| 摘要 |
PURPOSE:To accurately detect a noise level due to a multipath and the presence/ absence of the multipath, by detecting the generating state of the multipath, based on the noise level near a stereo pilot signal. CONSTITUTION:A pilot signal component in 19kHz is picked up from an FM detection output at a band pass filter(BPF)1 and is inputted to a PLL circuit 3 functioning as a 90 deg. phase shifter and to a multiplier 2. The multiplier 2 generates an output corresponding to the noise level distributed around 19kHz by multiplying 19kHz signals having 90 deg. phase difference from the BPF1 and a BPF4. The noise level around the 19kHz pilot signal has a correlation with the multipath and is outputted as a signal indicating the generating state of the multipath via a low pass filter 5 and an amplifier 6. |
