Search

Tangential targets are those targets travelling perpendicularly to the radial direction of the radar rotating antenna. These targets produce zero Doppler frequency shifts relative to the transmitted frequency. Consequently, these targets are considered as fixed targets to the radar Moving Target Indicator (MTI) and automatically removed. This problem is solved in pulse radar by passing the output of the matched filter into a parallel channel to the MTI channel containing a zero velocity filter (ZVF) and clutter map processor. In this paper, a similar approach is applied in Linear Frequency Modulated Continuous Wave (LFMCW) radars with de-chirping schemes. The output of the first Fast Fourier Transform (FFT) is split into two paths; a traditional one and a ZVF with clutter map processor one. The output of the traditional channel and the ZVF channel are then passed to a hit processor to produce a hit report. The capability of the proposed method in detecting tangential targets as well as slowly moving targets in LFMCW radar compared to traditional scheme is validated through the Receiver Operating Characteristic (ROC).

Across-track acceleration is a major source of estimation error of along-track velocity in synthetic-aperture radar (SAR) ground moving-target indication (GMTI). This paper presents the theory and a method of compensating across-track acceleration to improve the accuracy of along-track velocity estimated from single-channel SAR single-look complex data. A unique feature of the proposed method is the utilisation of phase derivatives in the Doppler frequency domain, which is effective for azimuth-compressed signals. The performance of the method was evaluated through experimental data acquired by TerraSAR-X and speed-controlled and measured vehicles. The application results demonstrate a notable improvement in along-track velocity estimates. The amount of along-track velocity correction is particularly significant when a target has irregular motion with a low signal-to-clutter ratio. A discontinuous velocity jump rather than a constant acceleration was also observed and verified through comparison between actual data and simulations. By applying this method, the capability of single-channel SAR GMTI could be substantially improved in terms of accuracy of velocity, and moving direction. However, the method is effective only if the correlation between the actual Doppler phase derivatives and a model derived from the residual Doppler rate is sufficiently high. The proposed method will be applied to X-band SAR systems of KOMPSAT-5 and -6.

Moving target indication (MTI) is the first component of a tracking radar's signal process. Being the fundamental component of a tracking radar, the reliability of the MTI process to detect a moving target must be effectively characterized in order to achieve the goal of characterizing the reliability of a tracking radar. Operational reliability metric is used to quantify the ability of an MTI radar to detect a moving target in various scenarios. The radar scenario investigated in this paper includes the detection of a small aircraft by a ground based MTI radar. MTI processing is applied to the received signal in order to remove the effects of the stationary ground clutter. An operational reliability analysis of the filtered data is performed to show the reliability of the MTI radar. The reliability analysis is repeated for different target altitude scenarios.

Radar imaging requires the use of wide bandwidth and a long coherent processing interval resulting in range and Doppler migration throughout the observation period. This migration must be compensated in order to properly image a scene of interest at full resolution and there are many available algorithms having various strengths and weaknesses. Here, a new subaperture-based imaging algorithm is proposed, which first forms range-Doppler (RD) images from slow-time sub-intervals, and then coherently integrates over the resulting coarse-resolution RD maps to produce a full resolution SAR image. The novelty is in the use of a two-dimensional backprojection approach to perform distortion-free integration of the RD maps, and in the application of the Keystone Transform to make the subaperture processing compatible with subsequent processing to detect and/or image moving targets.

CopSAR and OrthoCopSAR have been recently proposed in the literature to reduce the amount of data to be stored and processed and to extend the maximum swath width that can be imaged without introducing any degradation to the azimuth resolution. Such a High-Resolution Wide-Swath (HRWS) imaging capability is achieved by sampling the synthetic aperture using multiple interlaced sub-Nyquist PRFs. However, a limitation in such imaging modalities is in the assumption that the scene contains only stationary targets. Consequently, moving targets will appear shifted from their true location mostly in the azimuth direction. In this paper, CopGMTI is proposed to detect ground moving targets and estimate their radial velocities when the synthetic aperture is sampled at a sub-Nyquist rate according to CopSAR or OrthoCopSAR. This allows identifying the true azimuth location of such moving targets. Theoretical results provided in this paper are validated using the publicly available Air Force Research Laboratories (AFRL) multichannel SAR GMTI Gotcha data set.

