Sampling Repeater Jamming Research Articles

Complementary Sequences and Receiving Filters Design for Suppressing Interrupted Sampling Repeater Jamming

The realistic false targets caused by interrupted sampling repeater jamming (ISRJ) can mask the real target, leading to the failure of radar target detection. In this letter, a method based on jointly designing complementary sequences and receiving filters under the signal-to-noise ratio loss constraint is proposed to suppress ISRJ. A gradient-based nonlinear programming solver and the Lagrange multiplier method are used to optimize the sequences and filters alternately. Numerical results show that the proposed method can generate sequences and receiving filters with good correlation properties and anti-ISRJ performance.

Joint Design of Detecting and Screening Waveforms Against Interrupted Sampling Repeater Jamming with Inaccurate Jamming Knowledge

Joint Design of Detecting and Screening Waveforms Against Interrupted Sampling Repeater Jamming with Inaccurate Jamming Knowledge

A Truncated Matched Filter Method for Interrupted Sampling Repeater Jamming Suppression Based on Jamming Reconstruction

Interrupted sampling repeater jamming (ISRJ) is becoming more widely used in electronic countermeasures (ECM), thanks to the development of digital radio frequency memory (DRFM). Radar electronic counter-countermeasure (ECCM) is much more difficult when the jamming signal is coherent with the emitted signal. Due to the intermittent transmission feature of ISRJ, the energy accumulation of jamming on the matched filter shows a ‘ladder’ characteristic, whereas the real target signal is continuous. As a consequence, the time delay and distribution of the jamming slice can be obtained based on searching the truncated-matched-filter (TMF) matrix. That is composed of pulse compression (PC) results under matched filters with different lengths. Based on the above theory, this paper proposes a truncated matched filter method by the reconstruction of jamming slices to suppress ISRJ of linear frequency modulation (LFM) radars. The numerical simulations indicate the effectiveness of the proposed method and validate the theoretical analysis.

Parameter Estimation for Interrupted Sampling Repeater Jamming Based on ADMM.

By repeatedly sampling, storing, and retransmitting parts of the radar signal, interrupted sampling repeater jamming (ISRJ) based on digital radio frequency memory (DRFM) can produce a train of secondary false targets symmetrical to the main false target, threatening to mislead or deceive the victim radar system. This paper proposes a computationally-effective method to estimating the parameters for ISRJ by resorting to the framework of alternating direction method of multipliers (ADMM). Firstly, the analytical form of pulse compression is derived. Then, for the purpose of estimating the parameters of ISRJ, the original problem is transformed into a nonlinear integer optimization model with respect to a window vector. On this basis, the ADMM is introduced to decompose the nonlinear integer optimization model into a series of sub-problems to estimate the width and number of ISRJ’s sample slices. Finally, the numerical simulation results show that, compared with the traditional time-frequency (TF) method, the proposed method exhibits much better performance in accuracy and stability.

An Anti-Jamming Method against Two-Dimensional Deception Jamming by Spatial Location Feature Recognition

Interrupted sampling repeater jamming (ISRJ) is an effective method for implementing deception jamming on chirp radars. By means of frequency-shifting jamming processing of the target echo signal and pulse compression during image processing, a group of false targets will appear in different spatial locations around the true target. Extracting the features of these false targets is complex and limited to existing countering methods against ISRJ. This paper proposes an anti-jamming method to identify the spatial location characteristics of two-dimensional deception false targets. By adjusting the parameters of the radar transmitted signal, the method simultaneously transmits the anti-jamming signal and carries out false target identification and elimination in the range and azimuth dimensions. Eventually, the optimal signal parameter design of the anti-jamming signal is obtained by comparing different anti-jamming strategies in the range dimension. The validity of the proposed method is proved by deducing the mathematical model between the spatial distribution characteristics of the false targets and the radar transmitted signal parameters and demonstrated by simulations.

