| 摘要 |
PURPOSE:To prevent saturation of a high frequency amplifier at a pre-stage of a receiver and a mixer by attenuating an input high frequency signal by a prescribed quantity automatically when a reception signal level is excessively high and controlling the attenuation at each burst so that no attenuation is implemented at a normal level. CONSTITUTION:A variable attenuator 3 is connected between a band pass filter 2 and a high frequency amplifier 4, a comparator 12 is provided to a post-stage of a low pass filter 11, a digital signal outputted from the comparator 12 is stored in a D flip-flop 13 in matching with the trailing of a burst and outputted to the variable attenuator 3, and when the stored level is logical '1' a signal level outputted from the high frequency amplifier 4 is attenuated by a prescribed value, and when the stored value is logical '0' no attenuation is implemented. Thus, when one preceding burst reception level is larger than a prescribed level, attenuation is automatically implemented by the variable attenuator 3, and then the saturation of the high frequency amplifier or the like at the pre- stage of the receiver is prevented.
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