Linear frequency modulation (LFM) waveforms have high Doppler-shift endurance because of the relative wide modulation bandwidth to the Doppler variation. The Doppler shift of the moving objects, nevertheless, constantly introduces obscure detection range offsets despite the exceptional Doppler tolerance in detection energy loss from LFM. An up-down-chirped LFM waveform is an efficient scheme to resolve the true target location and velocity by averaging the detection offset of two detection pairs from each single chirp LFM in opposite slopes. However, in multiple velocity-vary-target scenarios, without an efficient grouping scheme to find the detection pair of each moving target, the ambiguous detection results confine the applicability of precise target estimation by using these Doppler-tolerated waveforms. A succinct, three-multi-Doppler-shift-compensation (MDSC) scheme is applied to resolve the range and velocity of two moving objects by sorting the correct LFM detection pair of each target, even though the unresolvable scenarios of two close-by targets imply a fatal disability of detecting objects under a cluttered background. An innovative clutter-suppressed multi-Doppler-shift compensation (CS-MDSC) scheme is introduced in this research to compensate for the critical insufficient of resolving two overlapping objects with different velocities by solely MDSC. The CS-MDSC has been shown to successfully overcome this ambiguous scenario by integrating Doppler-selective moving target indication (MTI) filters to mitigate the distorting of near-zero-Doppler objects.

Traditional synthetic aperture radar (SAR) deceptive jamming can effectively generate deceptive scenes or false targets in SAR images. However, these false targets or scenes can be easily distinguished or eliminated by the multichannel SAR system. To interfere with the multichannel SAR, we first analyzed the results of SAR deceptive jamming generated by one transponder and two transponders against three-channel SAR- ground moving target indication (GMTI). Then, we propose a new deceptive jamming method against three-channel SAR-GMTI by using three synergetic transponders. By modulating each transponder with a complex coefficient, three synergetic transponders can generate false moving targets with the controllable radial velocity and located azimuth position in three-channel SAR-GMTI. Besides, in this paper, we also introduce an algorithm to deploy three transponders reasonably by utilizing the minimum condition number. In the end, a general architecture of multiple transponders deceiving multichannel SAR is given. The proposed method can not only generate deceptive false targets against multichannel SAR-GMTI, but also guide the production of a deceptive digital elevation model (DEM) against multichannel interferometric SAR (InSAR). Simulations verify the effectiveness of the proposed method.

Velocity estimation of a moving target is an important yet challenging issue facing the special mode of high-resolution and wide-swath (HRWS) synthetic aperture radar. HRWS imaging is achieved by splitting the antenna into multiple receive channels in azimuth with each channel working at low pulse repetition frequency sampling. In this study, the authors propose a novel approach to estimate the velocity of a moving target in HRWS mode, along with a complete moving target indication, estimation, and imaging scheme. The proposed radial velocity estimation algorithm is called the equivalent along-track interferometry method, which is implemented by twice imaging after reconstructing the data of several leftmost and rightmost channels. Moreover, the along-track velocity is also estimated for focused imaging of the moving target. The motion-adapted reconstruction and imaging algorithm is applied to achieve unambiguous imaging of the moving target. Experimental results verify the performance of the algorithm and its superiority for a moving target with interference from clutter, noise, and channel mismatches. The proposed algorithm is free of search and iteration, and featured by high accuracy and low computational load.

A modified signal processing and target fusion detection method based on the dual platform cooperative detection model is proposed in this paper. In this model, a single transmitter and dual receiver radar system is adopted, which can form a single radar and bistatic radar system, respectively. Clutter suppression is achieved by an adaptive moving target indicator (AMTI). By combining the AMTI technology and the traditional radar signal processing technology (i.e., pulse compression and coherent accumulation processing), the SNR is improved, and false targets generated by direct wave are suppressed. The decision matrix is obtained by cell averaging constant false alarm (CA-CFAR) and order statistics constant false alarm (OS-CFAR) processing. Then, the echo signals processed in the two receivers are fused by the AND-like fusion rule and OR-like fusion rule, and the detection probability after fusion detection in different cases is analyzed. Finally, the performance of the proposed method is quantitatively analyzed. Experimental results based on simulated data demonstrate that: (1) The bistatic radar system with a split transceiver has a larger detection distance than the single radar system, but the influence of clutter is greater, (2) the direct wave can be eliminated effectively, and no false target can be formed after suppression, (3) the detection probability of the bistatic radar system with split transceivers is higher than that of the single radar system, and (4) the detection probability of signal fusion detection based on two receivers is higher than that of the bistatic radar system and single radar system.

As one of the emerging imaging sensors, multiple-input and multiple-output synthetic aperture radar (MIMO SAR) could provide more benefits for wide-swath imaging, ground moving target indication (GMTI) and three-dimensional imaging, thus making it a great threat for high value targets. To address this challenge, a Doppler history modulated jamming is proposed in this paper. By imposing an additional Doppler modulated phase on the signal of MIMO SAR which is received and stored in the digital radio frequency memory (DRFM), and then transmitting back to MIMO SAR, this jamming could effectively disturb the imaging of MIMO SAR, form jamming effect of both deception and suppression. Moreover, this jamming could counter GMTI processing of MIMO SAR. Experimental results demonstrate the effectiveness of the proposed algorithm.

