A 94-GHz On-Chip Metasurface Antenna Through Characteristic Mode Analysis

Antenna-on-Chip (AoC) technology has been increasingly recognized for its multiple advantages, particularly for applications requiring miniaturization and integration. Typically, AoC uses metasurface (MTS) primarily as a reflection component. However, this work presents a compact AoC using the MTS as a radiator. The MTS consists of four strips embedded between two thin silicon dioxide layers. Although individually challenging to isolate, the nine closely spaced modes identified through Characteristic Mode Analysis (CMA) enhance the antenna's versatility, enabling diverse radiation patterns through adjustments in feed type and position. For example, employing a single microstrip yields a maximum gain of 2.5 dB at around 94.55 GHz, while a double microstrip configuration achieves a gain of -0.5 dB at 94.5 GHz with diverse radiation patterns. We use proximity coupling to avoid the modifications to the ground plane, which works as a shield from the lossy silicon (Si).