Cryogenic test fixture for two-port calibration at 4.2 K and above

A test fixture for full 2-port-calibrated, error-corrected measurements at cryogenic temperatures has been built and tested. Through-reflect-line (TRL) calibrations have been demonstrated at frequencies up to 4.5 GHz and at temperatures as low as 4.2 K. Calibrated measurements of both passive filters and active devices, amplifiers have been demonstrated. The calibration standards are collocated with the device under test. The calibration and device measurement can be accomplished in a single cooldown. Mechanical switches at the cold stage are used to switch in the TRL standards and the device under test. Measurements of the repeatability of the calibration will be discussed. The amplitude accuracy is approximately ± 0.03 dB.