Oscillators – Automatic frequency stabilization using a phase or frequency... – Particular error voltage control
Patent
1975-11-07
1976-12-28
Grimm, Siegfried H.
Oscillators
Automatic frequency stabilization using a phase or frequency...
Particular error voltage control
325346, 325419, 329122, 331 4, 331 19, 331 23, 331 25, H03B 304, H03D 300
Patent
active
040004767
ABSTRACT:
A side lock detector to prevent side lock in coherent PSK demodulation. For demodulation purposes it is necessary to recreate the carrier at the receiver. This may be accomplished with a phase-locked loop. However, with plural phase PSK modulation the input signal to the phase-locked loop has energy at side bands spaced at modulation rate intervals from the desired lock frequency as well as at the desired lock frequency. To detect side band lock, a band pass filter monitors the phase detector output of the phase-locked loop. The center frequency of the filter is equal to the modulation rate and the filter band width is very narrow. Only during side lock will significant amounts of energy pass the filter. This energy may be detected by a simple diode detector or the like. A lock inhibit means is provided, responsive to the output of the detector, to drive the voltage controlled oscillator out of a side lock condition.
REFERENCES:
patent: 3421105 (1969-01-01), Taylor
patent: 3768030 (1973-10-01), Brown et al.
patent: 3810036 (1974-05-01), Bloedorn
Matthews David W.
Walker Andrew M.
Digital Communications Corporation
Grimm Siegfried H.
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