Title:
SAW FILTER
Document Type and Number:
Japanese Patent JP3154402
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To widen a band, without narrowing the cross width of resonators and the intervals of the resonators by installing a first cross finger electrode with a period length L, which converts input voltage into a surface acoustic wave, a second cross finger electrode with a period length L, which converts it inversely, and a first reflector group and a second reflector group, which have the specified period lengths by leaving specified intervals on both outer sides of the cross finger electrodes.
SOLUTION: A surface wave on a piezoelectric substrate 100 which is excited by the cross finger electrode 2 is reflected between the reflectors 4 and 5. Energy is confined and a standing wave (first vertical resonance) is generated. Partial energy leaks outside and is reflected between the reflectors 6 and 7. Then, the standing wave (second vertical resonance) is generated. First vertical resonance and second vertical resonance are mutually connected and the strength of connection and a frequency difference between vertical resonances change by the number of the reflectors 4 and 5. Since both the resonances have symmetric/asymmetric modes, four resonances in total are generated. Thus, the four resonances can be adjusted according to the appropriate frequency intervals by the number.
Inventors:
Sakairi, Natsuhiko
Application Number:
JP31022197A
Publication Date:
April 09, 2001
Filing Date:
November 12, 1997
Export Citation:
Assignee:
NEC CORP
International Classes:
H03H9/64; H03H9/25; (IPC1-7): H03H9/64
Attorney, Agent or Firm:
山下 穣平