Apparatus for extracting the fundamental frequency from a complex audio wave form
US4162461A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 25, 1977 |
| Grant date | Jul 24, 1979 |
| Priority date | — |
| Expiry date | Jul 25, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03H11/12
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
Apparatus for extracting the fundamental frequency from a complex audio wave form and for producing a pulse representation of said fundamental frequency includes a low pass filter having a frequency response characteristic which tends to exclude harmonics together with a control circuit including amplifier means, peak detector means and voltage to current converter means for supplying a control signal to the low pass filter thereby to vary the cutoff frequency of the filter and to maintain substantially constant amplitude of the fundmental wave form together with voltage comparator means for comparing the peaks of an alternating current quantity dependent upon the output of said filter with a direct current quantity proportional to the output of the filter, said comparator means thereby producing a pulse per cycle of said fundamental frequency.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.