A Dual-Component Electric Probe Embedded With a 0°/180° Hybrid Coupler for Near-Field Scanning

In this article, a Ka -band dual-component electric probe is proposed in low temperature co-fired ceramic for near-field scanning, which consists of a sensing part of two symmetric L-shaped strips and a 0°/180° hybrid coupler. The responses to the tangential and normal electric components are outputted to the difference and sum ports without post-processing, to avoid the errors due to phase measurements at high frequencies. A grounded coplanar waveguide (GCPW) is used as a standard kit. Equations are derived carefully to take the imperfect terminations into account. To further improve the sensitivity and measurement efficiency, a low noise amplifier (LNA) and an absorptive single pole double throw (SPDT) switch are integrated with the probe. Simulated and measured results indicate that the probe can characterize the near electric field distributions within the band of 27.2–30 GHz, and the sensitivity of the active probe prototype is improved by 17–18 dB at 28 GHz when compared with the passive one. The passive probe prototype is utilized to scan the near electric field of an integrated transmitting front-end module at 28.5 GHz.

I. Introduction

As both operating frequencies and integration densities increase, the electromagnetic (EM) compatibility of multi-functional and compact high-speed electronic systems becomes more and more important [1], [2], [3]. For the analysis and design of electromagnetic compatibility, the technique of near-field scanning is usually used as an effective way of diagnosing electromagnetic interference (EMI) sources and predicting far-field radiation for high-speed electronic systems [4], [5]. Near-field electromagnetic probes are key components for near-field scanning systems [6], [7], whose performance determines the accuracy and efficiency of near-field scanning.