Comparative Analysis of Several Near-Field Probes for Magnetic Field Measurements

The near-field magnetic probe ( ${H}$ -probe) is an essential diagnostic tool for analyzing electromagnetic interference in electronic products. Many types of ${H}$ -probes have been designed and manufactured in recent years. Nevertheless, the performance of these probes in practical magnetic field ( ${H}$ -field) measurement is not clear. In this article, six typical ${H}$ -probes with the same loop area, labeled as UHP11, SHP11, UHP12, SHP12, UHP22, and SHP22, are designed and fabricated. The key parameters that can evaluate the performance of ${H}$ -probes include frequency response (FR), intrusion of the probe to the device under test (DUT), spatial resolution (SR), common-mode electric field ( ${E}$ -field) suppression, and differential ${E}$ -field suppression. To analyze the key parameters of these probes, full-wave models of these ${H}$ -probes are simulated and compared with measurements. Meanwhile, the equivalent circuit models of these ${H}$ -probes are established to analyze ${E}$ -field suppression in ${H}$ -field measurement. The measurement results indicate that the shielded one-loop ${H}$ -probe with differential output ports (SHP12) achieves the best differential ${E}$ -field suppression, which is 26 dB at 5 GHz. In addition to the outstanding suppression performance on differential ${E}$ -field, its common-mode ${E}$ -field suppression is also the best and greater than 30 dB within 14.3 GHz. The SR of six ${H}$ -probes is basically consistent in the measurement. Except for the higher sensitivity of the two-loop ${H}$ -probes (UHP22 and SHP22), SHP12 shows the best comprehensive ${H}$ -field measurement performance.