| 摘要 |
PURPOSE:To stabilize a base band output level with simple constitution by controlling an AGC circuit gain at the input signal side with an added output of each output obtained through the application of two-multiplication to a base band output signal of both demodulated channels. CONSTITUTION:An input IF signal whose level is stabilized by the AGC circuit 1 is branched into two via a hybrid 2 and inputted to mixers 3, 4. An output having a phase different by 90 deg. is inputted to the mixers 3, 4 via a phase shifter 6 and a voltage controlled oscillator 5 whose oscillating frequency is controlled in a Costas loop 7 and the result is outputted as base band outputs I, Q. The base band output of both the channels are fed respectively to an adder 13 via two- multiplication devices 11, 12 and an output of the adder 13 controls the gain of the AGC circuit 1. Thus, the base band output signal of a stable level is obtained through simple constitution. |
