If Direct Bandpass Sampling Digital Correlator

In wireless communication,the relative movement between the transmitter and the receiver may cause the change of the electromagnetic wave propagation path,thus makes the channel become a random time-variety channel. In the spread spectrum communication, the continuous-waves signal is transmitted. This kind of random time-variety may cause the varieties of the amplitude, Doppler frequency and the phase of the received signal. The characteristic of the time-variety channel may be represented by Rayleigh fading and Doppler frequency shift. When the Doppler frequency shift is big and the Rayleigh fading is serious, it would affect the despread and demodulation algorithm of the signal badly.The project which the author of this dissertation undertakes, adopted the FPGA+DSP structure to design the general digital modulation, despread and demodulation module. And mainly studied the realization of the despread and demodulation of FH/DS/DQPSK, DS/DBPSK, DS/DQPSK and DS/D8PSK signals direct band-pass sampling on intermediate frequency. Compared to the analogy or the base-band sampling solution, this structure not only enhanced the system mobility, the flexibility and stability, but also reduced the cost, moreover it may be a public platform, which realize multi-purpose and multi-service patterns communication signal despread and demodulation, has fully reflected the thought of software radio. This module designation both satisfied the despread and demodulation of existing communication signal, and prepared space for the later function expansion, has achieved the generalization and modularization goal in definite significance. This dissertation made DS/D8PSK as the research object, creative and investigated work were made on the application of the despread and demodulation direct band-pass sampling on intermediate frequency, the concrete work was as follows:1. The spread spectrum communication channel characteristic was investigated. The application of SAW in spread spectrum communication was studied.2. The direct band-pass sampling on the intermediate frequency despread and demodulation algorithm of DS/D8PSK signal was investigated, a new despread and...