Abstract
As a new type of jamming, the interrupted sampling repeater jamming (ISRJ) derived from the digital radio frequency memory (DRFM) technology, can generate coherent multiple false targets after pulse compression. At present, the traditional interference suppression method and its improved methods have insufficient characteristics and poor detection performance under the condition of low signal-to-noise ratio (SNR). Aiming at addressing this defect, this paper proposes an interference suppression method for ISRJ based on singular spectrum entropy function (SSEF) from the aspects of singular value decomposition (SVD) and information entropy theories. In this method, firstly, considering the local fine characteristics and extraction efficiency, an adaptive multi-scale segmentation (AMS) method is proposed. The purpose of this processing is to extend the salient characteristics while to smooth the similar ones. In AMS, the segmentation criterion based on average energy of segments and the constraint of minimum segmentation is also proposed, then the improved delay embedded matrix is established from the improved trajectory matrix by AMS and delay embedded mapping. Secondly, the singular spectrum of the improved delay embedded matrix is extracted by SVD. Thirdly, because the recognition algorithms based on singular spectrum analysis (SSA), classical SSE and other characteristics fail at low SNR, this paper proposes a characteristic named as SSEF retrieved from the Shannon entropy model. The following proposed entropy-based threshold detection is carried out on the echo signal to realize the band-pass filtering and interference suppression. Finally, experiment results show that in comparison with other interference suppression approaches, SSEF can increase the probability of target detection and the peak-to-side-lobe ratio (PSR) after pulse compression, which validates its stability to noise and jamming especially in the condition of low SNRs.
Highlights
Electronic countermeasure (ECM) techniques such as active deception jamming aim at forming false targets to confuse the victim radar, for surrounding desired radar echoes with so many false targets that the target information cannot be extracted
interrupted sampling repeater jamming (ISRJ) has become more and more ubiquitous with the developed sampling, storage and repeater hardware in digital radio frequency memory (DRFM) and a great number of the improved interference algorithms are proposed based on related researches, which includes interrupted sampling and direct repeater jamming (ISDRJ), interrupted sampling and periodic repeater jamming (ISPRJ), interrupted sampling and cyclic repeater jamming (ISCRJ) [2,3,4,5], and new jamming patterns based on ISRJ such as frequency shift modulation [6], smart noise modulation [7], and interrupted sampling signal modulation [8,9,10]
Experiment results show that in comparison with other interference suppression approaches such as energy function detection and band-pass filtering (EFDBP), short time Fourier transform (STFT), particle filter (PF), Sliding-Truncation Matched Filter (STMF), the proposed method in this paper can increase the probability of target detection and the peak-to-side-lobe ratio (PSR) after pulse compression, which validates its stability to noise and jamming especially in the condition of low signal-to-noise ratio (SNR)
Summary
Electronic countermeasure (ECM) techniques such as active deception jamming aim at forming false targets to confuse the victim radar, for surrounding desired radar echoes with so many false targets that the target information cannot be extracted. Utilizing the discontinuity of the ISRJ in the frequency domain, the improved band-pass filtering interference suppression methods based on the energy function through the short time Fourier transform (STFT) were proposed in [14,15] These methods reduce the effects from the noise signal and improve interference suppression performance in condition of low SNR. Experiment results show that in comparison with other interference suppression approaches such as EFDBP, STFT, PF, STMF, the proposed method in this paper can increase the probability of target detection and the peak-to-side-lobe ratio (PSR) after pulse compression, which validates its stability to noise and jamming especially in the condition of low SNRs. The structure of this paper is as follows: in Section 2, the working mode of jammer and the mechanism of ISRJ is introduced, the echo signal model is established.
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