Based on the theory of cross-product modulation interference, a new method of generating motion false targets is proposed. The two-dimensional FFT (Fast Fourier Transform) transform is applied to the template image to quickly generate the cross-product modulation signal offline,. Then multiply the motion modulation signal. After the signal multiplication modulation is performed on the intercepted radar signal and then transmitted, a false target can be formed in the SAR-GMTI (Synthetic Aperture Radar-Ground Moving Target Indication) image, and the size and shape of the fake target are flexible and controllable. The paper is organized as follows. Firstly, the basic principle of product modulation interference is introduced. Then the feasibility of SAR-GMTI false target generation method is theoretically analyzed. Finally, the simulation verification is carried out, and the influence of reconnaissance error is studied. The result proves the feasibility and effectiveness of the method.

In a dual-channel circular synthetic aperture radar (CSAR) and ground moving target indication (GMTI) system, the antenna baseline is not parallel with the flight path due to a yaw angle. The angle causes a varying group-phase shift between the dual-channel signals and therefore degrades the correlation between the image pair. Therefore, the group-phase shift needs to be removed before channel equalization. To resolve the problem, the interferometric phase term was deduced and analyzed based on the geometry of a dual-channel CSAR system. Then, the varying phase term with respect to the Doppler frequency and the varying group-phase shift over the range were compensated for in the channel registration. Furthermore, blind channel equalization, including two-dimensional calibration and amplitude equalization, was applied to eliminate the amplitude and residual phase differences between the channels. Finally, the amplitude image obtained using a displaced phase center antenna (DPCA) was multiplied by the phase image obtained with along-track interferometry (ATI) to detect moving targets. The experimental results verified the effectiveness of the method for both uniform and non-uniform clutter suppression.

Ground moving target indicator (GMTI) radar processing attempts to distinguish between radar returns emanating from moving targets and stationary ground clutter. The task is confounded by the relative motion between the radar platform and the scene, as well as by the strength of clutter returns. Techniques such as space-time adaptive processing require an unknown interference covariance describing clutter, jammers, and thermal noise. The covariance is estimated from training data not under test, but, heterogeneous, contaminated, or limited training data degrade the covariance estimate and reduce the detection performance. State-of-the-art techniques for interference covariance estimation reduce the required amount of training data by imposing assumed structure on the covariance matrix. Here, a Bayesian signal model is adopted for jointly estimating targets and clutter in a single cell under test, allowing GMTI processing without training data. The approach incorporates the knowledge of an approximate digital elevation map, platform kinematics (velocity, crab angle, and antenna spacings), and the belief that moving targets are sparse in the scene. Low-complexity computation with the Bayesian model is enabled by recent algorithm developments for fast inference on linear mixing models. Results from the KASSPER I dataset show improved detection performance compared to existing techniques using scores or even hundreds of training bins.

Aiming at battlefield information transparency, situational awareness integration of RF sensor capacity requirements in the future, airborne radar of moving target detection capability for typical foliage penetration scenarios is being widely researching. Through analysis and calculation of penetration loss, clutter strength and space-time processing loss for different bands, the conclusion of the optimal band selection is provided for the same antenna azimuth and wiping angle conditions. Calculation and simulaition results verify the effectiveness of the design method.

When airborne radar is detecting the ground, how to reduce false alarm and improve detection accuracy becomes extremely important. The data analysis shows that no matter what radar signal processing method is used, there is still a lot of residual plots remained. Plot processing is a key step to solve this problem. Due to the strong ground clutter and multiple task types, the new algorithm of plot processing is necessary. Based on the analysis of practical flight data, this paper proposes an adaptive algorithm in the step-variant scanning for GMTI radar, which considers both radar work parameter and the environmental factors. In the end, the simulation proves that the adaptive algorithm can effectively improve target plot precision, reduce false alarm, improve tracking quality and reduce the burden of the data processing system.

In multichannel synthetic aperture radar (SAR) Ground Moving Target Indication (GMTI) systems, Doppler centroid (DC) is an essential parameter for spectral reconstruction and image focusing. However, conventional DC estimator for stationary scene faces many problems in moving target with multichannel SAR, such as low sampling rate and channels selection. To estimate the baseband DC of moving target, a modified CDE method for multichannel SAR GMTI system is proposed in this paper. Simulation results demonstrate the effectiveness of this method.

For Synthetic Aperture Radar (SAR) images, there are moving targets in the ground stationary scene. Since the motion parameters are unknown, the moving target shows azimuthal deviation and defocus in SAR image. Under the condition of the high resolution, the moving target is more likely to have cross-Range Cell Migration (RCM) phenomenon so as to affect the focus and image of moving target. This paper studied multichannel SAR-GMTI technology and proposed a moving target focusing imaging technology based on Clutter Suppression Interferometry (CSI) and Map Drift (MD). This method combines multichannel SAR image information, detects the moving target after using CSI, selects the region that includes moving target based on target defocus range, and then MD algorithm is used to estimate the azimuth frequency rate of the moving target, redesign the azimuth matching filter to image the defocused moving target in the region. The results of simulation data and measured data show that this method can realize the focus imaging of moving target better.

