| 摘要 |
PURPOSE:To band-limit the television signal of the wide band with a little group delay distortion by providing an elastic surface wave filter to band-limit a modulator and a modulated signal in a desired band and a demodulator of obtain an output to receive a desired band-control by demodulating the output of this elastic surface wave filter. CONSTITUTION:As a high-fidelity television (high-vision) signal, an AM modulator 102 converts wide band image information having a high frequency component from a direct current component to 30 MHz to the AM modulated wave of the high frequency, for example, about at 200 MHz and introduces this AM modulated wave signal to a elastic surface wave filter 103. In the elastic surface wave filter 103, with the number of teeth and their shape etc., of a facing comb shaped electrode, it is band-controlled to a desired transmitting band characteristic and the output of this elastic surface wave filter 103 is AM-demodulated with a demodulator 104 and image information to receive a desired band-control is obtained. Thus, for the elastic surface wave filter 103, basically, a group delay is flat and band-limited image information without a group delay distortion is obtained.
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