Surface acoustic wave device and communication apparatus

A surface acoustic wave device comprising:

• a piezoelectric substrate;
• at least one surface acoustic wave filter provided on the piezoelectric substrate and including at least two interdigital transducers arranged along a direction in which a surface acoustic wave propagates;
• and
• at least one surface acoustic wave resonator provided on the piezoelectric substrate and connected in series to said at least one surface acoustic wave filter;
• wherein
• said at least one surface acoustic wave resonator is arranged such that a resonant frequency thereof is located within a pass band of said at least one surface acoustic wave filter and such that an antiresonant frequency thereof is located outside the pass band, and a dummy electrode is disposed between an electrode finger and a bus bar of each of the at least two interdigitat transducers of said at least one surface acoustic wave resonator such that a spurious response caused by a surface skimming bulk wave is located within the pass band.

A surface acoustic wave device comprising:

• a piezoelectric substrate;
• at least one surface acoustic wave filter provided on the piezoelectric substrate and including at least two interdigital transducers arranged along a direction in which a surface acoustic wave propagates;
• and
• at least one surface acoustic wave resonator provided on the piezoelectric substrate and connected in series to said at least one surface acoustic wave filter;
• wherein
• said at least one surface acoustic wave resonator is arranged such that a resonant frequency thereof is located within a pass band of said at least one surface acoustic wave filter and that an antiresonant frequency thereof is located outside the pass band, and a dummy electrode is disposed between an electrode finger and a bus bar of each of the at least two interdigital transducers of said at least one surface acoustic wave resonator;
• and
• a gap between the dummy electrode and the electrode finger of the interdigital transducers of said at least one surface acoustic wave resonator is about 0.5λ or less, where a wavelength determined by a pitch between the electrode fingers of the interdigital transducers is indicated by λ.

A surface acoustic wave device comprising:

• a piezoelectric substrate;
• at least one surface acoustic wave filter provided on the piezoelectric substrate and including at least two interdigital transducers arranged along a direction in which a surface acoustic wave propagates;
• and
• at least one surface acoustic wave resonator provided on the piezoelectric substrate and connected in series to said at least one surface acoustic wave filter;
• wherein
• said at least one surface acoustic wave resonator is arranged such that a resonant frequency thereof is located within a pass band of said at least one surface acoustic wave filter and that an antiresonant frequency thereof is located outside the pass band, and a dummy electrode is provided between an electrode finger and a bus bar of each of the at least two interdigital transducers of said at least one surface acoustic wave resonator;
• and
• a length of the dummy electrode of said at least one surface acoustic wave resonator is at least about 0.25λ, where a wavelength determined by a pitch between the electrode fingers of the at least two interdigital transducers of said at least one surface acoustic wave resonator is indicated by λ.