| 摘要 |
PURPOSE:To attain narrow-band transmission of video signal by inserting a part of the low band component of the output of a frequency converting means that corresponds to the high band component of an input video signal, in a low band part neighboring the high band part of the input video signal. CONSTITUTION:A video signal is inputted to an input terminal 1. A carrier wave generating circuit 2 generates a carrier wave for frequency modulation from the horizontal synchronizing signal of the input video signal. The output from the carrier wave generator 2 is inputted to a balanced modulator 3 as a carrier wave, and a modulated video signal which is frequency-modulated is obtained from the output of the modulator 3. The said signal is inputted to an LPF 4 in order to eliminate its high-frequency components. The output signal from the LPF 4 is added to an original video signal inputted to the terminal 1 by an adder 5. The signal thus obtained is attenuated of its component, for instance, higher than fc/2 (fc is the carrier frequency) by an LPF 6. The frequency spectrum after this attenuation is as shown by the figure which means that the video signal is transmitted in a narrow band.
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