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.