Synthetic aperture radar (SAR) is an essential instrument for Earth observation but is vulnerable to intentional electromagnetic jamming during imaging. Two-dimensional (2-D) deceptive jamming can introduce highly realistic false targets into SAR images, severely impairing scene interpretation and undermining the reliability of remote sensing missions. Multichannel/static SAR systems exploit additional spatial degrees of freedom to locate the jammer and suppress its signals through spatial filtering, thereby achieving anti-deceptive jamming and ensuring the robustness of remote sensing operations. However, existing multichannel/static methods require excessive system channels and are effective only against limited types of jamming, such as range deception. This article proposes a bistatic SAR-based method for anti-2D deceptive jamming. The method requires only two channels and a single-pass imaging acquisition while effectively suppressing all types of deceptive jamming, including range, azimuth, and 2-D. Compared with existing methods, it achieves broader deceptive jamming type adaptability while reducing both channel and acquisition requirements. First, a method is developed to extract deceptive jamming discrepancy from the two channels of bistatic SAR, which simultaneously enables false target detection. Then, a unified mathematical relationship is established between the extracted jamming discrepancy and the jammer’s 2-D position, allowing accurate localization. Finally, the 2-D minimum variance distortionless response digital beamforming technique is applied to spatially filter the jammer signals and suppress the deception. Simulation results demonstrate the effectiveness and superiority of the proposed method.

Synthetic aperture radar (SAR) imaging is severely threatened by active deceptive jamming. Chirp-rate polarity switching is a technique that employs pulse-to-pulse switching of the chirp-rate polarity for the transmitted linear frequencymodulated waveform, so that the delayed deceptive jamming is chirp-rate mismatched to the receiver matched filter and loses pulse-compression gain, thereby enabling jamming suppression. However, conventional chirp-rate polarity switching only disrupts jamming compression in range, which yields insufficient suppression at high jamming-to-signal ratio (JSR). This paper proposes a two-dimensional chirp-rate polarity switching method for anti-deceptive jamming in SAR. Based on range chirp-rate polarity switching, initial phase coding is imposed on the transmitted waveform to form an azimuth-equivalent chirp-rate polarity switching, thereby jointly disrupting deceptive jamming compression in both range and azimuth. In addition, a signal suppression method based on adaptive nonlinear amplitude mapping is introduced to further reduce jamming power. Simulation results demonstrate that, compared with existing methods, the proposed method achieves effective deceptive jamming suppression at higher JSR.

Existing synthetic aperture radar (SAR) deceptive jamming algorithms for moving targets combine a low-order approximation of the instantaneous slant range with 2-D separation processing or a method based on the fast Fourier transform (FFT) and interpolation calculation to rapidly generate the jammer's frequency response (JFR). However, these methods struggle to balance the contradiction between the jamming modulation accuracy and efficiency, especially when generating multiple moving targets with varying motion parameters. In addition, the echo signals of a highly squint SAR system exhibit significant spatial variability and complex Doppler characteristics, which require the jammer to increase the azimuth sampling rate and construct complex cross-coupling terms, further exacerbating the contradiction. This article proposes a deceptive jamming algorithm for moving targets against highly squint SAR based on the keystone transform (KT) and extended nonlinear chirp scaling (ENLCS). The algorithm effectively reduces the azimuth sampling rate required for JFR construction and eliminates the main range-azimuth coupling by separating the linear range walk (LRW) term and introducing the KT. Based on the circular model theory, the algorithm accurately derives the spatial-variant high-order range cell migration (RCM) and Doppler phase, which are constructed by introducing a quartic perturbation function and the ENLCS method, respectively. Furthermore, the algorithm constructs the motion-parameter-related terms separately from the unrelated ones, reducing redundant processing steps and further improving jamming modulation efficiency. Simulation results and computational complexity analysis validate the effectiveness of the proposed algorithm.

Synthetic aperture radar (SAR) is an active microwave remote sensing technology that provides abundant data for Earth observation. However, the reliability of SAR data is threatened by advanced deception jamming techniques, which generate highly realistic false targets. Identification of these false targets is crucial for ensuring the reliability and interpretability of SAR imagery. With the growing volume of SAR image data and the increasingly realistic false targets, it is challenging for existing identification methods to achieve both high efficiency and accuracy. To address this issue, a deception jamming false target identification method based on efficient object detection and low-rank shadow extraction is proposed. This method introduces an efficient object detection network that incorporates a potential target proposal branch and non-overlapping feature map cropping, effectively reducing computational complexity and enhancing detection efficiency. Furthermore, a shadow extraction algorithm based on low-rank separation feature enhancement and adaptive correction is proposed, which further improves identification capability for highly realistic false targets. Experimental results demonstrate that the proposed method achieves efficient identification of deception jamming false targets and outperforms existing methods in terms of both identification efficiency and accuracy.

