| 摘要 |
PURPOSE:To retain always straight line phase characteristics by using an elastic surface wave filter having good phase characteristics in a high frequency area which contributes to contour characteristics among video signals and making its output level variable. CONSTITUTION:A video signal inputted into a terminal 2 is divided into two waves, one of which reaches a variable amplifier 14 through an elastic surface wave filter 13. The filter 13, because its amplitude and phase characteristics are independently designed, any amplitude frequency characteristics are realized while retaining a straight line phase characteristics. The filter 13 is composed of a pair of screen-formed electrodes 15 and 16 and has a delay time to be decided from its arrangement. The other wave inputs into a wide-band delay line 17 having a delay time equivalent to that of the filter 13. Both outputs are added by an adder 18, and the overall delay time characteristics are made constant, thereby always retaining the straight phase characteristics even when the amplitude characteristics arbitrarily change.
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