Sample-and-hold hybrid active RC filter
AssigneeThe Perkin-Elmer Corporation
InventorsGerald T. Volpe, Leonard S. Laskoski, Ralph J. Amodeo, William J. Swanson, Jerome D. Gottesman
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Abstract
A discrete-time analog filter for eliminating a variable frequency carrier of an amplitude-modulated signal. The filter comprises a plurality of unit delay circuits, each of which is sampled at a rate which varies in proportion to the frequency of the carrier so as to automatically tune the filter's reject band to follow the carrier frequency.
Claims6
A circuit for eliminating a variable carrier frequency from an input data signal, comprising in combination,
- filter means automatically tunable to provide a variable frequency reject band comprising first, second, third and fourth sample-and-hold circuits connected in tandem,
- input means providing said input data signal to said first sample-and-hold circuit,
- first means automatically tuning said filter means to vary the frequency reject band in accordance with variations in the carrier frequency to eliminate the carrier frequency from the input data signal,
- said first means comprising strobe pulse generating means,
- said strobe pulse generating means including second means causing the period of the strobe pulses to vary proportionately to variations in the carrier frequency,
- third means connecting said strobe pulse generator means to said filter means to cause said first, second, third and fourth sample-and-hold circuits to be strobed first, fourth, third and second, respectively.
A circuit for eliminating a variable carrier frequency from an input data signal, comprising in combination,
- filter means automatically tunable to provide a variable frequency reject band comprising first, second, third and fourth sample-and-hold circuits connected in tandem,
- input means providing said input data signal to said first sample-and-hold circuit,
- first means automatically tuning said filter means to vary the frequency reject band in accordance with variations in the carrier frequency to eliminate the carrier frequency from the input data signal,
- said first means comprising strobe pulse generating means for providing strobe pulses to sample each of said sample-and-hold circuit in a predetermined sequence,
- said strobe pulse generating means including second means causing the period of the strobe pulses to vary proportionately to variations in the carrier frequency,
- first differential amplifier means,
- negative feedback circuit means connected between the output of said third sample-and-hold circuit and the inverting input of said first differential amplifier means,
- positive feedback circuit means connected between the output of said second sample-and-hold circuit and the inverting input of said first differential amplifier means,
- second differential amplifier means connected between said third and fourth sample-and-hold circuits;
- first feedforward circuit means connected between the output of said second sample-and-hold circuit and the inverting input of said second differential amplifier means,
- second feedforward circuit means connected between the output of said first sample-and-hold circuit and the inverting input of said second differential circuit amplifier means.
Dependencies are inferred from the claim text.