High-resolution airborne synthetic aperture radar (SAR) systems frequently operate on non-linear trajectories, posing significant challenges for existing large-scene deceptive jamming algorithms to generate precise trajectory offsets that minimize defocused imagery. This letter proposes an inverse-scale transformation-based large-scene deceptive jamming algorithm against non-linear trajectory SAR. The algorithm avoids the coupling calculation of the trajectory offset term and the linear trajectory SAR deceptive jamming frequency response function (JFR). It forms a general framework for generating trajectory offsets in deceptive jamming of SAR signals. At the same time, the inverse-scale transform is used to generate the range migration offset accurately while requiring phase multiplication and Fourier transform calculations in the range direction, making the calculation simple and efficient. Finally, the efficacy and feasibility of the algorithm are confirmed by point target simulations and real-scene deceptive jamming camouflage tests.

To address the contradiction between modulation accuracy and efficiency of existing moving target deceptive jamming algorithms against synthetic aperture radar-ground moving target indication (SAR-GMTI) systems, as well as the azimuth ambiguity problem when generating fast-moving targets due to the limitations of the system's pulse repetition frequency (PRF), this article proposes a moving target deceptive jamming algorithm based on azimuth deramp-keystone (DKS) processing and scaled Fourier transform (SCFT). First, an azimuth DKS processing method with a variable regulatory factor is proposed to uniformly eliminate the linear range walk (LRW) term in the jammer's frequency response (JFR) and effectively control the range curvature by adjusting the regulatory factor, thereby ensuring jamming modulation accuracy. Combined with the azimuth SCFT, the quadratic and cubic Doppler phases of multiple moving targets with different motion parameters at different zero-Doppler ranges are simultaneously compensated to generate the JFR efficiently. Second, based on differences in Doppler spectrum distribution, a modified keystone transform (KT) method is proposed to effectively address the azimuth ambiguity problem in generating JFR for fast-moving targets. Additionally, a JFR generation strategy using two-stage sampling points is proposed, further enhancing the efficiency of jamming modulation. Compared with existing algorithms, the proposed algorithm requires only complex multiplication and fast Fourier transform (FFT) operations to simultaneously generate multiple moving targets with different motion parameters and fast-moving targets. Moreover, when generating multiple moving targets with identical motion parameters, the computational complexity is reduced by 53.34%. Simulation results further verify the effectiveness of the proposed algorithm.

With the increasing number of emitters and interference, coupled with the development of low probability of intercept techniques, the complexity of operational systems, and the integrated application of antijamming technologies, the pulse stream intercepted by reconnaissance receivers in modern electronic warfare exhibits characteristics such as high pulse missing rate, numerous spurious pulses, large observation noise, and complex pulse repetition interval (PRI) modulations. The previously described pulse stream is referred to as mixed radar pulse sequences in this article. Deinterleaving mixed radar pulse sequences is highly challenging due to the complexity of the electromagnetic environment. The existing methods suffer from issues such as insufficient consideration of complex electromagnetic environments and high-computational complexity. This article introduces the concept of the PRI spectrum and analyzes its properties. Based on this representation, a PRI estimation algorithm that adapts to different PRI types is proposed. In addition, an improvement to the pulse sequence retrieval algorithm based on directed acyclic graph (DAG) is proposed, enabling accurate separation of different pulse sequences. Simulation results show that the algorithm can successfully deinterleave of the mixed pulse sequences. When the jitter bound is 15%, the miss rate is 30%, and the spurious pulse count is 200 within 60 ms, merr and PRism achieved 0.71% and 80.79%, respectively, demonstrating strong performance.

For VHF-band autonomous aerial vehicles ground penetrating radar [autonomous aerial vehicle (AAV-GPR)] applications, a novel dual H-shaped dipole antenna (DHDA) is proposed in this letter. The DHDA comprises a resistor-capacitor loading folded dipole antenna, a split director (SD), and tuning stubs. For capacitive loading requirements in VHF and lower frequency bands, conventional slit-based approaches face practical implementation challenges due to the required extremely narrow gaps. The developed RC-loading folded technique provides an optimal solution for low-frequency antenna bandwidth expansion. To further enhance the antenna gain, SD is introduced above the radiator. The near-field induction of the SD structure enables in-phase stack of the induced and primary field, and this enhancement extends into the far-field region, thereby increasing the antenna gain. Furthermore, the integrated tuning stub effectively compensates for the imaginary component of the input impedance, extending the bandwidth to higher frequencies. A prototype of the antenna is fabricated and tested, exhibiting |S-11| < - 10 dB across the 30 MHz to 170 MHz frequency range, while maintaining a low profile of 50 mm (0.017 lambda(0) at 100 MHz). The antenna system is successfully integrated onto a AAV and demonstrates promising performance in subsurface geological detection.

