Surface acoustic wave filter

A surface acoustic wave filter including a piezoelectric substrate having two ends and a longitudinal axis;

• two surface acoustic wave resonators on said substrate which comprise respective interdigital transducers, each formed by interdigitating two comb-like electrodes, and two reflectors at opposite ends of said substrate on both sides of said interdigital transducers, each formed by a plurality of electrodes parallel to one another;
• said interdigital transducers and reflectors being disposed symmetrically about said longitudinal axis on said piezoelectric substrate;
• and
• an electrostatic capacity being bridged between an input terminal and an output terminal of the filter, said electrostatic capacity being formed on said piezoelectric substrate by interdigitating respective capacitive electrodes of said interdigital transducers of said two surface acoustic wave resonators;
• wherein a first pitch between said capacitive electrodes is smaller than a second pitch between said comb-like electrodes of said interdigital transducers.

A surface acoustic wave filter including a piezoelectric substrate having two ends and a longitudinal axis;

• two surface acoustic wave resonators on said substrate which comprise respective interdigital transducers, each formed by alternately interdigitating two comb-like electrodes, and two reflectors, at opposite ends of said substrate on both sides of said interdigital transducers by a plurality of reflector electrodes parallel to one another;
• said interdigital transducers and reflectors being disposed symmetrically about said longitudinal axis on said piezoelectric substrate;
• and
• an electrostatic capacity being bridged between an input terminal and an output terminal of the filter, said electrostatic capacity being formed on said piezoelectric substrate by interdigitating respective capacitive electrodes of said reflectors.