Patent ID: 6483883
Filing Date: 2002-11-19
Classification: H04L

Abstract:
An automatic gain control type demodulation apparatus comprising:an orthogonal demodulation circuit for receiving an analog input signal to generate a first I-signal and a first Q-signal orthogonal to each other; an analog/digital converter circuit, connected to said orthogonal demodulation circuit, for performing an analog/digital conversion operation upon said first I-signal and said first Q-signal to generate a second I-signal and a second Q-signal; an automatic gain control circuit, connected to said analog/digital converter circuit, for suppressing amplitude errors of said second I-signal and said second Q-signal to generate a third I-signal and a third Q-signal; a complex multiplier, connected to said automatic gain control circuit, for removing frequency and phase offset components of a carrier wave included in said third I-signal and said third Q-signal to generate a fourth I-signal and a fourth Q-signal; a phase detector, connected to said complex multiplier, for detecting first and second amplitude errors of said fourth I-signal and said fourth Q-signal, respectively, with respect to one normal signal point and calculating a phase error of said fourth I-signal and said fourth Q-signal; and a numerical control oscillator, connected to said phase detector, for converting said phase error into first and second angle signals orthogonal to each other, said automatic gain control circuit being connected to said phase detector and said numerical control oscillator, for controlling the amplitude errors of said second I-signal and said second Q-signal in accordance with said first and second amplitude errors and said first and second angle signals.