In airborne terahertz synthetic aperture radar (THz-SAR), the phase error caused by high-frequency vibration of the platform can result in not only defocusing, but also the emergence of unwanted ghost targets. To tackle this problem, we propose a vibration estimation and compensation method for the dual-channel THz-SAR based on along-track interferometry (ATI). Compared with the state-of-art single-channel-based compensation methods, the proposed method is advantageous in that it can stay effective without isolated dominant scatter points in the scene. This letter first analyzes the relationship between the along-track interferometric phase of the stationary targets’ echo and the instantaneous radial velocity of the platform’s high-frequency vibration. Then, by using the interferometric phase, the phase error caused by vibration is estimated and compensated. Simulation results show that the proposed method can effectively compensate the phase error caused by multicomponents high-frequency vibration without using the information of dominant scatter points.

The wavelength of synthetic aperture lidar (SAL) is very short; vibration of millimeter magnitude will significantly change the phase of echo signal and lead to the defocus of imaging in azimuth direction, so vibration estimation is a key step of SAL imaging. The existing Space Correlation Algorithm (SCA) used to estimate vibration of SAL is only suitable for the condition of narrow azimuth beam and high signal-noise ratio (SNR). Based on division of inner view field by two detectors along track, a new data obtaining model of SAL is established in this paper. Furthermore, a new vibration estimation method is proposed. Simulations validate that the vibration of SAL can be accurately estimated in the condition of wide azimuth beam and low SNR with the proposed method, meanwhile, good imaging result is obtained.

This paper utilizes Modified Uniformly Redundant Arrays (MURA) code as the criterion to realize sparse sampling in aperture plane, for the purpose of reducing bearing data storage. A geometry of microwave three-dimensional (3D) imaging is modeled, and the combination of ωK algorithm and Median Filter (MF) is adopted to achieve 3D image in the condition of sparse sampling. In addition, the imaging reconstruction based on Compressed Sensing (CS) and spatial sparsity is evaluated to make comparision. Numerical simulation and error analysis demonstrate the validity of proposed 3D imaging methods.

In this letter, we combine the airborne cross-track array synthetic aperture radar (SAR) technique and the sparse flight sampling method with a criterion of Barker code to generate a high-resolution downward-looking 3-D image. Furthermore, we propose an effective image reconstruction algorithm that is able to obtain image quality even with sparse sampling. Exploiting interferometry makes the SAR image sparsely represented in frequency domain, which can be naturally reconstructed with compressed sensing (CS) theory with sufficient precision and quality. The results of the simulation and experimental data of the anechoic chamber are presented, demonstrating the effectiveness of the algorithm.

Aimed at continuous scene imaging, this paper utilizes signal reconstruction method to eliminate random phases of scatter cells and reduce signal bandwidth, to achieve downward-looking 3D imaging in the condition of sparse flight for array SAR. With the sampling method of repeat flight such as 7 dense flights and 4 sparse flights with sampling criteria of [1 1 1 0 0 1 0] (Barker code sequence), [0 1 1 0 1 0 1] and [1 0 1 0 1 0 1] (uniformly-spaced sequence), respectively, the 3D imaging simulation is implemented in this paper. In addition, we compare the imaging quality before and after signal reconstruction. Simulation results illustrate that the adoption of signal reconstruction can significantly improve image quality; the combination of Barker code sparse flight and signal reconstruction presents the best performance among all the implemented methods.

An airship sparse array antenna radar system is investigated in this paper. The performance of the sparse array antenna is compared to the conventional dense array antenna. Ground moving target indication (GMTI) and real aperture radar (RAR) imaging mode are discussed. Some important parameters such as resolution and signal-to-noise ratio (SNR) of airship radar system are studied to prove the feasibility of the airship-mounted radar system.

This paper analyses the sparsity of SAR signal under the multi-antenna observation structure. Based on the sparsity of continuous scene spectrum and sparsity of target scene, a down-sampling method is proposed and side-looking 3D imaging of cross-track sparse array SAR is investigated. Imaging results on simulation and real data are given to verify the proposed method.

Side-looking three-dimensional (3D) imaging of cross-track three-aperture sparse array synthetic aperture radar (SAR) based on compressive sensing (CS) is investigated in this paper. Conventional SAR has accomplished high resolution imaging on two-dimensional (2D) azimuth-range plane. Using the array structure in cross-track direction, the height resolution can be obtained and 3D imaging is achieved. Conventional imaging approach and imaging based on compressive sensing are used for imaging processing. The performance of both methods is analyzed. Numerical experiments have been made and simulation results are presented in this paper.

Airborne interferometric synthetic aperture radar (InSAR) may exhibit highly non-linear flight paths, which cause the baseline to vary along the flight paths. In the following, a new airborne InSAR processing method which allows the baseline to vary along the flight paths is presented. It does not come to keep the assumption of a linear acquisition path and one constant interferometric baseline, which is adopted in conventional techniques. In addition, the validity of the proposed method was testified by both simulation and an example of its application.

The accuracy of the digital elevation model (DEM) generated by the interferometric synthetic aperture radar (SAR) partly depends on the accuracy of system parameters, so it is necessary to calibrate the system parameters. The traditional calibration method models the elevation error as a linear function of parameter biases, and solves the biases through the sensitivity equations. This paper presents a weighted calibration method applicable to interferometric SAR data. It introduces the weightings to the sensitivity equations to discriminate the ground control points (GCPs) with different correlation coefficients and locations. This weighted calibration method can improve the DEM accuracy, and this paper illustrates its successful application to airborne interferometric SAR data collected by Institute of Electronics, Chinese Academy of Sciences.

Three-dimensional imaging radar based on thinned array is investigated in the paper. The multiple phase center aperture synthesis method in time division mode is used to eliminate the high side lobes of thinned array. Using simulated annealing algorithm to optimize the location of antennas, so as to minimize the number of antennas used. Combined with motion compensation, the synthesized phase centers both in quantity and distribution are coincident with a full array. For the cross-track array length is far smaller than the scene width, three-dimensional imaging method is employed with sub-aperture imaging along cross-track. The simulation results denote the validity of the method proposed in the paper.

As the Doppler history depends both on the transmit range and the receive range in bistatic SAR, those targets, who have the same bistatic range but different locations, will have different doppler history. So the unknown terrain undulation will cause defocusing in bistatic SAR imaging. This paper firstly analyzes which parameters in bistatic configuration affect the defocusing severely, and then shows the simulation results to testify the analysis. Besides, it points out the 3D imaging ability (though very weak) of bistatic SAR based on the defocusing phenomena. And Finally the 3D imaging results are also exhibited.

In this paper, we consider the super resolution millimeter wave spotlight SAR imaging problem through the simulation under the given Strap-down Inertial Navigation System/Global Positioning System (SINS/GPS) and introduce the Phase Gradient Algorithm (PGA) into the Back-Projection (BP) for SAR focusing. The imaging results indicate that it is feasible to obtain super high resolution imagery at the millimeter wave using the SINS/GPS.

To enhance the computational efficiency and authenticity of Synthetic Aperture Radar (SAR) image simulation of man-made scenes, computer graphics (CG) method was introduced into imaging geometry simulation, graphical electromagnetic computing (GRECO) was used for the interested target scattering calculation. With these two methods, the targets' characteristics will be visualized in simulated image, such as shadow, foreshortening, layover and simple scattering property. The simulated SAR images can be used for target recognition, target detection, system verification and other researches.