PhDThis thesis undertakes thorough analytical designs, as well as numerical and experimental performance evaluations, of millimetre-wave beamforming networks based on the Rotman lens-based feeding concept. The developed passive switched-beam networks are intended for operation in the 28-GHz and 60-GHz bands, covering the whole frequency ranges of 18โ38 GHz and 50โ70 GHz, respectively. The primary objective of this work is to investigate the feasibility of designing a number of high-performance and low-profile array beamformers. This has been accomplished based on the flexible liquid-crystal polymer substrates, for the potential deployment in the next-generation wireless communications. The developed lens devices, and their output characteristics, in terms of the scattering parameters, accuracy, device efficiency, and surface current distributions, have been comprehensively evaluated. Moreover, this has been extended to the detailed designs of the lens beamformers based on the four different proposed flexural cases, namely the concave-axial bending, convex-axial bending, concave-circumferential bending, and convex-circumferential bending. Each of the flexures has been analysed in detail, and the performance in terms of the linear progressive phase behaviour, as the primary figure of merit, has been reported. Furthermore, based on the conducted analytical designs and validations a prototype has been accurately fabricated, using the laser-centric radio frequency circuit structuring technique, and a setup has been further deployed to carry out the measurements. This has been done in order to validate the analytical results, as well as to demonstrate the experimental 28-GHz beamforming. The presented array beamformers outperform other existing millimetre-wave beamformers, to be potentially utilised as the efficient integrated units of the transceiver modules and large-scale antennas, mostly in the multiple-input multiple-output systems. Lastly, the developed lens beamformers provide the next-generation conformal and flexible subsystems with the essential functional requirements for the millimetre-wave beam steering mechanisms
