Signal Synchronization And Demodulation Algorithm Study In OQPSK Blind Receiving

In recent years, the techniques for digital receivers have been rapidly developed. An adaptive receiver for blind signals become a new attractive design goal. However, it's difficult to realize fully now, since some key issues have not been well solved. An important issues is to design a new digital demodulator which can well adapt complex and severe input signal conditions.Based on completely analysis of the various synchronization techniques for digital receivers, and considering system requirements of adaptive receiver for blind signals, this thesis proposes an optimum system architecture, studies key algorithms for carrier recovery and timing recovery, and implements a new full-digital demodulator finally. The proposed demodulator has the ablity to demodulate OQPSK signal in both continuose mode and burst mode with complex and severe input signal conditions. And it has great tolerance for input signal's parameters, such as , carrier frequency deviation and timing deviation. Therefor, the performance of this demodulator meet system requirement of adaptive receiver for blind signals.The main specifications of this demodulator surpass to the design target. For example, compared with ideal coherent demodulator, this system's degradation is less than 0.5dB. In burst mode, acquisition time is less than 200T(T equal to symbol period), and frequency acquisition range is in continuous mode. Digital phase lock loop is a key part of the digital demodulator. This thesis proposes a novel method for digital phase lock loop, called "dynamical observation interval method". The novel method can solve the conflict between frequency acquisition range and phase stabilization in conventional digital PLL design, and can greatly increase frequency acquisition range of digital PLL in low condition.This demodulator has been successfully implemented and tested in a DSP based hardware plantform.