Collaborative Research: NeTS: Medium: Scalable Metasurface Array for mmWave Communication and Sensing

毫米波（mmWave）技术在5G通信和雷达传感应用中都展示了令人兴奋的前景。然而，毫米波有限的覆盖范围仍然是其实际可用性的主要挑战。该项目的目标是利用毫米波通信/传感系统和可打印材料/电子产品的协同创新来克服毫米波信号的内在局限性。PI团队正在探索超大和超宽带超表面阵列的设计，以扩大毫米波覆盖范围并优化相关的性能权衡。该项目的成果可能会为毫米波网络的设计提供信息，影响超5g （B5G）标准化，并推进许多B5G应用，特别是在具有挑战性的毫米波车载网络和汽车传感领域。该项目还可以以极低的成本提高5G毫米波的覆盖范围和可靠性，从而产生巨大的经济影响。该项目的影响将进一步扩大，通过参与不同群体的学生研究人员和工业合作伙伴，并通过传播开源实验硬件和先进毫米波设备的低成本制造工作流程。提出的研究结合了新的可印刷材料/电子器件，以推进毫米波超表面反射器领域。虽然有源和无源超表面在电磁研究中得到了广泛的探索，但它们在尺寸和带宽方面受到限制，并且大多用于单链路。有源超表面需要电源、高频元件、高精度衬底和制造工艺，以及与现有器件协调的单独控制通道，因此成本高，复杂性大。另一方面，由于缺乏可重构性，被动超表面反射器通常被认为是劣质的，只适用于静态场景。此外，目前最先进的主动/被动超表面仅限于厘米级，但实际部署需要米级（数百波长）的尺寸，这带来了严重的挑战，例如由于近场效应和频率选择性导致的严重光束畸变。为了应对这些挑战，PI团队提出了3个研究重点：(1)设计新的波束合成模型以实现超大型超表面，以及逐步重新配置无源超表面阵列（PMA）的新技术，从而扩大角度覆盖范围，波束形成增益，支持移动性，并避免附近基站之间的干扰；(2)设计利用PMA作为无源“编码器”的新机制，以解决毫米波传感中覆盖-分辨率-维度的权衡；(3)探索基于石墨烯的超表面结构，以扩展毫米波联合通信和传感，超越传统射频硬件的带宽限制。拟议的研究将导致各种社区工具集和可重复的制造工作流程，通过3D打印或模具压印创建低成本的毫米波元表面。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Millimeter-wave (mmWave) technologies are demonstrating exciting prospects in both 5G communications and radar sensing applications. However, the limited coverage of mmWave remains a major challenge to its usability in practice. The objective of this project is to harness synergistic innovations in mmWave communication/sensing systems and printable materials/electronics to overcome the intrinsic limitations of mmWave signals. The PI team explores the design of an ultra-large and ultra-wideband metasurface array to expand mmWave coverage and optimize the associated performance tradeoffs. The project outcome will likely inform the design of mmWave networks, influence the beyond-5G (B5G) standardization, and advance many B5G applications, especially in the challenging mmWave vehicular networking and automotive sensing domains. The project can also generate substantial economic impacts by boosting the 5G mmWave coverage and reliability at signifcantly low cost. The project impact will be further extended by engaging a diverse group of student researchers and industrial partners, and by disseminating open-source experimental hardware and low-cost fabrication workflows for advanced mmWave devices. The proposed research incorporates novel printable materials/electronics to advance the field of mmWave metasurface reflectors. Although active and passive metasurfaces have been extensively explored in electromagnetic research, they are limited in size, bandwidth, and mostly employed for a single link. Active metasurfaces bear a high cost and complexity as they need power sources, high-frequency components, high-precision substrate and fabrication processes, and a separate control channel to coordinate with existing devices. On the other hand, passive metasurface reflectors are often deemed inferior and suitable only for static scenarios due to lack of reconfigurability. In addition, state-of-the-art active/passive metasurfaces are limited to centimeter-scale, yet practical deployment entails meter-level (hundreds of wavelengths) in dimension, which induces non-trivial challenges such as severe beam distortion due to near-field effects and frequency-selectivity. To address these challenges, the PI team proposes 3 research thrusts: (1) Designing new beam synthesis models to enable ultra-large metasurfaces, and new techniques to incrementally reconfigure a passive metasurface array (PMA), so as to expand the angular coverage, beamforming gain, support mobility, and to avoid interference between nearby base stations; (2) Designing new mechanisms that leverage the PMA as a passive "encoder" to address the coverage-resolution-dimension tradeoff in mmWave sensing; (3) Exploring graphene-based metasurface structures to scale mmWave joint communication and sensing beyond the bandwidth limit of traditional RF hardware. The proposed research will lead to various community toolsets and reproducible fabrication workflows for creating low-cost mmWave metasurfaces through 3D printing or mold imprinting.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.