NSF Award
2301851
Cellular systems are shifting to mm-Wave frequency bands because of wider available bandwidth and high data rates; however, these systems suffer from severe propagation losses, signal blockage, and fading effects; therefore, it is difficult for the fifth generation (5G) base station to cover both the outdoor environment and indoor scenario effectively. Wideband and high-resolution beam-steering is needed to ensure consistent connectivity and it is a crucial factor for many applications beyond 5G, such as vehicle-to-vehicle communication, automotive radars, remote sensing, and satellite communications. This proposal will develop a K-band hybrid beamforming system comprised of dual-polarized low-profile antenna arrays and an analog beamforming mechanism using a subharmonic mixing-based phased shifting. In addition to the technical effects, the project will also impact education by supporting interdisciplinary workforce development and broadening participation in STEM for individuals from diverse backgrounds. The project will facilitate outreach activities, including annual summer camps for high school students and girls in the engineering program at Oakland University, and involve more undergraduate students in the research.<br/><br/>This proposal will develop a K-band hybrid beamforming system comprised of the antenna array and frequency-modulated continuous (FMCW) beamforming mechanism, resulting in a low-cost, miniaturized solution to fulfill complex communication environment problems such as multi-path effects and dynamic demands. To be specific, the following innovations will be pursued: a) Frequency mixing-based phase shifting at K-band will be developed to obtain low-magnitude variation while using lower-cost phase shifters at lower frequencies. The main components in these systems are filters, power splitters, phase shifters, Local oscillators, and antenna arrays. Doing phase shifting at a lower frequency makes the implementation simpler, and more techniques are available. The proposed system will be implemented using PCB technology and will be compared with the state-of-the-art 5G millimeter-wave phased array (integrated circuit level) for key performance parameters. (b) To achieve polarization diversity and beam-scanning capability, dual-polarization will be implemented and demonstrated using a vertically polarized and horizontally polarized antenna. The horizontally and vertically polarized antennas will be integrated into a single area without needing any multilayer PCB for implementation. Leaky-wave antennas will also be developed to simplify the feeding network further. (c) Non-Linear Transmission Line (NLTL) will also be explored as a controller in the feeding network of phased array antennas to achieve beam steering with higher bandwidths. Monolithically fabricated NLTL will provide small unit-cell lengths and average capacitances. Different NLTL circuits will be presented using analytical solutions, circuit simulations, and experimental characterization. Once completed, the developed architecture can be adapted to an extensive range of steerable frequencies with minimal circuit change while providing high resolution, improved sidelobe and null-area rejection levels, and improved beam-pointing accuracy.<br/><br/>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.
