AC line-correlated noise-canceling circuit

Details AC line-correlated noise-canceling circuit AC line-correlated noise-canceling circuit

1995-07-10

1998-01-06

Kuntz, Curtis

Electrical audio signal processing systems and devices

Noise or distortion suppression

Interpolation

381 71, 381104, 381107, H04B 1500

Patent

active

057063540

ABSTRACT:
A device is connected in a signal path for canceling an unwanted noise signal induced by and correlated to the AC power line. The noise signal is assumed to have relatively constant phase (with respect to the AC power line) and amplitude during the period of use. The desired signal is assumed to be temporarily mutable for a brief period during which the noise signal is acquired. A manually- or automatically-adjusted gain (or attenuation) stage and overload detector are at the front-end of the waveform acquisition/playback block. A manually- or automatically-adjusted stage, typically linked to the earlier gain (attenuation) stage and with complementary attenuation (or gain) is at the back-end of the waveform acquisition/playback block. In this way, maximum performance can easily be realized from a waveform acquisition/playback block of lower resolution over a wide range of noise signal levels. The device acquires N samples of the noise signal over one or more periods of the AC power cycle and in synchrony with the AC power cycle. The sampling is terminated and the stored signals are played back with the correct amplitude and summed 180 degrees out-of-phase with the original noise signal.

REFERENCES:
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patent: 4759071 (1988-07-01), Heide
patent: 4989179 (1991-01-01), Simko
patent: 5129003 (1992-07-01), Saruta
patent: 5259033 (1993-11-01), Goodings et al.
patent: 5406149 (1995-04-01), An et al.
patent: 5499301 (1996-03-01), Sudo et al.
patent: 5533136 (1996-07-01), Smith

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