| Spread-spectrum (SS) technique has been widely used in military and civilian communications for its advantages, such as anti-jamming (AJ) and low probability of detection (LPD). But modern electronic counterwork technic could exactly estimate the carrier frequency , signal period, even the pseudo-random (PN) sequence itself of direct sequence spread spectrum (DSSS). It is urgency to investigate a new DSSS to achieve Lower Probability of Detection(LPD) and higher Anti-Jamming.At 1999, Lim Nguyen first brought forward a novel self-encoded spread spectrum(SESS) system, which spread spectrum sequence is full builded by the source data. In SESS system, which does not use PN codes. It employs random spreading sequences that are extracted from the information data. Appropriate data compression methods are needed to assure the random nature of the information source and to enlarge its entropy.In this thesis, First, we present the theory of SESS system, Then the acquisition method of SESS system is discussed in detail, Finally, a acquisition model of SESS system is built and simulated in the AWGN channel, in the Raleigh fading channel and in multi-address interfere condition. The simulation results show the acquisition method of SESS system can be just as reliable as the conventional DSSS systems.Then we uses the scheme that has the variable gain based on the kalman filtering model realize two steps phase-locks ring circuit track technology, this kind has the advantage that when changed the gain the digital phase-lock link to be allowed simultaneously to realize the fast capture and the reliable track, the simulation analyzes its capture performance. It has to improve very much compared to the traditional numeral phase-lock link.Finally, we summarizes the work that had been done and point out some directions need to study in the future. |
