The Impact of On-Wafer Calibration Method on the Measured Results of Coplanar Waveguide Circuits

Abstract

This paper compares four commonly used on-wafer calibration methods including multiline thru-reflect-line (TRL), line-reflect-reflect-match, line-reflect-match, and short-open-load- thru, for three diverse coplanar waveguide (CPW) circuits. The magnitudes and phases of S 11 and S 21 of the CPW circuits are compared to quantify how the specific calibration method influences measured scattering parameters. Special care is taken to ensure that the measured scattering parameters are normalized to the same reference impedance and reference plane for accurate comparison. The measured results are compared with full-wave simulations to provide additional assessment of accuracy. A method to de-embed the discontinuity of the CPW at the probe tip and the CPW of the test structures is presented. The effect of probe-to-device-under-test discontinuity is effectively modeled by one- or two- section of shunt capacitor and series inductor. The results show that the multiline TRL calibration method provides the highest transmission coefficient repeatability on not well-matched circuits and highest accuracy on the three circuits in this paper up to 40 GHz.