Research On Detection And Recognition Of Weak Pulse Signal Under Lightning

High-altitude electromagnetic pulse(HEMP)can release high energy in a very short time,which can cause related electronic equipment disabled or permanently damaged.Therefore,it is of great significance to detect and recognize it.Satellite is an ideal platform for electromagnetic pulse detection due to its wide detection range and all-weather operation,which has led to the emergence of space-based electromagnetic pulse detection system.This paper focuses on the signal processing problems in space-based electromagnetic pulse detection system,and studies the detection and recognition of HEMP signal under lightning electromagnetic pulse(LEMP).The research contents of this paper are as follows:1.Analysis of the influence of the ionosphere on pulse signal.Firstly,the influence of the ionosphere on the propagation process of electromagnetic pulse signal is studied,including amplitude attenuation and phase delay.From the perspective of particle collisions,the frequency response method is used to establish the ionospheric channel model.Then the HEMP and LEMP signals are respectively used as the inputs of the ionospheric channel model to obtain the HEMP and LEMP signals passing through the ionosphere.Finally,the time-frequency characteristics of the two electromagnetic pulse signals passing through the ionosphere are studied,providing a basis for the subsequent signal detection and recognition.2.Detection of weak electromagnetic pulse signal.First of all,based on traditional time-frequency domain signal detection methods,the short-time fractional Fourier transform method is adopted to detect weak pulse signal under Gaussian noise,and the results show that the detection success rate of the algorithm can reach 98% or above;Then the short-time fractional Fourier transform method is implemented on FPGA;Finally,the effectiveness of the method is verified by comparing the FPGA simulation results with the computer simulation results.3.Recognition of weak electromagnetic pulse signal.Based on the characteristics of pulse signal in the fractional Fourier domain,a label consistent K-singular value decomposition algorithm based on fractional Fourier transform is adopted to recognize pulse signal.The recognition algorithm firstly extracts the features of signal in the fractional Fourier domain through fractional Fourier transform,and then transmits the feature parameters to the label consistent K-singular value decomposition algorithm for classification and discrimination,ultimately completing the recognition and classification of HEMP and LEMP signals.In summary,aiming at the problems in space-based electromagnetic pulse detection,this paper conducts in-depth research from three aspects: the influence of ionosphere on pulse signal and detection and recognition of weak electromagnetic pulse signal.Firstly,the influence of the ionosphere on pulse signal is studied,and an ionospheric channel model is established,which provides a basis for subsequent signal detection and recognition;Then,the short-time fractional Fourier transform method is used to detect the weak pulse signal,and its feasibility is verified by implementation on FPGA;Finally,a label consistent K-singular value decomposition algorithm based on fractional Fourier transform is proposed to recognize HEMP and LEMP signals,which provides strong support for the practical application of space-based electromagnetic pulse detection system.