| 摘要 |
PURPOSE:To attain a filter circuit with a large attenuation characteristic with less circuit constitution by connecting the 1st filter circuit switched to a different filter characteristic and the 2nd filter characteristic switched to a different filter characteristic in cascade. CONSTITUTION:In receiving a TV signal from an input terminal 1, the signal is amplified by a high frequency amplifier circuit 3 through an input filter switched by a reception band and the result is outputted from an output terminal 3 from an output terminal via the 1st mixing circuit 4, a band pass filter 6, the 2nd mixing circuit 7 and the 2nd IF amplifier 9. The input filter 2 consists of an HPF 11 and an LPF 12 and consists of the filter circuit 43 switched into the 1st high pass filter characteristic and the 1st low pass filter characteristic by switching diodes 16-19 and the 2nd filter circuit 44 consisting of the BPF 13, the HPF 14 and switching diodes 20-25 and switched into the 2nd bypass filter and band pass filter characteristics and the 2nd low pass filter characteristic by connecting in cascade through a capacitor 26.
|
