Substrate Integrated Waveguide Filters in Glass Interposer for mmWave Applications

This letter presents the first demonstration of substrate integrated waveguide (SIW) filters in glass interposers for $D$ -band (110–170 GHz). The material stack-up consists of 100- $\mu \text{m}$ -thick Asahi Glass Company (AGC) ENA1 glass with 15- $\mu \text{m}$ -thick Ajinomoto Build-up Films (ABF GL102) laminated on both sides. To demonstrate different frequency responses, cavities with two different shapes (square and rectangle) are used to design the filters. The cavities are fed using center coupled microstrip lines. Semi-additive process (SAP) is used to fabricate the filters. The diameter and pitch of the via side wall are designed to be 70 and $170 ~\mu \text{m}$ , respectively. The measured results are in excellent agreement with the simulation models. At ~130 GHz, first-, second-, and third-order square SIW filters show 1.54-, 2.7-, and 4.2-dB insertion loss, respectively. The relative bandwidth for the square filters is 12.8%, 9%, and 8.8%, respectively. The first- and second-order rectangular SIW filters show 1.65- and 2.85-dB insertion loss, respectively, and the relative bandwidth for these filters is 9.5% and 9%, respectively.