Image Defocus in an Airborne UWB VHR Microwave Photonic SAR: Analysis and Compensation

Xu, Weidi; Wang, Bingnan; Xiang, Maosheng; Li, Ruoming; Li, Wangzhe

doi:10.1109/tgrs.2021.3108571

Cited by 13 publications

(8 citation statements)

References 39 publications

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“…This article will validate the proposed algorithm in airborne mode [13][14][15][16][17][18]. The system parameters are set as follows: flight altitude of 5000m, flight speed of 120m/s, downward viewing angle of 60 degrees, system carrier frequency of 9.6GHz, effective length of azimuth antenna Da=0.6m, pulse width Tp=10e-6s, frequency modulation bandwidth Br=50e6Hz, mixing factor V_ Retio=1/2, system PRF is 600Hz, and system azimuth bandwidth is 936.383Hz.…”

Section: Simulation Verification and Analysismentioning

confidence: 95%

Anti aliasing algorithm based on sub aperture stitching

2024

International Conference on Algorithm, Imaging Processing, and Machine Vision (AIPMV 2023)

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High resolution synthetic aperture radar system will produce aliasing problem in the sliding spotlight mode, we propose a solution based on sub-apertures splice to solving the program, the simulation and analysis of airborne mode are given. The method use the sub-aperture division, respectively, each aperture frequency shift, scaling, compression distance, azimuth compression performed prior to stitching, the data will be spliced after azimuth compression and windowing. Simulation results show that the algorithm can effectively solve the problem.

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Section: Simulation Verification and Analysismentioning

confidence: 95%

Anti aliasing algorithm based on sub aperture stitching

2024

International Conference on Algorithm, Imaging Processing, and Machine Vision (AIPMV 2023)

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“…The latter three types of errors are all caused by the SAR system itself, so we refer to them as systematical errors. So far, most of the existing autofocus methods focused on the influence of motion errors, but only a few concerned the systematical errors [9]. Therefore, for MWP SAR, it is demanding to develop an imaging method that takes the unknown systematical errors into consideration and is capable of compensating for them.…”

Section: Introductionmentioning

confidence: 99%

“…In [33] and [34], the analytical structure of the phase error is explored, and a semi-blind method for 2-D phase error estimation and compensation is proposed, but they are based on the models considering only the motion errors. In [9], a 2-D autofocus strategy accounting for systematical errors in MWP SAR systems is developed. However, it just compensates for the range envelope error, i.e., 1st-order phase error in the range dimension, which is powerless to range defocus related to 2nd and even higher-order phase errors in the range dimension.…”

Section: Introductionmentioning

confidence: 99%

Analysis and Compensation for Systematical Errors in Airborne Microwave Photonic SAR Imaging by 2-D Autofocus

Chen

Qiu

et al. 2023

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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In the area of synthetic aperture radar (SAR), the ultra-high resolution is always a continuous pursuit for researchers. To realize ultra-high resolution, microwave photonics (MWP) technology is an excellent solution since it has advantages of low transmission loss, ultra-wide bandwidth (UWB), etc. However, with the improvement of resolution, new problems arise as the impact of more systematical errors becomes non-negligible. For example, the synchronization error between the transmit channel and the mixing channel, unknown system delay during signal reception, and fluctuation of frequency for UWB signals. These factors will bring degradation of the focusing quality of SAR images together with the motion errors and the trajectory measurement errors, not only cause residual range cell migration (RCM) and azimuth phase error (APE), but also higher-order phase error along the range frequency dimension. In this paper, we discuss the adverse influence of the above factors and give a detailed analysis of the 2-D phase error of the coarse focused image processed by range migration algorithm (RMA). Then, to compensate for the above unknown systematical errors, a 2-D autofocus method is proposed and the effectiveness is validated by experiments on both simulated and real data.Index Terms-Microwave photonic (MWP) synthetic aperture radar (SAR), ultra-wide bandwidth (UWB), systematical errors, 2-D autofocus, range migration algorithm (RMA).

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“…Motion errors usually consist of an envelope error and a phase one, and both types of errors satisfy the linear mapping relationship, that is, the ratio of the phase error to the envelope error is 4π/. Some researchers calculate the phase error by estimating the envelope error [14][15][16][17], but others convert the phase error estimated by phase autofocusing methods into the envelope error [2,6,18,19]. In the first class methods, the cross-correlation method based on oversampled data of range profiles is employed to estimate the envelope error.…”

Section: Introductionmentioning

confidence: 99%

“…Liu et al [24] use the SA image coherent superposition to achieve high-resolution real-time imaging for spotlight SAR. Xu et al [17] estimate the azimuth SA envelope and phase errors by the cross-correlation-based algorithm and map-drift method in the range-Doppler domain. Hai et al [25] propose an optimal SA division method to guarantee the coherence of each SA data in the Back-Projection imaging.…”

Section: Introductionmentioning

confidence: 99%

A High-Resolution Airborne SAR Autofocusing Approach Based on SR-PGA and Subimage Resampling With Precise Hyperbolic Model

Deng

Wang

Sun

et al. 2023

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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High-resolution airborne synthetic aperture radar (SAR) imaging requires long synthetic aperture time (LSAT). However, the LSAT invalidates the Fresnel approximation in the traditional autofocusing method, leaving a residual signal phase in the motion error. To solve the problem, a signal-reconstructionbased phase gradient autofocus (SR-PGA) and a sub-image resampling (SIR) methods are proposed. They are developed on the hyperbolic model. First, a sub-aperture division strategy divides the full-aperture high-order error into multiple low-order sub-aperture errors. Then, the SR-PGA is developed to estimate the sub-aperture error (SPE), in which the precise deramping is reconstructed to eliminate the residual signal phase in the SPE. Third, the SIR is proposed to eliminate residual Doppler-variant shift of the adjacent sub-images, improving the accuracy of the SPE combination. Finally, simulation and actual data processing verify the effectiveness and validity of the algorithm.

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Image Defocus in an Airborne UWB VHR Microwave Photonic SAR: Analysis and Compensation

Cited by 13 publications

References 39 publications

Anti aliasing algorithm based on sub aperture stitching

Anti aliasing algorithm based on sub aperture stitching

Analysis and Compensation for Systematical Errors in Airborne Microwave Photonic SAR Imaging by 2-D Autofocus

A High-Resolution Airborne SAR Autofocusing Approach Based on SR-PGA and Subimage Resampling With Precise Hyperbolic Model

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