Research On Orthogonal PN Code And Rapid Code Acquisition Scheme For Complex Spread Spectrum System

The direct-sequence spread-spectrum (DS/SS) technique has been applied for mobile communication, telemetry and orientation, radar system since it offers many advantages including anti-jamming, anti-eavesdropping, multiple access anti-fading and so on. The complex system has the function of communication and telemetry simultaneously because the DS/SS has the ability of strong discrimination and ranging.In this paper, the structure of complex system is ameliorated so that the inconsistent of technique parameters has been conciliated in traditional complex system. These parameters include the range of telemetry, the precision of telemetry, the real time ability and the velocity of communication.After analyzing the drawbacks of PN sequence, an orthogonal PN sequence is introduced. The new orthogonal PN sequence(modified m-Walsh sequence) is proposed based on original m-Walsh sequence, discussing its correlation property and other traits completely. The modified sequence has a similar or better correlation property compared with some other existed orthogonal sequences, especially in code balance and flexible construction method. From performance analysis and computer statistics, we can conclude that the new sequence has a good performance which is fit for the multiplex system.In order to improve the real time ability of the comples system and shorten the time of code acquisition, a modifed two-stage parallel code acquisition scheme is proposed. The mean acquisition time of new scheme is derived under the condition of white Gaussian noise. Comparing with other acquisition schemes, numerical results show that new scheme performs better in the real time ability of complex system and its probability of false alarm is also improved greatly.At last the new scheme is implemented by FPGA and the problems existing in the design are also optimized. Then integral system design is proposed and simulated by chip of CycloneⅡseries. The result show that the design can be implemented completely which pay strong matting on future SOPC development and also provide a support for application of this technique.