| 摘要 |
PURPOSE:To reduce a noise of a luminance signal extending over the whole band of its signal, by expanding the passing band width by setting the passing center frequency of a delaying circuit to a high band, and converting the frequency of the luminance signal in accordance with it. CONSTITUTION:As for a glass delay line used for a delaying circuit, the passing center frequency is almost proportional to the passing band width, and when the passing center frequency is made high, the passing band width fw of the glass delay line becomes wide in proportion to it. A delaying circuit 16 is used by utilizing this characteristic of the glass delay line and making the passing center frequency high. An FM-modulated luminance signal coming from an input terminal 1 is supplied to a demodulator 6, and also is supplied to a frequency converter 14. A signal is supplied to this frequency converter 14 from an oscillator 15, and the luminance signal is frequency-converted, and thereafter, is supplied to the delaying circuit 16. The delaying circuit 16 delays the FM-luminance signal which is supplied, by 1 horizontal scanning period and supplies it to a frequency converter 17. The frequency converter 17 frequency-converts this delayed FM- luminance signal by a signal supplied from the oscillator 15 and supplies it to a demodulator 3. |
