Study Of Synchronous Tracking Technique For Code-hopping DSSS Signals

The superior of Direct Sequence Spread Spectrum (DSSS) in high security has been weakened gradually and signal identification and parametric estimation technology have been developing rapidly. More and more points have been focused at improvement of probability of detections and confidentiality in DSSS. The synchronous tracking part of Code hopping direct sequence spread spectrum (CH-DSSS) that has a low probability of detection and high security must be recognized as very important design in whole receiver system.The thesis investigates synchronous tracking technology in both carrier wave and PN code, presents the method of precise code hopping synchronous tracking in CH-DSSS. Firstly, the fundamental theories and key technology of CH-DSSS is introduced. After analyzing several carrier tracking technology, CH-DSSS carrier tracking methods based on DSP technology and Costas Loop with CPAFC is proposed. Secondly, analyzing the producing method and functions of CH-DSSS, code-hopping tracking methods with a DDLL and CH-pattern technology is proposed. In thesis, production methods of loop filter design in CH tracking loop is also presented. Finally, the digital simulation models of CH-DSSS synchronous tracking loop and the result implementation of performance based on SystemView software are showed. Using these methods, the synchronous tracking loop for CH-DSSS achieves well tracking performance of signals tracking, errors estimation, clock pulse controlling and lock loosing treatment in the static environment and slow hopping speed.