| 摘要 |
PROBLEM TO BE SOLVED: To provide a longitudinally coupled surface acoustic wave filter for solving the problem of conventional SAW filter that the attenuation gets smaller at a frequency band apart from a pass band although the attenuation at frequencies in the vicinity of the pass band can easily be ensured. SOLUTION: Al least one 1-terminal pair SAW resonator 33 or over is connected as a parallel element to one side of a 2-terminal pair SAW resonator 32 wherein reflectors 1, 5 comprising shortened grating electrodes are disposed at both sides of at least two sets of IDTs 2, 3, 4 or over. The resonance frequency of the 1-terminal pair SAW resonator 33 is selected to be a frequency within a range of a multiple of 1.1 to 1.5 of the center frequency f0 of the pass band of the 2-terminal pair SAW resonator 32. Thus, the SAW filter having a great attenuation even at a frequency band of high frequencies apart from the pass band, a wide block band and a small loss in the pass band can be realized. COPYRIGHT: (C)2004,JPO
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