Miniature Active Differential Magnetic Field Probe With High Sensitivity for Near-Field Measurements

In this communication, a magnetic field probe with high common-mode rejection ratio (CMRR) and high sensitivity for the near-field measurement is proposed, fabricated, and calibrated. The proposed magnetic field probe consists of a differential dual loop (DDL) to improve the CMRR to the electric field, a balun to convert the differential end to the single end, and a two-stage amplifier achieving proper gain to further enhance the sensitivity. The sensitivity of the probe is raised by more than 50 dB at 30 MHz compared with the reference probes. The measured CMRR is more than 40 dB from 200 kHz to 1 GHz. The measurements of the passive circuits are conducted, and validating that the sensitivity of the proposed probe is significantly improved.