Voltage controlled oscillator circuit and automatic fine tuning

Details Voltage controlled oscillator circuit and automatic fine tuning Voltage controlled oscillator circuit and automatic fine tuning

1995-12-15

1996-11-12

Kostak, Victor R.

Television

Receiver circuitry

Tuning

348735, H04N 544

Patent

active

055745156

ABSTRACT:
A voltage controlled oscillator that completely eliminates the need for any externally mounted coil and capacitor, and an automatic fine tuning circuit for television which is inexpensive and highly accurate are provided.
A first loop and a second loop are provided, said first loop for band-limiting an output signal of an amplifier through a bandpass filter to provide oscillation at a frequency of a resonant point of the bandpass filter, and said second loop for controlling the oscillation amplitude, so that a lowpass filter output with a 90.degree. phase is extracted from the first loop, while a bandpass filter output with a 0.degree. phase is extracted from the second loop. Divide-by-N and divide-by-(N+1) operations selected according to a radio of the television IF frequency and reference frequency are performed multiple times, respectively, to output as its divided frequency an average of both divisions such that the average is close to the reference frequency; and an error signal corresponding to a phase frequency difference between the resulting divided frequency and the reference frequency is outputted to control the oscillation frequency of the TV tuner oscillation circuit to a constant level.

REFERENCES:
patent: 4397038 (1983-08-01), Rzeszewski
patent: 5233425 (1993-08-01), Rabii

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