Off-Grid Microwave Coincidence Imaging Based on Directional Grid Fission

Microwave coincidence imaging (MCI) is a novel staring imaging technique with high resolution in azimuth. In MCI, the continuous imaging area has to be discretized into a finite set of imaging grids, which usually leads to grid mismatch and deteriorated imaging performance. To solve this problem, a directional grid fission method for MCI (DGF-MCI) is proposed, in this letter. Unlike the existing fixed-grids-based MCI methods, in DGF-MCI, a grid-fission process is conducted in different dimensions iteratively based on the direction of position offsets; hence, new grids are generated near the true position of scatterers and off-grid errors are eliminated iteratively. Meanwhile, redundant grids are dropped out, by which computational complexity is significantly reduced. Finally, an imaging result of high quality can be obtained based on the updated nonuniform grids. The validity and effectiveness of the proposed method, along with the super-resolution ability of MCI, are verified by simulations and outdoor experiments.