| 摘要 |
PROBLEM TO BE SOLVED: To provide a duplexer that functions as a filter having variable frequency characteristics and is reduced in circuit area and number of components. SOLUTION: A duplexer includes a first port, a second port and a third port for external input/output, a first path is formed between the first port and the third port, a second path is formed between the second port and the third port, and a phase shifting part and a resonating part are formed in each path. At least one of resonating parts has a ring conductor having a length equal to one wavelength at a resonant frequency or an integral multiple thereof, a plurality of passive circuits, and a plurality of switches each of which is connected to a different part of the ring conductor at one end and to one of the passive circuits at the other end. A switch may simply be connected to a ground conductor instead of being connected to the passive circuit. COPYRIGHT: (C)2009,JPO&INPIT
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