Frequency discriminating apparatus

Details Frequency discriminating apparatus Frequency discriminating apparatus

1976-02-19

1977-03-22

Heyman, John S.

Demodulators

Amplitude modulation demodulator

Having specific distortion, noise or other interference...

307233R, 329142, H03D 316

Patent

active

040139700

ABSTRACT:
A frequency discriminating apparatus is constituted by a piezoelectric ceramic resonator, a reference capacitor, a pre-amplifier including a broad tuning circuit, a pair of amplitude detectors, and a differential amplitude limiter. The piezoelectric ceramic resonator is made of a piezoelectric lead titanate ceramic plate having a pair of electrodes covering the entire area of the major surfaces thereof, and the plate is poled with a poling field of not less than 50 kV/cm in the thickness direction. The thickness of the plate is chosen so as to cause the plate to vibrate in the thickness-extensional vibration of the 3rd harmonic overtone at a preselected frequency when an electrical signal is applied to the pair of electrodes. The differential amplitude limiter differentially adds the two signals detected by the two amplitude detectors and limits the peak output voltage amplitudes to a predetermined amplitude. The center frequency for the frequency discrimination by this apparatus can be stably maintained according to this apparatus, and the apparatus can be easily manufactured in the form of integrated circuits without necessitating many value adjustments of circuit elements.

REFERENCES:
patent: 2712600 (1955-07-01), Beckwith
patent: 2849607 (1958-08-01), Leister
patent: 3160822 (1964-12-01), Dix
patent: 3221271 (1965-11-01), Waard
patent: 3614640 (1971-10-01), Wolf
patent: 3659116 (1972-04-01), Sellers et al.
patent: 3934207 (1976-01-01), Fischman et al.

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