Multi-mode edge reflection saw filter device with ground electrodes between stages, duplexer, and communication device

A duplexer comprising:

• a piezoelectric substrate;
• a plurality of stages of multi-mode filters which are defined by a plurality of edge-reflection type surface acoustic wave devices and are electrically connected in series with each other, said plurality of stages of multi-mode filters are all located on said piezoelectric substrate and arranged to extend in a direction which is substantially perpendicular to a propagation direction of surface acoustic waves generated therein;
• and
• a plurality of ground electrodes located between respective stages of said plurality of stages of said multi-mode filters.

A communications apparatus comprising:

• a piezoelectric substrate;
• a plurality of stages of multi-mode filters which are defined by a plurality of edge-reflection type surface acoustic wave devices and are electrically connected in series with each other, said plurality of stages of multi-mode filters are all located on said piezoelectric substrate and arranged to extend in a direction which is substantially perpendicular to a propagation direction of surface acoustic waves generated therein;
• and
• a plurality of ground electrodes located between respective stages of said plurality of stages of said multi-mode filters.