| 摘要 |
PURPOSE:To realize a filter having a good frequency characteristic, by coupling two comb line filters having different center frequencies by their average frequencies. CONSTITUTION:The width of an electrode finger of the first comb line electrode 5 is determined by a wavelegth lambda1, and the width of an electrode finger of the second comb line electrode 6 is determined by a wavelength lambda2. A multistrip coupler which is coupled with a middle wavelength lambda0 between the lambda1 and the wavelength lambda2 is provided between comb line electrodes 5 and 6. The frequency characteristic of a surface acoustic wave filter is given by the product between respective frequency characteristics of comb line electrodes 5 and 6. Comb line electrodes 5 and 6 are so operated that ripple characteristics of them are canceled by each other, thereby realizing a filter where the pass band is flat and the shoulder characteristic is sharp. |
