Analytical and Numerical Evaluations of Flexible v-Band Rotman Lens Beamforming Network Performance for Conformal Wireless Subsystems

Abstract

This paper presents the analytical design and numerical performance evaluation of novel V-band millimetre-wave (mm-wave) beamforming networks (BFNs), based on the Rotman lens array feeding concept. The devices are intended for operation in the unlicensed 60-GHz frequency band. The primary objective of this work is to study the feasibility of designing flexible V-band beamformers, based on liquid-crystal polymer (LCP) substrates. The planar Rotman lens device has been initially developed, and the output performances, in terms of the scattering parameters and accuracy, have been analysed. This is further continued with the detailed designs of the Rotman lens BFNs based on the four different proposed flexural cases, namely the concave-axial bending, the convex-axial bending, the concave-circumferential bending, and the convex-circumferential bending. Each of the flexures has been analysed, and the performance in terms of the surface currents and phase distributions, as the primary functionality indicators, has been presented. The presented flexible beamformers exhibit significant characteristics to be potentially employed as low-cost and efficient units of the mm-wave transceivers with the in-built electronic beam steering capabilities for the conformal wireless subsystems.

Design and Performance Analysis of Millimetre-Wave Rotman Lens-Based Array Beamforming Networks for Large-Scale Antenna Subsystems

“…The LCP-based RLs have also remarkable potential to be deployed in the conformal wireless subsystems. Therefore, the thorough RF performance analysis can also be extended into the case of introducing the proposed flexures in [40], into the structures of the developed 28-GHz wideband and large-scale RLs. This would lead to the appropriate feasibility study of implementing such flexible large-scale Rotman lens-based beamformers according to the aerodynamic and hydrodynamic properties of the bearing surfaces, as well as the configurations of the intended wireless system infrastructures.…”

“…9(a) and (b) extensively illustrate the output phase division behaviour of the largescale lens-based beamformer, when the beam ports 1 and 6 are excited, respectively. It is worth noting that input ports 1 and 6 determine the minimum and maximum device efficiency boundaries, since they are placed on the furthest distance from the central focal point of the lens, as well as on the central axis of the RL, respectively [40]. The computed device efficiency at the centre frequency of 28-GHz is also obtained as 26.5%.…”

“…3 shows the characteristics of the dummy ports as an integral part of the lens, over the frequency range of operation, which are terminated with 50-Ω matched loads. The sidewall contours along with the dummy ports are efficiently designed and implemented to minimise the multiple reflections and standing waves from the sidewalls, which consequently results in the improved performance, in terms of the device efficiency [40,44]. Fig.…”

“…The design equations provide the method for thoroughly designing the mm-wave beamformers shown in recyclable, and multi-environmental LCP laminates, with the dielectric constant of ε r = 2.9, loss tangent of tan δ = 0.0025, substrate thickness of h = 0.18 mm, and top-and bottom-cladding of t = 17.5 µm, as in [37][38][39][40][41], with the port-pointing enabled; i.e., the beam and array ports are adjusted so that the boresight of each taper points to the centre of the opposite contour, rather than being normal to the lens surface; in order to enhance the performance of the proposed Rotman lenses.…”

A low‐profile 28‐GHz Rotman lens‐fed array beamformer for 5G conformal subsystems

“…For this purpose, the lens‐based switched‐beam networks are effectively employed to have control over the amplitude and phase at each element of the antenna array . This would lead to the feasibility of implementing the networks according to the aerodynamic and hydrodynamic properties of the site‐specific bearing surfaces, as well as the configurations of the intended infrastructures at the APs . This work has undertaken the thorough design and performance analysis of a lens‐based beamforming network (BFN) that is bent under the introduced conformal flexure, to be used in the integrated modules for the 5G systems .…”