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.