Research On Technology Of Wideband Parallel Software Receiver For Emergency Information Wide-area Release

Shortwave communication is an important means of emergency communication,with two transmission methods: sky wave transmission and ground wave transmission.Skywave transmission uses ionospheric reflection for transmission,and the transmission distance can reach thousands of kilometers,which can realize wide-area release of emergency information.Due to the unsteady nature of ionospheric skywave transmission,the communication window of shortwave skywave transmission changes rapidly.At different times of the day,the shortwave passable frequency point varies widely,and single-frequency communication is very likely to cause the problem of normal reception.To this end,this thesis proposes a shortwave broadband parallel software receiver solution.Compared with the currently widely used shortwave narrowband receivers,it can collect broadband signals in the shortwave band in real time,and can obtain multiple shortwave emergency information at the same time.The specific research contents are as follows:1.The basic principles of broadband parallel reception are studied,including signal sampling,signal extraction,and polyphase filtering.At the same time,on the basis of the channelization structure based on the low-pass filter bank,the multiphase DFT(Discrete Fourier Transformation)digital channelization structure is derived,and the mathematical model of the multiphase DFT digital channelization structure is obtained.The structure is simulated.Simulation results show that the structure can accurately perform digital channelization processing on wideband signals.2.The system scheme of the shortwave broadband parallel software receiver is designed.The system consists of two parts: broadband signal acquisition and digital channelization.The broadband signal acquisition part is realized by a software radio platform,and the digital channelization processing part is realized by a CPU+GPU heterogeneous platform.Based on the acquisition of a 6 MHz wideband signal,a digital channelization process is performed on this segment of the wideband signal through a heterogeneous platform of CPU+GPU to obtain a total of 2048 sub-channels.The bandwidth of each sub-channel is 2.929 KHz,and the adjacent channel rejection ratio can reach 80 d B.3.The specific implementation of each functional module of the shortwave broadband parallel software receiver is designed.According to the multiphase DFT digital channelization structure,the digital channelization processing part includes data extraction,polyphase filtering,DFT and other modules.After analyzing the parts that each module can execute in parallel,an Open CL(Open Computing Language)parallel processing algorithm is designed and compared with the time required for serial processing by the CPU.The results show that the Open CL parallel processing algorithm has higher processing efficiency than the CPU serial processing algorithm.4.The system test of the broadband parallel software receiver is carried out.Firstly,real-time voice signals through shortwave radio stations for actual testing is sended,after the receiver system processing is completed,the processing results of the broadband signal acquisition part and the digital channelization processing part are analyzed,and the processing time of the two parts is compared.The test results show that the receiver system can obtain multiple signals from the broadband signal in real time.Secondly,the adjacent channel rejection ratio of the receiver is tested by generating a wideband test signal,and the test results meet the system index requirements.Finally,on the basis of the system channel division method,a channel division method to improve the coverage of the blind zone is proposed,and the improved receiver system is compared with the original system for testing.The results show that the improved channel division method can effectively improve the coverage of blind area reception in the system.