Ultralow-Loss Substrate-Integrated Waveguides in Glass-Based Substrates for Millimeter-Wave Applications

This letter, for the first time, presents low-loss substrate-integrated waveguides (SIWs) in fused silica and borosilicate glass and a comparison of their performance with various organic-based low-loss substrates for millimeter-wave applications. Utilizing ring resonators designed for frequencies in the 5G New Radio (NR) n257 band (26.5-29.5 GHz), this letter begins with the determination of the dielectric constant of fused silica to model SIWs. This letter also introduces the designs of SIWs that are fed by conductor-backed coplanar waveguides and discusses the fabrication and measurement results with deembedding analysis. In addition to the excellent correlation between simulations and measurements, the characterization results show more than 2× reduction in the insertion loss compared to those of low-loss organic-based SIWs at the 28-GHz frequency band.