Research And Realization Of Transform Domain Interference Suppression Based On FPGA

It is an effective method for narrowband interference (NBI) suppression toensure further the direct sequence spread spectrum (DSSS) communication systemproperly, especially in the increasingly complex communications environment.Besides, it is also serious problem for engineers how to apply theoretical research ofNBI rejection technology into ingineering applications. This paper improvesoptimizational performance of available algorithms by analyzing the NBI suppressionalgorithm of transform domain from the engineering realization view, which canreduce the algorithm complexity and improve the FPGA module of the processingrate.Firstly, the theory of a variety of frequently-used frequency domain NBIsuppression algorithm is introduced, and window function selection principle and thetheory of FFT transform is analyzed. Then a MATLAB simulation platform is buildedto analye the simulation of anti-jamming capability of DS system according to theprinciple of spread spectrum system, as well as combining the Consecutive MeanExcision(CME), Forword Consecutive Mean Excision(FCME) and threshold NBIsuppression algorithm based the FCME to analyze the bit error rate(BER) of system.Simulation result shows that the double threshold algorithm has better performance ofinterference detection and suppression.Secondly, according to the principle of double threshold algorithm based on theFCME and the spectral characteristics of the spread spectrum signal, this paperimproves calculation methods of double threshold based on partition statistics. Also,this paper analyes the two elements of the improve algorithm: segmented lengthcoefficient and basic threshold value, and verifies the lower complexity of improvedalgorithms by contrasting the FCME’s double threshold algorithm. The BERperformance of DS system analysis also shows that two algorithms have obtained aconsiderable performance.Thirdly, the intensity of the useful signal becomes weaker in pace withstrengthen of the interference signal as a result of the front-end automatic gaincontroller (AGC) of the receiver. For this reason, this paper puts forword anon-symmetric improved algorithm with adaptive amplitude recovery. The improvedalgorithm can restore signal to the status of non-interference from interference suppression by adaptively amplifying coefficient and achive asymmetric IFFTtransformation by analyzing quantization bit width of suppressed signals, andtruncating appropriate bit-wide for the amplified spectrum signal based on lowestdemodulation level requirement of DS system. Adopting MATLAB simulationplatform to conduct performance analysis in succession, result indicate that theimproved algorithm can not only eliminate the amplitude jitter, but obtain better BERperformance, besides the algorithm saves the amount of resources of FFTtransformation.Finally, according to the above two improved algorithms, this paper realizesFPGA design based on frequency domain NBI suppression algorithm of1/2overlapping windowed. By analyzing and estimating the resource of whole algorithm,we can effectively choose the version of chip, besides adopting Xilinx ISE designsuite to achiveve Verilog HDL(VHDL) programming, logic resource analysis, statictiming analysis, board-level debugging and test analysis stc, as well as timingsimulation analysis in Modelsim software. Practical development analysis indicates,designed algorithm module completely reaches the requirements based on designatechip.As previously metioned, the proposed two menthods based on the availablealgorithm can improve system performance effectively to a certain extent, and haverelatively high practical significance and reference value for supplying requestedparameters of development and design on FPGA.