Accurate Cryogenic S-Parameter Measurement Technique Using Room-temperature SOLT Calibration and 2X-thru De-embedding

This work presents a new cryogenic S-parameter measurement technique that performs SOLT calibration at room temperature to overcome the challenges in conventional cryostat calibration. A 2X-thru de-embedding is subsequently applied to shift the reference plane to the device inside the cryostat, eliminating the need for multiple cooldown cycles or switch networks containing numerous signal paths. With only a minimal number of paths, the proposed approach effectively reduces mismatch-related uncertainty. In addition, calibration kits are not placed inside the cryostat, removing concerns of the parasitic characteristics at low temperatures and avoiding degradation caused by repeated cooling. Measurements at 300 K and 7 K show that the de-embedded S-parameters of a LNA agree with its intrinsic data within a maximum deviation of 0.17 dB across 5 GHz. These results correspond to a relative error better than −34 dB (<2%), demonstrating the accuracy and reliability of the proposed method for cryogenic microwave characterization.