RF Switch Considerations for Automatic Test Equipment Making Vector Measurements

Modern Radio Frequency (RF) Automatic Test Stations employ switching to connect a multitude of measuring and stimulus instruments to the Unit Under Test (UUT). These switches add efficiency at the potential risk of increased measurement error due to switch repeatability. Switch match repeatability, a little-known performance characteristic, can add significant, unanticipated error to vector measurements. Electromechanical RF switches add to the overall measurement uncertainty due to their repeatability performance. In this paper, switch match repeatability is reviewed along with measurement data shown. Methods to address this repeatability issue is presented including process step ordering, in situ calibrations, and time domain techniques.