Phase and Amplitude Correction for Adaptive Beamforming of Phased Array Weather Radar

Adaptive digital beamforming (DBF) techniques offer a promising solution for mitigating signals originating from antenna sidelobes, such as clutter echoes from the ground, in phased array weather radars (PAWRs). However, adaptive DBF is sensitive to amplitude and phase errors of reception signals from each antenna element, and its performance can be degraded if antenna elements output large errors. In the present study, we demonstrate a calibration method of amplitude and phase errors by detecting aircraft as a hard target. Obtained calibration parameters are applied to fair weather and precipitation observation data acquired with an X-band single-polarized PAWR at Osaka University, Japan. Compared to the conventional Fourier (nonadaptive) method, the sidelobe level is suppressed by more than 40 dB, even suppressed by more than 10 dB compared to the adaptive DBF without the amplitude and phase correction. Moreover, this method is useful to detect malfunctioning antenna elements with large phase errors which are difficult to detect during normal operation. This study demonstrates that the amplitude and phase corrections are necessary to maintain the best performance of adaptive DBF, and the present method facilitates a periodical calibration.