| Software radio is an open architecture which central conception is to make a modular, standardized and reconfigurable hardware platform and realize various wireless communication functions via loading software. Modulation and demodulation is a crucial technology in mobile communiction, its performance can contribute directly to communication system. Phase shift keying(PSK) has become the major modulation method of many mobile communiction systems because of its outstanding advantages such as high utilization rate of frequency bandwidth, good bit-error-rate(BER) performance, flexible implement and applicability in high speed data transmission and fast declines channel. This paper studied mainly BPSK/QPSK demodulator algorithm based on software radio, then carried out the algorithm simulation in MATLAB and realized modulator by programming on hardware.This paper researched and proved all digital BPSK/QPSK orthogonality demodulation scheme which adopts the way of concerned demodulation. The key of demodulation is to realize local carrier synchronization and bit synchronization. This paper studied the principle, structure and performance of analog PLL and digital PLL; Put forward software PLL algorithm which is used for synchronizing local carrier in BPSK/QPSK demodulator; According to Gardner algorithm, calculate the error information of bit synchronization and give a kind of simple software scheme of bit synchronization that is easy to realize.On the foundation of algorithm research, this paper simulated the process of demodulation in time domain by MATLAB programming;gave difference simulated signal waveform and corresponding constellation;analysed the BER performance of demodulation algorithm.This paper realized the demodulator algorithm of BPSK/QPSK on DSP hardware platform via C language programming and gave related software flow chart. Finally,this paper put forward optimization for hardware scheme, established foundation to realize high performance software radio receiver further. |
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