Simulating the radiation loss of superconducting submillimeter wave filters and transmission lines using Sonnet EM

Abstract

Superconducting resonators and transmission lines are fundamental building blocks of integrated circuits for millimeter-submillimeter astronomy. Accurate simulation of radiation loss from the circuit is crucial for the design of these circuits because radiation loss increases with frequency, and can thereby deteriorate the system performance. Here we show a stratification for a 2.5-dimensional method-of-moment simulator Sonnet EM that enables accurate simulations of the radiative resonant behavior of submillimeter-wave coplanar resonators and straight coplanar waveguides (CPWs). The Sonnet simulation agrees well with the measurement of the transmission through a coplanar resonant filter at 374.6 GHz. Our Sonnet stratification utilizes artificial lossy layers below the lossless substrate to absorb the radiation, and we use co-calibrated internal ports for de-embedding. With this type of stratification, Sonnet can be used to model superconducting millimeter-submillimeter wave circuits even when radiation loss is a potential concern.

Development of Double Flare Angle bowtie slot Antenna for Multichroic CMB Polarization Detectors

“…Both antenna's ground plane and microstrip are made of Niobium, which exhibits kinetic inductance when in a superconducting state. For accurate 3D simulations of the superconducting antenna, CST is calibrated to align with Sonnet [24] -despite its primary focus on planar structures, a renowned software for its high accuracy in simulating high-frequency superconducting circuits Fine-tuning involves the microstrip width (msW ), and the stub's radius (stubR) and angle (stubA) to obtain the optimized S 11 as in Fig. 3b.…”