In situ 1-Port Cryogenic Vacuum Device Calibration

We present a method for a 1-port vacuum cryogenic in-situ calibration of a Vector Network Analyzer (VNA) using Commercial Off The Shelf (COTS) RF latching electro-mechanical switches. This procedure is being developed for use in a closed-cycle cryogenic test bench to measure the reflection coefficient of a single port connectorized Device Under Test (DUT) which is loaded onto a cold plate alongside calibration standards. The RF switch allows for the calibration and device measurement to be carried out in a single thermal cycle as opposed to a minimum of 4 cycles, which is required for industry standard Open-Short-Load (OSL) device calibration. This test procedure has been carried out on an arbitrary DUT at ~ 3K temperature, over a 6 GHz bandwidth. However, the goal is to develop a setup and procedure for measuring the frequency and temperature dependent complex impedance of superconducting devices such as Hot Electron Bolometer (HEB) mixers, which are used for down converting the signal in the IF chain of astronomy instruments. Characterization of superconducting devices while they are at their operating temperature is challenging using traditional calibration methods. This COTS alternative is less expensive and more efficient in terms of thermal cycles and set up.