| 摘要 |
PROBLEM TO BE SOLVED: To prevent a local oscillation signal from leaking to an LNA side to cause deterioration of the reception sensitivity and to prevent a DC offset from occurring between a demodulation output of an I signal and a demodulation output of a Q-signal, even when the receiver adopts the direct conversion system which directly demodulates a received RF signal, so that no DC offset is produced. SOLUTION: An isolator 4 is provided between the LNA 3 and multipliers 6A, 6B which configure a demodulation circuit. An inverse passing characteristic of the isolator 4 can prevent the local oscillation signal from being leaked to an output side of the LNA 3, so as to suppress deterioration in the sensitivity of a received signal and distortion in the LNA. Furthermore, the receiver is provided with a branching filter 5 which acts as a directional coupler, to distribute the signal from the LNA into two paths. The branching filter 5 can suppress leakage of the local oscillation signal from one multiplier 6A or 6B to the other multiplier 6B or 6A, thereby suppressing the occurrence of a DC offset of a base band signal.
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