| 摘要 |
PURPOSE:To prevent the deterioration of a noise figure due to the attenuation of a variable attenuator attended with the increase in an input signal of a high frequency reception circuit by constituting a pre-stage high frequency amplifier with the 1st high frequency amplifier, the 1st variable attenuator, the 2nd high frequency amplifier and the 2nd variable attenuator connected sequentially in cascade. CONSTITUTION:An output 116b of an automatic level control circuit 116 operates only the 2nd stage variable attenuator 12d in the pre-stage high frequency amplifier 12 until a level where the distortion characteristic of the 2nd stage high frequency amplifier 12b is a problem after an input signal 100 of a high frequency reception circuit reaches a certain level. When the input signal 100 of the high frequency reception circuit reaches the level of over, an output signal 116a of the automatic level control circuit 16 operates the 1st stage variable attenuator 12c in the pre-stage high frequency amplifier 12. Then the output of the high frequency reception circuit is made constant.
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