Chang’e-7 (CE-7), which is an important project of the fourth phase of China’s lunar exploration program, is expected to be launched in 2026. The CE-7 mission consists of a mini-flying probe, an orbiter, a lander and a rover. The lunar penetrating radar (LPR), installed on the rover, is designed to probe the microwave characteristics of the shallow lunar surface and provide scientific data for the study of the Moon’s shallow structure. It offers both single-polarization and multi-polarization detection capabilities and is tasked with measuring the thickness and layered structure of the lunar regolith, as well as detecting subsurface stratification. It also has the ability to identify water ice. CE-7 LPR is a pseudo-random coding system radar which uses the Golay complementary code signal as the transmitted signal. To meet both depth and resolution requirements, it is equipped with both high-frequency and low-frequency channels. The low-frequency (LF) channel operates at the frequency range of 10 ∼ 110 MHz, with the code length of 1024 bits, the detection depth of no less than 400 m, and the layer thickness resolution of better than 2 m. The high-frequency (HF) channel operates at frequency range of 100 ∼ 1500 MHz, with the code length of 128 bits, the detection depth of no less than 40 m, and the layer thickness resolution of better than 15 cm. This paper provides a detailed description of the dual-channel design of the equipment and presents the results of some field tests.

For VHF-band unmanned aerial ground penetrating radar (UAV-based GPR) applications, a novel dual H-shaped dipole antenna (DHDA) is proposed in this paper. The DHDA comprises a resistor-capacitor loading folded dipole antenna, a split director (SD), and tuning stubs. For capacitive loading requirements in VHF and lower frequency bands, conventional slit-based approaches face practical implementation challenges due to the required extremely narrow gaps. The developed RC-loading folded technique provides an optimal solution for low-frequency antenna bandwidth expansion. To further enhance the antenna gain, SD is introduced above the radiator. The near-field induction of the SD structure enables in-phase stack of the induced and primary field, and this enhancement extends into the far-field region, thereby increasing the antenna gain. Furthermore, the integrated tuning stub effectively compensates for the imaginary component of the input impedance, extending the bandwidth to higher frequencies. A prototype of the antenna is fabricated and tested, exhibiting |S11| < − 10 dB across the 30-170 MHz frequency range, while maintaining a low profile of 50 mm (0.017λ0 at 100 MHz). The antenna system is successfully integrated onto a UAV and demonstrated promising performance in subsurface geological detection.

Synthetic aperture radar (SAR) operating mode recognition plays a crucial role in SAR countermeasures and serves as the foundation for effective SAR interference. To address the limitations of current SAR operating mode recognition algorithms, such as low recognition rates, poor generalization, and limited engineering applicability under low signal-to-noise ratio (SNR) conditions, an enhanced algorithm named dual-input feature fusion ShuffleNet (DIFF-ShuffleNet) based on intercepted SAR signal data is proposed. First, the SAR signal is processed by combining pulse compression and time–frequency analysis technology to enhance anti-noise robustness. Then, an improved lightweight ShuffleNet architecture is designed to fuse range pulse compression (RPC) maps and azimuth time–frequency features, significantly improving recognition accuracy in low-SNR environments while maintaining practical deployability. Moreover, an improved coarse-to-fine search fractional Fourier transform (CFS-FRFT) algorithm is proposed to address the chirp rate estimation required for RPC. Simulations demonstrate that the proposed SAR operating mode recognition algorithm achieves over 95.00% recognition accuracy for SAR operating modes (stripmap, spotlight, sliding spotlight, and scan) at an SNR greater than −8 dB. Finally, four sets of measured SAR data are used to validate the algorithm’s effectiveness, with all recognition results being correct, demonstrating the algorithm’s practical applicability.

