To make a circuit structure simple and to secure a sufficient reception level detection range by equipping a gain variable means and an amplitude limiting means for limiting a level of a radio signal from the gain variable means up to a level equivalent to a dynamic range of an optical transmission line.
An input radio signal is led to a gain compression circuit 1 after it is received by a receiver of a radio part. In a gain control means in the gain compression circuit 1, a gain control signal for variable controlling a level of the input radio signal is generated. Next, in an amplitude limiting means 2, a level of the radio signal from the gain variable means is limited up to a level equivalent to a dynamic range of an optical transmission line and outputted. As it is constituted like this, sufficient detection of an input signal level range and a sufficient amplitude restricting ability are simultaneously realized by performing gain compression by the gain variable means only in a range where detection of the input signal level is necessary and limiting an amplitude in areas other than that.
HAMADA TOMOICHI
OGASAWARA MAMORU
SHIRATO TADASHI
MIYAKOSHI SHINICHI
NIPPON TELEGRAPH & TELEPHONE
SHIMADA PHYSICAL CHEM IND CO
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