Air-Filled SIWs Using Laminate Dielectrics on Glass Substrate for D-Band Applications

This article presents the first demonstration of Astra-based air-filled Substrate Integrated Waveguides (SIWs) in D-band (110 to 170 GHz). The material stack-up consists of two 63.5~\mu \text{m} thick Astra MT77 layers laminated together by 5~\mu \text{m} thick Ajinomoto Buildup Film (ABF) GL102 dry film. The top metal layer is patterned on the first Astra layer using a Semi-additive process (SAP) whereas the bottom metal layer is supported on a 200~\mu \text{m} thick laminated glass. To demonstrate the advantage of the proposed approach, solid SIWs were also designed using the same material stack up and fabrication process. The proposed SIWs were simulated using Ansys High-Frequency Structure Simulation (HFSS). Grounded Coplanar Waveguide (GCPW) to SIW transitions were added to probe the designed structures using Cascade infinity probes. Two-tier calibration was used to measure the designed SIWs. First, LRRM calibration was used to move the reference plane to the edge of the probe tips. These measurements included the effects of GCPW to SIW transitions. Then, TRL calibration was performed to de-embed the response of the designed SIWs. For 4.5 mm long air-filled SIW, the measured insertion loss varies from 0.17 to 0.98 dB with an average of 0.6 dB. For 5 mm long solid SIW, the measured insertion loss varies from 1 to 2.5 dB with an average of 1.7 dB. The measured per unit insertion loss (dB/mm) for solid and air-filled SIW is 0.34 and 0.13 dB/mm, respectively. The measured results are in good agreement with the simulation models. The performance of the proposed SIWs has been compared with other state of the art materials.