Patent ID: 6046630
Filing Date: 2000-04-04
Classification: H04L

Abstract:
A .pi./4 QPSK digital modulation method of a digital demodulation apparatus of a QPSK receiver which demodulates an input signal being modulated in QPSK method by separating into an I (In Phase) channel signal and a Q (Quadrature) channel signal by a local carrier which is synchronized with the transmitter, comprising the steps of:mixing the input modulated signal with one-symbol delayed reference signal to derive phase information of the I channel signal and the Q channel signal;recovering data by sampling the phase information of the derived I channel and the Q channel;converting the recovered I and Q channel data to serial data to recover parity data and basic data on the basis of the converted serial data and previous data which is delayed by a predetermined symbol unit; andcorrecting errors of the recovered basic information data and the parity data by a predetermined modular operation.