Research On The Jamming Of Adaptive Nulling Antenna In DSSS System

The adaptive nulling antenna in DSSS system has powerful anti-jamming ability. It is of great military application value to interfere with the adaptive nulling antenna in DSSS system. This thesis studies jamming effects on the adaptive nulling antenna in the system with different jamming patterns in different conditions, such as Gaussian white noise jamming, noise frequency modulation jamming, periodic PN code jamming and time-frequency atom jamming, and completes the FPGA design and functional simulation of every jamming pattern and other related modules. The main contents of this thesis are as follows:1. The basic concepts and features of DSSS system are described. Adaptive nulling antenna algorithms are especially presented, which include the minimum-variance distortionless response (MVDR) algorithm, as well as its two iterative algorithms:least mean squares (LMS) algorithm and recursive least squares (RLS) algorithm.2. The criterias of communication system are summarized, which contain time criteria, frequency criteria, pattern criteria and power criteria. The related theories of Gaussian white noise, noise frequency modulation, periodic PN code and time-frequency atom are described. Moreover, the simulation model of Chirplet atom from time-frequency atom is set up.3. Based on the array antenna theory, adaptive beam-forming algorithm and direct sequence spread spectrum technology, we set up the simulation model of DSSS system with adaptive nulling antenna.4. With the same average jamming power, we simulate the effects of different jamming patterns in the continuous and flashing (intermittent) conditions, which are compared to that of the single continuous Gaussian white noise, and the patterns are noise frequency modulation, periodic PN code and raised cosine purfled Chirplet atom. The results show that increasing the number of the jamming can greatly improve the jamming effect. Moreover, the effect of flashing (intermittent) jamming is slightly better than that of continuation jamming, but the difference is very small.5. According to the requirements of the jammer, we give its general hardware design in this thesis. In addition, the FPGA design and functional simulation of Gaussian white noise jamming, noise frequency modulation jamming, periodic PN code jamming, raised cosine purfled Chirplet atom jamming and other related modules are completed.