De-Embedding Method for Accurate Electromagnetic Analysis of Differential Circuits with Discontinuities

Phased array transceivers at 300 GHz enable high directivity and compact system designs for 6 G communication. To meet miniaturization requirements, power matching circuits, such as transformers and transmission-line matching circuits, must be carefully designed. However, discontinuities in cross-sectional structures between components, such as MOSFETs with ground planes and transformer matching circuits without ground planes, cause boundary mismatches that degrade electromagnetic (EM) analysis accuracy. This paper proposes a four-port de-embedding method that considers discontinuities in both odd mode and even mode to improve divided EM analysis in differential circuits. The method is validated through the design of a two-stage differential amplifier, where it reduces the odd mode gain $S_{0021}$ error at 125 GHz from 0.72 dB to 0.24 dB. This method enables efficient EM analysis for large-scale layouts, such as 300 GHz phased array transceivers, without full EM analysis. It provides an accurate and computationally efficient solution for high-frequency circuit design.