Precise microwave characterization of MgO substrates for HTS circuits with superconducting post dielectric resonator

TL;DR

This study employs a superconducting dielectric resonator to precisely measure the complex permittivity of MgO substrates at cryogenic temperatures, crucial for designing high-temperature superconductor microwave circuits.

Contribution

It introduces a novel measurement setup using a superconducting post dielectric resonator for accurate characterization of MgO substrates at cryogenic temperatures.

Findings

MgO substrates have an average relative permittivity of 9.63.

Loss tangent varies from 3.7×10⁻⁷ to 2×10⁻⁵ at 10.5 GHz.

Measurements are consistent across three manufacturing batches.

Abstract

Accurate data of complex permittivity of dielectric substrates are needed for efficient design of HTS microwave planar circuits. We have tested MgO substrates from three different manufacturing batches using a dielectric resonator with superconducting parts recently developed for precise microwave characterization of laminar dielectrics at cryogenic temperatures. The measurement fixture has been fabricated using a SrLaAlO3 post dielectric resonator with DyBa2Cu3O7 end plates and silver-plated copper sidewalls to achieve the resolution of loss tangent measurements of 2 {\times} 10-6. The tested MgO substrates exhibited the average relative permittivity of 9.63 and tan {\delta} from 3.7 {\times} 10-7 to 2 {\times} 10-5 at frequency of 10.5 GHz in the temperature range from 14 to 80 K.