Letao Xu

A Three-Stage Active Cancellation Method Against Synthetic Aperture Radar

Echo cancellation is of great potential for a radar cross section reduction in stealth technology. All the techniques developed in the last decade rely primarily on the assumption that cancellation echo and target echo synchronize in the time domain. However, the cancellation echo may lag behind the target echo when countering a synthetic aperture radar (SAR). This is because the cancellation echo generation requires extra processing time when the SAR transmits and receives large time bandwidth product signal such as linear frequency modulation pulses. Thus, the cancellation echo and target echo cannot cancel each other perfectly. In this paper, we develop a novel three-stage active cancellation method using frequency and delay-time modulation to cancel out the target echo. In this scenario, the cancellation echo will intentionally lag behind the target echo. Theoretical analyses and simulation results verify the effectiveness of the proposed method.

An Improved Digital False-Target Image Synthesizer Method for Countering Inverse Synthetic Aperture Radar

Digital false-target image synthesizer (DIS) has been proposed as a deceptive jamming method for countering inverse synthetic aperture radar (ISAR) with an RF imaging false-target capability. However, to efficiently generate jamming signal in real time, a specific-designed generator is unavoidable for the implementation of this algorithm, where parallel and pipeline processing are both included because jamming signal is generated according to each range bin. This paper proposes an improved two-stage DIS method (T-DIS). The implementation of the T-DIS can be effectively simplified by separating the modulation process of a repeat jammer into two stages: the offline stage and the real-time stage. The modulation signal can be easily extracted from the modulation-matrix buffered in the offline stage. Only an element-by-element matrix multiplication between the modulation signal and the intercepted ISAR signal is needed in the real-time stage. In contrast to the conventional DIS method, the proposed algorithm exhibits simplicity and flexibility significantly, which reduces the computation time and hardware constraints. Experimental results of scattering model of the Yak-42 plane and real data illuminate the validity of the proposed method.

High-Resolution Range Profile Deception Method Based on Phase-Switched Screen

High-resolution range profile (HRRP) has been useful in the support of target characterization and thus receives intensive attention. It is still a challenging task to design a deception method capable of both generating false-target HRRPs and concealing the real-target HRRP. In this letter, an HRRP deception method based on phase-switched screen (PSS) is proposed. This method utilizes PSS to impose phase modulation onto the radar reflected signal so that multiple false targets with verisimilar HRRP characteristics appear symmetrically around the real-target position. Meanwhile, the real-target HRRP is concealed and may not be detected by radar. Experimental results are used to verify the correctness of the analyses.

Jamming Wideband Radar Using Interrupted-Sampling Repeater

Interrupted-sampling repeater jamming (ISRJ) provides a novel coherent-jamming mode against wideband radar. ISRJ allows the single-antenna jammer to periodically sample and repeat a fraction of the intercepted signal, which reduces the sampling rate and achieves transmit-receive isolation. The coherent-jamming signal generated by ISRJ can form multiple verisimilar false targets when received and processed by the victim radar receiver. Moreover, some false targets can precede the real target. This paper surveys the use of ISRJ in linear frequency modulated (LFM) radar jamming. The theory and application of ISRJ has been researched for more than one decade, but what is missing is a completed summary for the framework of this technique. In this paper, mathematic principles of ISRJ against LFM radars, which utilize matched-filter processing, stretch processing, and range-Doppler processing, are developed. The unique jamming effects in radar systems are focused on when the interrupted sampling frequency of the jammer is smaller than the bandwidth of the radar signal. Specifically, the false-target characteristics, including amplitude, space distribution, and phase, are discussed, respectively. On this basis, the key jamming elements, which determine these false-target characteristics, are pointed out and analyzed in detail. At last, simulation and real data are used to verify the correctness of the analyses. Experimental results highlight the potential application of the proposed jamming mode.

Bistatic ISAR Imaging with a V-FM Waveform Based on a Dual-Channel-Coupled 2D-CS Algorithm

Due to the sparsity of the space distribution of point scatterers and radar echo data, the theory of Compressed Sensing (CS) has been successfully applied in Inverse Synthetic Aperture Radar (ISAR) imaging, which can recover an unknown sparse signal from a limited number of measurements by solving a sparsity-constrained optimization problem. In this paper, since the V style modulation(V-FM) signal can mitigate the ambiguity apparent in range and velocity, the dual-channel, two-dimension, compressed-sensing (2D-CS) algorithm is proposed for Bistatic ISAR (Bi-ISAR) imaging, which directly deals with the 2D signal model for image reconstruction based on solving a nonconvex optimization problem. The coupled 2D super-resolution model of the target’s echoes is firstly established; then, the 2D-SL0 algorithm is applied in each channel with different dictionaries, and the final image is obtained by synthesizing the two channels. Experiments are used to test the robustness of the Bi-ISAR imaging framework with the two-dimensional CS method. The results show that the framework is capable accurately reconstructing the Bi-ISAR image within the conditions of low SNR and low measured data.

Influence of Estimate Error of Radar Kinematic Parameter on Deceptive Jamming Against SAR

The influence of intelligence gathering inaccuracy, especially the estimate error of radar kinematic parameter, on the performance of deceptive jamming against synthetic aperture radar (SAR) is studied in this paper, filling a knowledge vacancy in the field of SAR electronic countermeasures. For the first time, an equivalence relationship between non-ideal jamming and ground moving target is derived and verified in raw phase history data domain and radar image domain. A novel and elegant way to quantify the defocus and displacement of false target in radar image is proposed based on the equivalence relationship. Work presented in this paper can guide the design of jammers intelligence gathering subsystem and optimize jamming configuration, from the view of jammer. The results also avail electronic counter-countermeasures, from the view of radar.