Research On Target Detection Methods Based On Subcarrier-Domain Sparse Representation In Passive Radar Using OFDM Waveform

The orthogonal frequency division multiplexing(OFDM)waveform-based passive radar uses the non-cooperative OFDM waveform signal in the electromagnetic space as the system transmitter source,making targets in complex clutter environments susceptible to masking in the clutter and its sidelobes.With the development of sparse representation theory,new directions have been brought for target detection in passive radar.However,the uncertainty of the target parameters in the radar detection region makes the dictionary matrix suffer from the problem of excessive dimensionality,which leads to the challenge of high computational complexity of target detection method based on sparse representation in passive radar,and this challenge is even more severe when detecting low signal-to-noise ratio targets.In addition,the use of transmit signals that are not designed for radar applications make it difficult for sparse representation based passive radar target detection methods to detect weak targets in complex clutter backgrounds.In this context,benefiting from the multi-carrier modulation distinctive characteristics of OFDM signals,this paper studies the OFDM waveform-based subcarrier domain sparse representation of passive radar target detection problem,proposes an average effective subcarrier(AES)sparse representation model that can greatly reduce the dimensions of the dictionary matrix,and then studies the AES-based target detection method.In order to further reduce the computational complexity and improve the detection performance for weak targets,a stepwise target detection method for passive radar based on AES sparse representation is proposed.The specific research contents are as follows:(1)Starting with the working principle of OFDM signals,the received signal model of passive radar using OFDM waveform,and matched filtering technology,this paper theoretically analyzes the principle,advantages and disadvantages of conventional clutter suppression methods,then according to the basic theory of sparse representation,the sparseness of the detection scene of passive radar is used to derive the target detection model based on the sparse representation in time-domain,which paves the way for the sparse representation model proposed and the research on the target detection method of passive radar in the later paper.(2)To address the problem of high computational complexity,combined with the OFDM waveform passive radar received signal characteristics,the sparsity of OFDM waveform passive radar data in the average effective subcarrier domain(AES)is first analyzed,and a sparse representation model and target detection method based on AES are proposed.Then,the effectiveness of this method in target detection is verified by simulation data validation.Finally,the performance and computational complexity of the method are compared and analyzed,the results show that the proposed method performs better and reduces computational complexity by about 50%.(3)To address the challenges of poor detection performance of weak targets with low signal-to-noise ratio,and to further reduce the computational effort of the AES sparse representation-based target detection method,the intensity differences and distribution characteristics of the sparse coefficients of the echo components of the received radar signals from the passive radar in the range-Doppler map are exploited,and the AES-based stepwise method(AES-S)is innovatively proposed.The detection ability of the proposed method for weak targets is verified and analyzed through both simulation and measurement results.