Ultrawideband Differential Magnetic Near Field Probe With High Electric Field Suppression

In this paper, an ultrawideband differential magnetic near field probe with high electric field suppression is developed. A pair of differential loops, via fence and shielding vias below the loops are designed to reduce the electric field coupling. It is shown that the electric field suppression of the proposed magnetic-field probe is higher than 30 dB up to 12.9 GHz and 21 dB up to 14 GHz. Due to the differential loops and shielding vias, the proposed magnetic-field probe shows better electric field suppression and sensitivity performance, while maintaining similar spatial resolution. Two other probes with single loop for sensing and without shielding vias are prepared for comparison.

I. Introduction

The applications of high-speed integrated circuit (IC) are increasing rapidly nowadays. In this context, the electromagnetic interference (EMI) becomes an important issue to evaluate the performance of the IC. Near field scanning [1]–[5] is a popular and effective technique to detect the near field and evaluate the electromagnetic (EM) emission of an IC. A common method to map the near field of the surface of IC is standardized in [6], in which a probe is installed on a movable platform and detects the electromagnetic field along the surface spot by spot. A 2-D magnetic field distribution is usually extracted for further evaluation and diagnosis of EMI. For example, by detecting the magnetic field along a clock generator IC, the common-mode EMI current can be localized from one particular power to another particular ground pin, even though the IC contains many pairs of power and ground pins [7]. With a miniature magnetic field probe the cryptographic circuit can be targeted [8] in a cryptographic large-scale IC. Especially, magnetic field probe is applied [9] recently to evaluate the electromagnetic field shielding effectiveness of the metallic shielding materials in system-in-package device.