An Ultrawideband Electric Probe Based on U-Shaped Structure for Near-Field Measurement From 9 kHz to 40 GHz

A normal electric probe with miniature size and ultrawideband characteristic is proposed in this letter. The probe is fabricated in a four-layer printed circuit board (PCB) with a high-performance dielectric RO4003C and RO4450. The minimum width of the probe is 4 mm, and the length of probe is 48 mm. The probe can be used in compact and complex space like PCB and integrated circuit. The designs of U-shaped structure and tuning element matrix are used to expand the work band and optimize the impedance of signal via. The work band of probe can cover from 9 kHz to 40 GHz. It can improve the test efficiency in ultrawideband application compared with series probe. The sensitivity of the probe is higher about 12 dB than commercial probe above 1 GHz, and the spatial resolution is 1 mm when the height of probe is 0.3 mm. The proposed probe is verified with simulation in full-wave tool and measurement.

I. Introduction

The noise location and electromagnetic interference estimation have become more attractive for printed circuit board (PCB) designers and electromagnetic compatibility engineers [1]. The interest frequencies of antenna and probe range from 9 kHz to 40 GHz [2], [3]. Recently, the research into near field–far field conversion has been paid more attention. The far-field distribution can be calculated based on near-field scanning [4], [5]. The spectral peak point and location of noise source can be quickly detected by a wideband probe. The narrowband probes are not compatible with the modern millimeter-wave electric system.