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To achieve verisimilar target deceptive jamming effect, the jamming signals from different targets in different kinds of situation must be acquired. However, it is difficult to be implemented by the methods using deception-template model. In this letter, a novel target deception jamming method against spaceborne synthetic aperture radar based on electromagnetic (EM) simulation is presented. To improve the computational efficiency, an equivalent bistatic scattered fields are used to simulate the scattering characteristics of false target. The proposed method, which consists of the computer-aided-design model, the deceptive jamming model and the involved EM scattered fields, improves the performance of deceptive target in achieving the jamming results. The simulation results demonstrate the validity of the proposed method.

Compared with ground radars, space-borne bistatic radar shows great advantages in higher signal-to-noise ratio (SNR) and robuster security. Firstly, this study establishes space-borne geosynchronous satellite-low orbiting satellite (GEO-LEO) space–time two-dimensional model considering the influence of the rotation of the earth together with the curvature of the earth surface. Then the Doppler trajectory distance dependence of the clutter angle is analysed. Finally, the characteristics of the space-borne GEO-LEO model are proved to be beneficial to clutter suppression and ground-moving targets indication. Simulation results show that the space-borne GEO-LEO model has good performance.

With the development of synthetic aperture radar (SAR) technologies in recent years, the huge amount of remote sensing data bring challenges for high-speed transmission and real-time processing. The general platform with GPU, CPU or digital signal processor (DSP) cannot meet the requirement for short delay and low power. Therefore, a field-programmable gate array-digital signal processor (FPGA-DSP) SAR imaging accelerate platform has become a solution for processing performance with a lower latency and power. In this study, an effective mapping strategy is adopted to the FPGA-DSP hybrid heterogeneous architecture to accelerate the processing performance according to the analysis of Chirp Scaling SAR imaging algorithms. As a proof of concept, a FPGA-DSP hybrid heterogeneous accelerating platform is designed and realised. The platform requires 12 s to focus a stripmap SAR raw data with a granularity of 16,384 × 16,384.

Sliding spotlight synthetic aperture radar (SAR) is a hot imaging mode in space-borne SAR. It can acquire high-resolution and large azimuth scene size simultaneously. The main challenges for sliding spotlight SAR processing in real time are the huge volume of raw data and complex imaging algorithm. The rapid development of the graphics processing units (GPUs) provides a new computing platform for high-performance SAR processing. This work presents a parallel processing of sliding spotlight SAR imaging algorithm on GPU via compute unified device architecture and tests the speedup of each module of the algorithm on the K20c GPU platform from the aspect of a small granularity and a large granularity of point target images. Compared with traditional CPU-based SAR imaging technology, the proposed GPU-based sliding spotlight SAR imaging obtains a speedup of 186.80 when processing data with a granularity of 16,384 × 8192 and gets a speedup of 49.72 when processing data with a granularity of 65,536 × 32,768, thereby greatly improving the real-time imaging processing.

The estimation of target moving trajectory by the multiple receivers based on global positioning system (GPS) forward scattering radar has been first presented in the study, which cannot be obtained by the traditional method. A new estimation approach has been considered using the following information. First, the starting and ending time at which the target pass through the baseline of GPS transmitter–receiver can be obtained. Second, the azimuth and elevation angles of GPS satellites are extracted in combination with the satellite sky map at the recording time. On the basis, the target moving trajectory can be obtained by the established model. In order to validate its feasibility, the experiment has been completed in the open area of Beihang University, which regards the human as the target. Four GPS receivers have been employed to record the data. The experimental results show that the estimation of target trajectory is consistent with the real situation, which proves the practical applicability of the proposed technique.

This study proposes a sparse linear array synthetic aperture radar (LASAR) on a spaceborne dual platform. The transmitting elements are placed at the LASAR tips that form a satellite's dual platform, and the receiving elements are placed on the large deformation composite pine which is between the satellite's dual platform. Based on the principle of phase centre of approximation and multiple input multiple output, LASAR with the sparse array could obtain a high-resolution imaging in the cross-along direction, which is crucial to a three-dimensional SAR system. Furthermore, the LASAR system has different modes, such as interferometry and ground moving target indication.

