The traditional methods of jamming against synthetic aperture radar (SAR), which are implemented based on linear frequency-modulated (LFM) signals, are currently unable to meet the needs of electronic countermeasures. Compared with the LFM signal, the frequency of the nonlinear frequency-modulated (NLFM) signal varies nonlinearly with time. Because of this time-frequency structure, the NLFM signal is naturally mismatched with the linear matched filter of SAR; thus, a stronger and more flexible jamming effect is produced. In this paper, the NLFM signal is used in the SAR jamming field for the first time, and a smart jamming method against SAR based on the NLFM signal is proposed, which can produce the following two jamming effects: barrage and deceptive. First, the shaping factor is defined to generate the expected NLFM signal. The shaping factor controls the jamming range in the fast time direction for barrage jamming. For deceptive jamming, a jamming method involving piecewise weighting is proposed. The shaping factor is used to control the defocusing degree of false targets. Subsequently, the pulse compression results of the jamming signal are deduced, and the influence of different parameters on the jamming effect is theoretically analyzed. Experimental results based on simulation show that the method can control the jamming range and effect in the fast time direction while achieving a flexible deceptive jamming effect.

Traditional jamming methods protect scene targets by generating barrage jamming or deceptive jamming effect, but the single jamming effect is currently difficult to meet the increasingly complex electromagnetic environment. To meet the complex electromagnetic environment, a 2-D precise controllable smart jamming method is proposed in this letter, which can produce two kinds of jamming effects: barrage jamming and deceptive jamming. Based on the synthetic aperture radar (SAR) imaging properties of linear frequency modulation (LFM), the range and azimuth modulation terms have been designed to generate precise controllable jamming. First, both the range and azimuth jamming positions can be controlled by first-order phase error modulation. Subsequently, multiple phases sectionalized modulation is performed in the range direction, quadratic phase error or periodic phase error modulation is performed in the azimuth direction. Different jamming effects can be generated by changing the jamming modulation item. Theoretical analysis and simulation results show that the proposed method can produce 2-D precise controllable smart jamming effects.

Due to advantages such as low power consumption and high concealment, deceptive jamming against synthetic aperture radar (SAR) has received extensive attention in electronic countermeasures. However, the false targets generated by most of the deceptive jamming methods still have limitations, such as poor controllability and strong regularity. Inspired by the idea of waveform coding, this paper proposed a repeater-type SAR deceptive jamming method through the joint encoding of amplitude and phase in intra-pulse and inter-pulse, which can generate a two-dimensional controllable deceptive jamming effect. Specifically, the proposed method mainly includes two parts, i.e., grouping and encoding. The number of groups determines the number of false targets, and the presence of the phase encoding produces false targets. The amplitude encoding affects the amplitude of the false targets. For the intra-pulse cases, the proposed method first samples the intercepted SAR signal. Meanwhile, the sampling points are grouped in turn. For the inter-pulse cases, the grouped objects are the pulses. Subsequently, the joint encoding of amplitude and phase is performed on each group, which generates jamming signals with deceptive effects. In this paper, the imaging effect of the generated jamming signals is analyzed in detail, and the characteristics of false targets, including numbers, position, and amplitude, are derived. The simulation and experimental results verify the correctness of the theoretical analysis. In addition, the superiority of the proposed method is verified by comparing it with other methods.

Azimuth multichannel synthetic aperture radar (SAR) possesses high-resolution and wide-swath (HRWS) imaging capabilities, posing a significant threat to the survivability of critical targets during wartime. However, due to the constraints of multichannel reconstruction processing, existing jamming technology will produce a periodic jamming effect in the azimuth direction when against HRWS-SAR. This unique periodic repetition related to the number of channels will make the jamming easy to detect and eliminate. Meanwhile, the amplitude of the jamming signal suffers from the modulation of sine functions, which causes a waste of jamming energy. Against the above problems, this article introduces a pre-segmentation idea, effectively circumventing the aforementioned problems. Meanwhile, this article proposes a two-dimensional (2-D) precise controllable smart jamming method designed for HRWS-SAR. The proposed method can generate two jamming effects, barrage and deceptive, at designated locations within the targeted area. First, 2-D expand factors are defined respectively to achieve precise control of the barrage jamming range. Then, by controlling multiple jamming parameters, a highly controllable deceptive jamming effect can be achieved. Additionally, a parameterized jamming model is established, which can achieve 2-D precise control of the jamming position through the cooperation of the signal and spatial domain. Notably, this study focuses not only on the impact of different jamming parameters on imaging results but also on evaluating jamming effectiveness under parameter estimation errors to guide optimal jamming strategies. Finally, extensive numerical simulation experiments and comparisons with other methods are conducted to verify the superiority of the proposed method.

Currently, most barrage jamming methods can only generate jamming effects with fixed shapes. If faced with a region of interest with a specific geometric shape, jamming energy will inevitably be consumed in irrelevant areas, compromising overall jamming efficiency. To mitigate these challenges, this article pro poses an irregular-shaped noise jamming template generation and modulation method against SAR, which enables the generation of noise jamming with a specific shape at a designated position in the SARimage. First, a design process for a two-dimensional frequency domain filter with an arbitrary shape is proposed. By applying this filter to the pre-generated noise template, a noise jamming template tailored to specific scenarios can be generated, thereby allowing for precise matching of the jamming template with the target area and reducing the waste of jamming energy. Secondly, against the shortcomings of frequency-shift jamming (FSJ), i.e., an inherent linear relationship between the center frequency of the jamming signal and the frequency shift modulation amount, an improved parameterized high-efficiency FSJ (PHE-FSJ) is proposed to enable precise control of the jamming position. PHE-FSJ not only changes the inherent jamming characteristics of FSJ but also further reduces the waste of jamming energy. Besides, to adapt to the above jamming technology, a jamming modulation process is proposed. Notably, this study focuses not only on the impact of different jamming parameters on imaging results but also on evaluating jamming effectiveness under parameter estimation errors to guide jamming strategies. Finally, simulation experiments and comparisons with other methods are conducted to verify the superiority of the proposed method.