Due to the advantages of large coverage, short revisit time, and long synthetic aperture time, medium-earth-orbit (MEO) synthetic aperture radar (SAR)-ground moving target indication (GMTI) system is an attractive tool for space-to-ground surveillance and reconnaissance. However, the nonlinear motion of MEO SAR and the significant earth rotation dramatically complicate the relative motion between the radar and a ground moving target. Thus, the signal modeling and the design of GMTI methods for MEO SAR are challenging. To provide a basis for addressing this problem, this paper studies the issue of ground moving target range equation modeling for MEO SAR-GMTI systems. In this paper, the range equation of a ground moving target is developed, and the second-order Taylor approximation of the target's range equation is derived. Moreover, numerical simulations are conducted to investigate the accuracy of the derived range equation.

NRIET-developed high-resolution InSAR/GMTI airborne radar system featuring high-resolution SAR imaging, InSAR and GMTI is introduced. The design of radar system specifications is described, and the airborne flight tests are also presented.

This study develops a signal processing chain for a joint communications and multiple-input multiple-output (MIMO) ground moving target indicator (GMTI) radar receiver. Communications signals and radar returns are simultaneously received within the same spectrum. The system must discern the transmitted message while also estimating parameters of a target being observed from the reception. Ground clutter interferes with both functions. By taking advantage of the angle-doppler response characteristic of clutter, this interference can be suppressed. Some communications capacity is sacrificed to permit GMTI radar functionality, which operates as if the communications user was not present.

As an important applications of synthetic aperture radar (SAR), slow moving target detection is causing more concern from people. Commonly, with the increase of computer computational efficiency and utilization of GPU, convolutional neural network has been becoming an efficient approach for target detection and classification. Here we propose a method using Faster R-CNN to detect the slow moving target in SAR images. When using existing datasets to detect moving targets, the detection accuracy is low due to the small defocusing of slow moving targets. So we use the bidirectional imaging mode to create the dataset. By increasing the displacement, it is more conducive to detect slow moving targets. At the same time, neural network provides a feasible way for target detection in this mode. In order to close to the reality echo, we use FEKO to simulate the target echo and use measured ground data to generate the ground echo. Deep learning combined with the forward and backward beams can detect slow moving target more effectively. The simulation results validate the effectiveness of the proposed method.

Ground Moving Target Indication (GMTI) for Near-space Hypersonic vehicle borne Synthetic Aperture Radar (NH-SAR) is an important part of remote sensing applications. However, the ultra-long range and the ultra-high flight speed of NH-SAR causes the lower echo signal-to-noise ratio (SNR) and the expanded clutter spectrum, which reduces the performance of traditional GMTI methods such as Displaced Phase Centre Antennas (DPCA), along track interferometry (ATI) and Space Time Adaptive Processing (STAP). In this paper, a method based on Track Before Detect (TBD) in image domain is proposed to perform GMTI for NH-SAR. This method obtains the multi-frame images of NH-SAR firstly, and tracks the trajectories of the moving targets in the images. The simulation results validate the effectiveness of the proposed method, and show that this method has lower false alarm probabilities under the low-SNR condition.

Space-borne early warning radar has great military and civil significance in ground, air, and space moving target detection in virtue of its wide-area coverage ability, where air moving target indication (AMTI) is an essential task for space-borne early warning radar. As for the AMTI mode, it is inevitably to handle the ground strong clutters due to the large surveillance area, and space-time adaptive processing (STAP) technique can be successfully applied to suppress the troubled clutter effectively. However, the clutter rejection performance of STAP will be restricted by many non-ideal factors, such as range ambiguity, channel number, and yaw angle induced by earth's rotation; thus it is necessary to analyze the influence of these practical non-ideal factors. In this paper, the multichannel signal model of clutter and air moving target in a space-borne radar (SBR) system are deduced. Then, we analysis the adverse influences of these non-ideal factors on STAP in detail. Finally, some simulation processing results are provided to validate the STAP performance with the consideration of these engineer factors, which can provide some useful guides of SBR system design with AMTI mode.

