| 摘要 |
PURPOSE:To accomplish the demodulation method of television voice multiplex with a low distortion factor, by obtaining a signal difference through the application of a composite voice multiplex signal and a main voice signal to the input side of a differential amplifier respectively and picking up a subvoice signal through the demodulation of the signal difference using an FM detector. CONSTITUTION:For example, a composite voice multiplex signal Fcomp from an input terminal 1 is an FM+FS signal via a frequency trap 2 except a control signal FQ of 3.5fH and inputted to one of a differential amplifier 3. The main voice signal FM only is picked up and coupled to another input via an LPF4 of 15kHz and also coupled to a main-, subswitching circuit 5. Further, at the output of the differential amplifier 3, a subchannel signal FS as an FM signal eliminated with the amplitude modulating component and the amplitude overlapped component is obtained, and it is picked up as subvoice signal Fs by demodulating it at an FM detector 6. Thus, a subvoice signal with a low distortion factor and less cross talk from the main channel and ease of IC formation is accomplished without using the expensive band pass filter. |
