Saw multiplexer using tapered transducers

Claim 1

A SAW multiplexing device comprising a substrate suitable for conducting surface acoustical waves (SAWs), transducer means formed of interdigital, electrode fingers located on said substrate for launching a plurality of SAW components, each of which comprise a predetermined center frequency and a band of frequencies about said center frequency, and each of which travels along its own predetermined path on said substrate wherein said fingers exhibit a variable separation along the length of said transducer means, and a plurality of pickup means each disposed on said surface so as to receive one of said SAW components, wherein said pickup means are each constructed to be selectively responsive to the center frequency and the band of frequencies around said center frequency of an associated one of said SAW components, and said center frequency and said band of frequency are determined by the spacing dimensions of said fingers of said transducer means at a predetermined portion of said transducer means, and wherein said interdigital electrode fingers are each formed as segments of hyperbolic curves positioned such that the spacing between said fingers varies from point-to-point along said transducer means and the spacing between said fingers is substantially constant at any given point, and said electrode fingers comprise a pair of outer electrode fingers and a plurality of inner electrode fingers, said outer electrode fingers are relatively wider than said inner electrode fingers, said inner electrode fingers are subdivided into a plurality of hyperbolically curved sections, and said transducer means comprises interconnection electrode connection means for connecting each of said sections to one of said outer electrode fingers.