The Research Of PSK Soft-Modulation And Soft-Demodulation Based On Audio-Card And DSP

Along with the rapid development of VLSI technology and computer technology, DSP has been used widely in communications areas, software radio has been strongly supported for its notable advantage since it was brought forward in 1995. In this paper, according to the thinking of software radio, a PSK soft-modulation and soft-demodulation system based on audio-card and DSP is studied and implemented.Firstly, on the base of analyzing PSK's theory and audio-card's constitute and data transfers, BDPSK and QDPSK soft-modulation and soft-demodulation systems based on audio-card are studied and implemented, including generating digital carrier sequence, synchronizing carrier, designing filter, sampling and judging, etc. The system adopts coherent demodulation method, synchronizing carrier adopts costas loop. Phase-lock part of the system was simulated in system View that is a EDA tool, including picking-up carrier synchronization algorithm and designing filter,etc.Finally, a demodualtion program except for sampling and judging is studied and successfully implemented on the DSP(TMS320C542) target board, with satisfactory result.The soft-modulation and soft-demodulation method put forward in this paper is relatively new, achieving a high practicality.