Noise cancellation circuit

Details Noise cancellation circuit Noise cancellation circuit

1978-08-18

1981-03-03

Martin, John C.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358167, H04N 508, H04N 521

Patent

active

042544360

ABSTRACT:
A noise cancellation circuit is provided for cancelling impulse noise in a composite video signal. A composite video signal which may be contaminated with impulse noise is coupled to a noise inverter and an active filter. The noise inverter generates an inverted noise pulse for each noise pulse in the composite video signal which exceeds a predetermined threshold level. The active filter delays the composite video signal and combines the delayed video signal with the inverted noise pulses, resulting in cancellation of the impulse noise. The noise-free video signal is amplified by the active filter for subsequent signal processing. The threshold level of the noise inverter varies in response to the signal level at the output of the active filter. The active filter utilizes a feedback capacitor to delay the video signal and to improve the transition time of the leading edges of synchronizing signal components of the video signal. The feedback capacitor may be constructed from N+P+ semiconductor material, which is especially advantageous in integrated circuit manufacture.

REFERENCES:
patent: 3624288 (1971-11-01), Hofmann
patent: 3860750 (1975-01-01), Ueda
patent: 3979683 (1976-09-01), Ikeda
patent: 4042959 (1977-08-01), Klein
1977 RCA Linear Integrated Circuit Databook, pp. 355-358.
"RC Filter Design by the Numbers", The Electronic Engineer, vol. 27, No. 10, Oct. 1968, pp. 57-64.

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