| 摘要 |
PURPOSE:To simplify the connection between an electronic tuner and an external circuit by incorporating a circuit which counts a signal frequency as soon as a frequency division signal of a fixed frequency divider is outputted and outputs a reception frequency band switching signal in response to the said count into the electronic tuner. CONSTITUTION:The reception is enabled by biasing band pass filters 2, 4 and a VCO6 to a prescribed tuning voltage with respect to a desired reception RF signal fed to an RF signal input terminal 1, the RF signal via the band pass filter 2, an amplifier 3 and the band pass filter 4 is frequency-converted by using a signal of the VCO6 into an IF signal, which is outputted at an output terminal 8 via an IF amplifier 7. A voltage fed to a tuning voltage terminal 11 controls the VCO6 that its output is frequency-divided by a fixed frequency divider 9 and then inputted to a PLL circuit. In this case, the fixed frequency divider 9 counts a signal being the frequency division of the oscillated signal of the VCO6 and outputs a reception frequency band switching voltage. The voltage is fed to the band pass filters 2, 4 and the tuning circuit of the VCO to select the reception band.
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