Research And FPGC Design On The Interference Suppression Method For Broadband Background Digital Signals

With the rapid growth of the communication demand in modern life,the desire for communication quality is getting stronger and stronger.However,The interference problem in the communication system seriously affects the effectiveness of information transmission,further hindering the overall development of communication.Therefore,the anti-jamming technique,which enhances the performance of the communication system,has drawn extensive interests in recent days.The spread spectrum communication system,which is widely used in the field of communication,already has certain anti-jamming capability.Whereas when the power of the wide-band blanket interference signal exceeds the interference margin of the spread spectrum communication system,the anti-jamming performance of the system will suffer from serious deterioration.To solve the above wide-band blanket interference problem in the spread spectrum communication system,this paper proposes an interference suppression scheme based on the waveform reconstruction.In this scheme,we mainly establish an interference reconstruction model and then offsets the reconstructed interference signal from mixed signals,which improves the anti-jamming capability of the original system.This paper analyzes the performance of the proposed interference suppression method by MATLAB simulation.Then FPGA design is carried out to build the interference reconstruction model.In addition,we compare the reconstructed interference signal by MATLAB simulation with that of the FPGA result.The comparison result demonstrates the validity of FPGA design.The main work of this paper is as follows:1.We study the theoretical fundamental technologies of interference suppression,including signal carrier frequency and bandwidth estimation techniques,signal power spectrum estimation,wavelet transform theory,PCMA signal separation technology and so on.These technologies lay the theoretical foundation for the research of the interference suppression approach.2.In this paper,an interference reconstruction model is proposed,which consists of interference signal parameter estimation,interference signal demodulation,and interference signal reconstruction.The implementation process of the proposed interference suppression approach is as following.In the first step,we estimate the interference signal amplitude,carrier frequency and signal bandwidth.In the second step,the interference signal can be correctly demodulated according to the estimated parameters.In the third step,we obtain the reconstructed signal by exploiting the demodulated interference sequence and the estimated parameters.Finally,we obtain the desired signal from the mixed signal by offsetting the reconstructed interference signal.3.Based on the spread spectrum communication,this paper builds a system by MATLAB simulation.And the key modules in this simulation system are all correctly carried out.Then,simulation results demonstrate that the whole system meets design requirements.Moreover,when considering the demodulation of the interference signal,an improved symbol synchronization timing scheme is proposed to make the symbol synchronization timing more rapid and accurate.4.In FPGA design,this paper emphasizes on the design of the key modules involved in the reconstruction of the interference signal.The design idea and the realization procedure for each module are described in details.Finally,the interference signal is approximately reconstructed by FPGA design.Furthermore,this paper compares the behavioral simulations by Modelsim software with MATLAB simulation.The comparison results demonstrate the the feasibility of FPGA design.