| 摘要 |
PROBLEM TO BE SOLVED: To control the gain of an amplifying means to an analog modulated signal, based on the amplitude information of a base-band signal. SOLUTION: Received analog modulated signals (QPSK signals and QAM signals) are amplified by an amplifier 14 and the amplified signals are converted into digital modulated signals by means of an A/D-converting section 16. An orthogonal detecting section 20 detects the digital modulated signal by multiplying the signals by a reproduced carrier shifted in phase from that of the signals by 90 deg.. An amplitude detecting section 30 synthesizes the vectors of two base- band signals I and Q obtained by detection and detects the amplitude level A= (I<2> +Q<2> )<1/2> } of the base-band signals. A D/A-converting section 18 converts the digital amplitude level into an analog signal and supplies the analog signal to the amplifier 14 as a gain control signal. Therefore, the gain of the analog modulated signals is controlled in accordance with the amplitude level of the base-band signals. |
