Spread Spectrum Wireless Data Transmission Equipment

Spread spectrum techniques which is used by the army, have the excellent characteristics of being secret, concealed and to reject interference and multi-path decline. Therefore it has a spread application foreground. Many foreign companies have developed many powerful spread spectrum application ICs, which have the disadvantage that the secondary-development is very limit. The traditional analogy systems exist the disadvantages of big cubage, high power consume, and low dependability. With the fast development of microelectronics and Electronics Design Automation (EDA) techniques, the programmable logic devices such as FPGA and CPLD have been widely used in the field of digital signal processing for its flexible design and fast verifying. This paper implements a part of baseband system of direct-sequence spread spectrum (DSSS) with FPGA technology.The first chapter introduces the general situation of spread spectrum system. Then the current situation of spread spectrum IC that is emphasized on STEL-2000A IC is introduced. Then the paper analyzes and forecasts the development of the widely-used of FPGA technology. Furthermore, the Quartus II development platform and VHDL is simply discussed.The second chapter discusses the basic theory of spread spectrum, and the analysis of direct-sequence spread spectrum theory is emphasized. Then, according the structure of each module, from the PN sequence, the relative despread spectrum of the signal, channel coding, channel interlacings, baseband modulation and demodulation to the synchronization, the paper discuss the deep theories.The third chapter has given the general implement solution and the charts of each unit of the baseband of DSSS system.The fourth and the fifth chapter has given the design and the implement of the transmitter and the receiver unit. The transmitter unit mainly consisted of the serial-to-parallel conversion, differential encoder, spectrum spreading and QPSK modulator and so on. The receiver unit mainly consisted of the digital down converter, matched filter, differential demodulator and AFC module. What's more, it lists some parts of the VHDL programs and the results of behavior and timing simulation of all modules also have been represented.