Abstract
In order to resolve the range and azimuth ambiguity in MIMO-SAR imaging, this paper proposed a joint two-dimensional ambiguity resolving method based on space-time filtering, which according to the ambiguity in different subscene is relative to different nearest echo range, and different azimuth time is relative to different instantaneous incidence angle, to make two-dimensional space-time steering vector for resolving ambiguity of the echo, which also can finish the imaging processing at the same time. Simulation results validate the proposed processing approach for the MIMO-SAR system.
Highlights
Multiple-input and multiple-output spaceborne synthetic aperture radar (MIMO-SAR), as a high resolution and wide swath microwave remote sense system [1,2,3,4,5], is proved to be an extremely useful surveillance tool for moving target indication, wide swath imaging, and three-dimensional imaging.ScanSAR can obtain wide unambiguous swath coverage at the cost of a degraded azimuth resolution [6]
Multichannel line arrays can be arranged by range or azimuth [7], for the range multichannel can obtain wide swath coverage, utilizing digital beamforming to resolve range ambiguity, but there is still blind zone [8, 9]
One can lower the requirement on pulse repetition frequency (PRF) to achieve wider swath imaging without impairing azimuth resolution; in other words, one can broaden the Doppler spectrum to obtain finer azimuth resolution without reducing the swath coverage
Summary
Multiple-input and multiple-output spaceborne synthetic aperture radar (MIMO-SAR), as a high resolution and wide swath microwave remote sense system [1,2,3,4,5], is proved to be an extremely useful surveillance tool for moving target indication, wide swath imaging, and three-dimensional imaging. With the emergence of techniques such as displaced phase center [10] and multiple aperture reconstruction [11, 12], a number of displaced azimuth subapertures are used to receive echoes in one pulse repetition interval (PRI), thereby increasing the effective azimuth sampling rate without changing the pulse repetition frequency (PRF) In this way, one can lower the requirement on PRF to achieve wider swath imaging without impairing azimuth resolution; in other words, one can broaden the Doppler spectrum to obtain finer azimuth resolution without reducing the swath coverage. A joint two-dimensional ambiguity resolving method for MIMO-SAR is proposed, which uses deferent targets relative to deferent range as steer vector which is independent of the downlooking angle.
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