Research On Parameter Estimation And Modulation Recognition Technology Of Non-Cooperative Frequency Hopping Communication System

Frequency-Hopping communication has been widely used in military and civilian fields because of its strong anti-interference ability,good security and easy networking.Especially in the military field,parameter estimation and modulation recognition of non-cooperative Frequency-Hopping signal have a great influence on the research of anti-interference technology in Frequency-Hopping system.At the same time,these two technologies are also research focus and hotspot in the field of Frequency-Hopping communication.Based on the non-cooperative Frequency-Hopping communication system,this paper mainly studies the technology of FH signal parameter blind estimation and modulation automatic blind recognition.In the aspect of Frequency-Hopping parameters estimation,this paper mainly studies the blind estimation technology of Frequency-Hopping parameters based on time-frequency analysis.Several common time-frequency analysis methods are analyzed,including WignerVille distribution,short time Fourier transform,spectrogram,and wavelet transform and their advantages and disadvantages.Through the research and summary of parameters of estimation methods based on short time Fourier analysis and wavelet transform,improved algorithm on the basis of the original are proposed.Combined with the six modulation modes suitable for Frequency-Hopping system including BPSK,QPSK,8PSK,2FSK,4FSK,MSK,improved algorithm for the frequency modulated signal is simulated.The simulation results show that the proposed algorithm can be used for various types of modulated Frequency-Hopping signals and it is accurate and effective.In the aspect of modulation recognition,the automatic blind recognition technology of digital signal modulation in non-cooperative communication system is studied.Based on statistical pattern recognition method,existing feature parameters extraction methods are summarized,the feature parameters extraction method based on signal spectrum information is improved.Considering the influence of signal modulation index on signal spectrum characteristics,the number of peaks of the square spectrum envelope is proposed for inter and inner class recognition.Double frequency component prominent degree is proposed for 2FSK/MSK recognition.Based on the improved spectrum feature parameters extracting method and the support vector machine classifier,we recognize several modulations suitable for FH systems including BPSK,QPSK,8PSK,2FSK,4FSK,MSK.The simulation results show that the recognition method has high accuracy.Finally,combined with the aforementioned parameter estimation and automatic modulation recognition technology of FH signal,a joint process of parameter estimation and modulation recognition of non-cooperative FH signal is studied,the non-cooperative FH signals parameter estimation and modulation recognition software is designed.The estimation and recognition results of the software are consistent with the theoretical results.