Design of an Ultrawideband Air-Filled Grounded Coplanar Waveguide for Near-Field Probe Calibration

This article proposes a novel air-filled grounded coplanar waveguide (AGCPW) structure for calibrating near-field probes. The structure uses a grounded coplanar waveguide (GCPW) with a cutout ground as the connector taper part to achieve a smoother impedance transition. Additionally, an AGCPW capable of exciting high-purity TEM fields serves as the probe calibration region. The designed cutout ground structure ensures good impedance control for the AGCPW, while a dual-row staggered via array suppresses high-order modes and resonance in the frequency range of 9 kHz–40 GHz. Subsequently, the field characteristics above the AGCPW structure are analyzed, revealing an undesired electric-field rejection ratio (UERR) and an undesired magnetic-field rejection ratio (UMRR) of 36 and 26.5 dB. Applying AGCPW to calibrate an H-field probe with a four-layer PCB structure, the results show that, compared to using other structures, AGCPW yields a smoother and more stable probe calibration factor (CF) and more accurate electric-field rejection ratio (ERR) results.

I. Introduction

As high-speed integrated circuits advance, the emergence of electromagnetic interference (EMI) has become a prominent concern limiting the performance of electronic devices. Near-field probes, recognized as effective tools for electromagnetic emission detection, are employed for the precise localization and analysis of EMI sources within integrated circuits [1], [2]. Another application involves using near-field probes to acquire near-field electric and magnetic field data from integrated circuits or boards, facilitating the establishment of radiation emission source models [3], [4], [5]. These models prove valuable for EMI prediction [6] and far-field estimation [7], [8].