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

目前的无线通信系统主要工作在3ghz以下的微波频率上，这已经成为一种拥挤而有限的资源。然而，在30-300 GHz的毫米波频谱中，可用带宽超过100倍，为下一代设备提供了数据速率大幅提高的潜力。目前，成功实现毫米波通信系统面临着几个挑战。其中一个挑战是信号在毫米波频率上的传播受到严重的路径损耗的影响。应对高频段路径损耗增加的自然方法是在每个终端使用多个天线的发射和接收波束形成网络。因此，开发工作在毫米波频率下的高效率、高增益集成电路天线阵列是非常必要的。拟议阵列的潜在应用包括毫米波短距离通信链路、卫星通信、雷达、遥感、安全和医疗成像。这项研究不仅将推进先进小型化天线阵列的研究，而且还将支持俄亥俄州立大学射频微系统领域的课程开发。pi将通过顶点设计项目和独立研究为本科生研究人员提供建议，旨在利用毫米波天线的独特功能、材料的电气特性、3D打印超材料表面和微制造工艺。其他教育影响包括通过夏令营和各种推广活动来培训学生无线技术的实践经验，以吸引本科生和工程领域代表性不足的学生。目前用于硅阵列集成的毫米波技术的一个主要缺点是效率低（5-10%），因此实现增益低。因此，本提案的中心目标是在硅集成电路上开发具有大于85%辐射效率的扫描阵列。这种紧凑高效的毫米波阵列至今尚未实现。此外，可操纵的毫米波天线阵列非常适合满足下一代高数据速率通信的需求。本研究旨在了解和解决集成电路天线效率的基本限制。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)使用微机电系统（MEMS）工艺悬浮辐射元件，b) 3d打印人工（各向异性）介电层。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，可以去除有损耗的硅衬底。此外，在辐射元件上方制作3d打印的介质透镜或超材料层，以增强相控阵的扫描体积。作为一种补充制造技术，3D打印等增材制造非常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-结合扫描体积、增益和人工介电层提供的带宽的增强-在系统小型化方面提供了巨大的优势，并且对下一代有源电子扫描阵列至关重要。这种新颖的跨学科方法对集成电路天线具有潜在的变革意义。

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.