Saw resonator filter with bridged-T configuration
AssigneeOki Electric Industry Co., Ltd.
InventorsHisanori Ehara, Hajime Shimamura, Yoshiaki Fujita, Tomokazu Komazaki
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Abstract
A surface-acoustic-wave filter has a pair of series-arm surface-acoustic-wave resonators and a shunt-arm surface-acoustic-wave resonator coupled in a T configuration. An additional bridging surface-acoustic-wave resonator is coupled between the input and output terminals, in parallel with the series arm. The bridging surface-acoustic-wave resonator provides enhanced attenuation of spurious signals at multiples of the passband frequency.
Claims16
A surface-acoustic-wave filter having a T-type configuration with a series arm, a shunt arm, an input terminal, an output terminal, and a ground terminal, the series arm having a node, a first surface-acoustic-wave resonator coupled between said node and the input terminal, and a second surface-acoustic-wave resonator coupled between said node and the output terminal, the shunt arm having a third surface-acoustic-wave resonator coupled between said node and the ground terminal, the third surface-acoustic-wave resonator having an antiresonance frequency, the first surface-acoustic-wave resonator having a resonance frequency substantially equal to said antiresonance frequency, the surface-acoustic-wave filter also comprising:
- a fourth surface-acoustic-wave resonator coupled between the input terminal and the output terminal, in parallel with the series arm.
A surface-acoustic-wave filter comprising:
- an input terminal;
- an output terminal;
- a ground terminal;
- first and second surface-acoustic-wave resonators coupled as series-arm resonators between the input terminal and the output terminal, the first surface-acoustic-wave resonator having a resonance frequency;
- a third surface-acoustic-wave resonator coupled as a shunt-arm resonator between the first surface-acoustic-wave resonator and the ground terminal, the third surface-acoustic-wave resonator having an antiresonance frequency substantially equal to the resonance frequency of the first surface-acoustic-wave resonator;
- and
- a fourth surface-acoustic-wave resonator coupled between the input terminal and the output terminal in parallel with the first and second surface-acoustic-wave resonators.
Dependencies are inferred from the claim text.