Achieving Wireless Cable Testing of High-order MIMO Devices with a Novel Closed-form Calibration Method

Highly integrated multiple-input-multiple-output (MIMO) system designs have posed great challenges to MIMO device performance testing in conventional cable conducted setups. A wireless cable method, which can achieve cable testing functionality without actual radio frequency (RF) cable connection, has recently been considered a strong alternative to conductive testing method. However, its applicability to high-order MIMO antenna systems is mainly limited by the calibration complexity in the literature. To tackle this issue, a novel closed-form calibration method is proposed, which can largely speed up the calibration procedure and make the testing method practical for MIMO devices of arbitrary orders. Some practical factors affecting the calibration performance are discussed with numerical simulations. The proposed algorithm is further experimentally validated for a device under test (DUT) with four antennas in the 3.45-3.55 GHz frequency band. The detailed theoretical analysis together with numerical simulations and experimental validations have demonstrated the effectiveness and robustness of the proposed algorithm.