TSD versus TRL calibration and applications to beam impedance measurements

At FNAL, bench measurements of the longitudinal impedance of various beam line components have been performed using stretched-wire methods. Two network analyzer (NWA) calibration procedures have been implemented and tested in an effort to improve the accuracy of these measurements. The methods, Thru-Short-Delay (TSD) and Thru-Reffect-Line (TRL), each named for their respective calibration standards, are mathematical procedures to extract the S-parameters of a test device from NWA measurements which include the effects of measurement fixtures. The implementation of both these methods has been tested and compared on computer models of the test device and measurement fixtures, whose S-parameters can be exactly computed. The TRL method has been found to be more general and less susceptible to measurement errors. Application of the TRL method to actual stretched-wire impedance measurements has yielded accurate results for a high-Q resonator test device