The article is devoted to the analysis of adaptive devices of moving target indication which are intended for clutter protection. For adaptive systems of interperiod processing the theoretical principles of construction based on adaptive whitening filters are shown. A semi-natural experiment was carried out, which allowed comparing the effectiveness of target detection in the same conditions with the use of non-adaptive and adaptive types of such devices. On the basis of theoretical and experimental data, conclusions have been drawn about the effectiveness of using adaptive systems of moving target indication

At present, space-borne phased-array synthetic aperture radar (SAR) are widely used for remote sensing of the Earth. In such systems, the tasks of detecting and selecting moving targets are solved. The paper describes the method of computer simulation of the statistical characteristics of the moving target indication (MTI) system of space-based SAR with displaced phase center arrays. Graphic characteristics of the standard deviation of the estimated radial velocity of moving target for different values of the signal-to-noise ratio at the MTI system input are obtained. These characteristics allow you to estimate the potential possibility of the MTI system.

For ground moving target indication (GMTI) in heterogeneous terrains, most detectors could not effectively solve the problem of a high probability of false alarms (PFA) due to the presence of isolated interference with large radar cross section (RCS). To address this issue, we construct a new criterion called as energy loss, which is the energy difference between input and output in the adaptive processing, and develop an enhanced approach based on energy loss for multichannel synthetic aperture radar (SAR)-GMTI systems in heterogeneous environment. In this method, the magnitude-based detection after clutter suppression is first applied to detect potential targets with a relatively low threshold. Then, a complementary detection based on energy loss test is performed to reduce false alarms. To compute the detection thresholds, the statistics of the energy loss test and the overall PFA of the detection approach are analyzed theoretically. Finally, the experimental results on simulations and real data, collected in China's urban area, demonstrate the superiority of the proposed approach compared with state-of-art methods.

Detecting moving targets in synthetic aperture radar (SAR) imagery has recently gained a lot of interest as a way to augment optical moving target detection and classification in adverse (e.g., cloudy) weather conditions. In this paper, we primarily focus on the problem of detecting and imaging moving targets in single-channel (or summed multichannel) SAR data. Single-channel-based methods provide the ability to do detection well below the normal minimum detectable velocity (MDV) of multichannel-based GMTI. This can be particularly important for small radar antennas, which tend to have high conventional GMTI MDV. We also show results for multiple channel geolocation after single-channel detection and imaging. The algorithms consist of the following steps. We first suppress the stationary scene by comparing noncoherent time-subimages. We then detect the movers by applying a set of possible motion corrections to the image and use a novel matched filter to detect the movers in this space. We can then image the moving targets using standard SAR focusing techniques and geolocate the movers using multichannel (if available) along-track interferometry. We demonstrate and evaluate our algorithms using data collected from the Lincoln Multimission ISR Testbed airborne radar system.

In this paper, we describe three digital moving target indication (MTI) and moving target segmentation techniques (based on target speed) and apply them to short-range frequency-modulated continuous wave (FMCW) radar data. The described approaches are applicable to many short-range radar sensors. In particular, we focus on FMCW radar, which are ubiquitous in numerous applications, including gesture recognition radar, automotive radar, and imaging radar. The three digital MTI filtering methods explored are background subtraction, finite impulse response (FIR) filtering, and infinite impulse response (IIR) filtering. Each of the methods is implemented in the time domain for simpler logic implementation. We apply the MTI methods on data sets gathered using a C-band FMCW radar in both a short-range, direct line-of-sight scenario and a complex cluttered through wall radar scenario. Based on the analyses, it is shown that each of the MTI techniques are extremely effective when deployed in the right scenario. Background subtraction is found to be well suited for slow-moving targets. FIR and IIR filtering techniques provide the simplest, one-step processes for moving target segmentation.

It is shown that the detection performance can be significantly improved using the recent technology of multiple-input multiple-output (MIMO) radar systems. This is a result of the spatial diversity in such systems due to the viewing of the target from different angles. On the other hand, the moving target indication (MTI) processing has long been known and applied in the traditional pulse radars to detect weak moving targets in the presence of strong clutter signals. The authors propose a procedure based on the compressive sensing idea, in order to apply the MTI processing in a MIMO radar with widely separated antennas. Although a clutter is included in the signal model and a different radar cross-section value for each transmitter-receiver pair is considered which makes the problem more complex, the complexity dimension is preserved as low as possible by converting the block sparse problem into a regular sparse problem.

Multiple-input multiple-output synthetic aperture radar (MIMO SAR) system has drawn considerable attention because of its extra degrees of freedom for high resolution and wide swath compared with the traditional multichannel SAR system. But how to extract the matched signal without the unmatched interferences is the foremost task for MIMO SAR system. In this paper, by using the orthogonal frequency division multiplexing chirp signals as the transmitted signals, it is demonstrated that the robust principal component analysis (RPCA) method can be successfully employed for ground moving target indication (GMTI) with no need for separating the matched signal and unmatched interferences. It is because the unmatched interference is proven to have low-rank property and noise-level magnitude, which can be separated apart from the matched signal with the RPCA method. However, the traditional RPCA methods may be restricted by the high computational burden due to the complex decompositions and multiple iterations. Hence, a fast interferometry RPCA method is proposed specially for GMTI mode, which takes full advantage of the characteristics of along-track interferometry SAR system. It can improve the probability of detection under low signal-to-clutter-and-noise ratio. Additionally, it will dramatically shorten the computational time. Furthermore, the proposed method can also estimate the radial velocities of the moving targets simultaneously. The results by applying the proposed method into a set of real SAR data are consistent with the analysis presented in this paper.

