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.
Abstract-This paper presents the comprehensive analytical design and numerical performance evaluation of novel millimetre-wave (mm-wave) switched-beam networks, based on the Rotman lens (RL) array feeding concept. These passive array devices have been designed for operation in the 28-GHz frequency band, covering the whole 18-38 GHz frequency range. The primary objective of the work is to conduct a thorough feasibility study of designing wideband mm-wave beamformers based on liquid-crystal polymer (LCP) substrates, to be potentially employed as low-cost and high-performance subsystems for the advanced transceiver units and large-scale antennas. The presented RLs exhibit significant output behaviours for electronic beam steering, in terms of the scattering (S) parameters, phase characteristics, and surface current distributions, as the feeding systems' primary functionality indicators.
This paper presents a detailed analysis of the human body limb movement influence on the radiation pattern of a wearable antenna during different activities. The analysis is carried out at 3, 6, 9 GHz of the 3-10 GHz UWB range of frequencies. Simulations are carried out on a human body model in CST microwave studio with a compact wearable antenna to obtain the body-worn antenna radiation patterns for lower and higher frequencies. This study gives an insight into the variation of the radiation patterns of a compact UWB antenna depending upon the position of the wearable antenna on the body. Results conclude that the radiation pattern of the wearable antenna changes significantly in terms of shape, size, level of distortion, and direction of maximum radiation with different limb movement activities and also depends upon the placement of the antenna on the limbs. The coverage area of the wearable antenna radiation pattern becomes highly directive and shrinks in coverage area for the shoulder/thigh node in comparison to the wrist/ankle wearable node by 10-15%. The bending of the limbs leads to deformation and reduction in area of the radiation pattern with values as high as 30-40% compared to free space scenario as the bending angle between the upper and lower arm/leg reduces. The analysis presented gives directional information regarding maximum radiation and the field strength of the radiation pattern for various activities performed. The present study reports results on the influence of the wearable antenna position, on detection and tracking performance of RF and microwave biomedical devices/sensors suitable for various healthcare applications such as tracking of human subject, patient monitoring, gait analysis, physical exercises, yoga, physiotherapy, and rehabilitation.
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