Tuner station selecting apparatus
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsAkira Mishima, Kazuhiko Kubo, Akira Usui
Life of this patent
Estimating the term…
Abstract
A tuner station apparatus includes a first mixer for combining an input signal and a first local oscillation signal, and a second mixer for combining an output of the first mixer and a second local oscillation signal. The first and second local oscillation signals are generated by first and second PLL circuits, respectively. Each of the first and second PLL circuits include a frequency divider, a variable frequency divider, a phase comparator, a low pass filter, and a voltage controlled oscillator. The frequency divider of the first PLL circuit has a higher frequency division ratio than that of the second PLL circuit.
Claims1
A tuner station apparatus comprising:
- a first mixer for combining an input signal and a first local oscillation signal;
- a second mixer for combining an output of said first mixer and a second local oscillation signal;
- a first PLL circuit including (a) a first voltage controlled oscillator for generating the first local oscillation signal, (b) a first frequency divider for frequency dividing in accordance with a fixed first frequency division ratio 1:N the first local oscillation signal output by said first voltage controlled oscillator, (c) a first variable frequency divider for frequency dividing in accordance with a first variable frequency division ratio an output of said first frequency divider, (d) a first phase comparator for comparing an output of said first variable frequency divider and a reference signal, and (e) a first low-pass filter having input thereto an output of said first phase comparator and outputting a first voltage control signal for said first voltage controlled oscillator;
- and,
- a second PLL circuit including (a) a second voltage controlled oscillator for generating the second local oscillation signal, (b) a second frequency divider for frequency dividing in accordance with a fixed second frequency division ratio 1:M the second local oscillation signal output by said second voltage controlled oscillator, (c) a second variable frequency divider for frequency dividing in accordance with a second variable frequency division ratio an output of said second frequency divider, (d) a second phase comparator for comparing an output of said first variable frequency divider and the reference signal, and (e) a second low-pass filter having input thereto an output of said second phase comparator and outputting a second voltage control signal for said second voltage controlled oscillator;
- wherein M<N, and wherein a value of N is such that a high frequency disturbance of the input signal caused by said first PLL circuit is relatively small, and wherein a value of M is such that a fine tuning adjustment of the second PLL circuit is facilitated.
Dependencies are inferred from the claim text.