In this letter, a new parameter estimation and multi-pulse coherent integration method for the high-speed and maneuvering target detection is proposed in a nonuniform sampling radar system. In the proposed method, the signal recovery with respect to the missing pulse data is firstly realized by using the iterative adaptive approach (IAA) in the range frequency domain. Then, the generalized nonuniform time-scaled transform (GNTST) is applied to decouple the complex coupling terms induced by the target maneuvering motion and irregular radar waveforms, where the velocity ambiguity caused by target high speed is considered. Finally, the well-focused target imaging result can be obtained after accomplishing the target signal recovery, reconstruction, and phase decoupling. Simulations and real-measured radar data experiments are conducted to validate the proposed method.

Ground moving target focusing performance and processing efficiency are two important metrics in the synthetic aperture radar (SAR) system. Owing to the complex nonstationary phases caused by target motions, ground maneuvering targets are commonly smeared and distorted in an SAR image. To realize the ground maneuvering target imaging, exhaustive high-order parameter searching and optimization processing are usually needed to achieve the optimal processing performance. However, the large computational resource consumption may limit their real-time processing capabilities. To deal with this issue, an efficient SAR imaging approach for ground maneuvering targets is proposed by adopting the mixed symmetric function (MSF) transform. After performing the multichannel SAR clutter rejection and target initial detection by applying the constant false alarm rate (CFAR) technique, the linear envelop shift of detected ground target is eliminated by using the well-known Keystone transform (KT). Then, an MSF is constructed to rectify the range curvature and relieve the Doppler broadening after carrying out the nonuniform fast Fourier transform (NUFFT) corresponding to the second-order time variable. After removing the second-order Doppler spreading influence, the quadratic chirp parameter is estimated via the NUFFT after the symmetrical correlation processing. Finally, after accomplishing the motion compensation, the ground maneuvering target can be well focused and relocated in the SAR image. Compared with the traditional approaches, the proposed approach not only realizes the high-precision Doppler parameter estimation, but is also computationally efficient without grid searching procedure. Numerical simulation and real-measured SAR experiment results are depicted to verify the correctness and effectiveness of the proposed approach.

Employing azimuth multi-channel array configuration can effectively enhance the high-resolution and wide swath - synthetic aperture radar (HRWS-SAR) imaging performance by increasing the spatial sampling frequency along the azimuth direction. 1However, the ground moving targets with unknown radial velocities, may induce azimuth "ghost" points in a well-focused HRWS-SAR image with the imaging function related to ground static scene. To address this issue, the paper introduces a novel ground moving target imaging method in a multi-channel HRWS-SAR system. The multichannel HRWS-SAR simulation results verify the effectiveness and feasibility of the proposed method.

This paper proposes a fast two-step method which aims to address the SAR pose estimation problem and enable Unmanned Aerial Vehicles (UAVs) the self-localization capability under harsh conditions. Firstly, the monocular SAR pose estimation is formulated as a Circular-n-Point (CnP) problem based on frequency-domain SAR imaging mechanism. Then, we propose to decouple the motion components of radar platform and solve the overdetermined equations of direction and location sequentially. Experimental results validate the effectiveness, accuracy, and efficiency of the proposed method.

In this paper, a method aimed at removing the linearly continuous false alarm caused by the artificial building with unignored elevation in a multichannel synthetic aperture radar (SAR) system with ground moving target indication (GMTI) mode is proposed. In the proposed method, the Hough transform is firstly utilized to obtain the potential false alarms during the iteration procedure. After that, the linearly continuous false alarms are finally obtained and removed based on the phase similarity characteristic of those building scatters. Real-measured SAR data processing results are presented to verity the effectiveness and feasibility of the proposed method.

In this paper, the influence of different receiving array element weighting manners on the space-time adaptive processing (STAP) technique is analyzed. Firstly, the element-based echo signal in a space-borne early warning radar (SBEWR) system is established, and then the STAP procedure by utilizing two alternative receiving array element weighting models are introduced. After that, the antenna patterns with respect to two weighting manners are discussed and the target output signal-to-clutter-plus-noise ratio (SCNR) after STAP are evaluated. The numerical results show that the subarray element weighting manner obtains a better STAP performance without channel mismatch compensation while a slightly inferior STAP performance with channel mismatch compensation compared with the whole antenna weighting manner.

