Abstract
Channel phase calibration is a crucial issue in high resolution and wide swath (HRWS) imagery with azimuth multi-channel synthetic aperture radar (SAR) systems. Precise phase calibration is definitely required in reconstructing the full Doppler spectrum for precise HRWS imagery without high-level ambiguities. In this paper, we propose a novel calibration for HRWS SAR imagery by optimizing the reconstructed unambiguous Doppler spectrum. The sharpness of the reconstructed Doppler spectrum is applied as the metric to measure the unambiguity quality, which is maximized to retrieve the element phase error caused by channel imbalance. Real data experiments demonstrate the performance of the proposed calibration for ambiguity suppression in HRWS SAR imagery.
Highlights
Calibration for High-Resolution and Synthetic aperture radar (SAR) techniques require generating imagery with simultaneous high resolution and wide swath (HRWS) capability
In order to receive unambiguous echoes in range or/and Doppler, conventional synthetic aperture radar (SAR) observed swath should be restricted by the fundamental trade-off between Doppler ambiguity and spatial resolution for a single-channel radar system [1]
We developed a sharpness optimization-based phase calibration for HRWS SAR imagery with azimuth multi-channel configuration
Summary
Calibration for High-Resolution and Synthetic aperture radar (SAR) techniques require generating imagery with simultaneous high resolution and wide swath (HRWS) capability. Among the data-driven calibration algorithms, subspace projection algorithms [16,17,20,21] have been well investigated in many works They generally estimate the channel phase errors for multi-channel SAR HRWS imagery with the same basic principle. Subspace projection-based channel calibrations are very popular in HRWS imaging with multi-channel SAR systems In these works, the imbalance phase errors are usually assumed to be spatial-invariant. In the azimuth phase calibration, the estimation of the channel phase errors turns into maximizing the sharpness of the reconstruction full Doppler spectrum by correcting phase errors within ambiguity resolving, which simplifies the problem of calibration due to no need for additional spatial freedom degrees In contrast to the former approaches, this method proposed in this paper calibrates phase imbalance in a robust manner by using all range bins as calibration sources.
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