| 摘要 |
PROBLEM TO BE SOLVED: To prevent a reduction in the reception sensitivity of signals with a plurality of frequency bands different from each other. SOLUTION: A signal reception circuit includes: a main antenna 3 capable of receiving signals with a plurality of predetermined reception frequency bands; and a sub-antenna 4 capable of receiving a signal with one selected out of the reception frequency bands of the main antenna 3. A filter 6 for interrupting a signal with the same frequency band as the reception frequency band of the sub-antenna 4 is provided on a conduction path 10 of a reception signal of the main antenna 3. A filter reflection signal with the same frequency band as the reception frequency band of the sub-antenna 4 is induced in the sub-antenna 4, due to the antenna coupling thereof. The phase of the filter reflection signal is adjusted by a phase shift circuit 5 between the main antenna 3 and the filter 6, so that the induced signal of the sub-antenna 4 is in phase with the reception signal of the sub-antenna 4. As a result, the level of the composed signal of the induced signal and the reception signal to be transmitted from the sub-antenna 4 to a signal processing unit is greatly improved. COPYRIGHT: (C)2004,JPO
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