A Technique to Improve Accuracy of S-Parameter Measurements of Coaxial Connectorized Devices at Cryogenic Temperatures

Recent developments in microwave-based quantum computing technologies have motivated the need for the development of new and improved cryogenic microwave devices packaged in coaxial connectorized technology, and for their performance to be accurately characterized through S-parameter measurements made at cryogenic operating temperatures. To facilitate such accurate characterization, S-parameter measurement systems utilizing in-situ calibration techniques at cryogenic temperatures have been developed. This required use of cryogenic RF switches inside cryostats to select between calibration standards and devices to perform calibration and measurement in a single cooling cycle. However, this caused significant measurement errors due to non-identical signal paths due to differences in switch paths limiting the measurement accuracy of such measurement systems. In this work, a new technique is proposed to significantly improve the accuracy of cryogenic S-parameter measurements of coaxial connectorized devices by accounting for non-ideal effects in such switch-based cryogenic calibration units. The technique is demonstrated at room temperature (296 K) and cryogenic temperature (1.5 K) through S-parameter measurements of coaxial devices with up to two ports.