SAW filters with high stopband rejection based on a cascadeconnection of selective elements

摘要

To achieve a high stopband rejection in surface acoustic waven(SAW) filters a construction that includes a cascade of some elementsn(interdigital transducers (IDT) and multistrip couplers (MSC)) is used.nIn this case each element has to maintain a comparatively low frequencynselectivity, and this permits a simple model and a high-speedncalculation process to be employed for its design. The proposednconstructions have an apodized transducer with a metal coating insteadnof a passive electrode region as the input IDT and broadband withdrawalnweighted unapodized transducer as the output IDT. One or two group-typenmultistrip couplers (MSC) provide an additional frequency selectivity.nThe original synthesis algorithms have been developed for design of IDTnand MSC structure