Cylindrical Luneburg Lens Antenna for Multi-Beam Small Cell Wireless Backhaul Applications

Abstract:

This thesis explores the possibility of replacing several high directive antennas with one single, multi-beam antenna for small cell microwave backhaul. An unconventional 28 GHz multi-beam backhaul antenna, built around a cylindrical Luneburg lens, has been designed and simulated. Additionally, a cylindrical Luneburg lens with permittivity distribution governed by air holes has been designed and simulated. This type of cylindrical lens antenna operates in a single plane and the two fundamental modes are determined by the lens thickness h, with TM₀-mode propagation for h < λ/2 and TE₁-mode propagation for λ/2 < h < λ. A vertically polarised antenna with nine coaxial ports in an arc array has been designed with a lens thickness of h = 2.25 mm and a lens diameter of 16λ. Port separation is 15.7º and the port arc array span 141.3º. The gain of each individual beam is above 20.6 dB with beam widths of less than 5.4º. The hole lens antenna exhibits good matching between 26 GHz to 29.8 GHz with a return loss below 16 dB for TM₀-mode propagation and gain of 19 dB. The combination of these results show that a multi-beam backhaul antenna for smallcell wireless backhaul applications is plausible, including a possibility to construct the lens through 3D printing.