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The azimuth multichannel synthetic aperture radar (MC-SAR) is an effective means of earth observation due to its high-resolution and wide-swath (HRWS) imaging capability. Compared with the traditional MC-SAR, the two-dimensional (2D) spectrum of the squint multichannel synthetic aperture radar (SMC-SAR) is skewed, leading to the severe coupling between azimuth signals and range signals. Therefore, the traditional imaging algorithms are inapplicable to SMC-SAR. Currently, the existing imaging algorithms for SMC-SAR need interpolation or sub-aperture processing, which results in low efficiency. This paper proposes a novel imaging scheme for spaceborne SMC-SAR to handle this issue. With the squint angle known, the Doppler centroid can be compensated for by the spectrum shift function. Additionally, the frequency correlation method (FCM) is utilized to estimate the channel phase imbalance. After that, the azimuth multichannel data are reconstructed by the filter banks to eliminate the Doppler spectrum aliasing. Finally, the data are imaged based on the modified equivalent slant range model (MESRM). Both the simulation and Gaofen-3 (GF-3) data experiments demonstrate the effectiveness and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

In multichannel Synthetic Aperture Radar (SAR) data processing, the phase and amplitude characteristics of all channels should be well calibrated before multichannel data reconstruction; otherwise, the imaging result will be degraded and suffer from ghost targets. The yaw and pitch of the SAR platform, which change in azimuth and range, respectively, will cause phase mismatch among different channels. The currently developed attitude-aided phase mismatch calibration method does not consider the topographic relief. On the basis of the external Digital Elevation Model (DEM) and attitude information, a new phase mismatch calibration method is proposed in this study. The proposed method performs better than other methods in mountainous areas. A simulation experiment and the corresponding quantitative assessment are conducted. Then, the newly proposed method is applied to airborne multichannel SAR experimental data for further verification.

The azimuth multichannel synthetic aperture radar (MC-SAR) is an effective means of earth observation due to its high-resolution and wide-swath (HRWS) imaging capability. Compared with the traditional MC-SAR, the two-dimensional (2D) spectrum of the squint multichannel synthetic aperture radar (SMC-SAR) is skewed, leading to the severe coupling between azimuth signals and range signals. Therefore, the traditional imaging algorithms are inapplicable to SMC-SAR. Currently, the existing imaging algorithms for SMC-SAR need interpolation or sub-aperture processing, which results in low efficiency. This paper proposes a novel imaging scheme for spaceborne SMC-SAR to handle this issue. With the squint angle known, the Doppler centroid can be compensated for by the spectrum shift function. Additionally, the frequency correlation method (FCM) is utilized to estimate the channel phase imbalance. After that, the azimuth multichannel data are reconstructed by the filter banks to eliminate the Doppler spectrum aliasing. Finally, the data are imaged based on the modified equivalent slant range model (MESRM). Both the simulation and Gaofen-3 (GF-3) data experiments demonstrate the effectiveness and efficiency of the proposed method.

As one of the most important means to achieve a High-Resolution and Wide-Swath (HRWS) imaging of the earth, multichannel in azimuth Synthetic Aperture Radar (SAR) have attracted considerable attention in recent years. However, prior to the unambiguous reconstruction of the multichannel SAR signal, each channel needs to be well calibrated, otherwise the performance of the reconstruction processor may degrade or even lose its effectiveness. Accurate baseband Doppler centroid estimation are critical for channel mismatch calibration and high-resolution imaging in the multichannel SAR systems. However, in the multichannel HRWS SAR system, the signal acquired by each channel is under-sampled that renders the traditional Doppler centroid estimation methods obsolete. In this paper, an eigen-structure method has been used to achieve a robust estimation of the baseband Doppler centroid and the phase mismatch in the multichannel SAR system. Processing with simulated and experimental C-band, four-channel airborne SAR data validates the effectiveness of this method.