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Fundamental Frequency Extractor

IP.com Disclosure Number: IPCOM000093845D
Original Publication Date: 1966-Mar-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Harr, JD: AUTHOR

Abstract

The circuitry isolates a fundamental pitch frequency from complex waveforms. The isolation of the fundamental pitch frequency is accomplished by repeated integration of the waveform by integrators 10. As shown by the waveform equations, each integration reduces the proportionate amplitude of the higher frequencies, leaving primarily the fundamental frequency. The integration is continued until the higher harmonics are reduced sufficiently so that the resulting waveform has either only one major peak per period or only one zero crossing per period. If the former, the fundamental can thus be recovered by peak detector 11. If the latter, the fundamental can be recovered with a zero-crossing detector.

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Fundamental Frequency Extractor

The circuitry isolates a fundamental pitch frequency from complex waveforms. The isolation of the fundamental pitch frequency is accomplished by repeated integration of the waveform by integrators 10. As shown by the waveform equations, each integration reduces the proportionate amplitude of the higher frequencies, leaving primarily the fundamental frequency. The integration is continued until the higher harmonics are reduced sufficiently so that the resulting waveform has either only one major peak per period or only one zero crossing per period. If the former, the fundamental can thus be recovered by peak detector 11. If the latter, the fundamental can be recovered with a zero- crossing detector.

In order to control the output voltage so that it is maintained within a predetermined voltage range throughout the range of fundamental frequencies, AGC is employed. The AGC can take the form of one feedback loop 12 per integrator or one AGC control 13 for all integrators.

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