| Spread spectrum communication is an anti-interference communications system which is widely used for the moment. In order to improve anti-interference capability, we often apply narrowband interference suppression at the end of receiver. This thesis researches frequency domain narrowband suppression basic principles and forward consecutive mean excision(FCME) algorithm. For FCME algorithm iterative time-consuming, without ability to adapt to a wide range of SNR defects, it proposes an improved adaptive spectral domain three threshold interference suppression algorithms. Simulation results show this algorithm can adapt to a greater range of SNR. Finally, using FPGA to achieve the improved algorithm, it is applied in actual project.Thesis regards overlapping windowed FFT interference suppression algorithm as the basic method. Firstly, stating windowed choice, FFT, IFFT, interference detection, interference suppression and so on sub-module principle. For interference detection methods, the thesis study single-threshold algorithm, dual-threshold algorithm and FCME algorithms. Programming simulates FCME interference suppression algorithm performance. Through analysis, we find that the algorithm in high SNR results in signal serious loss and is not able to adapt to the received signal SNR over a large dynamic range conditions.In order to solve above-stated problems, the thesis proposes three threshold adaptive narrowband Interference suppression algorithms. The algorithm, based on the prior parameters of system interference tolerance, interference signal bandwidth ratio, designs high, medium and low threshold to achieve interference detection and suppression. Simulation results show the algorithm can adaptively process strong and weak SNR input.Finally, Using FPGA to achieve adaptive three threshold interference suppression algorithms. At the same time, depending on simulation analyzes the actual performance of algorithm and resource consumption. |
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