Abstract
Local oscillator (LO) leakage caused by in-phase/quadrature (I/Q) offsets severely degrades the performance of direct-conversion multiple-input multiple-output (MIMO) transmitters in 5G and emerging 6G systems. Existing LO leakage calibration methods often require many measurements or suffer from slow convergence, making them inefficient for multi-channel and multi-frequency applications. To address this challenge, this paper proposes a fast LO leakage calibration method based on Newton’s method. For each channel at each frequency point, the I/Q offset compensation values are determined from only nine groups of I/Q settings and the corresponding LO leakage measurements. Simulations and experiments on an 8-channel MIMO transmitter show that the proposed method achieves an average LO leakage suppression of −55.6 dBc while reducing the number of calibration samples by more than 95% compared with traditional methods, demonstrating its efficiency and practicality for large-scale MIMO transmitters in 5G and 6G communications.