Anomalies in multiline-TRL-corrected measurements of short CPW lines

Microwave probes in on-wafer measurements contribute to a number of parasitic effects deteriorating the accuracy of multiline Thru Reflect Line (mTRL) calibrations. The accuracy of mTRL calibration is especially sensitive in Devices under Test (DUTs) of shorter line length. It has been demonstrated in previous experimental studies that the calibrated results are often only reliable as long as the length of the line is at least 2 mm. However, the reasons behind this phenomenon have not yet been clarified. Therefore, this paper reports on a systematic analysis of the dependency of the mTRL calibration accuracy on probe effects with a focus on coplanar waveguides (CPW) of shorter line length. For the first time, investigations with regard to the probe effects in shorter CPWs are presented.