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

To achieve a high stopband rejection in surface acoustic wave (SAW) filters a construction that includes a cascade of some elements (interdigital transducers (IDT) and multistrip couplers (MSC)) is used. In this case each element has to maintain a comparatively low frequency selectivity, and this permits a simple model and a high-speed calculation process to be employed for its design. The proposed constructions have an apodized transducer with a metal coating instead of a passive electrode region as the input IDT and broadband withdrawal weighted unapodized transducer as the output IDT. One or two group-type multistrip couplers (MSC) provide an additional frequency selectivity. The original synthesis algorithms have been developed for design of IDT and MSC structure.<
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