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High Q Narrow Band Tone Recovery Filter

IP.com Disclosure Number: IPCOM000089359D
Original Publication Date: 1977-Jul-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Delaporte, F: AUTHOR [+2]

Abstract

Shown in the figure is a filter arrangement for extracting a tone frequency F from a wide-band spectrum input signal which passes to zero at instants equally spaced by 1/F sec.

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High Q Narrow Band Tone Recovery Filter

Shown in the figure is a filter arrangement for extracting a tone frequency F from a wide-band spectrum input signal which passes to zero at instants equally spaced by 1/F sec.

A first set of conventional bandpass filters 1 cancels undesirable harmonics from the input signal. Bandpass filters 1 are tuned at a frequency different from the tone frequency to get rid of their phase sensitiveness to component accuracy. The output from bandpass filters 1 is applied to a first switched filter 2 centered at tone frequency F, which cancels lower frequencies that have been boosted by the offset bandpass filters 1. Switched filter 2 has a moderate Q in order to exhibit a reasonably short rise time. A second switched filter 3 precisely tuned at tone frequency F picks up the tone frequency from adjacent noise. A phase shift buffer 4 is provided for gain and phase adjustments. A second set of conventional bandpass filters 5 cancels harmonics generated by the switched filters 2 and 3.

Bandpass filters 5 are also centered at a frequency different from tone frequency F. Phase shift buffer 4 compensates for phase and gain discrepancies created by bandpass filters 1 and 5.

The filter arrangement shown in the figure provides an accurate and jitter-free tone frequency signal at its output.

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