The Design And Implementation Of The IF-digitalized DS-BPSK Receiver With Anti-jammer Based On MLT

Direct sequence spread spectrum (DSSS) communication systems have many advantages, including low probability of intercept (LPI) transmission, multiple accessing, multipath suppression and narrowband interference suppression.It is widely used in the third generation mobile communication systems, broadband wireless access systems and satellite communication system, especially in military satellite communication systems. In many cases, the inherent processing gain of spread spectrum systems will provide the system with interference rejection capabity.But the higher processing gain will get the receiver more complex.It is shown by research that we can improve the interference immunity significantly by using signal processing techniques without increase the processing gain.This thesis deeply research the narrowband interference suppression techniques based on modulated lapped transform in the DSSS system. Modulated lapped transform principle, structure, filter performance and basic type are analyzed. On this basis, the simulation model of DSSS system using narrowband interference suppression techniques based on modulated lapped transform。Simulation results show the BER performance of this model. Accord with the character of FPGA, we choose the correct fast algorithm of MLT and modify this algorithm. This paper presents the fast algorithm for IMLT computation via the length-M/2 fast Fourier transform (FFT) and butterfly structures and the computational complexity is analysed. Furthermore, the module of narrowband interference suppression via MLT is implemented in FPGA.The hardware design and debug of the DS-BPSK modulation transmitter and the IF-digitalized DS-BPSK receiver with anti-jammer based on MTL is given. Then we test the whole system. The experiment result of this systems shows that the narrowband interference suppression techniques based on MLT can improve the interference immunity significantly, especially when the frequency of interference is changed.