A New Differential Magnetic Probe With Out-of-Phase Balun and Differential Loops

In this letter, a new differential magnetic field probe with high sensitivity is presented. The differential magnetic probe includes a 180° out-of-phase balun, a pair of differential detection loops, and an output port with a 50 Ω impedance match. Unlike conventional magnetic probes with a single detection loop, a pair of differential detection loops is used to measure double magnetic-field components. Moreover, a 180° out-of-phase balun is utilized to process the differential-mode signals from these differential detection loops, which can make these probes directly connected to the oscilloscope and no longer rely on vector network analyzers. Finally, the differential magnetic probe is designed, simulated, and measured to verify the design effectiveness, and a near-field scanning system is used to characterize the developed probe. Measured results reveal that the designed differential magnetic probe not only can measure more magnetic-field energy, but also directly connect to the oscilloscope due to its own differential mode operation function in the out-of-phase balun. Therefore, the probe is very suitable for actual interference source location testing.

I. Introduction

In recent years, with the rapid development of communication systems [Baudry 2007, Dubois 2008, Zhang 2013, Huang 2017, Shen 2017, Yan 2017], integrated circuits (ICs) are developing toward high-frequency, high-density, and small size, which inevitably introduces many electromagnetic interference (EMI) problems.