Research on Jamming to Coherent FA Radar Based on Intermittent Sampling Repeater

Due to integration of the frequency agility (FA) technology and coherent technology, Coherent FA radar has natural advantage in ECCM performance and represents one of important development trends of new radar types. Aiming at the technical characteristics of coherent FA radar, this paper proposed a jamming method to coherent FA radar based on intermittent sampling repeater. Theory models of coherent FA radar and intermittent sampling repeater jamming are established at first and the jamming effect is analyzed. The proposed jamming method is validated to be able to achieve the expected jamming effect to coherent FA radar by simulation at last.

Optimal design of anti‐interrupted sampling repeater jamming waveform for missile‐borne radar based on an improved genetic algorithm

The optimal design of transmitted waveforms to improve the performance of missile-borne radar in suppressing interrupted sampling repeater jamming (ISRJ) is studied here. The waveform diversity property requires that the waveform group has excellent orthogonality (good auto- and cross-correlation properties), which is an effective waveform optimisation design method for missile-borne radar electronic counter-countermeasures. The principle of orthogonal phase coding waveform against ISRJ is studied and the use of chaotic sequences is proposed to initialise the population, as well as a simulated annealing selection operator, which improves the convergence speed of the improved genetic algorithm (IGA) and enhances the global optimisation ability. The IGA improves the shortcomings of GA, that is, easily falling into a local optimum and slow search speed, and can realise a global search for longer orthogonal polyphase coding sequence sets. The simulation examples demonstrate the good jamming suppression performance of the proposed method.

A Method Against Interrupted Sampling Repeater Jamming Based on Genetic Algorithm and Compressed Sensing Reconstruction

By analyzing the discontinuous character in time domain, a jamming suppression method is propose to counter Interrupted sampling reperter jamming(ISRJ, which is an effective coherent jamming to wide-band linear frequency modulation signal. The discontinuous character of ISRJ and the instantaneous frequency change rule after stretch is firstly analyzed. Secondly, by controlling the adjustment parameters, the generalized S transform is utilized to obtain the time-frequency grayscale image of received signal. Then, the grayscale image can be segmented by using genetic algorithm to construct a time-domain filter, and the time-domain filter can be used to extract the echo band without jamming signal. Finally, the extracted signal is used as compressed data to construct a compressed sensing minimization model, and the compressed sampling matching pursuit algorithm is used to reconstruct the target echo signal. Simulation shows that this method has good jamming suppression performance.

Non-Linear Frequency Modulated Radar Echo Signal Cancellation using Interrupted Sampling Repeater Jamming

Non-Linear Frequency Modulated Radar Echo Signal Cancellation using Interrupted Sampling Repeater Jamming

Improved Blanket Jamming Against ISAR Based on Nonperiodic Interrupted Sampling Modulation

Imaging jamming of inverse synthetic aperture radar (ISAR) has been studied extensively in recent decades. Among them, the periodic interrupted sampling repeater jamming (P-ISRJ) technology can generate a series of false targets through matching filtering. However, with the rapid development of anti-jamming technology, it is necessary to improve the existing periodic sampling method to achieve better jamming effects. The latest research proposes that the two-dimensional square jamming strip can be generated based on the nonperiodic interrupted sampling repeater jamming (NP-ISRJ) to cover the target. In this article, the influence of NP-ISRJ on ISAR is studied with the model of escort free-flight. A linear weighted optimization method is proposed to improve the uneven energy distribution. The experimental results show that a square jamming strip with better blanket effects can be generated under the traditional range Doppler imaging method. While for the compressed sensing imaging method, the imaging fails because the sparse condition is no longer satisfied. The validity of the proposed blanket jamming method in different ISAR imaging reconstruction methods is verified.

Suppression Method for Main-Lobe Interrupted Sampling Repeater Jamming in Distributed Radar

Main-lobe interrupted-sampling repeater jamming is a coherent type of interference. As this interference is injected through the main lobe of the antenna into a radar system, the interference heavily degrades the performance of the radar system. In this paper, we propose an anti-jamming method based on minimum variance distortionless response (MVDR) that estimates a covariance matrix by obtaining small-sample pure jamming signals through jamming recognition. Time–frequency analysis is performed in the one-dimensional range profile of the pulse-compressed radar echo, and the snapshot sampling of pure jamming is achieved by searching the range gates for the target and the jamming in a two-dimensional range–frequency graph considering the time–frequency differences between the target and jamming signals. Assuming that the available data of snapshot sampling are insufficient, a covariance matrix for pure jamming is reconstructed through an iterative adaptive approach (IAA) and used as the training sample for the MVDR beamformer to suppress main-lobe interrupted-sampling repeater jamming. Finally, the method is validated by comparing the simulation results with the measured results.

