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IEEE Sensors Journal

Field Analysis for Superconducting Grounded Coplanar Waveguide Transmission Lines

Mohammad Hossein Amini, Ayaz Ghorbani, Abdolali Abdipour

Published Feb 14, 2024• 3 citations
Publisher

Abstract

Several studies have been conducted on field solutions of superconducting planar transmission lines; however, no study has been performed on superconducting grounded coplanar waveguides (GCPWs) which is a promising element, from the viewpoint of immunity to electromagnetic interference, in superconducting circuits. The purpose of this article is to analyze the superconducting GCPW to achieve the electrical parameters of the transmission line. In this regard, first, the magnetic field within the superconducting film is described through a 2-D wave equation. By introducing the proper boundary conditions acquired through the field solution of the structure, the proposed wave equation is solved and the magnetic field is obtained. Accordingly, the current distribution and the inductance of the line are evaluated which are of interest in the superconducting community. Compared with conventional coplanar waveguide (CPW), the GCPW structure experiences less current density at the edges. Hence, it supports a much more sustainable current. Further, it is shown that the GCPW exhibits less kinetic inductance during data transmission.

DOI
10.1109/jsen.2024.3358009

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We present calculations of the properties of the first coplanar waveguide transmission line resonators patterned from high-Tc superconducting films at 8.8 and 6.5 GHz [1, 2]. Based on field calculations of the corresponding coplanar waveguides with infinite conductivity, performed by a partial wave synthesis (mode-matching method) [3], we obtain the superconductor losses subsequently using London's theory. Due to the high conductivity of the superconductive material both the electric and magnetic fields within the superconductor may be assumed to be parallel to the surface planes. For the small conductor thickness the tangential electrical field on each surface plane depends on the tangential magnetic fields on both surface planes. This relation is modelled by the surface impedance matrix Zs. The substrate losses are treated in the field calculations and are also taken into account. The calculated overall Q values are compared with the measured values and it has to be pointed out, that the superconducting thin films are due to the available material datas of the YBaCuO superconductor and the used substrate materials of a very good quality, because they reach nearly their upper limit given by the known material datas.
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