| 摘要 |
PURPOSE:To detect stably the threshold level at a squelch operating point by using an automatic tracking-type band-pass filter in the squelch circuit which prevents needless noise from being received in a FM wave receiver. CONSTITUTION:Though intermediate frequency signals from input terminal 1 are amplified by amplifier 2 and reach output terminal 4 through gate circuit 3, a part of these signals has needless high-frequency components eliminated by automatic tracking-type filter 10 to control gate circuit 3 thro gh detector 6 and buffer amplifier 9. Automatic tracking-type filter 10 consists of phase difference detector 11, filter 12 and filter 5, where a variable capacity diode changing by receiving the output control voltage of filter 12 is added, and causes the center frequency of filter 5 to agree with the frequency of input terminal 1. |