The azimuth multichannel synthetic aperture radar (SAR) system is used in ground moving target indication (GMTI). But for Ka-band SAR, the conflicts between high gain and wide swath coverage are very strict. The digital beamforming (DBF) scan-on-receive (SCORE) algorithm can solve this problem very well. This letter introduces a multichannel SAR system with three receiving antennas in the azimuth direction. For each azimuth antenna, eight subapertures are arranged in the elevation direction in order to obtain higher gain and a lower data rate through the DBF-SCORE algorithm. Airborne flight experiments with this system are accomplished successfully and quantities of experimental data are acquired. In this letter, we first derive the signal forms and weighting coefficients in the DBF-SCORE procedures. Then, different GMTI methods including along-track interferometry and displaced phase center antenna are introduced for azimuth multichannel SAR–GMTI based on the DBF-SCORE technology. Finally, airborne raw data with cooperating moving targets are processed successfully, and the estimation errors of the radial velocities meet the expected accuracy requirements.

An anti-deception jamming technique is proposed for moving target indication in a pulse-Doppler (PD) radar. The deceive targets are produced by digital radio frequency memory, which tries to pull off the range and velocity gates of real targets. Similar to orthogonal frequency division multiplexing, we use different sets of orthogonal sub-carriers in consecutive coherent pulse intervals (CPIs). By changing sub-carriers in different CPIs, we show that the deceive targets appear as interference in receiving signals. The generalized likelihood ratio test is used for detection and discrimination of real targets. The performance of the proposed method is achieved analytically and by simulations. Furthermore, we implement a hardware block using a TMS6416-DSK DSP for a PD radar prototype exploiting the proposed algorithm to deception discrimination. The presented results demonstrate the good accordance with theoretical predictions.

This paper develops a framework based on enhanced shadow-aided decision for multichannel synthetic aperture radar-based ground moving target indication system according to the relationships between the moving target and its shadow information in position, dimensions, and intensity. As a sort of feature information available, the moving target shadow may improve the ground target detection performance. A critical precondition for shadow utilization is to obtain the good detection performance for the moving target shadow. However, shadow detection performance will deteriorate inevitably as a result of target motion that blurs its shadow. To address this issue, a knowledge-aided shadow detection algorithm with adaptive thresholds is proposed to improve the shadow detection performance in the developed framework. Furthermore, the theoretical performance analysis is performed, which indicates that the proposed knowledge-aided shadow detection algorithm has a better performance than that of the conventional shadow detection algorithm with a fixed threshold. Finally, numerical simulation experiments are presented to demonstrate that the developed framework can obtain good results for extended ground moving target detection.

Ground moving target indication (GMTI) is one of the important applications of synthetic aperture radar (SAR). This paper introduces a GMTI method for local detection of the ground moving targets in SAR image based on normalized relative speed (NRS) hypotheses. The input of the GMTI method is a complex SAR image where areas of interest for GMTI are locally selected. The output of the method includes the detected targets, the NRSs with respect to the SAR platform, the locations where the detected targets are focused, and the SAR images of the detected targets. The mathematical background of the GMTI method is presented in detail. The method is validated with the data delivered by the Coherent All-Radio Band Sensor, an airborne ultrawideband-ultrawidebeam low-frequency SAR system. The shortcomings of the introduced method are investigated and followed with the solutions.

Synthetic aperture radar (SAR) ground moving target indication (GMTI) has attracted a lot of interest from researchers for its ability of simultaneously obtaining high-quality images of stationary scenes and detection of moving targets. In recent years, the research on moving target tracking besides detection by using SAR-GMTI has also raised interest. Compared with standard SAR, the long observation time of circular SAR (CSAR) makes it possible for moving target trajectory reconstruction. By using a prior knowledge of the road information, an effective method for moving target trajectory reconstruction in single-channel CSAR is proposed in this paper. First, the radar echo is segmented according to subapertures, and the Doppler filtering is performed on each subaperture echo for clutter suppression. Second, the range walk induced by target motion is compensated by the keystone transform, and trajectories in range–Doppler domain are obtained. Last, the moving target trajectory in ground coordinate is reconstructed by using the dynamic programming algorithm with road information restrain. Experimental SAR data processing results show that the method is effective for the moving target trajectory reconstruction.

