| 摘要 |
<p>A three-transducer SAW filter (Fig. 2) that includes a central input transducer (109) requiring only one-half of the interdigital fingers normally required by prior art three-transducer SAW filters (Fig.1). As a result, two input transducers (305 and 306 in Fig. 3) may now be provided in the space normally occupied by one prior art input transducer (103 in Fig. 1). The only requirement is that each input transducer (305 and 306 in Fig 3) have an axis of symmetry (310) about which surface waves propagate symmetrically to output transducers (301 and 302). Since each input transducer (305 and 306) may have a different frequency response, such as (401 and 402 in Fig. 4), a dual-passband SAW filter (Fig. 3) may now be provided in the space normally occupied by a single prior art SAW filter. Furthermore, a multi-passband SAW filter (Fig. 6) may be provided by arranging pairs of input transducers (602, 603 and 605, 606) between three or more output transducers (601, 604 and 607) which are electrically coupled in parallel. In addition, the input and output connections of a multi-passband SAW filter (Fig. 5) may be interchanged such that an input signal, applied to the parallel connected output transducers (506 and 509) is frequency sorted by the passbands of each of the input transducers (507 and 508). </p> |
