8,695 research outputs found
Antenna Design with Characteristic Mode Analysis for Internet of Things Applications
PhDThe TV white space (TVWS) is one of the promising technologies to provide wide
coverage, energy effcient and cost effective Internet of Things (IoT) services. However,
its low operating frequency and wide bandwidth poses significant challenges to antenna
designs.
In this thesis, three antennas are developed using the characteristic mode analysis (CMA)
for IoT devices operating over the TVWS.
First, a very-low profile circular small antenna is transformed from a vertical monopole
antenna. The CMA is used to determine the mode to be excited and to design a specific feeding structure. After being printed on Rogers 5880 substrate, the final antenna
structure operates at 474 MHz with a V SWR < 2 bandwidth of 2.2 MHz. Its lateral
radius is just 5.2% of the wavelength of its resonant frequency.
Second, a compact U-shaped printed UWB monopole antenna is proposed to operate
over the entire UHF TV spectrum. This antenna measures 0:36 0 0:06 0 0:01 0
where 0 is the wavelength of its lowest operating frequency. Its V SWR < 2 bandwidth
is 87.5%, and the UWB behaviour is discussed by the CMA.
Third, a novel antenna design method is established on annular ring-shaped structures
with modal characteristics revealed by the CMA. Following the proposed method, another
UWB antenna is achieved by creating and exciting multiple modes with resonant
frequencies distributed across the UHF TV spectrum.
All antenna designs are verified thorough simulations and measurements. Furthermore,
antennas are also integrated into IoT devices and their system performance is measured
under different communication scenarios. The system measurements also verify the good
propagation property and the abundant spectrum resource of the TVWS
Wearable flexible lightweight modular RFID tag with integrated energy harvester
A novel wearable radio frequency identification (RFID) tag with sensing, processing, and decision-taking capability is presented for operation in the 2.45-GHz RFID superhigh frequency (SHF) band. The tag is powered by an integrated light harvester, with a flexible battery serving as an energy buffer. The proposed active tag features excellent wearability, very high read range, enhanced functionality, flexible interfacing with diverse low-power sensors, and extended system autonomy through an innovative holistic microwave system design paradigm that takes antenna design into consideration from the very early stages. Specifically, a dedicated textile shorted circular patch antenna with monopolar radiation pattern is designed and optimized for highly efficient and stable operation within the frequency band of operation. In this process, the textile antenna's functionality is augmented by reusing its surface as an integration platform for light-energy-harvesting, sensing, processing, and transceiver hardware, without sacrificing antenna performance or the wearer's comfort. The RFID tag is validated by measuring its stand-alone and on-body characteristics in free-space conditions. Moreover, measurements in a real-world scenario demonstrate an indoor read range up to 23 m in nonline-of-sight indoor propagation conditions, enabling interrogation by a reader situated in another room. In addition, the RFID platform only consumes 168.3 mu W, when sensing and processing are performed every 60 s
Structural behaviour of beam with HDPE plastic balls subjected to flexure load
This paper presents the structural behavior of reinforced concrete beam embedded with high density polyethylene balls (HDPE) subjected to flexural load. The HDPE balls with 180 mm diameter were embedded to create the spherical voids in the beam which lead to reduction in its self-weight. Two beam specimens with HDPE balls (RC-HDPE) and one solid beam (RC-S) with dimension 250 mm x 300 mm x 1100 mm were cast and tested until failure. The results are analysed in the context of its ultimate load, load-deflection profile, and crack pattern and failure mode. It was found that the ultimate load of RC-HDPE was reduced by 32% compared to RC-S beam while the maximum deflection at its mid span was increased by 4%. However, RC-HDPE is noticed to be more ductile compared to RC-S beam. Both types of beams experienced flexure cracks and diagonal tension cracks before failur
On the Feasibility of Multi-Mode Antennas in UWB and IoT Applications below 10 GHz
While on the one hand 5G and B5G networks are challenged by ultra-high data
rates in wideband applications like 100+ Gbps wireless Internet access, on the
other hand they are expected to support reliable low-latency Internet of Things
(IoT) applications with ultra-high connectivity. These conflicting challenges
are addressed in a system proposal dealing with both extremes. In contrast to
most recent publications, focus is on the frequency domain below 10~GHz.
Towards this goal, multi-mode antenna technology is used and different
realizations, offering up to eight uncorrelated ports per radiator element, are
studied. Possible baseband architectures tailored to multi-mode antennas are
discussed, enabling different options regarding precoding and beamforming
Multi-frequency antenna for quasi-isotropic radiator and 6G massive IoT
An isotropic antenna radiates and receives electromagnetic wave uniformly in
magnitude in 3D space. A multi-frequency quasi-isotropic antenna can serve as a
practically feasible solution to emulate an ideal multi-frequency isotropic
radiator. It is also an essential technology for mobile smart devices for
massive IoT in the upcoming 6G. However, ever since the quasi-isotropic antenna
was proposed and achieved more than half a century ago, at most two discrete
narrow frequency bands can be achieved, because of the significantly increased
structural complexity from multi-frequency isotropic radiation. This limitation
impedes numerous related electromagnetic experiments and the advances in
wireless communication. Here, for the first time, a design method for
multi-band (>2) quasi-isotropic antennas is proposed. An exemplified
quasi-isotropic antenna with the desired four frequency bands is also presented
for demonstration. The measured results validate excellent performance on both
electromagnetics and wireless communications for this antenna
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