Radiated Emission from Superconducting Coplanar Waveguide Transmission Lines

Radiation from superconducting transmission lines is an undesirable phenomenon in a superconducting circuit due to the degradation of signal integrity. This reduces the performance of the circuit. While much analysis has been performed on radiated emission in normal circuits, no study has been conducted on superconducting circuits, which are recognized as a new generation of electronic devices. In this article, the radiated emission from superconducting coplanar waveguide (SCPW) transmission lines is investigated. To this end, the current density distribution in the SCPW cross section is required. A procedure is presented in this article through which the current in the ground plane is related to that in the superconducting strip. This is based on the conformal mapping approach. Therefore, by using the current in the strip available in our recently published article, the current in the ground plane and subsequently the electromagnetic radiation from the SCPW can be obtained. The radiation from the SCPW is examined at different temperatures as well as different film thicknesses and different SCPW gaps. Results show that as the temperature increases, the SCPW radiates a lower amount of power. The same behavior is seen for decreasing the SCPW gap. Furthermore, our study reveals that the SCPW with a thinner film radiates a lower amount of power.