Demodulators – Frequency shift keying or minimum shift keying demodulator
Patent
1988-01-27
1989-12-12
Grimm, Siegfried H.
Demodulators
Frequency shift keying or minimum shift keying demodulator
375 82, 375 94, 329341, H03D 300, H04L 2714
Patent
active
048870447
ABSTRACT:
The demodulation circuit includes a Schmitt trigger circuit, first and second monostable multivibrators, a quartz oscillator, first and second low-pass filters, and a comparator. The Schmitt trigger circuit converts a modulated signal modulated by data into a pulse signal. The first monostable multivibrator converts an output from the Schmitt trigger circuit into a PPM signal. The quartz oscillator oscillates at the same frequency as the center frequency of the modulated signal. The second monostable multivibrator is formed on the same chip as the first monostable multivibrator and responsive to an output signal from the quartz oscillator. The second monostable multivibrator generates a signal comprising a pulse train having the same pulse width as that of the PPM signal output form the first monostable multivibrator and a constant pulse separation. The first low-pass filter receives an output from the first monostable multivibrator. The second low-pass filter receives an output from the second monostable multivibrator. The comparator compares an output signal from the first low-pass filter with an output signal from the second low-pass filter as a threshold level, and obtains modulation data.
REFERENCES:
patent: 3233181 (1966-02-01), Calfee
patent: 3529247 (1970-09-01), Nelson
patent: 4389621 (1983-06-01), Futatsuishi
Grimm Siegfried H.
NEC Corporation
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