Abstract
Sixth-generation cellular networks (6G) are expected to involve not only data communications but also sensing capabilities, enabling a wide range of applications. This paper proposes a novel Dual Functional Shared Aperture reconfigurable intelligent surface (RIS) design that enables the coexistence between radar sensing and millimeter wave (mm-wave) communication. Some RIS meta-elements integrate radio-frequency (RF)-feeds to support the transmission/reception of multiple-input multiple-output (MIMO) radar signals, permitting holographic beam focusing/forming in near/far fields without phase shifters. The designed Dual Functional RIS provides a synergy between communication and sensing modalities, particularly in scenarios where both far-field and near-field interactions play critical roles. Primarily, we emphasize far-field conditions and antenna-related aspects which serve as a foundational framework for future work considering that both communication and radar detection take place in the near field. We show adding an RF-feed to the meta-element incurs additional amplitude loss in the spectrum of interest. At the same time, increasing the number of radar antennas (i.e., elements with RF-feed) improves the radar angular accuracy.