UCLA

Contemporary wireless networks are experiencing an era of unprecedented advancements, driven by the escalating demand from new wireless applications such as augmented and virtual reality, and further bolstered by the widespread deployment of the Internet of Things (IoT). These advancements encompass a range of technologies, comprising progress in wireless communication, wireless sensing, and wireless power transfer. mmWave technology is considered the key enabler of ultra-high data rates and capacity for future wireless communication, addressing the escalating demands of applications like high-definition video streaming and augmented reality. WiFi technology, the cornerstone of indoor wireless communications, has also undergone significant advancements in the various generations, offering higher throughput and network capacity. Meanwhile, the proliferation of wireless access points has sparked interest in harvesting power from Radio Frequency (RF) signals to power up the mass number of IoT devices. Despite these advancements in wireless technology, there remains a distinct disconnect between the evolution of wireless protocols and antenna hardware, with each failing to fully benefit from the progress of the other. In this thesis, we adopt a combined hardware-software co-design methodology to address the challenges of modern wireless networks, synergizing the latest developments in both wireless network protocols and antenna technology. In particular, we draw inspiration from the passive beamforming principle of Frequency Scanning Antenna (FSA), traditionally utilized in the field of radar and imaging, and integrate it in the field of wireless communication, sensing, and power transfer. In contrast to active beamforming technology, which uses intricate and energy-consuming electronic components to steer the beam, FSA utilizes the physical structure of the antenna to steer the beam based on signal frequency. We integrate this unique passive beamforming feature of FSA with wireless protocols to enhance the range and performance of future wireless systems.

In this thesis, we first explore the challenges of modern-day wireless networks then discuss how we can address them using passive beamforming with FSA. A key challenge of mmWave networks is the significant signal attenuation due to high frequency. To compensate, base stations transmit mmWave signals using narrow beams that can be easily blocked by physical obstacles, greatly impacting their real-world deployment. In the first part of this work we propose mmXtend, a low-cost, low-power mmWave repeater that uses passive beamforming to provide high-data-rate links to a large number of users simultaneously in scenarios where the line-of-sight path is blocked. Following this, we explore the evolution of WiFi technology. Despite the advancements of WiFi protocol over the years, the performance of WiFi networks is still constrained by the inherent limitations of its antenna hardware design. Today's WiFi devices mainly use omni-directional antennas, which fail to capitalize on the advancements in WiFi protocols, and conversely, these protocols do not leverage the potential of antenna technologies. This disconnect markedly hampers the overall performance of WiFi systems. In the second part of this thesis, we introduce Wi-Pro, a plug-and-play module, which enhances WiFi performance by integrating passive beamforming with the WiFi protocol. It can be deployed on any WiFi device without requiring firmware or chipset modifications. Additionally, for wireless power transfer, although it has been a long-standing topic of discussion, its practical applications in the real world remain limited. The main barriers include the restricted range for energy transfer and the lack of an efficient, low-power method for beam alignment, which is essential for effective energy transfer. In the third part of this thesis, we introduce mmCharge, a mmWave power harvesting system which uses passive beamforming to increase the range of mmWave wireless power transfer.

Our research shows that by integrating the concept of passive beamforming in the field of wireless communication, sensing, and power transfer, we can enhance performance and enable new capabilities. This thesis provides a comprehensive exploration into the development of end-to-end wireless systems that employ passive beamforming via FSA, which paves the way for future research in this area.