Joint Design of Transmit Waveform and Mismatch Filter in the Presence of Interrupted Sampling Repeater Jamming

In this letter, a method is proposed to suppress the interrupted sampling repeater jamming (ISRJ) by jointly designing the radar waveform and mismatch filter. The joint design problem under multiple constraints is formulated with the optimization criterion of minimizing the integrated sidelobe levels (ISLs) of waveform mismatch filter output and integrated levels (ILs) of ISRJ signal mismatch filter output. An iterative algorithm is proposed to optimize the waveform and mismatch filter using Lagrange multiplier method and alternating direction multiplier method (ADMM), respectively. Simulation results demonstrate that the proposed method achieves good pulse compression performance while suppressing the ISRJ.

Orthogonal phase‐frequency coded signal in a pulse against interrupted sampling repeater jamming

Interrupted sampling repeater jamming (ISRJ) uses the under sampling technology to transmit and repeat the radar intercepted signals. As a new kind of coherent interference, it is widely used in self-defence interference. At the same time, the existing radar anti-jamming technology cannot effectively combat it. In this study, the principle of ISRJ is analysed. In view of the mismatch between the jamming signal and the radar transmitting signal, an orthogonal phase-frequency coded signal in a pulse is designed. In signal processing, matching and filtering are processed separately through each sub-signal. The simulation results show that the designed signal has a good inhibitory effect on ISRJ.

An Inverse Synthetic Aperture Radar Image Modulation Method Based on Coding Phase-Switched Screen

Multiple false target images deception is an effective strategy to protect vital military targets from detection and recognition by inverse synthetic aperture radar (ISAR). Previous research about it focuses mainly on the interrupted-sampling and sub-Nyquist sampling repeater jamming based on digital radio frequency memory (DRFM). The digital image synthesis (DIS) technique or scatter-wave modulation is used to simulate electromagnetic scattering of the real target. However, it is difficult to realize due to the high reconnaissance accuracy requirement and a heavy computational burden. Moreover, the protected target remains in the same location and the false targets' amplitude envelope based on periodic modulation is relatively fixed, which is not conducive to deception. In this paper, an ISAR image modulation method based on coding phase-switched screen (PSS) is proposed against ISAR. The method uses the target bait made of PSS or attaches the PSS to the protected target surface to impose phase modulation onto the reflected signal. As a result, multiple false target images with verisimilar properties are formed around the protected target position when the reflected signal is received and processed by the victim ISAR. Besides, the protected target is concealed and the flexible amplitude control of false targets is achieved. The simulation results are performed to verify the effectiveness of the proposed method.

Bayesian Compress Sensing Based Countermeasure Scheme Against the Interrupted Sampling Repeater Jamming.

The interrupted sampling repeater jamming (ISRJ) is considered an efficient deception method of jamming for coherent radar detection. However, current countermeasure methods against ISRJ interference may fail in detecting weak echoes, particularly when the transmitting power of the jammer is relatively high. In this paper, we propose a novel countermeasure scheme against ISRJ based on Bayesian compress sensing (BCS), where stable target signal can be reconstructed over a relatively large range of signal-to-noise ratio (SNR) for both single target and multi-target scenarios. By deriving the ISRJ jamming strategy, only the unjammed discontinuous time segments are extracted to build a sparse target model for the reconstruction algorithm. An efficient alternate iteration is applied to optimize and solve the maximum a posteriori estimate (MAP) of the sparse targets model. Simulation results demonstrate the robustness of the proposed scheme with low SNR or large jammer ratio. Moreover, when compared with traditional FFT or greedy sparsity adaptive matching pursuit algorithm (SAMP), the proposed algorithm significantly improves on the aspects of both the grating lobe level and target detection/false detection probability.

