Abstract
Multiple-Input Multiple-Output (MIMO) radar provides much more flexibility than the traditional radar thanks to its ability to realize far more observation channels than the actual number of transmit and receive (T/R) elements. In designing the MIMO imaging radar arrays, the commonly used virtual array theory generally assumes that all elements are on the same line. However, due to the physical size of the antennas and coupling effect between T/R elements, a certain height difference between T/R arrays is essential, which will result in the defocusing of edge points of the scene. On the other hand, the virtual array theory implies far-field approximation. Therefore, with a MIMO array designed by this theory, there will exist inevitable high grating lobes in the imaging results of near-field edge points of the scene. To tackle these problems, this paper derives the relationship between target’s point spread function (PSF) and pattern of T/R arrays, by which the design criterion is presented for near-field imaging MIMO arrays. Firstly, the proper height between T/R arrays is designed to focus the near-field edge points well. Secondly, the far-field array is modified to suppress the grating lobes in the near-field area. Finally, the validity of the proposed methods is verified by two simulations and an experiment.
Highlights
Ground-based Synthetic Aperture Radar (GB-SAR) is a kind of radar system which can realize two-dimensional high-resolution imaging by linear motion on a slide rail with synthetic aperture technology [1,2,3,4]
Radar imaging is the focus of coherent data on a certain observation aperture, multiple-input multiple-output (MIMO) imaging radars generally adopt the collocated mode [11], whose transmit and receive (T/R) elements concentrate on the same observation angle of the target
As is mentioned in the introduction, it is unavoidable to consider the defocus caused by the height difference between the T/R arrays and the grating lobes caused by the non-uniform virtual array
Summary
Ground-based Synthetic Aperture Radar (GB-SAR) is a kind of radar system which can realize two-dimensional high-resolution imaging by linear motion on a slide rail with synthetic aperture technology [1,2,3,4]. Without any spatial resolution loss, MIMO imaging radar outperforms the traditional GB-SAR with its high temporal resolution and freedom from motion compensation problems This key advantage provides a basis for vibration measurements.
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