Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Patent
1982-08-03
1984-03-20
Ng, Jin F.
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
455183, 455164, 455165, H04B 126
Patent
active
044385285
ABSTRACT:
In a channel selection system using a PPL frequency synthesizing method in which the local oscillation frequency of a tuner is frequency-divided and compared with the frequency and the phase of a reference oscillator thereby to control the tuning voltage of a tuner, a channel selection system disclosed by this invention comprises a controller, a variable frequency divider the frequency division ratio of which is controlled by the above controller, an AFC circuit connected to this tuner, a first comparator having a first threshold voltage for detecting an H level of the inverted S character output of the AFC circuit, a second comparator having a second threshold voltage for detecting an L level of the inverted S character output, and a delay circuit connected to the output of at least one of the first and second comparators and delaying the rising edge of the comparison output.
REFERENCES:
patent: 4280140 (1981-07-01), Skerlos
patent: 4367558 (1983-01-01), Gercekci et al.
patent: 4387469 (1983-06-01), Miyazaki et al.
patent: 4397038 (1983-08-01), Rzeszewski
Hitachi , Ltd.
Ng Jin F.
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