A Miniature Multi-Component Probe for Near-Field Scanning

In this paper, an electromagnetic probe is proposed for the near-field scanning. Its detection section is made of a miniature loop-wire hybrid structure, which can measure H_x, H_y, and E_z simultaneously. It is optimized to achieve a wide working band from 0.1 to 15 GHz. The calibration and measurement error of the probe are discussed in detail. The probe is fabricated as a four-layer printed circuit board (PCB) with the RO4350B dielectric. A near-field scanning system with the manufactured probe is set up to test the near fields above a Z-type microstrip line and an inverted-F antenna. By comparing the measurement and simulation results, the accuracy of the proposed multi-component probe is verified. It greatly improves the near-field scanning efficiency compared to the traditional single-component probe.

I. Introduction

Near-field scanning technology has a long history in antenna measurement [1]. In comparison with the far-field measurement, it is more cost-effective and is preferred in radiation pattern prediction and antenna array diagnosis [2]. Recently, there is a great demand of the near-field scanning for the electromagnetic interference (EMI) diagnosis [3]. For the compact and high-speed electronic systems, passive components and traces on printed circuit boards (PCBs) become unwanted antennas [4]. Their near-field coupling and far-field radiation tend to be more serious. Planar near-field scanning technology becomes an effective method to locate radiation sources and predict the far-field radiation [5].