Target Information Extraction And Anti-Jamming Performance Analysis Of Frequency Agile Signal

At present,most pulse Doppler radars adopt a relatively simple working mode.In a coherent processing time,the repetition frequency,the pulse width,the modulation pattern and the carrier frequency of the transmitted signal are usually unchanged,which is a great convenience to the receiving processing.However,under the complex electromagnetic environment,especially under the condition of strong confrontation war,this working mode has the problems of easy reconnaissance,sorting and interference,and is difficult to adapt to future wars.For this problem,the waveform of complex modulation pulse sequence has attracted wide attention.Specifically,with inter-pulse frequency hopping sequence,the purpose of destroying jammer reconnaissance and jamming can be achieved by changing the carrier frequency between different pulses.There is generally a problem of decorrelation between different pulse echo signals when the inter-pulse frequency hopping sequence is used as the transmission waveform.Therefore,it is necessary to focus on target information extraction and target detection performance evaluation.On the other hand,the jammer should be adjusted according to the change of radar working mode,and the challenge of the inter-pulse frequency hopping to the jammer is also an important issue worth studying.In this paper,the radar detection and anti-jamming problems with the working mode of the inter-pulse frequency hopping sequence are studied.The main research contents are as follows:1.The working principles of pulse Doppler radar and digital radio frequency storage deception jammer are analyzed,where the limitations of digital radio frequency storage jammer are studied.The frequency measurement error and the detection error of the jammer are parameterized to reasonable mathematical models,where the system errors of the frequency measurement module of the jammer and the detection module of the jammer are assumed to be a normal distribution and an uniform distribution,respectively.The performance loss caused by these errors is studied using mathematical quantitative analysis methods:(1)The influence of intra-pulse modulation caused by the error on matched filtering.(2)The influence of inter-pulse Doppler modulation caused by the error on velocity measurement.(3)The influence of inter-pulse modulation caused by the error on inter-pulse coherent accumulation gain with random phase amplitude vector and theory.2.For the target information extraction with the inter-pulse frequency hopping sequence used as the transmission waveform,an ADMM-based extraction method is proposed.Since different pulse carrier frequencies are different,the problem of inter-pulse decorrelation between echo signals needs to be handled.A range-velocity two-dimensional search method can be generally used to extract high-precision range-velocity information of the target from the echo signal.However,this kind of methods is usually restricted to a large computation.For this problem,a sparse reconstruction method based on ADMM algorithm is introduced,where dictionary matrix is adopted to learn the sparse characteristic of echo signal to extract high-precision range-velocity information of the target.The performances of ADMM algorithm and traditional OMP algorithm are compared in terms of computational complexity and algorithm accuracy.3.The anti-jamming performance of radar in the anti-jamming mode of the inter-pulse frequency hopping sequence are analyzed and evaluated.The suppression jamming and the deception jamming are respectively applied to the pulse sequence with the same working parameters and the inter-pulse frequency hopping sequence.The anti-jamming effects of the two pulse sequences against distance deception jamming,frequency deception jamming,speed deception jamming and suppression jamming are comprehensively considered and discussed.Based on this,a comparison of the anti-jamming performances of the two pulse sequences is given.By synthesizing the advantages of various jamming strategies,a frequency joint jamming strategy is proposed.The performance loss of broadband signals in target detection is studied with the inter-pulse frequency hopping sequence as the object.