Research On BDPSK Direct Sequence Spread Spectrum Communication System Based On FPGA

Direct sequence spread spectrum(DSSS)technology has been widely used in military and civilian fields in recent years due to its excellent anti-jamming ability,bandwidth utilization and data security.This paper designs a wireless digital spread spectrum communication system based on FPGA.The design and implementation of this spread spectrum communication system include transmitter and receiver,each module,including the important carrier generator(NCO),filter,and digital loop filter,PLL modules,are all integrated in one FPGA chip,which improved the stability and reliability of this system.This paper researches several classical spread spectrum algorithms;each module of the transmitter and receiver is completed and debugged.The main Tasks are described as following:(1)Aimed at the characteristics of FPGA,we improved the synchronization methods of spread spectrum code.Proposed a PN code synchronization method for FPGA devices.The capability of anti-white noise can reach-25.38 dB,and the capability of resisting single frequency noise interference can reach-18.3dB.(2)In the design of carrier synchronous circuit,we improved the traditional Costas loop structure.The test result shows that the reliability of the synchronous circuit is improved.(3)In the design of synchronous circuits,this paper proposed a bit synchronization algorithm based on Clock hopping and frequency word adjustment.The accuracy of this algorithm lies between the traditional bit synchronization algorithm and Gardner bit synchronization algorithm,which combines the advantage of those two algorithms.It has simpler structure and easy to implement,which is more suitable for FPGA devices.(4)This paper designed a peripheral interface circuit.The host computer can communicate with each other by using this communication system through a RS232 cable also enormously enhanced the system probability.