Analytical Expressions for Antenna On-Chip Efficiency at mm-Wave and Sub-THz Frequencies

This paper aims to propose a systematic analysis tool for computing the efficiency of Antenna on-Chip (AoC) while prior knowledge on the material stack and current distribution is available. The aim of this work is twofold. First, the developed analytical expressions may enable AoC designers to evaluate antenna efficiency and effectively compare design options during the predesign phase without relying extensively on numerous full-wave simulations. Second, the proposed tool allows one to quantify the impact of each loss source in the AoC design: surface waves and material ohmic/dielectric losses. Expressions for AoC efficiency are derived in this paper for two widely used antenna types -patch and dipole antennas with current distributions following a truncated sine pattern- but the methodology is generalizable to any current distribution and lossy material stack. The model is validated with full-wave simulation for both a shielded and unshielded silicon chip stack with typical dimensions (i.e. with and without a metal plane shielding the antenna from the substrate) up to 350 GHz.