Two-Dimensional Blanket Jamming Against ISAR Using Nonperiodic ISRJ

Interrupted sampling repeater jamming (ISRJ) against inverse synthetic aperture radar (ISAR) attracts great attention in the past decades. Conventional ISRJ mainly produces multiple false targets by periodically sampling and retransmitting the intercepted radar signal at sub-Nyquist rates. However, the rapid development of the anti-ISRJ technique and the difficulty in guaranteeing the real-time reaction make it urgent to propose novel ISRJ-based jamming methods. In this paper, a blanket jamming method against ISAR is proposed by utilizing the unique property of the nonperiodic ISRJ. By nonperiodic interrupted sampling modulation on the intercepted ISAR signal in both fast- and slow-time domains, the target image will be covered by the square-shaped jamming strips spreading along both the range and azimuth direction. Then, the target can get shielded by the two-dimensional blanket jamming. Besides, the proposed method is more effective compared with the conventional blanket jamming method, such as the noise jamming due to the signal coherence. Simulations via the Yak-42 aircraft data demonstrate the validity of the proposed method.

A Novel Interference Suppression Method for Interrupted Sampling Repeater Jamming Based on Singular Spectrum Entropy Function.

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.

ECCM Scheme against Interrupted Sampling Repeater Jammer Based on Parameter-Adjusted Waveform Design.

Interrupted sampling repeater jamming (ISRJ) is an effective way of deceiving coherent radar sensors, especially for linear frequency modulated (LFM) radar. In this paper, for a simplified scenario with a single jammer, we propose a dynamic electronic counter-counter measure (ECCM) scheme based on jammer parameter estimation and transmitted signal design. Firstly, the LFM waveform is transmitted to estimate the main jamming parameters by investigating the discontinuousness of the ISRJ’s time-frequency (TF) characteristics. Then, a parameter-adjusted intra-pulse frequency coded signal, whose ISRJ signal after matched filtering only forms a single false target, is designed adaptively according to the estimated parameters, i.e., sampling interval, sampling duration and repeater times. Ultimately, for typical jamming scenes with different jamming signal ratio (JSR) and duty cycle, we propose two particular ISRJ suppression approaches. Simulation results validate the effective performance of the proposed scheme for countering the ISRJ, and the trade-off relationship between the two approaches is demonstrated.

Parameter estimation and suppression for DRFM‐based interrupted sampling repeater jammer

By partial interception and multiple forwarding of a radar transmitting signal, digital radio frequency memory-based interrupted sampling repeater jamming can yield a partial processing gain and form multiple false target groups in the range direction, achieving jamming effects of both suppression and deception. Various improved jamming strategies have been proposed, while jamming suppression problems have not been fully addressed. In this study, a jamming suppression method based on the idea of `reconstruction and cancellation' is proposed by analysing the jamming principle. The method firstly analyses the pulse compression results with time-frequency analysis to obtain the intercepted slice number and forwarding times; then, the slice width is estimated by deconvolution processing; finally, iterative cancellation is used to suppress the jamming. Performance of the method was verified by Monte Carlo simulation. The results show that the normalised error of the slice width estimation is 16 dB.

An Adaptive Transmitting Scheme for Interrupted Sampling Repeater Jamming Suppression.

The interrupted sampling repeater jamming (ISRJ) based on a digital radio frequency memory (DRFM) device is a new type of coherent jamming. This kind of jamming usually occurs as main-lobe jamming and has the advantages of low power requirements and easy parameter adjustment, posing a serious threat to the modern radar systems. In order to suppress the ISRJ, this paper proposes an adaptive transmitting scheme based on a phase-coded signal. The scheme firstly performs jamming perception to estimate the jamming parameters, then, on this basis, optimizes the waveform with genetic algorithm. With the optimized waveform, the jamming signal is orthogonal to the target echo, thus it can be easily suppressed with pulse compression. Simulation experiments are performed to verify the effectiveness of the scheme and the results suggest that the peak-to-side-lobe ratio (PSR) and integrated side-lobe level (ISL) of the pulse compression can be improved by about 16 dB and 15 dB, respectively, for the case where the jamming-to-signal ratio (JSR) is 13 dB.