High-Precision Phase Compensation Algorithm for Millimeter Wave Radar Near-Field Imaging of Static Random Targets

In near-field millimeter-wave imaging, the phase processing is crucial. Target randomness challenges phase accuracy. Phase error analysis reveals its origin in inaccurate range parameters. This paper proposes a high-precision phase compensation algorithm to address low phase accuracy and enhance imaging quality of random targets. An imaging window containing a two-dimensional target plane is established using the synthetic aperture radar-range gate localization method. A phase extraction method is proposed to estimate range parameters within this window. Utilizing the initial range parameters of the imaging window, a self-correction function is derived. Subsequent coherent accumulation of this function separates nuisance parameters. The extracted phase factor is then integrated into the imaging algorithm for compensation. Simulation results show the range error within $\pm$ 0.5 mm. These tolerances directly improve matched-filtering performance and suppress image artifacts. Experimental validation verifies the algorithm’s capability to achieve both subwavelength-resolution phase compensation and distortion-free imaging in the near-field.