Wave transmission lines and networks – Coupling networks – Electromechanical filter
Reexamination Certificate
2005-02-08
2005-02-08
Summons, Barbara (Department: 2817)
Wave transmission lines and networks
Coupling networks
Electromechanical filter
C333S196000, C333S133000, C310S31300R
Reexamination Certificate
active
06853270
ABSTRACT:
A surface acoustic wave filter includes a first reflector, a first IDT, a second IDT, a third IDT, and a second reflector arranged in that order on a piezoelectric substrate. The first IDT and the third IDT, connected in parallel, are together also connected to an unbalanced signal terminal. The second IDT includes two separate comb-like electrodes arranged in the direction of propagation of a surface acoustic wave, and electrically connected in series to each other at a serial junction. The comb-like electrodes are respectively connected to balanced signal terminals. The outermost electrode finger of the first IDT is connected to the unbalanced signal terminal, and the outermost electrode finger of the third IDT is grounded. The first IDT only or both the first IDT and the third IDT are weighted so that the number of excitation regions of the surface acoustic wave between the second IDT and the first IDT becomes equal to the number of excitation regions of the surface acoustic wave between the second IDT and the third IDT.
REFERENCES:
patent: 5835990 (1998-11-01), Saw et al.
patent: 20020021195 (2002-02-01), Takamine
patent: 20020145361 (2002-10-01), Shibata et al.
patent: 198 18 826 (1999-11-01), None
patent: 1 168 611 (2002-01-01), None
patent: 11-97966 (1999-04-01), None
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
Summons Barbara
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