Wide-angle Beamscanning Gradient Index Lens Antennas for Wireless Communications

The trend in wireless communication is moving towards higher frequencies, offering increased data rates and broader spectrum availability. However, these benefits come with the challenge of higher path loss, necessitating antenna systems with highly directional beams. Consequently, antennas require high gain, greater than 20 dBi, but with narrow beamwidths, making beam scanning capabilities essential to cover wide fields-of-view, exceeding ±50°. Additionally, a broad operational bandwidth ($>$50\%) is preferred to support various applications. This dissertation aims to design a high-gain antenna with wide-angle beam scanning across a broadband. Considering the need for massive deployment, the proposed antenna should also be low-cost and energy-efficient. Gradient Refractive Index (GRIN) antennas present a promising solution, meeting performance and constraint requirements. However, improvement in beam scanning range and scan loss is needed. To address these challenges, this dissertation introduces a novel lens impedance matching structure and a lens ray tracing simulation technique. Both designs then enable two types of beam scanning lenses. By reformulating taper theory, the impedance matching tapers achieve broadband matching from 8 to 78 GHz with a uniform physical layer length. The ray tracing solver incorporates the complex electrical field, allowing evaluation of lens radiation patterns within a minute for lenses with arbitrary shapes and permittivity profiles. Using these tools, a 3D compound lens was designed with a fast hybrid optimization workflow involving three solvers, conducting over 50,000 simulations in four days. The resulting lens design achieves an average scan loss exponent of $n_s = 2.17$ within ±55° across the Ka-Band. Additionally, a proposed phased array fed lens (PAFL) demonstrates improved beam scanning capabilities by using a small number of feeds with nonuniform amplitude and phase excitation. Two PAFL designs were developed: one with a 0.7$\lambda$ spacing feed array, requiring around half the feeds compared to the standard 0.7$\lambda$ spacing, which reduces cost and power consumption while improving $n_s$ from 5 to 3.6 at 29 GHz, and another with a broadband feed array that achieves beam scanning improvements from 15 GHz to 50 GHz.