| 摘要 |
PROBLEM TO BE SOLVED: To easily attain low voltage and low power consumption, and to obtain proper filter characteristics. SOLUTION: An emitter-grounding amplifier 21 is used for a preceding circuit of a surface acoustic wave filter 10, a base grounding amplifier 31 is used for a succeeding circuit of the surface acoustic wave filter 10, and the output impedance of the preceding circuit is set larger than the input impedance of the succeeding circuit. At least one combination among a combination of the surface acoustic wave filter 10 and the preceding circuit and a combination of the surface acoustic wave filter and the succeeding circuit is set to an impedance-mismatched state. The surface acoustic wave filter the preceding circuit and the succeeding circuit are constituted as modules. Since the preceding circuit is not set to a low output impedance, low power consumption and low voltage can be attained. Since at least one combination among the combination of the surface acoustic wave filter and the preceding circuit and the combination of the surface acoustic wave filter and the succeeding circuit is set to the impedance-mismatched state, the effective filter characteristics having small TTE can be obtained. COPYRIGHT: (C)2006,JPO&NCIPI
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