SURFACE-WAVE REJECTION FILTER Russian patent published in 1998 - IPC

FIELD: radio engineering; acoustoelectronics. SUBSTANCE: filter has piezoelectric substrate mounting two interdigital transducers connected in series and parallel-tuned to resonance at rejection frequency. Novelty is that inserted between common point of connection of two interdigital transducers and filter case is structure placed on piezoelectric substrate and built up of three impedance units arranged in single surface-wave propagation channel; extreme impedance units are interdigital transducers resonance-tuned in series at rejection frequency and central unit is shorted-out grating with same period of electrodes as extreme ones; all three impedance units are interconnected in series by topological connection of lower contact pads of first and second units and upper pads of second and third units as well as their acoustic connection in phase. EFFECT: improved noise immunity. 2 dwg