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Fundamental Frequency Detector

IP.com Disclosure Number: IPCOM000073416D
Original Publication Date: 1970-Dec-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Buron, R: AUTHOR

Abstract

An acoustic detector for determining pitch in which an applied acoustic wave is modulated by a carrier at half the frequency initially detected. If the resulting product signal shows the DC component, then the original detected frequency was a harmonic. If the product signal shows no DC component, then the original frequency was the pitch or fundamental. In the figure, an input signal E is applied to detector D. The detector is of a type that will produce time spaced pulses, of the type shown in the IBM Technical Disclosure Bulletin, Volume 11, Number 5, October, 1968, at page 489. The output signal of detector D is applied in parallel to two signal generators G1 and G2 which both generate carrier signals at the frequency 2 .

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Fundamental Frequency Detector

An acoustic detector for determining pitch in which an applied acoustic wave is modulated by a carrier at half the frequency initially detected. If the resulting product signal shows the DC component, then the original detected frequency was a harmonic. If the product signal shows no DC component, then the original frequency was the pitch or fundamental. In the figure, an input signal E is applied to detector D. The detector is of a type that will produce time spaced pulses, of the type shown in the IBM Technical Disclosure Bulletin, Volume 11, Number 5, October, 1968, at page 489. The output signal of detector D is applied in parallel to two signal generators G1 and G2 which both generate carrier signals at the frequency 2 . The signal output from generator G2 is 90 degrees phase shifted, with respect to the signal output of generator G1. These carrier signals are respectively applied to modulators M1 and M2, which combines the carriers with input signal E. The modulated signals in spaced quadrature pass through respective low pass filters LPF 2 and LPF 1, rectified at R2 and R1, and applied to summing network epsilon. The summed signal is compared to a threshold in comparator C. A reference threshold is used, above which comparator C will decide that the reference signal is a useful signal. The output signal generated by adder epsilon is lower than the threshold (the situation where F equals F(0)), then the output of comparator C...