| 摘要 |
PURPOSE:To eliminate almost all signal components of a video signal, and to easily obtain an integrated circuit, by constituting a beat detector of the first and the second detectors, eliminating a low band component of the video signal, and taking the difference between detecting output signal in a carrier signal of the first and the second signal components. CONSTITUTION:A synthesizing signal component of video IF and sound IF signals from an input terminal T2 is supplied to a carrier wave regenerating circuit 33, and a synchronizing carrier wave whose phase is different by pi/2 from a carrier wave of the video IF signal is regenerated to its output side. Also, the synchronizing carrier wave from a line 341 and the composite signal from a line 341 are inputted to the first multiplier 34, and in the multiplier 34, the video IF signal is detected by a quadrature phase axis, and a composite signal of a high band component of a video signal and a 4.5Hz beat signal is outputted. Also, a signal whose sound IF is eliminated by a sound signal suppressing circuit 36 and a signal from the circuit 33 are inputted to the second multiplier 35, and only the high band component of the video signal is outputted. Subsequently, the difference between detecting outputs of the multipliers 34, 35 is outputted by a subtracter 37, and all the signal components of the video signal are eliminated. |
