Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Patent
1991-01-23
1993-06-15
Eisenzopf, Reinhard J.
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
4551961, 455260, 331 25, H04B 126, H03L 706
Patent
active
052206840
ABSTRACT:
In a channel selecting circuit, there are four dividers. A first divider divides a local oscillating signal from a tuner. A second divider divides a reference output signal from a reference oscillator. A third divider divides the output from the first divider. A fourth divider divides the output from the second divider. A first controller changes the ratio of the frequency division in the first divider so as to obtain a synchronous voltage, which is supplied to the tuner, according to a selected channel. That is, the outputs from the first and the second dividers are compared by a phase comparator. The output of the phase comparator is supplied to the local oscillator of the tuner as the synchronous voltage. After the synchronous voltage becomes stable, a second controller tunes the real frequency of the broadcasting signal of the selected channel by changing the ratio of the frequency division in the first divider according to the output of a detector. This detector detects a difference between a predetermined frequency of an intermediate frequency signal. In this case, first, the outputs from the first and second dividers are compared by the phase comparator. Then, the outputs from the third and fourth dividers are compared by the phase comparator, and the output of the phase comparator is supplied to the tuner as the synchronous voltage.
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Charouel Lisa
Eisenzopf Reinhard J.
Kabushiki Kaisha Toshiba
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