Ultra-Low-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\times $ reduction in the insertion loss compared to those of low-loss organic-based SIWs at the 28-GHz frequency band.