| 摘要 |
PURPOSE:To improve the deterioration in characteristic of a signal due to distortion of a transmission system and a frequency demodulator by inverting the polarity of modulation of a TV signal at the reception side and transmission side to provide only a maximum frequency shift to an output signal of a frequency modulator. CONSTITUTION:The TV signal inputted to a TV signal input terminal 21 is inverted according to a control signal 22 by a polarity inverting circuit 23 and the average value is eliminated. Then an output signal of the circuit 23 is inputted to a frequency modulator 24, becomes a frequency modulator output signal 25 and then a signal 27 subject to the frequency detuning at the transmission system 26. Then an intermediate frequency signal 29 frequency-detuned by a frequency converter 28 of the reception system and the signal 29 is demodulated by a frequency demodulator 30. This demodulated output is fed back to the frequency converter 28 to suppress frequency detuning. The output signal of the frequency demodulator is inverted according to the control signal 22 at a polarity inverting circuit 31 and the result is outputted to an output terminal 32. |
