Research And Implementation Of Frequency Hopping Network Sorting Technology In Complex Electromagnetic Environment

Frequency hopping(FH)is the most effective technology in anti-jamming of tactical communication,which is widely used in military and civil fields.Based on the characteristics of FH signal,the sorting of FH network station is an important part of FH communication investigation.In the actual FH communication system,the electromagnetic environment is complex,and there are not only serious noise interference but also various kinds of interference.In addition,because of the large number of users,synchronous and asynchronous radio stations will exist at the same time,and there is a high probability of frequency collision,so only through network station sorting can we get effective information.Therefore,in this paper,the sorting of FH signals in complex electromagnetic environment is studied.The specific research contents and results are as follows:(1)Aiming at the problem of time-frequency information extraction under the condition of low signal-to-noise ratio,a combined time-frequency analysis method based on short-time Fourier transform(STFT)and smooth pseudo Wigner-Ville distribution(SPWVD)is proposed by comparing the existing time-frequency analysis methods and considering the algorithm complexity and estimation accuracy in practical application.The algorithm improves the anti noise performance by adaptive noise reduction of time-frequency signals.The time-frequency information is extracted by the modified k-means clustering algorithm,which improves the frequency resolution.Then,the precise estimation of the time hopping is carried out by SPWVD,which improves the accuracy of the time hopping estimation.The simulation results show that the time-frequency information extraction method based on STFT-SPWVD proposed in this paper not only has low algorithm complexity,high accuracy of parameter estimation,but also has good anti noise performance.(2)In order to eliminate all kinds of interference in complex electromagnetic environment.Firstly,the characteristics of all kinds of interference in the short wave band are analyzed,such as the duration of frequency,occurrence of frequency and so on.Then,the corresponding elimination methods are proposed for all kinds of interference characteristics.Simulation results show that this method can effectively eliminate all kinds of interference.(3)In order to solve the problem of frequency hopping network sorting in complex electromagnetic environment,a method of multi-dimensional information network sorting based on time,frequency and space is proposed.Firstly,the network station is preliminarily sorted based on the multi-dimensional information of time,frequency and space,and then the first and last hops and collision signals are subdivided.To solve the problem of frequency collision,firstly,the missing signal is located according to the classified hopping frequency,and the time-domain information of the collision signal is extracted.Singular value decomposition algorithm is used to estimate the number of source signals in each segment and find the location of the hopping time.Then,the collision signal is separated by blind source segmentation according to the estimated hopping time.The multi-dimensional information of each segment is estimated and spliced.Finally,the time-frequency information of the collision signal is sorted into the appropriate network station,which completes the whole process of network station sorting.In addition,to solve the problem of multi frame signal splicing,a multi frame signal splicing method is proposed.Simulation results show that the method can sort the network station real-time,and the splicing accuracy is high.(4)For the GUI implementation of FH network station sorting system in complex electromagnetic environment.Firstly,enter the user login interface,need to use personal user name and password to enter.Then,the user needs to agree the software protocol to enter the next step.When the user enters the software operation interface,the mixed signal can be generated by setting the common parameters of the source signal and the parameters of each source signal.Then click the corresponding button to display the time-domain waveform,frequency-domain waveform,time-frequency-domain waveform and the sorting results of the network station in the graphic display area.In addition,the standard value,estimated value and estimated error of frequency hopping,hopping time and hopping period can be displayed in the data display area through the button.The GUI design enables users to use the platform sorting system more flexibly.