Asymmetric Calibration and Characterization for Diff-Port Magnetic Field Probing System

Strict symmetry limits the application of the differential port (diff-port) magnetic field probing system (DMPS). Asymmetric calibration is very meaningful for DMPS. Ultrawindband asymmetric calibration theory was first proposed and applied to the electromagnetic field measurement system. However, the asymmetric calibration theory is not clear for the DMPS because only the magnetic field is concerned. This article proposes an ultrawideband asymmetric calibration method (UACM) for the DMPS. The output voltage and asymmetric factor of the DMPS are redefined using the UACM. Compared with the previous asymmetric calibration method, the proposed method is based on a symmetry calibrator with a grounded coplanar waveguide (GCPW) structure. The proposed method is validated by eliminating a severe asymmetry in the DMPS, whose severe asymmetry is achieved by introducing a connector intentionally. The proposed method has been verified with a frequency of up to 20 GHz by measuring a standing wave magnetic field on an open-terminated transmission line. The key parameters of the DMPS, including unwanted field suppression, spatial resolution, and sensitivity, are also estimated.