A Near-Field Calibration Method for Linear Arrays Operating in Reflective Environments

Phased array calibration is typically performed within an anechoic chamber to mitigate the degradation of calibration accuracy induced by multipath reflections. However, under conditions involving lower operational frequencies or extremely compact chamber dimensions, reflections within the anechoic chamber intensify, resulting in a significant impairment of calibration precision. This article presents, for the first time, a novel near-field calibration method and model for linear arrays in environments characterized by multipath reflections. The measured signals obtained by probe scanning can be decomposed into direct signals and reflected signals. The direct signal model can be constructed following the plane wave spectrum (PWS) theory. A novel model for reflected signals is proposed by applying image theory to these plane waves, considering different reflective boundaries. An evaluation function is established on the basis of the constructed signal model, and the initial excitations are determined by minimizing the evaluation function. The genetic algorithm (GA) is utilized to find the minimum, while the singular value decomposition (SVD) method is employed to improve the algorithm’s efficiency. Using the proposed method, a linear array is calibrated in an experimental reflective environment, with a probe scanning aperture covering 1/3 of the AUT aperture. The results indicate a calibration accuracy of ±0.37 dB in amplitude and ±4.6° in phase, demonstrating the effectiveness of the proposed method.