AUTOMATIC GAIN CONTROL METHOD AND DEMODULATOR PROVIDED WITH AUTOMATIC GAIN CONTROL

摘要

PROBLEM TO BE SOLVED: To prevent error rate characteristic from being degraded even when the multi-level modulation system of a short distance between two-dimensional(2 D) signals is used by outputting I and Q signals while suppressing an amplitude error through closed loop automatic gain control based on positive and negative error signals and sin and cos rotary angle signals. ;SOLUTION: An AGC circuit 10 inputs an I signal 1 and a Q signal 1 and outputs an I signal 2 and a Q signal 2 to which automatic gain control is performed for suppressing the amplitude error while using error signals Ei and Eq inputted from a phase detector 7 and rotary angle signals sin and cos inputted from an NCO 9. A complex multiplier 6 inputs the I signal 2 and the Q signal 2 and outputs an I signal 3 and a Q signal 3 from which the frequency components of carrier waves contained in the I signal 1 and the Q signal 1 are removed while using the rotary angle signals sin and cos inputted from the NCO 9. As a result, even when the multi-level modulation system of a short distance between 2D signals is used, automatic gain control is performed without making the error rate characteristics adverse.;COPYRIGHT: (C)1999,JPO