Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Patent
1979-11-09
1982-03-16
Ng, Jin F.
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
455183, 331 1A, 331DIG2, H04B 116
Patent
active
043205305
ABSTRACT:
A tuner comprises a local oscillator including a variable capacitance diode. The output signal of the local oscillator is frequency divided by a prescaler and the frequency divided output is applied to a phase locked loop. The phase locked loop is structured such that the phases of the output signal of the prescaler and a reference frequency signal are compared and the signal associated with the phase difference is smoothed by a low pass filter and the smoothed output is applied to the variable capacitance diode as a tuning voltage. The low pass filter includes a smoothing capacitor. A tuning unlocked state is detected when the terminal voltage of the smoothing capacitor is stabilized at the source voltage or is stabilized at 0V. Upon detection of the tuning unlocked state, the tuning voltage applied to the variable capacitance diode is increased (when the smoothing capacitor is stabilized at the source voltage) or decreased (when the smoothing capacitor is stabilized at 0V), thereby to forcibly return to a lockable region. Thereafter a locked state or a normal reception state is established by a normal operation of the phase locked loop.
REFERENCES:
patent: 3821650 (1974-06-01), Kase et al.
patent: 3949305 (1976-04-01), McClaskey et al.
patent: 4023116 (1977-05-01), Alfke et al.
patent: 4031549 (1977-06-01), Rast et al.
patent: 4034310 (1977-07-01), Coe
patent: 4218657 (1980-08-01), Rast
Ng Jin F.
Sanyo Electric Co,. Ltd.
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