Near-Field Uniform Linear Array Calibration Based on the Extrapolation of Measured Complex Signals

Rigorous phased array calibration is critical to ensure accurate array radiation performance. This communication presents a novel phased array calibration method based on extrapolation of the measured complex signals under near-field conditions. The proposed method enables calibration of large aperture phased arrays with a small probe array aperture. A single probe antenna is employed and moved in a sparse grid to obtain the amplitude and phase of the electric field over a planar region close to half of the aperture of an antenna under test (AUT). The operating principle is to fit and extrapolate the amplitude and phase of the measured complex signals, which are envisaged to have a parabola shape, after compensation using the known probe radiation pattern and the free space transfer function. The amplitude of the initial excitation is calculated by the average parabolic difference, while the initial phase excitation is obtained by the vertices of parabolas. A uniform linear array (ULA) is calibrated in near-field using the proposed method with a scanning range of only half of the ULA aperture. From the obtained results, a ±0.49 dB in amplitude and ±4.7° in phase calibration accuracy are achieved, respectively, demonstrating the effectiveness of the proposed method.