METHOD AND DEVICE FOR AUTOMATIC GAIN CONTROL OF SPREAD SPECTRUM SIGNAL

摘要

PURPOSE:To attain the automatic gain control regardless of the synchronization of a pseudo random series by receiving corelatively a received spread spectrum signal with a pseudo random signal of the same pattern as that of the transmission side, and using the peak of said signal to control the gain of an amplifier. CONSTITUTION:A spread spectrum signal 150 extracted from a power line via a coupler 100 is amplified by a variable gain amplifier 101 and undergoes correlative detection through a multiplier 102 together with a pseudo random code 152 fed from a pseudo random code generator 106. Thus a wave detection output 153 is obtained. A clock 157 supplied to the generator 106 is extremely approximate to the clock that is used for generation of the signal 150. The undesired band of the output 153 is deleted by an LPF103. A pulse having the peak value corresponding to the power of the signal 150 emerges at the output of the LPF103 since the synchronization is not always secured between the signal 150 and the code 152. This pulse is detected by a peak value detector 104 and held by a holding circuit 105. When the peak value is large, the circuit 105 reduces the gain of the amplifier 101. While the gain of the amplifier 101 is increased when the peak value is small.