In this letter, a synthetic aperture radar (SAR) image transform method is proposed using the periodic-coded phase modulation. By modulating the intercepted radar signal with the periodic-coded phase pulse, multiple false targets can be formed along the range direction in the radar image. Then, the target of interest (TOI) can get protected by the deception jamming effect. On this basis, the jamming property and parameter design principles are further discussed. Finally, the mini-SAR data experiment indicates that multiple false targets approximately from 15 to 30 dB higher than the low-level background are generated in the SAR image and then demonstrates the validity of the proposed image transform method.

Stepped frequency chirp signal obtains high-resolution radar images by synthesizing multiple narrowband chirp pulses. It has been one of the most commonly used wideband radar waveforms due to its lower demand for radar instant bandwidth. In this paper, we propose a radar jamming method using two-dimensional nonperiodic phase modulation against stepped frequency chirp signal imaging radar. Using the unique property of nonperiodic phase modulation, the proposed method can generate high-level sidelobes that perform as a special blanket jamming along both the range and azimuth directions and make the target unrecognizable. Then, the influence of different modulation parameters, such as the code width and duty ratio, are further discussed. Based on this, the corresponding parameter design principles are presented. Finally, the validity of the proposed method is demonstrated by the Yake-42 plane data simulation and measured unmanned aerial vehicle data experiment.

Forward scatter radar (FSR) can achieve target detection by capturing the signal disturbance caused by targets crossing the baseline, which provides a countermeasure to stealth/small targets. Firstly, the FSR net model based on the Global Navigation Satellite System (GNSS) is constructed. Then, the statistical features in the time and frequency domains are used to describe the fluctuation characteristics of the forward-scatter signal. Moreover, the influences of the relative position of the target and baseline on the statistical features are analyzed through dynamic simulations, and the change regulation of time and frequency features is revealed. Finally, a FSR experiment is carried out in an anechoic chamber and the results validate the theoretical analysis. This work provides a meaningful reference for detection and parameter estimation of targets crossing the baseline in a FSR.

In this letter, tensor ring decomposition (TRD) was proposed to estimate the two-dimensional direction-of-departure (2D-DOD) and two-dimensional direction-of-arrival (2D-DOA) in bistatic multiple-input multiple-output (MIMO) radar with uniform planar array structure. The advantages of TRD lie in its ability to flexibly establish a connection between adjacent two factors in a higher order tensor. To effectively utilize TRD, it is necessary to have a high-order tensor with real-value factors. Initially, an eight-dimensional (8D) tensor was derived through the delay cross-covariance tensor. Then, by employing tensor permutation and the generalized tensorization of the 8D tensor, a four-dimensional (4D) tensor with factor matrices containing the difference coarray of transmit and receive arrays was obtained. Subsequently, four unitary matrices were applied to perform real valued processing on the constructed 4D tensor factor matrix. The TRSVD algorithm was then used to estimate the three-dimensional (3D) TR core tensors of the 4D real-valued tensor. Finally, the 2D-DOD and 2D-DOA were successfully estimated by utilizing the obtained 3D sub-tensors. Simulation results demonstrate the effectiveness of the proposed algorithm

This letter proposes a novel algorithm to estimate the 3-D attitude using bistatic full-polarization information. First, tilt angles of bistatic Huynen target parameters are extracted from the Sinclair matrix. Then, extracted tilt angles are used to recover the linear-type target attitude by parametric space searching and noncoherent accumulation. Anechoic chamber experiment results demonstrate that the max relative error is smaller than 3% for an iron wire object with two attitude placements.

The parameter estimation in the forward scatter radar (FSR) network is the focus of attention in the radar field. In this letter, a parameter estimation method by using the crossing time difference and Doppler rate is proposed in the FSR network. The continuous position and velocity estimation of the uniform moving target is realized. Then, the factors affecting the estimation accuracy are theoretically analyzed, including parameter measurement error and receiver locations. The effectiveness and adaptability of the method are validated through Monte Carlo simulations. Compared with the parameter estimation method only based on the crossing time, higher accuracy can be achieved and fewer receivers or transmitters are needed, so it should be easier to be deployed in the real application.

Radar faces various interferences from the reconnaissance and other devices when conducting target imaging and recognition. The properties of traditional modulation methods, such as linear frequency modulation (LFM) and phase code modulation (PCM), have been investigated in detail. Therefore, it can be intercepted and recognized easily so that the target image is difficult to be obtained. To improve the complexity of radar signals, the pulse signal design and imaging method is proposed in this paper based on coded modulation. Taking LFM signal as an example, it is modulated by the code sequences firstly. As the spectrum of LFM signal is aliasing after coded modulation, the false peaks appear in target high resolution range profile (HRRP). To eliminate the false peaks in HRRP, the plus-minus coded modulation is designed according to the duty ratio of the first coded modulation signal. Then, the HRRP can be recovered for target imaging. The whole procedure of the coded modulation and imaging is provided and analyzed. Besides, based on different coded modulation signals, the entropy of signal time-frequency image is discussed to illustrate the anti-jamming performance. Simulations and experiments are conducted to verify the effectiveness of the proposed signal design and imaging method.

Due to the high cost of obtaining echo data for space targets in real cases, most of the research usually relies on the simulation. The electromagnetic (EM) calculation is well known as one of the simulation tools. In this letter, the relationship between the calculated complex radar cross-section data and the baseband echo signal is analyzed. Then, the difference in the polarization reference plane of the radar coordinate system and EM calculation coordinate system is pointed out. For simulating the baseband echo signal with full polarization, the scattering matrix obtained by EM calculation should be rotated according to the radar position, the target position, and the target attitude. At last, a simulation of the baseband echo signal with full polarization for a cone-shaped target is given to verify the simulation algorithm.

When a pulse radar signal is implemented in a range-limited anechoic chamber for radar measurement, the transmitted and reflected signal will be coupled at the receiver. To solve this problem and equivalently simulate the whole process of pulse radar measurement in an anechoic chamber, the interrupted transmitting and receiving method is proposed in this letter based on interrupted sampling. The constraints of the transmitting and receiving parameters are deduced with the sizes of the anechoic chamber and target. The pulse compression of the proposed method is performed. Then, the window function is applied to extract the main peaks after pulse compression. Both the simulation and experimental results are provided to demonstrate the effectiveness of the proposed method in overcoming the coupling between the transmitted and reflected pulse signals.

Feature extraction and recognition of wobbling targets are very important in spatial target surveillance. It has been shown that the scattering centers are slipping on the edge of the rotational symmetry target with the target micro-motion according to the electromagnetic scattering theory and electromagnetic computation analysis. Based on the slippery scattering center model, the micro-motion model and high-range resolution profile (HRRP) model of a wobbling rotational symmetry cone-shaped target are introduced, and the observed HRRP sequence is used to construct a time-range distribution matrix, then a estimation method of the wobbling period is proposed based on time-range distribution matrix correlation, which is validated by electromagnetic computation data and dynamic simulation.

The 2-D image of a spinning target obtained by monostatic radar is modified by the angle between the spinning axis and the radar line of sight, so it usually cannot describe the real size of the target. The T/R-R bistatic radar is proposed to solve this problem. First, the bistatic geometry and bistatic echo signals of a spinning target are modeled. Then, a novel 2-D imaging algorithm is presented based on the connections between the mono- and bistatic echoes of the same scatterer and the classical Hough transform, allowing both the mono- and bistatic 2-D images of the spinning target to be obtained simultaneously. The theoretical analysis is carried out by the electromagnetic calculation and numerical simulations.