Many jamming methods have been proposed against three-channel synthetic aperture radar (SAR) ground moving target indication based on the stationary jammer. To generate a verisimilar moving target based on a moving jammer, the scattered wave deception jamming method is proposed against displaced phase center antenna (DPCA) process. The jammer is set at an unmanned aerial vehicle and moves with the protected moving targets. By comparing the slant history range of the echo with that of the jamming signal, the position of the jammer beam footprint and the velocity of the moving jammer are calculated based on the analysis of the range, azimuth, Doppler rate mismatch, and the altitude distortion after DPCA processing. The intercepted SAR signal is retransmitted to the calculated area covered by the jamming beam footprint based on the specific velocity of the jammer. Thus, after DPCA processing, the jamming result is similar to the real moving target. This method reduces the algorithm complexity and avoids the signal jamming modulation compared to traditional methods. The effectiveness and correctness of the algorithm are verified by simulations.

While there are recent researches on hypersonic vehicle-borne multichannel synthetic aperture radar in ground moving target indication (HSV-MC-SAR/GMTI), this article, which specifically explores a robust GMTI scheme for the highly squinted HSV-MC-SAR in dive mode, is novel. First, an improved equivalent range model (IERM) for stationary targets and GMTs is explored, which enjoys a concise expression and therefore offers the potential to simplify the GMTI process. Then, based on the proposed model, a robust GMTI scheme is derived in detail, paying particular attention to Doppler ambiguity arising from the high-speed and high-resolution wide-swath. Furthermore, it retrieves the accurate two-dimensional speeds of GMTs and realizes the satisfactory performance of clutter rejection and GMT imaging, generating the matched beamforming and enhancing the GMT energy. Finally, it applies the inverse projection to revise the geometry shift induced by the vertical speed. Simulation examples are used to verify the proposed GMTI scheme.

This paper investigates a novel ground moving target indication (GMTI) scheme for a hypersonic vehicle-borne multichannel synthetic aperture radar (MC-SAR) system with Doppler ambiguity. First, after the range compression and azimuth chirp Fourier transform (CFT), by applying the eigenspace-based adaptive sum and difference beams (EASDB) on the coarse-focused images, the high-precision cross-track velocity (CTV) can be retrieved. Then, utilizing the high-precision CTV to construct an accurate moving target steering vector to extract the moving target energy. With the proposed CFT-two-step method, we have avoided cumbersome CTV search, and simplified the process of range walk correction, resulting in lower computational complexity. Compared to the CFT-center and CFT-two-step methods, the proposed scheme obtains the accurate two-dimension motion parameters of a moving target, and has better performance and robustness in the detection, focusing, and location, preserving the moving target envelope and achieving higher signal-to-clutter-and-noise ratio (SCNR). Finally, using the processing results of simulation and real measured MC-SAR data, we verify the effectiveness and feasibility of our proposed scheme.

Radar tracking of aircraft targets at low elevation angles can be complicated by clutter from wind turbines, which we define to be clutter. In this paper, we study detection in a staring pulse-Doppler radar. By exploiting the second-order correlation structure of this wind-turbine clutter we derive a target detector that uses a sequence of adaptive coherence scores. The detector uses a multipulse coherence statistic consisting of an incoherent geometric average of coherently computed adaptive coherence scores. The detector compares favorably to a multipulse coherence detector that uses no modeling or estimation of the clutter.

Multiple-input multiple-output (MIMO) radar with multiple transmitters and multiple receivers can achieve a larger virtual antenna array and more system degrees of freedom; thus applying it to ground moving target indication (GMTI) radar can improve the performance of GMTI. Doppler division multiple access (DDMA) waveforms are approximately orthogonal providing good minimum detectable velocity (MDV) performance. However, in such DDMA systems, a sufficient pulse repetition frequency (PRF) design freedom is required. Furthermore, these waveforms suffer from blind velocities which are serious problems, especially in radar systems with high carrier frequency or low PRF. This paper analyses the blind velocities problem and show that blind velocities are relative to variation of the PRF and/or the carrier frequency. Variable PRF techniques are widely used in conventional GMTI radar including multiple PRFs and variable pulse repetition intervals (PRI). Combined with the characteristics of the DDMA MIMO GMTI radar, this paper proposed two methods to mitigate blind velocities: “multi-PRF DDMA” which employs multiple PRFs over successive coherent processing intervals, and “PRI-dithered DDMA” which employs nonuniform sampling by dithered PRI in slow time. Simulation results demonstrate that both the methods are effective ways to mitigate blind velocities in DDMA MIMO GMTI radar systems.

