Vertically Stacked Double-Layer Substrate-Integrated Nonradiative Dielectric Waveguides for THz Applications

Nonradiative dielectric (NRD) waveguides have been studied and exploited to address the leakage issue in dielectric waveguides caused by discontinuities. With the proliferation of substrate integration technologies, planarized substrate-integrated NRD (SINRD) waveguides have emerged, which are found to be more suitable for terahertz (THz) integrated circuits and systems. However, in the making of SINRD waveguides, a process-related conflict may arise between the air-hole perforation of a hosting substrate and its essential residual metallic coating on the perforated region. In this work, a solution to this problem using a multilayer topology is formulated, where the size difference between entrance and exit of the drilled air holes is reduced. Moreover, the exposed metallic coating over both sides of the multilayer SINRD waveguide is well preserved. Therefore, a dense air-hole perforation is allowed when needed. In this letter, a vertically stacked double-layer guiding structure is presented, studied, and experimentally verified, which demonstrates the interesting features of this technique.