Suspended High-gain Millimeter-wave Antenna Arrays: Hybrid Fabrication using MEMS and 3D-Printer Technologies

当今的无线通信系统大多工作在3 GHz以下的微波频率，这已经成为一种拥挤和有限的资源。然而，在30-300 GHz的毫米波频谱中，可用的带宽超过100倍，这为下一代设备提供了大幅提高数据速率的潜力。目前，毫米波通信系统的成功实现面临着几个挑战。其中一个挑战是毫米波频率上的信号传播受到严重路径损耗的影响。应对在较高频段增加的路径损耗的自然方法是使用发射和接收波束成形网络，每个终端具有许多天线。因此，开发工作在毫米波频率的高效率和高增益的集成电路天线阵是非常必要的。建议的阵列的潜在应用包括毫米波短程通信链路、卫星通信、雷达、遥感、安全和医学成像。这项研究不仅将推动先进的小型化天线阵列的研究，还将支持俄亥俄州立大学在射频微系统领域的课程开发。PIS将通过顶石设计项目和独立研究为本科研究人员提供建议，这些项目旨在利用毫米波天线的独特功能、材料的电特性、3D打印的超材料表面和微制造工艺。其他教育影响包括通过夏令营对学生进行无线技术培训的实践经验，以及吸引工程专业本科生和任职人数不足的学生的各种外联活动。目前用于在硅上集成阵列的毫米波技术的一个主要缺点是效率低(5%-10%)，因此实现的增益低。因此，这项提议的中心目标是在硅集成电路上开发辐射效率高于85%的扫描阵列。到目前为止，还没有实现这样紧凑、高效的毫米波阵列。此外，可定向毫米波天线阵非常适合满足下一代高数据速率通信的需求。这项研究旨在了解和解决集成电路天线效率的根本限制。提出的提高低辐射效率和低增益的方法是跨学科的，并利用混合制造方法：a)采用微电子机械系统(MEMS)工艺的悬浮辐射元件，以及b)3D打印人造(各向异性)介质层。通过使用MEMS制造工艺将相控阵的所有辐射元件悬浮在空气中，去除了有损的硅衬底。此外，在辐射单元上方制作了3D打印的介质透镜或超材料层，以提高相控阵的扫描体积。作为一种互补的制造技术，3D打印等附加制造技术特别适合波长在几毫米范围内的毫米波阵列。天线与集成电路的集成--再加上人造介质层提供的扫描体积、增益和带宽的增强--在系统小型化方面提供了巨大的优势，对下一代有源电子扫描阵列至关重要。这种新颖的、跨学科的方法对集成电路天线具有潜在的变革作用。

Today's wireless communications systems operate mostly in the microwave frequencies below 3 GHz, which has become a crowded and limited resource. Yet more than 100 times bandwidth is available in the millimeter-wave spectrum of 30-300 GHz, offering the potential of huge increases in data rates for next generation devices. Currently, there are several challenges for successful realization of millimeter-wave communication systems. One such challenge is that the signal propagation at millimeter-wave frequencies is impaired by severe path loss. Natural approach to counter the increased path loss at higher frequency bands is to use transmitting and receiving beamforming networks with many antennas per terminal. As a result, it is highly desirable to develop high-efficiency and high-gain integrated circuit antenna arrays operating at millimeter-wave frequencies. Potential applications for the proposed arrays include millimeter-wave short-range communication links, satellite communications, radars, remote sensing, security, and medical imaging. This research will not only advance the research of advanced miniaturized antenna arrays but also support curriculum development at The Ohio State University in the area of RF microsystems. The PIs will advise undergraduate researchers through capstone design projects and independent studies intended to harness the unique features of millimeter-wave antennas, electrical characterization of materials, 3D printed meta-material surfaces, and microfabrication processes. Other educational impact includes hands-on experiences to train students in wireless technologies through summer camps and a variety of outreach activities to attract undergraduates and underrepresented students in engineering. One major drawback of current millimeter-wave technologies adopted for integration of arrays on silicon is the low efficiency (5-10%) and consequently low realized gain. Therefore, the central objective of this proposal is to develop scanning arrays on silicon integrated circuits that exhibit radiation efficiency of greater than 85%. Such compact high-efficiency millimeter-wave arrays have not been realized to date. Moreover, steerable millimeter-wave antenna arrays are well suited to meet the needs for next-generation high data-rate communications. This research aims to understand and address fundamental limitations in efficiency of integrated circuit antennas. The proposed approach for increasing low radiation efficiency and low gain is interdisciplinary and utilizes hybrid fabrication approach: a) suspended radiating elements using micro-electro-mechanical systems (MEMS) process, and b) 3D-printed artificial (anisotropic) dielectric layers. By suspending all radiating elements of a phased array in air using MEMS fabrication processes, the lossy silicon substrate is removed. In addition, a 3D-printed dielectric lens or meta-material layer is fabricated above the radiating elements to enhance the scanning volume of the phased array. As a complementary fabrication technique, additive manufacturing such as 3D printing is uniquely suited for millimeter-wave arrays where the wavelengths are in the range of a few millimeters. The integration of antenna with integrated circuits - combined with enhancements in scanning volume, gain, and bandwidth delivered by artificial dielectric layer - provide enormous advantage in miniaturization of the systems and is essential for next-generation active electronic-scanning arrays. This novel and interdisciplinary approach is potentially transformative to integrated circuit antennas.