| 摘要 |
PURPOSE:To attain ALC (automatic level control) with a simple constitution by using a consine wave component outputted from a demodulating mixer for the ALC control of a receiving section in the Q (quadrature) AM transmission system using a leaked carrier wave. CONSTITUTION:A DC offset voltage Vdc is applied to any of I system data DIin and Q system data DQin, e.g., to the I system data, causing the leaked carrier wave in a modulated signal component. A receiving section 200 regenerates a carrier by a carrier wave regenerating circuit 202 based on the said leaked carrier wave and applies the carrier wave to mixers 203, 204 for demodulation. A receiving signal is shared into the I, Q system data at a hybrid 201 via an ALC circuit 230. The ALC circuit 230 monitors the level of a cosine component included in an output of the I system mixer 203 and controls the level of receiving signal to a constant value. |
