Low-cost high-performance resonator and coupled-resonator design: NSPUDT and other innovative structures

A design philosophy for low-cost, high-volume SAW resonators and coupled resonators is presented. In view of the low-cost constraint, only configurations requiring a single level of metallization are considered. To illustrate the design concepts involved, examples are given of alternate resonator topologies and their important performance characteristics are discussed. Design emphasis was on resonators having good out-of-band characteristics. Two novel resonator structures that have been developed with essentially symmetric out-of-band responses are described. Both use only single-level metallization and no grooves. The fundamental difference between the two approaches is that the first structure requires NSPUDT (Natural Single-Phase Unidirectional Transducer) orientations, while the second can be built on conventional crystal orientations