Designing Optimal Surface Currents for Efficient On-Chip mm-Wave Radiators With Active Circuitry

Kaushik Sengupta and Ali Hajimiri

Integrated antennas have become the attractive solution as the electromagnetic (EM) interface for mm-Wave and terahertz ICs. However, on-chip antennas lying at the interface between two different dielectrics (such as air and substrate) can channel most of its power into multiple nonradiative surface- wave modes, reducing efficiency drastically. In this paper, we consider the following problem: given a dielectric substrate, what is the theoretical optimal 2-D surface-current configuration that collectively suppresses surface waves and maximizes radiation efficiency with the desirable radiation pattern? This paper also discusses demonstrative examples of a circuit-EM codesign approach to realize the approximation of such current configurations. Measurement results of radiating arrays in CMOS at mm-Wave frequencies (250–300 GHz) are presented and compared with theoretical predictions.