UGCPW Structure-Based Embedded Resonator with High Quality Factor for Microwave Substrate Characterization

Longzhu Cai

doi:10.3390/electronics10020113

Abstract

In this paper, an ungrounded coplanar waveguide-based embedded resonator method for microwave substrate characterization was presented. The effective dielectric constant of the structure and the dielectric constant of microwave substrates can be calculated by the measured resonant frequency. The measured insertion losses at resonant frequencies and the 3 dB bandwidth can be used to determine the loaded and unloaded quality factors, including the dielectric quality factor which is related to dielectric loss tangent. The radiation loss and the extra length due to fringing effect caused by the open-end structure were taken into account to improve the extraction accuracy. The experimental unloaded quality factor of the proposed resonator at resonance order 1 reaches 211.3. The extracted dielectric constant and dielectric loss tangent of Taconic TLY at resonance order 1 are, respectively, 2.218 and 9.286×10−4, which are only 0.018 (relatively 0.82%) and 0.286×10−4 (relatively 3.18%) deviations from the datasheet values, respectively. The proposed resonator method is especially suitable for dielectric characterization of newly developed materials with the difficulty of realizing metal via holes, in which case substrate-integrated-waveguide (SIW) resonator methods are not applicable. When comparing with microstrip resonator methods, the proposed method is of higher quality factor, and it is more reliable and economical as well.

Highlights

Printed circuit board (PCB) technology is widely applied in microwave frequency applications, and accurate dielectric information of used PCB substrates is essential for the development of microwave devices, as the performances of these devices are greatly affected by the dielectric properties of PCB substrates [1,2]
In order to evaluate the proposed method, we designed an embedded resonator with high quality factor based on ungrounded coplanar waveguide, where the substrate Taconic TLY is applied, and this substrate is considered to have the minimum dielectric loss tangent value
Each resonator was fed by two Subminiature version A (SMA) connectors, and the frequency response of the two-port ungrounded coplanar waveguide (UGCPW) resonator was measured using a Vector Network Analyzer (VNA), whose model is Agilent Technologies N5230A with a frequency range of 10 MHz to 20 GHz

Summary

Introduction

Printed circuit board (PCB) technology is widely applied in microwave frequency applications, and accurate dielectric information of used PCB substrates is essential for the development of microwave devices, as the performances of these devices are greatly affected by the dielectric properties of PCB substrates [1,2]. Various methods and techniques for extracting the dielectric characterization of microwave substrates have emerged in the literature These measurement techniques can be divided into two main categories: transmission/reflection technique and resonator technique. Among the reported resonator techniques, the resonator method based on substrateintegrated-waveguide (SIW) structure is widely used, as it possesses the merits of high quality factor, low cost, and ease of fabrication [6,9,10,11,12]. SIW structure is a type of fully shielded transmission line which is compatible with standard PCB technology, while SIW-based resonator method is not appropriate to extract the dielectric properties of these newly developed materials due to processing issues.

The Proposed Resonator Method with Theoretical Analysis

The Calculation of Substrate Dielectric Loss Tangent tanδ

Experimental Results and Analysis

41. Conclusions

Conclusions