A Near-Field Calibration Method for MMW Massive MIMO Antenna Array

Millimeter-wave (MMW) massive multiple-input multiple-output (MIMO) antenna arrays have wide applications. However, as the antenna scale increases, the system complexity of the antenna arrays rises, and the differences between transmitting-receiving antenna pairs caused by system errors become non-negligible. The differences primarily consist of delay deviation and initial phase deviation, which can significantly degrade the performance of antenna arrays. Current calibration methods have limited application scope and cannot effectively calibrate massive antenna arrays in the near-field. To address this issue, we propose a calibration method using a metal cylinder as the cooperative target to calculate these deviations. This method first efficiently calculates the key parameter, the RF signal propagation distance. Subsequently, based on this key parameter, these deviations between the transmitting-receiving antenna pairs are derived, along with the corresponding calibration coefficients. The paper showcases the results of near-field imaging using a nine-subarray with 1152 transmitters and 1152 receivers. The paper verifies the feasibility of the calibration method through near-field imaging. Imaging results of the calibrated echo data reveals clear details of the target, demonstrating the proposed method’s advantages of high efficiency and good performance.