Surface acoustic wave resonator filter with a weighted asymmetrical interdigital electrode

摘要

A three-electrode longitudinally-coupled-type SAW resonator filter has an improved level of selectivity by effectively suppressing unwanted large spurious responses generated in a range higher than the pass band. A first ID electrode, a second ID electrode and a third ID electrode are disposed on a piezoelectric substrate. Reflectors are provided on one side of each of the second and third ID electrodes, respectively. A center distance L1 between the most adjacent electrode fingers of the respective first and second ID electrodes is differentiated from the center distance L2 between the most adjacent electrode fingers of the respective first and third ID electrodes. Further, the first ID electrode is weighted to more effectively suppress undesired spurious responses.