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.
