Dual Function Metasurface: mm-Wave Radiator and Gain Enhancement Surface for Antenna-on-Chip

With the advent of 6G, Antenna-on-Chip (AoC) is becoming more relevant than ever. However, due to the lossy nature of silicon (Si) in standard chip fabrication processes, these antennas suffer from poor gains and radiation efficiencies. An elegant solution is to incorporate an Artificial Magnetic Conductor (AMC) structure beneath the AoC to isolate the Si substrate. This solution works well for mm-Wave frequencies, however, the AMC is typically a large structure, as compared to the AoC, and is limited to a single function of isolating the Si substrate. Enhancing the functionality of the AMC can optimize the performance of such compact designs, where efficient use of space as well as integration of multiple functionalities is of paramount importance. Therefore, this work explores the potential of employing the AMC as a metasurface (MTS) antenna within the framework of AoC systems. The key focus of this work is to design a dual-functional MTS, which works as an AMC to enhance the gain and radiation efficiency of an AoC at one frequency, and as an independent radiator at another frequency. As a proof of concept, we have shown that an on-chip monopole antenna’s gain and radiation efficiency is enhanced by 5.5 dBi and 20% respectively at 79 GHz through an integrated AMC structure. It is shown that this AMC can be optimized to radiate as an independent MTS antenna through Characteristic Mode Analysis (CMA) with a variety of radiation patterns for various modes. The fabricated prototype demonstrates one of these modes, where the MTS antenna shows a measured peak gain of 4.0 dBi at 94 GHz with a broad boresight radiation pattern.