As humanity’s first sample return mission from the lunar farside, China’s Chang’E-6 mission provides a unique window into understanding the dichotomy in lunar nearside-farside evolution. Chang’E-6 landed in the southwestern Apollo basin (~2.79 Ga) within the South Pole–Aitken basin, providing a valuable record of early solar system impacts. Equipped with a Multi-Input-Multi-Output Lunar Regolith Penetrating Radar, the mission enabled the first detailed investigation of the shallow subsurface structure at the farside. By employing a tailored data processing approach, we obtained high-resolution subsurface images and revealed a distinct two-layer structure to a depth of 3 m. The upper layer (~1.7 m thick) consists of fine-grained, highly weathered regolith, while the lower layer (extending to 3 m) contains coarse, unweathered ejecta. Furthermore, by integrating data from Apollo and Chang’E missions, we identified a potential relationship between the lunar surface geological age and the shallow regolith’s electromagnetic losses. Specifically, geologically older regions exhibit lower electromagnetic attenuation, suggesting a possible link between regolith maturity and electromagnetic properties. These findings provide critical insights into the geological evolution of the Moon, and also offer unprecedented opportunities for correlating in-situ radar measurements with laboratory analyses of the farside samples, fundamentally advancing our understanding of lunar exploration. An analysis of subsoil structure using lunar regolith penetrating radar at the Chang’E-6 landing site indicates a distinct 2-layer structure, and when compared with Apollo mission data, suggests a link between regolith maturity and electromagnetic properties.

The subsurface structure of the Moon has recorded key information about the Moon's formation and evolution,therefore,precise exploration of the subsurface structure of the Moon is an important scientific goal of China's lunar exploration project.Ultra-wideband(UWB)penetrating imaging radar is the most effective technology for acquiring the subsurface structure of the Moon.China's lunar probes,Chang'e-3 and Chang'e-4,have been pioneers in employing UWB penetrating imaging radar for the exploration of extraterrestrial bodies,achieving significant advancements.This paper conducts a comparative analysis and selection of signal used by UWB penetrating imaging radar,summarizes the features of the penetrating imaging radar systems used in the Lunar exploration project and their key technological breakthroughs,and provides an analysis and summary of the subsurface detection results of the Moon.It provides valuable references for the instrument design and scientific research of subsequent missions.

Acceleration grid power supply (AGPS) rated 200 kV/28 A is an important part of the negative neutral beam injection (NNBI) system. Dynamic performance is the focus of the design of the closed-loop system for AGPS. For special power applications, the single voltage mode of the control system is determined in AGPS. On this basis, a type-III compensator is introduced to optimize the control system. For the problem of the type-III compensator parameter tuning, the traditional $k$ -factor method is introduced in this article. However, it is inadequate to deal with the system of parameter variation. Given this problem, an improved type-III compensator based on the radial basis function (RBF) neural network is proposed in this article. The algorithm can identify the system and train the optimal compensator parameters, which enhances the system’s robustness. In this article, the performance of the traditional type-III and the RBF-type-III compensator is compared under experimental conditions of different bus voltages. Simulation and experimental results validate the efficacy of this design.

Acceleration grid power supply (AGPS) is the energy provider of the negative neutral beam injection (NNBI) system. With the construction of the Comprehensive Research Facility for Fusion Technology (CRAFT), higher parameter requirements are proposed and a high-voltage power supply (HVPS) rated $-$ 200 $\sim$ $-$ 400 kV/28 A has been developed. This article introduces the design of each part of the AGPS in detail, such as the neutral-point-clamped (NPC) inverter, step-up transformer, and diode rectifier. The control system is also discussed and an optimized mathematical model from the duty cycle of the inverter to the dc output of the power supply (PS) is given. A scheme is put forward to solve the special grid breakdown (GB) condition of NNBI AGPS. The experimental results demonstrate that AGPS can meet the rated output requirements of the NNBI system and it can be quickly turned off to protect the AGPS in GB condition, which provides a related reference for the subsequent development of other HVPS for auxiliary heating of nuclear fusion.

Deception jamming of synthetic aperture radar (SAR) has attracted extensive attention due to its low power consumption and high fidelity advantages. However, existing SAR deception jamming algorithms assume that SAR operates on a linear trajectory. In practice, SAR trajectories often become nonlinear due to factors such as atmospheric turbulence, which results in the jamming signals lacking the two-dimensional spatial variability of nonlinear-trajectory SAR echo signal and affects the imaging quality of deception jamming. This paper proposes a new algorithm for nonlinear-trajectory airborne SAR deception jamming based on hybrid domain efficient (HDE) modulation. This algorithm derives the jamming frequency response (JFR) with SAR trajectory deviation in the azimuth time–frequency hybrid domain. Based on the hybrid domain modulation, the jammer calculates the JFR of the linear trajectory in the azimuth frequency domain and constructs for the real-time trajectory deviation pulse by pulse at each azimuth moment. The real-time modulation process of the algorithm only involves range domain Fourier transform and complex multiplication, combining computational efficiency and modulation flexibility. The validity constraints of the algorithm have been analyzed to ensure the focusing ability of the jamming signal. Simulation and computational complexity analysis validate the excellent performance of the algorithm in imaging quality and efficiency.

