Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1987-04-30
1989-06-06
Chin, Tommy P.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358163, 358336, H04N 514
Patent
active
048376248
ABSTRACT:
Digital video signals are subjected to band limiting by a high pass filter with a pass band terminating somewhat above half of the digital sampling frequency. The filtered signal is in effect subtracted from the original signal in an addition circuit with suitably phased inputs in order to make available a substitute signal of the interpolation low pass filtered kind. A circuit for determining the presence of an erroneous digital word accepts the high pass filtered signal, differentiates it twice and then digitally rectifies it in order to detect a possible maximum at half the sampling rate. When such a maximum is found, a changeover switch is caused to substitute the interpolation-low-pass-filtered signal for the orginal signal. Only a single digital filter is necessary for this operation. The high pass filter is a FIR filter of, for example, eleventh order and the middle coefficient is in effect changed from minus 1 to 0 when the delay equalized original signal is added to the output of the high pass filter.
REFERENCES:
patent: 4090221 (1978-05-01), Connor
patent: 4272785 (1981-06-01), Fuhrer
patent: 4647972 (1987-03-01), Strehl
patent: 4688089 (1987-08-01), Uhlenkamp
Digital Television Error Correction Without Overhead Bits, by A. A. Goldberg; et al., Television Technology in the 80's, pp. 80-88.
Heitmann Jurgen
Wagner Peter
Chin Tommy P.
Robert & Bosch GmbH
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