Spaceborne synthetic aperture radar (SAR) systems operating at low frequency, such as L- and P-bands, are significantly influenced by ionospheric effects. One of the remarkable effects is Faraday rotation (FR), which is known as a serious error source for the polarimetric SAR (PolSAR) application. The FR effect mainly results from the background ionosphere so that the FR angles (FRAs) within a SAR image tend to take on a potential spatial-variable distribution. The typical estimator is used to accurately estimate FRA from the PolSAR data. Moreover, a step-to-step procedure is proposed to derive FRA map. On the basis of the real data processing, the experimental results validate the effectiveness of the FRA map, which indicates the immense capability of the PolSAR data to retrieve a spatial distribution of the FRA.

The classification and detection of maritime targets are widely used in shipping navigation and military fields. With the development of spaceborne synthetic aperture radar (SAR) technology, more and more very high-resolution SAR images can be acquired for maritime targets recognition. However, due to the different imaging mechanisms between SAR images and optical images, it is difficult and laborious to interpret SAR images manually. This study uses a modified Alexnet structure to realise maritime targets classification on the Gaofen-3 spaceborne SAR images. The maritime targets dataset (MTD), including boats, cargo ships, container ships, windmills, oil tankers, and iron towers, is conducted. Moreover, the proposed convolution neural networks (CNNs) structure is trained and tested on the MTD. Experimental results show that the model can get an accuracy of 92.10% in classifying the six kinds of targets, and the performance is superior compared with other CNNs and traditional supportive vector machine algorithms.

This article addresses a high-resolution wide swath (HRWS) Terrain Observation by Progressive Scans (TOPSAR) mode which integrates the azimuth multichannel HRWS imaging technique and TOPSAR technique. More equivalent phase centres are obtained through the azimuth single-input and multiple-output technique, which would provide more azimuth samples. Hence, a more reliable and accurate imaging results of the large width terrain profile would be obtained. The performance of this HRWS TOPSAR mode is evaluated theoretically. A new processing method for this mode is provided and the results of simulation data processing validate the analysed results and the new method.

Geosynchronous synthetic aperture radar (GEO SAR) has the characteristics of wide coverage and short revisit time, which makes GEO SAR moving target indication more valuable than other platforms. This article analyses the influence of moving target on ‘Stop-and-Go’ error in GEO SAR, and then the accurate slant range model of moving target is constructed. The signal-to-noise ratio of the raw data echoes for moving ship target is very low because of the high satellite orbit altitude, so it cannot be detected by constant false alarm detection. Based on the accurate slant range model of moving target in GEO SAR, three kinds of integration methods are reconstructed, including moving target detection, Radon transform and generalised Radon Fourier transform (GRFT). The performance of these methods is compared through numerical simulation. GRFT can provide the best detection performance in a reasonable integration time.

The rapid development of remote-sensing data acquisition technology means that the resolution of remote-sensing image has been continuously improved, resulting in the large scale of remote-sensing image data and the increase of redundant information, which restricts the image processing and analysis. However, super-pixel segmentation method mainly aimed at the general image segmentation algorithm, rarely for remote-sensing image. Therefore, here, the polarisation decomposition of full-polarised remote-sensing images is used to synthesise pseudo-colour images. Then, based on the region, the image segmentation algorithm based on the colour feature of SLIC super-pixel segmentation algorithm is used to make it have important application value in remote-sensing image target extraction. Here, the image of Danjiangkou reservoir obtained by high-resolution space-borne SAR is selected as the research object. Finally, the polarisation decomposition and segmentation of full-polarised remote-sensing images are realised, and the advantages of SLIC super-pixel algorithm are proved.

Compared with the repeat-pass interferometry synthetic aperture radar (InSAR) system, the single-pass InSAR system, such as TanDEM-X and TanDEM-L, has better performance and less decorrelation. However, InSAR measurements can be seriously influenced by the background ionosphere, especially for InSAR system operating at lower frequencies, such as L-band and P-band. Low-frequency signals propagating in the ionosphere suffer serious group delay, dispersion, scintillation and Faraday rotation, which further induce the image shift and decorrelation of SAR interferometry pairs. Since the ionosphere shows significant space-varying and time-varying features, the conventional ionosphere spatial invariant model is invalid for space-borne single-pass InSAR system. It is supposed that the time variance of ionosphere in short integration time can be neglected for low-earth orbit InSAR system. The effect of the spatial variant ionosphere on single-pass InSAR measurement is analysed and a correction method for InSAR products based on the prior knowledge is presented in this paper. Simulations are performed by using total electron content data obtained from the international reference ionosphere model, and the results indicate the significant error induced by spatial variant ionosphere.

