Broadband Calibration of Long Lossy Microwave Transmission Lines at Cryogenic Temperatures Using Nichrome Films

A one-port method to calibrate the S-parameters of a long, lossy microwave transmission line in a cryogenic system is presented. This method exploits the relative temperature independence and frequency stability of NiCr (nichrome) thin films used as a known termination load. We have used the calibration on coaxial lines 1.5 meters long from 0.5 to 12 GHz and at temperatures down to 100 mK.