Effects Degrading Accuracy of CPW mTRL Calibration at W Band

On-wafer measurements of a Device Under Test (DUT) can yield accurate results only if the properties of the measurement environment are well defined and unwanted effects can be removed from the data. This is commonly achieved through a calibration process using a set of different calibration elements. However, various effects may degrade accuracy of this calibration, particularly at higher frequencies. This paper deals with the case of coplanar waveguide (CPW) lines and the multiline Thru Reflect Line (mTRL) method and discusses two of such issues, the influence of CPW ground width and of prober geometry.