Moving ships imaging is an important issue in marine remote-sensing by spaceborne synthetic aperture radar (SAR). As the moving ships defocus generally in high-resolution spaceborne SAR images, the refocusing step is demanded for the following processing in classification and identification. A new refocusing method based on Doppler parameters search is proposed to enhance the performance of ship images. This method is applied directly on the single-look complex image data. Furthermore, the space-variant characteristic of Doppler parameters is taken into account within this method. Finally, the GF-3 satellite SAR data refocusing results of moving ships verify the effectiveness of the proposed method.

Due to the curve of the LEO synthetic aperture radar (SAR) orbit and the rotation of the earth, the high resolution imaging for LEO SAR is always facing the problem of obtaining accurate range history. Meanwhile, with the increase of squint angle, it will take longer azimuth time to meet the same high resolution. In this paper, an improved hyperbolic range equation (IHRE) is presented to model the accurate range history for high squint LEO SAR. First, the state vectors of satellite are used to estimate the Doppler parameters. Then, the improved hyperbolic range equation is recovered based on the estimation of the Doppler parameters. Compared with other existing methods, the superiority of IHRE is more precise in the condition of high squint LEO SAR which can provide sufficient azimuth time for high resolution imaging. The simulation and analysis validate the precision of the proposed range history model.

Synthetic aperture radar (SAR) has a good ability to detect the microwave scattering characteristics of the target and has a good capability of slant range Doppler positioning. Using multi-view SAR images in combination with image matching and positioning equations, the 3D position of the target can be obtained. In the past, multi-view 3D reconstruction mainly used side-looking images with parallel trajectories but different incident angles. That method is not universal for different configurations and lacks analysis of the relationship between solution and parameter error. This study aims at the problem of multi-view SAR 3D reconstruction. The authors establish general 3D reconstruction equations that can be used for non-parallel track and non-side-looking and the solution method is deduced. Based on this, an analysis method of error sensitivity is proposed and the dependence relationship between the reconstruction error and configuration, velocity, position, and slant range is analysed. The correctness of this method is verified by simulation experiments, which provides guidance for selection of configuration and sensor accuracy when applying 3D reconstruction.

Ionospheric disturbance is one of the most serious factors that limit the accuracy of deformation measurement of interferometric synthetic aperture radar (InSAR) especially for spaceborne SAR systems in low frequency such as L-band. Especially in imaging modes with a large coverage, ScanSAR mode for example, ionospheric disturbance phase screen almost submerges other useful geographical information. In this study, two ALOS-2 (L-band) full-aperture ScanSAR images (October 2015 and October 2016) are used to study ground deformation in Beijing from 2015 to 2016. The split range-spectrum technique is adopted to extract ionospheric distortion. The authors splice the differential interferograms of adjacent subswaths by resampling them to perform the overall ionospheric extraction. Also non-local filtering is used to improve the coherence of interferograms. Spatial deformation distribution that was obtained by differential interferometric synthetic aperture radar (D-InSAR) technique using the two ALOS-2 ScanSAR images is highly consistent with the result obtained by persistent scatterer interferometric synthetic aperture radar (PS-InSAR) technique using Sentinel Tops mode images (October 2015–February 2017). The comparison results show the effectiveness of the ionospheric distortion extraction method used in this study. Moreover, the spatial distribution is also highly consistent with the results before 2014, which means that the deformation trend in Beijing continues.

In the detection of SAR image of sea targets, the simple statistical distribution models such as Gaussian distribution, normal distribution, Weibull distribution etc. are obviously not suitable for the fitting of the background clutter of missile-borne SAR images. The target of the sea surface in SAR image usually has a heavy tail caused by the sea spike, while the KK distribution can better fit it. A two-stage CFAR detector with KK distribution is designed. The results show that KK distribution can fit the data well and the two-stage CFAR detector based on the KK distribution has good performances.

Spaceborne bistatic multichannel synthetic aperture radar (MC-SAR) system employed inclined geosynchronous Earth orbit (GEO) transmitter and low-Earth-orbit (LEO) receiver can provide fine spatial resolution and a vast area of surveillance, which presents great potentials for future Earth observation. Nevertheless, owing to special geometry and big differences of orbital characteristics, the conventional effective phase centre (EPC) operation for unambiguous SAR signal reconstruction cannot be directly used. To address the issue, starting from geometry model of GEO-LEO bistatic MC-SAR, the new effective positions of the receiving channels are obtained. Then, the time-variant characteristics of residual phase error after the presented EPC processing is analysed. Finally, the method of reconstructing unambiguous SAR signal is presented. Simulation results show the validity of the proposed method, which can efficiently reconstruct the unambiguous signal for GEO-LEO bistatic SAR.

