Anti-jamming Algorithm Based On Beam Forming In Communication And FPGA Implementation

Satellite communication, as a supplement to the ground communication network, is playing more and more important role in life, military field, and the development of science and technology and other fields in the modern society. When the ground network have an malfunction, satellite communication plays an important role to ensure the normal connection of the national communication network. In terms of the truth that satellite signal is weak and susceptible to be disturbed, here we propose an anti-jamming algorithm based on beam formation in the array antenna. Because the satellite position can be obtained by satellite ephemeris, the position of the expected signal is available. Through the beam formation of the array signal, we point the main lobe of the antenna array in the direction of the signal source, and then we use the synthesized beam as the expected signal to do anti-interference cancellation, eventualltually anti-interference is achieved and the signal to noise ratio is improved as well. This thesis researches on anti-jamming of satellite communication based on digital beam formation technology and focuses on the beam forming algorithm based of a sum and difference network.We carry out some simulation and discuss the anti-jamming ability and the improvement of the SNR. Besides, we implement the anti-jamming algorithm on FPGA. Specific research is divided into four parts:1) Proposed an anti-jamming algorithm based on beam forming for a signal with know direction of arrival. We build an array antenna and interference model, and rotate the array antenna pattern map, and steer the main lobe of the antenna to the expected signal. Then we use steered signal go through the sum and difference network, and we use signal from sum channel as a reference signal to achieve interference suppression through the signal cancellation. In the algorithm, as a result of the superposition of the useful signal,the sum channel obtain the gain, which improves the signal to noise ratio of the output signal and improves the quality of communication.2) Build a simulation model of an array antenna, and generate the simulation of the anti-jamming algorithm based on the sum and difference network. Simulation results show that in the case of sixteen picket line uniform array, the SNR of the output signal of the beam forming jamming algorithm based on the sum and difference network has an improvement of 12 dB than the input signal. Besides, we carry out comparison between algorithms with different weights. In addition, simulation was carried out for the direction error of the main lobe of the array pattern and the angle difference between the signal and the jamming,and discusses the impact of these two factors on the pattern.3) Design the FPGA implementation structure of the anti-jamming algorithm based on the sum and difference network. Design the signal preprocessing module that transfer the signal to the complex signal, correct the channel and pointing direction. According to the parameters that need to be configured in FPGA such as the expected signal information, define the serial communication protocol, program the software in personal computer that is used to test the anti-jamming system. The anti-jamming algorithm uses the delay least mean square(DLMS) algorithm which is easy to implement by FPGA, and design the structure of DLMS algorithm in FPGA and the implementation details of each part of the algorithm.4) Complete the testing of anti-jamming system, verify the correctness of channel correction and beam pointing module and test the performance of anti-jamming algorithm.