This paper considers target detection via dynamic-programming based track-before-detect (DP-TBD) for radar systems. The clutter is modeled usingenlr G0 distribution, which is usually used to model clutter received from high-resolution radars and radars working at small grazing angles. Two target models, namely, Swerling 0 and 1 models, are considered to capture the radar cross section changes over time. DP-TBD techniques that integrate amplitude suffer from significant performance loss in this case due to the high likelihood of target-like outliers. In this paper, the log-likelihood ratio (LLR) is used in the integration process of DP-TBD, taking the place of amplitude, to enhance radar detection performance. The expressions for the LLR for the above target models are derived first. However, neither of them has a closed-form solution. In order to reduce the complexity of evaluating the LLR, efficient but accurate approximation methods are proposed. Then the approximated LLR is used in the integration process of DP-TBD. Simulations are used to examine the efficiency of the approximation methods as well as the performances of different DP-TBD strategies.

This study proposes a clutter suppression approach and the corresponding ground moving target imaging algorithm for hypersonic vehicle (HSV) borne synthetic aperture radar (SAR) system with multiple-input-multiple-output (MIMO) antenna. HSV-borne radar platforms fly with a high speed, which can lead to severe Doppler ambiguity, and the radar system usually cannot provide enough channel freedom degree for clutter suppression. In this study, an SAR ground moving target indication (GMTI) approach with MIMO antenna is presented for HSV-borne radar. Compared with the traditional multichannel SAR GMTI methods, the proposed approach can provide more space freedom degree and obtain a wider imaging swath without decreasing pulse repetition frequency. Besides, the improved deramp space-time adaptive processing method decreases the ambiguity times of the ground clutter and focuses the moving target. The simulation results validate the effectiveness of the proposed method.

This paper studies the range equation modeling of a ground moving target for multichannel medium-Earth-orbit (MEO) synthetic aperture radar (SAR) ground moving target indication (GMTI), an issue which is challenging to tackle due to the non-linear motion of the radar platform and the Earth rotation. In the paper, the coordinates of the multichannel MEO SAR and the target, as well as the target’s range equation with respect to each channel, are developed. Moreover, an expression of concise form is derived for the target’s quadratic-approximated range equation, which will benefit the design of GMTI methods. Furthermore, theoretical analyses are conducted to reveal the dependency between the accuracy of the quadratic-approximated range equation and the parameters of the radar and the target. Numerical simulations are carried out to investigate the influence of the quadratic approximation of the range equation on the GMTI performance and to figure out the quadratic-approximated range equation’s scope of application.

For ground moving target indication (GMTI) sensor tracking, the existence of the Doppler blind zone (DBZ) seriously deteriorates tracking performance. In order to minimize the adverse effects of the DBZ factor, this paper puts forward the idea of using sensor fusion technique to suppress the DBZ masking problem. First, we derive the probability hypothesis density (PHD) fusion under the generalized covariance intersection (GCI) framework and its Gaussian mixture (GM) implementation for fusing local PHDs from the local trackers. However, we find that there is the problem of cardinality underestimation (CUE) in the original PHD fusion, which is exacerbated when targets are masked by the DBZ. After analyzing this problem in detail, we propose an improved PHD fusion algorithm through operations such as scale coefficient correction, GM component partition, and fused label correction. Finally, the feasibility and effectiveness of the proposed fusion are verified through numerical examples, and it is proved that it alleviates the CUE problem and is significantly better than local trackers.

Phase noise refers to the instability of an oscillator, which is the cause of instantaneous phase and frequency deviations in the carrier wave. This unavoidable instability adversely affects the performance of range–velocity radar systems, including synthetic aperture radars (SARs) and ground-moving target indicator (GMTI) radars. Phase noise effects should be considered in high-resolution radar designs, operating in millimeter wavelengths and terahertz frequencies, due to their role in radar capability during the reliable identification of target location and velocity. In general, phase noise is a random process consisting of nonstationary terms. It has been shown that in order to optimize the coherent detection of stealthy, fast-moving targets with a low radar cross-section (RCS), it is required to evaluate the integration gain and to determine the incoherent noise effects for resolving target location and velocity. Here, we present an analytical expression for the coherent integration loss when a nonstationary phase noise is considered. A Wigner distribution was employed to derive the time–frequency expression for the coherent loss when nonstationary conditions were considered. Up to now, no analytical expressions have been developed for coherent integration loss when dealing with real nonstationary phase noise mathematical models. The proposed expression will help radar systems estimate the nonstationary integration loss and adjust the decision threshold value in order to maximize the probability of detection. The effect of nonstationary phase noise is demonstrated for studying coherent integration loss of high-resolution radar operating in the W-band. The investigation indicates that major degradation in the time-frequency coherent integration due to short-term, nonstationary phase noise instabilities arises for targets moving at low velocities and increases with range. Opposed to the conventional model, which assumes stationarity, a significant difference of up to 25 dB is revealed in the integration loss for radars operating in the millimeter wave regime. Moreover, for supersonic moving targets, the loss peaks at intermediate distances and then reduces as the target moves away.