A Low-Loss High-Frequency Transmission Line Structure for Ceramic Substrate

An increase in signal frequency will lead to high transmission loss, the paper presents a novel high-frequency transmission line (HFTL) with low loss on the ceramic substrate. Based on the grounded coplanar waveguide (GCPW), the HFTL adds a parallel conductor under the center conductor strip, forming a two-layer structure interconnected by vias. It lowers the conductor's surface current density and surface impedance, significantly reducing losses. The transmission line structure is easy to integrate with RLC components and can be fabricated using existing HTCC processes. The characteristic impedance of the HFTL is derived to facilitate impedance matching, and the influence of geometric parameters on the characteristic impedance are also studied. The results from simulation and test show that the HFTL can achieve a 105.4% increase in bandwidth when the 3 dB bandwidth of GCPW is 31.2 GHz, and a 28.7% reduction in loss within the pass band compared to GCPW.