Reseach On The Algorithm Of MSK Modem Under Pulse Noise And Impliment With FPGA

Long wave communication refers to the transmission of signals using a very low frequency wave with a frequency range of 3~30k Hz.The application of long wave communication at sea is very extensive,mainly used in various forms of submarine communication and navigation system.Modulation of long wave communication system is mainly MSK(Minimum Shift Keying now)and GMSK(Gaussian Filtered Minimum Shift Keying).in this paper the research of modulation implementation is MSK.However,atmospheric noise or impulse noise always exist in the long wave communication channel,which will bring a strong interference on the communication process,severely affecte the quality of communication.therefore,in the long wave communication system the anti-jamming ability is of critical significance,the content of this paper is mainly implemented in the FPGA(Field Programmable Gate Array)hardware platform to simulate the process of communication and the channel condition of ocean fading and atmospheric noise,in the same time apply a new impulse noise preprocessing algorithm to obtain greater communication performance.The theoretical analysis and experimental test results show that the system has good communication performance and anti-interference performance.The main contents of this paper include the following parts:(1)The MSK modulation technology under the sferic noise or impulse noise environment is introduced and analyzed,and in the same time the ways and methods of improving the performance of long wave communication system under the condition of sky noise are pointed out;(2)Implementation need to simulate the atmospheric noise and ocean fading channel,thus the mechanism of generation and suppression to static noise as well as the principle and modeling of ocean channel is introduced and analyzed in this paper.(3)Design of MSK modulation and demodulation and processing of signal flow sampling,variable sampling,frequency conversion,ocean fading compensation and filtering are implemented on the FPGA platform of XILINX Vertex-5 series.(4)Considering the significant influence of atmospheric noise and ocean channel to the performance of long-wave communication,this article will focus on the core part the principle and implementation of key technology in XILINX Vertex-5 series FPGA platform of processing against atmospheric noise and ocean fading effect,among which the nonlinear preprocessing technology adopts relatively better Clipper method,and also the synchronization system,including frequency offset compensation and frequency synchronization,timing synchronization,phase synchronization and frame synchronization;(5)Test the communication BER performance of the whole hardware system under the simulation communication channel environment,which includes the Gaussian performance,the Gaussian performance under ocean channel and impulse noise channel performance,the test results show that the communication performance of the system is close to the simulation performance under the Gauss and the ocean channel.In the impulse noise channel,the nonlinear preprocessing technology used in this paper also obviously improves the communication performance.and in the mean time analyze the reason and also,the direction and suggestions for the improvement of the follow-up work are given.