Owing to the spatial separation of transmitter and receiver, bistatic SAR is able to image the area in front of the moving direction of transmitter or receiver, but the geometry model is more complex than that of monostatic SAR, which brings great difficulties to system design and imaging process. Besides, the special geometry configuration of geostationary spaceborne-airborne bistatic forward-looking SAR results in non-orthogonal and non-uniform ground resolution, which is not considered in the traditional range and azimuth resolution. To solve this problem, the resolution ellipse based on the generalised ambiguity function (GAF) is used to maintain the best and worst ground resolution in the resolution cell. The receiver's flight direction is designed to obtain the optimal uniform ground resolution distribution, which has great value for system design and the receiver's path planning. Finally, the accuracy of the resolution ellipse and correctness of the deduced formulas are verified by simulation.

Geosynchronous earth orbit synthetic aperture radar (GEO SAR) has the advantages of short revisit period and wide observation range. However, compared with low earth orbit SAR (LEO SAR), GEO SAR has the distinct characteristics of long synthetic aperture time, large amount of data, curvilinear motion trajectory, slow satellite speed, and long signal return delay etc. Hence, in this paper, a generalisation design technique of real-time quick look imaging systems for both GEO SAR and LEO SAR is first proposed. Then, we present the corresponding system structure and its components. Finally, based on back projection algorithm (BPA), the validity of this quick look imaging system is verified by the simulation.

Tiangong-2 interferometric imaging radar altimeter (InIRA), the first space-borne radar altimeter in the world, applying a new mechanism of interferometry with short baseline and small incident angle, can achieve wide swath and high accuracy sea surface height measuring. Comparing to traditional altimeter, InIRA can obtain SAR image of observation area, which means InIRA needs higher AD sampling rate. Due to the limitation of satellite on-board storage and downlink speed, in order to extend the working time of InIRA, data compression algorithm for InIRA must be studied. Block adaptive quantisation (BAQ) is an efficient and widely adopted approach for space-borne SAR raw data compression. Based on the characters of InIRA echo waveform, this study discusses compressing InIRA raw data by changing quantisation bits and size of blocks of BAQ algorithm to achieve higher compression ratio and less sea surface height error.

YaoGan 13 (YG-13) represents the most advanced Chinese synthetic aperture radar satellite currently in use. This paper reports on experiments conducted to assess the slant-range accuracy of YG-13. Error sources in the YG-13 ranging system, such as atmospheric path delay and the internal electronic delay of the instrument were analysed. A real-time atmospheric delay correction model was established to consider both tropospheric and ionospheric delays. Six corner reflectors (CRs) were set up to ensure the accuracy of validation methods. Results showed that pixel location accuracies of up to 0.427 m standard deviation could be achieved. Furthermore, adjustment of the CRs can cause a marginal loss of ranging precision. After eliminating this error, the ranging accuracy was improved to 0.162 m. For YG-13, a single frequency GPS receiver is used and the orbital accuracy is the biggest factor restricting its slant-range accuracy. Results show that the YG-13 slant-range can achieve decimetre-level accuracy. YG-13 provides convenience in terms of access to control points and target locations that does not depend on ground equipment.

Compared with the conventional single-channel sampling or azimuth multichannel sampling of SAR system, the multiple-input multiple-output (MIMO) sampling has the potential to realise the high-resolution wide swath (HRWS) imaging and the ground moving target indication (GMTI) simultaneously. As a key parameter in the design of SAR system, the pulse repetition frequency (PRF) has important impacts on the performances of HRWS and GMTI. From this perspective, the impacts of PRF design on GMTI performance of MIMO-SAR for hypersonic platform with curved trajectory have been analysed here. Specifically, the steering vectors of the ambiguous clutter and moving target are derived first under the curved trajectory model. Furthermore, according to MIMO-SAR system parameters, the optimum PRF design is simulated from the aspects of the blind velocity, the spatial ambiguity, and the detection probability. Finally, the real clutter data are further used to verify the effectiveness of PRF design on GMTI performance optimisation.