On-Chip Integration of Orthogonal Subsystems Enabled by Broadband Twist at 220–325 GHz
Mohammad Mehrabi Gohari, Oleksandr Glubokov, Suxian Yu, Joachim Oberhammer
Abstract
In this article, we report for the first time on a low-loss compact platform that enables the integration of H-and E-plane rectangular waveguide subsystems enabled by 90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> polarization rotation of rectangular waveguide sections on a silicon-micromachined chip. The proposed platform offers unprecedented design flexibility for a 2.5D fabrication technology such as silicon micromachining, since orthogonal waveguide device sections with full design freedom in H-plane geometries can be cofabricated with sections with full design freedom in E-plane geometries, enabled by novel, integrated waveguide twists optimized for 2.5D fabrication. The platform is developed for use in broadband millimeter-and submillimeter-wave waveguide circuits and prototypes are implemented in the 220–325-GHz band. A prototype chip demonstrating the platform, implemented by bonding three stacked silicon chips, is fabricated. The measured results of the twist prototype exhibit a very low insertion loss of less than 0.2 dB and a return loss of 20 dB or better in most of the 220–325-GHz band. An integrated eighth-degree lowpass waveguide filter with axial ports having a cut-off frequency of 280 GHz is codesigned with the twist transition and fabricated on the platform to demonstrate its application. The filter shows 0.4-dB measured insertion loss and has a measured return loss in the passband of better than 14 dB.