Ungrounded Coplanar Waveguide Based Straight Line Methods for Broadband and Continuous Dielectric Characterization of Microwave Substrates

Abstract

This work presents a novel method for fast characterization of broadband and continuous dielectric properties of microwave substrates based on an ungrounded coplanar waveguide (UGCPW) structure containing two simple straight lines. The proposed method could, to some extent, alleviate the derivation error due to connector soldering and device fabrication. To verify this point, theoretical analysis and result comparisons are carried out. By considering both the conductor loss and radiation loss, the dielectric loss tangent can be retrieved with a high precision. The deviation of the measured dielectric constant and dielectric loss tangent are found to be within 0.03 (0.68%, 4.37 vs 4.40) and 0.0013 (6.5%, 0.0213 vs 0.02), respectively, in the range from 12 to 20 GHz, which is more accurate than the results reported in the literature, all while the proposed extraction approach is simpler than other methods such as the wave cascading matrix (WCM) algorithm. Due to the UGCPW configuration, this method is suitable for property evaluation of emerging synthesized dielectric materials, as a single round of electroplating process is required for device design, which can eliminate possible consistency error in conductor thickness and roughness caused by multiple electroplating process.