SPUDT-based tunable resonant coupling of different acoustic channels

Resonant coupling between two non-waveguide acoustic channels is considered and analyzed in detail. A pair of electrically parallel, while placed in different channels, single-phase unidirectional transducers, loaded by matching inductance, may be used in order to fold the SAW propagation path. Such a possibility provides the additional degree of freedom in the design of SAW filters, being applicable even to weak piezocrystal cuts. Some device architectures are examined to demonstrate possible significant improvement of filter selectivity. It's shown that this aim may be achieved even when using unweighted SPUDTs by proper combinations of reflectivity and lengths of transducers and reflectors placed within each a channel. Influence of re-radiator's load on the filter performances is illustrated too.