| 摘要 |
A surface acoustic wave filter includes a length-weighted interdigital transducer (T1) on one side of which are bus bar parts (BP1, BP2) which are within the transducer acoustic aperture (A), are inclined at an acute angle to the propagation path (P) and which closely follow the major lobe (L1). These bus bar parts each have a width (W) along the propagation path (P) defined by 2W=n lambda /2 where n is an odd integer and lambda is the wavelength of surface acoustic waves at substantially the maximum amplitude response frequency of the transducer (T1). The components of the surface acoustic waves reflected from the two edges of each inclined bus bar part along the propagation path, that is to say the component reflected waves (SW1) reflected from the edge closest to the overlap envelope and the component reflected waves (SW2) reflected from the edge which forms part of one end of the transducer, are in antiphase at that maximum response frequency and so spurious signals due to the component reflected waves (SW1 and SW2) at that frequency are substantially suppressed.
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