Demodulators – Amplitude modulation demodulator – Having specific distortion – noise or other interference...
Patent
1982-03-15
1984-12-11
Laroche, Eugene R.
Demodulators
Amplitude modulation demodulator
Having specific distortion, noise or other interference...
329124, 331DIG2, 331 23, 331 12, 375 76, H03D 322
Patent
active
044881207
ABSTRACT:
In an FSK demodulator, the output of the phase detector of a phase locked loop (PLL) is capacitively coupled to one input of an FSK voltage comparator, the capacitive coupling blocking d.c. and d.c. being restored at the comparator input by diodes connected between the two comparator inputs. The other input of the comparator is supplied with a reference voltage corresponding to a nominal center frequency of the FSK signals. A buffer amplifier permits rapid charging of the coupling capacitor, which is set to a determined state when there is no phase lock of the PLL. The arrangement facilitates demodulation of narrow-band FSK signals whose center frequency is subject to change.
REFERENCES:
patent: 3164773 (1965-01-01), Daniel
patent: 3543169 (1970-11-01), Hill
patent: 3688205 (1972-08-01), Burger
patent: 3909735 (1975-09-01), Anderson et al.
patent: 4237424 (1980-12-01), Weiner
patent: 4463317 (1984-07-01), Kuskabe
Exar Integrated Systems, Inc., Specification Sheets for XR-2211 FSK Demodulator/Tone Decoder Integrated Circuit.
Haley R. John
LaRoche Eugene R.
Northern Telecom Limited
Paxman W. R.
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