| 摘要 |
PURPOSE:To obtain an excellent pattern by using a band pass filter in extracting a low frequency conversion chrominance signal from a reproducing signal outputted from a video head so as to eliminate noise generated from a switching power supply from a reproduced chrominance signal processing system. CONSTITUTION:A reproduced signal reproduced by a video head 8 is inputted to a high pass filter (HPF)10 and a band pass filter (BPF)17 via a head amplifier 9. The luminance signal component is extracted by an HPF10 and becomes a demodulated luminance signal through a demodulator 11 and a deemphasis circuit 12 and the demodulated luminance signal is inputted to a mixer 16. A low frequency conversion chrominance signal component is extracted at the BPF17 and inputted to a balanced modulator 14. Since the transmission characteristic falls down rapidly near 200kHz in the transmission characteristic of the BPF17, switching noise of f0, 2f0, 3f0 cannot transmit through the said BPF. Thus, the noise component generated from the switching power supply is not mixed to the color signal processing system comprising a balance modulator 14, a BPF15 and a mixer 16. |
