Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1983-11-09
1986-03-25
Groody, James J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
3581931, 455164, H04N 550, H04B 1132
Patent
active
045787069
ABSTRACT:
A synchronous receiver having a reduced pull-in time without requiring a frequency error detection circuit using a differentiator is provided with a voltage-controlled oscillator, a 90.degree. phase shifter which shifts the phase of an output from the voltage controlled oscillator by an angle of 90.degree., first and second synchronous detectors which detect an in-phase component and a quadrature component of a video carrier signal, a phase detector for detecting a phase difference between the video carrier signal and the output of the voltage-controlled oscillator, a first low pass filter for filtering the output of the phase detector, a frequency discriminator for discriminating the frequency of an audio IF signal generated by the first synchronous detector and a second low pass filter for filtering the output of the frequency discriminator. The output of the first and second low pass filters are fed back to the voltage-controlled oscillator so that the phase difference between the output of the first and second synchronous detectors is made equal to 0.
REFERENCES:
patent: 4271434 (1981-06-01), Sakamoto
patent: 4461035 (1984-07-01), Sakamoto
Carter Howard L.
Groody James J.
Matsushita Electric - Industrial Co., Ltd.
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