In this letter, the clutter range dependence issue caused by crab angle is investigated in an airborne multi-channel radar system. A new method is proposed to accomplish the crab angle estimation and the non-stationary error compensation. Firstly, from the center-biased and spectrum-broadened characteristics of the clutter space-time spectrum in the case of non-neglected crab angle, a 1-D cost function based on space-time spectrum broadening degree is constructed to achieve the accurate crab angle estimation. Then, the clutter non-stationary errors can be effectively compensated in the post-Doppler domain, significantly improving the subsequent space time adaptive processing (STAP) performance. Simulation results are presented to validate the feasibility and effectiveness of the proposed method.

Multiple-input–multiple-output (MIMO) technique has recently received great attention due to its promising prospect for ground moving target indication (GMTI) applications in a synthetic aperture radar (SAR) system. In this article, an SAR-GMTI processing technique in an MIMO-SAR system with dual-channel configuration is proposed. In the proposed method, up and down chirps are adopted as the transmitted waveforms. Then, the baseline estimation and clutter rejection are simultaneously accomplished in the raw Doppler data domain, after which two separated range-compressed echo signals corresponding to two transmitters can be obtained without the influence of cross-correlated interferences of the clutters. Subsequently, a ground moving target can be detected, clustered, finely refocused based on the Doppler chirp parameter estimation, and accurately relocated by using the along-track interferometry (ATI) processing technique. Simulated experiments are implemented to validate and evaluate the feasibility of the proposed method.

In this letter, we propose a novel range and Doppler sampling mismatch compensation method for moving target detection, which can effectively improve the output signal-to-noise ratio (SNR) of a moving target. In the proposed method, after performing the target coherent integration by using the well-known Keystone transform (KT), the range and Doppler sampling mismatch errors (SMEs) are estimated and compensated based on the constructed optimization model with the consideration of the change rate of a moving target peak amplitude. In order to improve the computational efficiency, the Hooke–Jeeves method is applied to achieve the optimal solution of the constructed optimization problem, thus efficiently solving the target energy diffusion problem caused by the SMEs. Simulated experiment is presented to verify the effectiveness and feasibility of the proposed method.

In this paper, we propose a novel long-time coherent integration detection method to detect an uncooperative moving target in a frequency and pulse repetition interval randomly jittering radar system based on signum coding (SC). In the proposed algorithm, an additional reference waveform is applied to eliminate the third-order harmonic influence induced by SC. Then, a generalized Keystone transform (GKT) is proposed to resolve the complex coupling among the range frequency, jittered carrier frequency, and nonuniformly sampled time. Simulation results are presented to validate the effectiveness and feasibility of the proposed method.

In a multichannel synthetic aperture radar (SAR) system, because of the target uncooperative motion, a ground moving target (GMT) is usually smeared, distorted, and shifted in an SAR image. In this article, a novel approach for multichannel SAR-GMT indication (GMTI) processing is proposed. The main innovations of this method are that a GMT can be well refocused and relocated since the target high-order Doppler parameters can be precisely estimated based on a high-order polynomial phase signal (PPS) model, and the target statistical amplitude and phase information is jointly applied to improve the radial velocity estimation robustness. Compared with the current SAR-GMTI algorithms, the improvements of this method over the existing methods are: 1) the topography interferometric phase can be effectively compensated by applying an adaptive 2-D spectrum filtering technique via iterative processing; 2) a GMT can be well imaged since the target Doppler chirp rate and the quadratic chirp rate can be well estimated via the 2-D coherent integration in the time–frequency plane; and 3) a GMT can be precisely relocated into its original position by applying the generalized amplitude and phase weighting technique. Real-measured SAR data processing results are presented to validate the effectiveness and feasibility of the proposed method.