Influence of Material and Geometry of the Dielectric on the Characteristics of the Tank Circuit Resonators for High-Tc RF-SQUID-Based System

Characteristics of a lumped element L-C tank circuit resonator of high-Tc rf-SQUIDs, which plays an important role in the device operation, have been experimentally investigated, according to the corresponding simulations obtained by COMSOL Multiphysics. We experimentally investigated the characteristics of the resonators by measuring their scattering parameters, as well as evaluating the rf-SQUID signal. Our SQUIDs are made of sputtered YBCO thin films with 3-mm-diameter washer areas. Different configurations of the resonator are investigated, and it is observed that, by increasing the thickness of the dielectric in a specific range, the reflection coefficient (S
₁₁
) increases. For the experimental verifications, we constructed resonators with different dielectric thicknesses and different configurations. The resonators are made of a dielectric board with a hole in its middle to hold the inductors for close coupling to the SQUID mounted on the backside. An increase in the thickness of the dielectric board confines the RF field distribution close to the SQUID, while also making further distance between the contact pads and the SQUID reducing their parasitic effects on the device signal. This is observed to improve the stability of the operating point of the SQUIDs, while also reducing the noise for measured frequency range of 0.1 to 100 Hz.