.pi./4 QPSK digital demodulating apparatus and a method thereof

Details .pi./4 QPSK digital demodulating apparatus and a method thereof .pi./4 QPSK digital demodulating apparatus and a method thereof

1998-06-18

2000-04-04

Lee, Benny

Demodulators

Phase shift keying or quadrature amplitude demodulator

329336, H03D 300

Patent

active

060466308

ABSTRACT:
In a digital demodulation apparatus of a QPSK receiver which demodulates an input signal being modulated in the 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, A .pi./4 QPSK digital modulation apparatus includes a bandpass filter part to remove unnecessary signals from input QPSK modulated signals, a channel separation part for mixing the modulated signals input from the bandpass filter and a one-symbol delayed modulated previous signal to separate a Q channel signal and an I channel signal, a first low-pass filter part and a second low-pass filter part for cutting off carrier component from the Q and I channel signals which are separated by the channel separation part to derive baseband signals of orthogonal component and cophase component, a first data recovery part and a second data recovery part respectively for sampling the baseband signals of the Q and I channels respectively input from the first and the second low-pass filter parts to decide and recover the data, a parallel/serial conversion part for converting the two recovered data into serial data, and an error correction part for obtaining phase differences on the basis of the converted serial data and previous data and operating the phase differences with predetermined module values, thereby providing data of which error is recovered.

REFERENCES:
patent: 5007068 (1991-04-01), Simon et al.
patent: 5490176 (1996-02-01), Peltier
patent: 5539355 (1996-07-01), Nakamura
patent: 5905405 (1999-05-01), Ishizawa

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