An Advanced Forward Asymmetric Correction Method for an Electromagnetic Near-Field Probing System

Solving the asymmetric problem is essential for an asymmetric two-port electromagnetic near-field probing system (ATPS). In this article, an advanced forward two-sided asymmetric correction method (FTACM) has been proposed. Unlike the traditional inverse asymmetric calibration method (IACM), it needs two independent electromagnetic excitations created by the calibrator; the solution process of the FTACM is forward and independent of the calibration process. The FTACM only needs the self-parameter of the ATPS, including theS-parameter of the symmetric two-port probe and theS-parameter of two asymmetric elements. Compared with the IACM, the FTACM has the advantages of no complex mechanical movement (CMM), no symmetry requirement on a calibrator, easy to ultrawideband measurement, greater noise adaptability, and extensible to multiport probing system. A typical calibration result in Case 1 shows that the FTACM can effectively eliminate calibration ripple. The evaluation results of uncertainty prove the reliability of the FTACM, and its maximum uncertainty in Case 2 is 0.12 dB and 1.32° at 18 GHz. The influence and effectiveness of the FTACM on near-field measurement are also analyzed, which shows that the FTACM can correct for asymmetry up to 20 GHz and achieve almost the same characteristics as the original symmetric system.