Phase locked loop circuit

Details Phase locked loop circuit Phase locked loop circuit

1980-12-09

1982-10-19

Bookbinder, Marc E.

Telecommunications

Receiver or analog modulated signal frequency converter

Signal selection based on frequency

331 17, 455208, 455260, H04B 126, H03L 718, H03L 724

Patent

active

043554130

ABSTRACT:
A phase locked loop circuit includes a reference signal oscillator, a voltage controlled oscillator providing an output oscillation signal at its output, a programmable divider connected to the output of the voltage controlled oscillator, a phase comparator supplied with output signals from both the reference signal oscillator and the programmable divider to produce an error signal in response to the phase difference therebetween, and an active low pass filter for processing the error signal to produce a DC control signal supplied to the voltage controlled oscillator to lock the phase of the output oscillation signal to that of the reference signal. This low pass filter includes a time constant circuit whose time constant governs the transfer function of the filter and a damping factor control circuit to adjust the time constant of the time constant circuit in accordance with the level of the DC control signal.The phase locked loop circuit of this invention is favorably applied in an FM broadcast receiver to provide a tuning signal over an extended range, for example, a range encompassing both the FM band of the U.S. and that of Japan.

REFERENCES:
patent: 2676262 (1954-04-01), Hugenholtz
patent: 4097810 (1978-06-01), Aschwanden

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