| 摘要 |
PROBLEM TO BE SOLVED: To prevent an excess input at amplification of a digital modulation signal. SOLUTION: A plurality of high frequency signals including at least one digital modulation signal is supplied to an input terminal 2, and an amplifier 8 amplifies the high frequency signals. A variable attenuator 6 attenuates the high frequency signals before being applied to the amplifier 8 and gives the attenuated signals to the amplifier 8. An excess input detector 12 is placed between the output of the variable attenuator 6 and the output of the amplifier 8 and increases the attenuation of the variable attenuator 6 when the level of the received high frequency signals is greater than a reference level required to bring a bit error rate of the digital modulation signal into a predetermined rate or below. |
