Study On The Suppression Of Narrowband Interference In Direct Sequence Spread Spectrum Communication System

The Direct Sequence Spread Spectrum (DSSS) communication system has been widely used in wireless communication, its anti-interference ability is decided by the limited processing gain. Narrow-band interference is the most common interference in DSSS communication system. When the interference has a great intensity or complex statistical characteristics, the processing gain can not meet the requirements of anti-interference, the system can not function properly. How to introduce the narrow-band interference suppression technology into the system to improve the anti-interference ability is one of the key technologies in DSSS communication system, it has an important application prospect.In view of the above situation, the thesis has the following tasks:①The equivalent model of DSSS communication system was introduced, the signal processing process was analyzed, and the relationship between the anti-interference ability and processing gain was clarified. On the basis, the most common narrow-band interference in the system was described, and the most serious single-frequency interference analysis was derived in order to further explain the necessity of introducing anti-interference techniques.②Combing system model, the transform domain and time domain narrowband interference suppression techniques were studied. The commonly used frequency domain techniques and time domain prediction technologies were designed. The designed time-domain LMS prediction had little damage to the signal, occupied fewer resources and had a simple hardware implementation. On the basis of different types of narrowband interference, the simulation was completed, and the performances of designed techniques were compared.③The disadvantages of the traditional uniform tap interval filter were analyzed. In view of high-order, inaccurate forecast, incomplete filtering and other issues, a variable tap interval prediction filter structure was designed with the relevant principle. With different types of narrowband interference, the simulation was used to compare and analyze the performances of different filter structure. The results showed that the variable tap spacing predictor reduced the order of the filter, and the loss of the useful signal was very little. Less resource was occupied, the hardware implementation was simple, and the NBI suppression was accurate and complete. It's suitable for practical applications.④Simulation for frequency domain processing and the improved time-domain predictor was used to compare the performance, anti-jamming technology resource occupying, algorithms and complexity inherent to the system loss. On the basis, the thesis synthetically concerned about the actual DSSS communication system working environment, anti-interference requirements, hardware resources available and other factors, then achieved hardware implementation by using 7-tap variable tapped delay line adaptive filter. The system testing was completed, actual anti-interference ability and theoretical analysis results were consistent.The results of the study in the thesis showed that the improved time-domain linear predictor significantly improved the capacity of anti-NBI for the DSSS communication system. The prediction filter has been effectively applied in practice.