A New Low Profile Differential Magnetic Probe With Enhanced Sensitivity

In this work, a new differential magnetic probe with a low profile and high sensitivity is showcased. First, a traditional U-shaped differential loop as a driving component is developed to test the magnetic field component. Second, two pairs of grounded U-shaped loops as parasitic components are placed on both sides of the U-shaped loop to enhance detection sensitivity in this proposed probe. Owing to these grounded U-shaped loops being able to test more magnetic field energy, the proposed differential magnetic probe has a high sensitivity. In addition, unlike traditional parasitic loops placed on the inner layers of the probe, a pair of grounded U-shaped loops and these ground planes are arranged at the outer layers of the differential magnetic probe, which can effectively reduce the probe’s profile. Based on this clever design, the presented differential magnetic probe only requires a five-layer printed circuit board (PCB) for processing rather than a seven-layer PCB. As a result, the designed probe is etched, simulated, and tested to verify its effectiveness. A near-field scanning measurement system with a standard microstrip line is used to characterize the presented differential magnetic probe. Measured results reveal that the presented differential magnetic probe not only has a high sensitivity but also has a low profile.

I. Introduction

The near-field probe is a key component in a near-field scanning measurement system, which is often used to convert the electromagnetic signals it detects into electrical signals of the receivers [1], [2]. The performance of near-field probes directly determines the accuracy of the near-field measurement system during testing. As an electromagnetic sensor, near-field probes are widely used in material characteristic imaging [3], noise measurement from printed circuit boards (PCBs) [4], crack detection [5], and surface imaging [6]. Due to the small size and weak radiation of the test pieces in near-field measurement, current research on near-field probes mainly focuses on expanding the operation band, achieving multiple component measurement, suppressing undesired fields, and enhancing detection sensitivity.