Symmetrical double‐loop H‐field probe with floating shield for improving sensitivity and electric field suppression

Abstract

A magnetic near-field probe (H-field probe) with dual output has been developed using a four-layer printed circuit board (PCB) technique. To achieve the improvement of detection sensitivity, the symmetrical double-loop is adopted to double the detection signal while suppressing the electric field coupling, which is also illustrated in a circuit model. The calibration factor (defined as the ratio of the external magnetic field to the induced response voltage of the probe) of the proposed H-field probe reaches 37.74 [dB (A/m)/V] at 0.5 GHz with the loop area of 0.8 mm 2 , resulting in a better sensitivity than the single-loop probe. For the suppression of unwanted electric field a floating shield is added to the bottom of the probe, leading to an excellent common electric field suppression ratio of 29 dB in the frequency range up to 10 GHz. The probe is also characterised by parameters such as high differential electric field suppression, spatial resolution and probe influence on the device under test. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

A miniature shielded‐loop active H‐field probe design with high spatial resolution for near‐field measurement

“…13 The differential electric field suppression η d is defined as the maximum of H-field distribution measublack by the probe at θ ¼ 90 divided by the maximum of H-field distribution measublack by the probe at θ ¼ 0 . 19 Figure 8 shows that the η d is 14 dB at 10 GHz. The η d from 500 MHz to 20 GHz is shown in Figure 9.…”

“…In Equation ( 1), it can be seen that the sensitivity is related to the noise floor of the spectrum analyzer after composing the system and the frequency response (S 21 ) of the probe. Further, the reliable measurement H-field intensity sensitivity δ H can be calculated by 19 δ…”

“…The third probe is the popular passive probe as a reference probe (shown in Figure 10). 14,19 The current sensitivity of system (δ I ) with the same liftoff = 500 μm by using these probes RF-R 3-2, RF-U 2,5-2, reference probe and proposed probe are shown in Table 2. In order to obtain the current sensitivity, a spectrum analyzer (FSW43, manufactublack by ROHDE & SCHWARZ) is used to measure the noise floor, the internal attenuation is set to 0, the internal preset amplifier is set to off, and RBW refers to IEC61967-1.…”

A two‐turn loop active magnetic field probe design for high sensitivity near‐field measurement

“…The voltage induced by detected structure in the frequency domain can be calculated by where is the number of turns. Figure 5b shows the equivalent circuit model of proposed probe [22]. the output voltage of the probe can be expressed as where = 50 is internal resistance of the instrument, is the self‐induction of the detected structure, it is positively related to the number of turns and the area .…”

“…At this time, the probe senses different electric fields on the left and right metal walls of the detection loop, one direction is down, the other direction is up. But sometimes, will also appear at y = 0, which may be due to leaked magnetic fields [22]. For the above two cases, Equation (10) has some representational significance, and to some extent, it represents the ability of the probe to suppress the unwanted field.…”