| 摘要 |
An object of the invention is to receive a weak signal with high sensitivity and reduce distortion and signal suppression when a strong interference signal exists. When a high-frequency signal received by an antenna is to be amplified by an antenna amplifier and when an interference wave of high field strength exists, a switch circuit is switched by an output switchover circuit from the output of an amplifier to a through-circuit. The through-circuit guides the high-frequency signal, directly to the output side without passing through the amplifier. When the switching operation of the switch circuit is performed based on low-frequency components which are highly correlated with distortion components due to intermodulation, the switching operation can be performed more adequately. Noises can be reduced by performing a smoothing process on the switching operation, and the use of an inverting amplifier can prevent occurrence of oscillation.
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