Due to the complex range migration characteristics of large squint angle synthetic aperture radar (SAR), it is difficult for traditional SAR deceptive jamming algorithms to balance focusing ability and computational efficiency. There is an urgent demand for proposing a deceptive jamming algorithm against large squint angle SAR in the field of SAR jamming. This article proposes a deceptive jamming algorithm against SAR with large squint angles based on non-linear chirp scaling and low azimuth sampling reconstruction (NLCSR). The NLCSR algorithm uses a high-order approximation of a high-precision model to accurately construct the jammer’s frequency response (JFR) function. In line with the notion of low azimuth sampling processing of the transformation domain, the construction of the space-variant azimuth modulation phase item is completed using the non-linear chirp scaling method. Compared with the traditional deceptive jamming algorithms against the large squint angle SAR, the NLCSR algorithm only needs Fourier transform and complex multiplication while ensuring the focusing ability, which is easier to implement on an efficient parallel digital signal processor based on fast Fourier transform (FFT). Simulation results prove the superior property of the NLCSR algorithm in focusing ability and computational efficiency. Compared to the existing large squint angle SAR deceptive jamming algorithm, the focusing ability of the NLCSR algorithm is almost the same, and the calculation efficiency is improved by at least 52.1%.

This paper proposes a novel design method for pyramid horns which are under the constraints of 3 dB beamwidth. It is based on the general radiation patterns of E/H planes derived from Huygens’ principle. Through interpolation and fitting techniques,the E/H plane’s maximum aperture error parameter of the pyramid horn is obtained as a function of the angle and aperture electrical size. Firstly, the aperture size of the E（or H） plane is calculated with the help of the optimal gain principle. Secondly, the constraint equation of another plane is derived. Finally, the intersection of constraint equation and interpolation function, which can be solved iteratively, contains all the solution information.The general radiation patterns neglect the influence of the Huygens element factor which makes the error bigger in large design beamwidth. In this paper, through theoretical analysis and simulation experiments, two correction formulas are employed to correct the Huygens element factor’s influence on the E/H planes. Simulation experiments and measurements show that the proposed method has a smaller design error in the range of 0–60 degrees half-power beamwidth.

On 1 December 2020, China’s Chang’E-5 (CE-5) probe successfully landed in the northeastern Oceanus Procellarum. This work mainly presents the results of Lunar Regolith Penetrating Radar (LRPR) equipped on the CE-5 Lander. The lunar regolith structure of the landing site from the surface to 3-m depth is unveiled by LRPR, which found that abundant rock fragments are distributed in uniform lunar regolith. The imaging result proved that the drilling and sampling process was prevented by big rocks at about 100 cm depth. On the basis of the response of lunar soil to electromagnetic (EM) wave, the EM properties of the landing site estimate that the relative dielectric constant and the loss tangent are 2.520 ± 0.186 and 0.0133 ± 0.0020, respectively.

China's Tianwen-1 probe carrying the Zhurong rover successfully landed on the southern Utopia Planitia of Mars. The Zhurong rover is first equipped with a full-polarimetric Mars Rover Penetrating Radar (FP-RoPeR) system, aiming to map the fine structure and potential water-ice distribution of Martian regolith. However, the ground experiment on earth indicates that the RoPeR data is severely affected by noises, clutters, and signal misalignment. More importantly, an imbalance between the data from two cross-polarized channels is observed which is considered to be the interference of the rover. The interference prevents the accurate assessment and analysis of field FP-RoPeR data and may even become the trap in the interpretations of future radar data from Mars. In this article, we first analyze the interference in detail and achieve the suppression of noises, clutters, and signal misalignment; subsequently, a polarized orientation calibration method is proposed to calibrate the imbalance of cross-polarized channels. Finally, we introduce a field experiment at the Ulanhada volcanic geopark in Inner Mongolia Autonomous Region, China. Based on the field RoPeR data and the proposed processing methods, we propose three types of data processing strategies for different aims and present how to use field FP-RoPeR data to analyze subsurface structures and properties.