New Resonant Probes With High Detection Sensitivity and Measurement Characteristic of Two Orthogonal Magnetic-Field Components

In this article, two new magnetic-field resonant probes, which have high detection sensitivity and measurement characteristic of two orthogonal magnetic-field components, are developed and fabricated on a four-layer printed circuit boards (PCBs). Designed probes are composed of a U-shaped loop with a shorted strip (Probe A), two orthogonal shorted loops (Probe B), two 50- $\Omega $ strip lines, and a pair of inductor–capacitor (LC) resonant strips. In order to prevent unwanted electromagnetic modes, several rows of via fences are inserted into these probes. First, two different detection structures are utilized to test two magnetic-field components. Second, a pair of LC resonant strips are used to enhance the detection sensitivity by exciting the resonant point at 1.575 GHz. Finally, the proposed probes are simulated, manufactured, and measured experimentally to evaluate the accuracy of design. Experimental results demonstrate that these new resonant probes can not only simultaneously test two orthogonal magnetic-field components but also exhibit high detection sensitivity at 1.575 GHz.

I. Introduction

As integrated circuits develop toward miniaturization, higher speeds, multifunctionality, and high levels of integrations, electromagnetic interference (EMI) is expected to become increasingly problematic. Near-field scanning systems [1], [2], [3], [4] are commonly used to identify the EMI positions and track transmission paths. The core component of such systems is the near-field probe, which commonly uses an electrically small shorted loop to measure a magnetic-field component and an open-ended monopole to receive a vertical electric-field component. Recent research efforts have focused on increasing the bandwidth [5], [6], enhancing the sensitivity [7], [8], [9], [10], improving the electric-field suppression [11], [12], [13], and expending the spatial resolution [14], [15], [16], [17] of the probes. High-sensitivity probes are used to capture low EMI radiation signals that cannot be sense by conventional probes. In general, it has been found that the introduction of the inductor–capacitor (LC) resonant circuits and active amplifier circuits can significantly improve the detection sensitivity of the probes [5], [6], [7], [8], [9]. Multicomponent probes [18], [19], [20], which could measure multiple field components simultaneously and thus save measurement time, are also currently a popular research topic. However, there is no existing research on high-sensitivity, multicomponent probes. From an application perspective, there is much value to be had from the development of a multicomponent resonant probe.