Cross-line characterization for capacitive cross coupling in differential millimeter-wave CMOS amplifiers

An electrically symmetric cross-line and its characterization are proposed for capacitive cross coupling in differential amplifiers. The characterization of the device is done using two structures. L-2L method is applied to achieve virtual-thru connection of Ground-Signal-Signal- Ground (GSSG) pads and fixtures used in cross-line characterization structures. Pad parasitics are modeled with Tmodel which provides more accurate results than Π-model. Characterization of cross-line is done using one structure and verified with the other. Comparisons show well aggrement in terms of four-port S-parameter responses up to 67 GHz.