined relationship with said first signal; and (d) selectively coupling said first signal to a prescribed signal processing operator in response to said second signal, said prescribed signal processing operator generating an output signal representative of said input signal with said signal anomalies suppressed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. For use with a signal processing apparatus in which an input signal to be processed may contain randomly occurring noise impulses, amplitudes of which and the rate of change of which are significantly greater than the amplitude and the rate of change of said input signal, a method of controllably suppressing said noise impulses from said input signal, so that said input signal may be processed substantially free of said noise impulses, comprising the steps of:
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(a) successively sampling said input signal so as to generate a plurality of sequential sample values respectively representative of the amplitude of said input signal at successive sample times; (b) storing successive ones of said plurality of input signal samples; (c) for each one of the stored sample values, comparing said one of the stored sample values with others of the stored sample values and generating a second signal in response to said one stored sample value satisfying a predetermined relationship with said other stored sample values; and (d) selectively coupling said one stored sample value to a prescribed signal processing operator in response to said second signal, but otherwise preventing said one stored sample value from being coupled to said prescribed signal processing operator, the output of which is representative of said input signal effectively absent noise impulses. - View Dependent Claims (10, 11)
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12. For use with a signal processing apparatus in which an input signal to be processed may contain randomly occurring noise impulses, amplitudes of which and the rate of change of which are significantly greater than the amplitude and the rate of change of said input signal, a preprocessing selective filtering device which controllably suppresses noise impulses from said input signal, so that said input signal may be processed substantially free of said noise impulses comprising:
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a sample and hold circuit coupled to receive said input signal, said sample and hold circuit producing successive samples of said input signal,; first means, coupled to the output of said sample and hold circuit, for generating a first signal representative of the average value of the contents of said sample and hold circuit; second means, coupled to receive said input signal and said first signal for comparing said input signal with said first signal and generating a second signal in response to said input signal satisfying a predetermined relationship with said first signal; and
third means for selectively coupling said sample and hold circuit to a prescribed signal processing operator in response to said second signal, said prescribed signal processing operator generating an output signal representative of said input signal with said noise impulses suppressed. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. For use with a signal processing apparatus in which an input signal to be processed may contain randomly occurring noise impulses, amplitudes of which and the rate of change of which are significantly greater than the amplitude and the rate of change of said input signal, a device for controllably suppressing said noise impulses from said input signal, so that said input signal may be processed substantially free of said noise impulses, comprising:
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a plurality of cascaded sample and hold circuits coupled to successively sample said input signal and store a plurality of sequential sample values respectively representative of the amplitude of said input signal at successive sample times; first means, coupled to selected ones of said sample and hold circuits, for comparing one of the stored sample values with others of the stored sample values and generating a first signal in response to said one stored sample value satisfying a predetermined relationship with each of said other stored sample values; and second means for selectively coupling said one stored sample value to a prescribed signal processing operator in response to said first signal, but otherwise preventing said one stored sample value from being coupled to said prescribed signal processing operator, the output of which is representative of said input signal effectively absent noise impulses. - View Dependent Claims (20, 21)
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Specification