Surface acoustic wave filter including saw resonators with transmission spaces therein
AssigneeHitachi, Ltd.
InventorsMitsutaka Hikita, Toyoji Tabuchi, Kazuhito Kurosawa, Nobuhiko Shibagaki
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Abstract
Disclosed is a SAW filter employing a SAW resonator which is constructed of a plurality of pairs of electrode fingers formed on a piezoelectric substrate, and in which a plurality of SAW transmission spaces are included. The SAW transmission spaces do not have the function of exciting a SAW, and they have electric lengths which match the phases of SAWs excited by the resonator. In accordance with frequency characteristics required of the filter, such SAW transmission spaces are introduced into, for example, one of a plurality of SAW resonators located on the electric power input side of the filter.
Claims30
A SAW (surface acoustic wave) filter comprising:
- an input portion receiving input electric signals;
- an output portion emitting output electric signals;
- a plurality of SAW resonators being electrically connected so as to form a filter, each one of said plurality of resonators having a plurality of first and second electrode fingers interleavedly disposed on a piezoelectric substrate, a first SAW resonator generating surface acoustic waves in accordance with said input electric signals, and a second SAW resonator converting said surface acoustic waves into said output electric signal,
- wherein one of said plurality of resonators includes SAW transmission spaces being interposed between the first and the second electrode fingers, said transmission spaces having an electric length greater than a half-wavelength of the surface acoustic waves so as to transmit the surface acoustic waves generated in the resonators and equalize the surface acoustic waves as to have the same phase.
A SAW (surface acoustic wave) filter comprising:
- a plurality of SAW resonators, each one of said plurality of resonators having a plurality of electrode fingers being spacedly arranged on a piezoelectric substrate in a SAW propagation direction which is perpendicular to the electrode fingers, and one of said plurality of resonators also having SAW transmission spaces having a predetermined electric length greater than a half-wavelength of surface acoustic waves generated in the SAW resonators so as to transmit the surface acoustic waves generated in the resonators and equalize the surface acoustic wave as to have the same phase.
A SAW (surface acoustic wave) filter comprising:
- an input portion receiving input electric signals;
- an output portion emitting output electric signals;
- and
- a plurality of surface acoustic wave (SAW) resonators, each one of said plurality of SAW resonators including first and second electrode fingers being interleavedly disposed on a piezoelectric substrate, and having a resonant frequency and an antiresonant frequency respectively;
- wherein each of said plurality of SAW resonators is electrically connected between said input portion and said output portion, and forming a filter construction, wherein at least one of said plurality of SAW resonators has SAW transmission spaces interposed between the respective electrode fingers, resulting in different intervals between the resonant frequency and the antiresonant frequency among the plurality of resonators.
Dependencies are inferred from the claim text.