128 research outputs found
Planar Antennas
This article reviews the state of the art in broadband antennas for emerging UWB applications and addresses the important issues of the broadband antenna design for UWB applications. First, a variety of planar monopoles with finite ground planes are reviewed. Next, the roll antennas with enhanced radiation performance are outlined. After that, the planar antennas printed on PCBs are described. A directional antipodal Vivaldi antenna is also presented for UWB applications. Last, a UWB antenna for wearable applications is exemplifie
Study and miniaturisation of antennas for ultra wideband communication systems
PhDWireless communications have been growing with an astonishing rate over the past
few years and wireless terminals for future applications are required to provide
diverse services. This rising demand prompts the needs for antennas able to cover
multiple bandwidths or an ultrawide bandwidth for various systems.
Since the release by the Federal Communications Commission (FCC) of a bandwidth
of 7.5 GHz (from 3.1 GHz to 10.6 GHz) for ultra wideband (UWB) wireless
communications, UWB has been rapidly evolving as a potential wireless technology
and UWB antennas have consequently drawn more and more attention from both
academia and industries worldwide.
Unlike traditional narrow band antennas, design and analysis of UWB antennas are
facing more challenges and difficulties. A competent UWB antenna should be
capable of operating over an ultra wide bandwidth as assigned by the FCC. At the
same time, a small and compact antenna size is highly desired, due to the integration
requirement of entire UWB systems. Another key requirement of UWB antennas is
the good time domain behaviour, i.e. a good impulse response with minimal
distortion.
This thesis focuses on UWB antenna miniaturisation and analysis. Studies have been
undertaken to cover the aspects of UWB fundamentals and antenna theory. Extensive
investigations are also conducted on three different types of miniaturised UWB
antennas.
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The first type of miniaturised UWB antenna studied in this thesis is the loaded
orthogonal half disc monopole antenna. An inductive load is introduced to broaden
the impedance bandwidth as well as the pattern bandwidth, in other words, an
equivalent size reduction is realised.
The second type of miniaturised UWB antenna is the printed half disc monopole
antenna. By simply halving the original antenna and tuning the width of the coplanar
ground plane, a significant more than 50% size reduction is achieved.
The third type of miniaturised UWB antenna is the printed quasi-self-complementary
antenna. By exploiting a quasi-self-complementary structure and a built-in matching
section, a small and compact antenna dimension is achieved.
The performances and characteristics of the three types of miniaturised UWB
antennas are studied both numerically and experimentally and the design parameters
for achieving optimal operation of the antennas are also analysed extensively in order
to understand the antenna operations.
Also, time domain performance of the Coplanar Waveguide (CPW)-fed disc
monopole antenna is examined in this thesis to demonstrate the importance of time
domain study on UWB antennas.
Over the past few years of my PhD study, I feel honoured and lucky to work with
some of the most prestigious researchers in the Department of Electronic
Engineering, Queen Mary, University of London. I would like to show my most
cordial gratitude to those who have been helping me during the past few years. There
would be no any progress without their generous and sincere support.
First of all, I would like to thank my supervisors Professor Clive Parini and Professor
Xiaodong Chen, for their kind supervision and encouragement. I am impressed by
their notable academic background and profound understanding of the subjects,
which have proved to be immense benefits to me. It has been my great pleasure and
honour to be under their supervision and work with them.
Second of all, I would like to thank Mr John Dupuy for his help in the fabrication
and measurement of antennas I have designed during my PhD study. Also, a special
acknowledgement goes to all of the staff for all the assistance throughout my
graduate program
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Optically transparent UWB antenna for wireless application & energy harvesting
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Transparent UWB antennas have been the focus of this PhD research. The use of transparent UWB antennas for stealth and energy harvesting has been the underlying applications that have given impetus to this research. Such transparent antennas being
built on materials that are discreet, flexible, conformal, conductive and having the ability to provide good antenna performance on glass to serve as the âlast mileâ link in subsequent generation communications after 4G have been the basis for this contention. UWB in this regard is able to provide the transmission and reception of high data rates and fast video transmission that is an elementary demand of even a 4G wireless communications system. The integration of UWB antennas with photovoltaic to provide integral energy harvesting solutions that will further enhance the value of the UWB system in terms of cost effectiveness and performance are thus the basis of this work. This work hence starts with the study of a transparent conductive oxide polymer, AgHT and its properties, and culminates in the development of a transparent UWB antenna, which can be integrated with photovoltaic for window glass applications on homes and buildings. Other applications such transparent antennas can find use for like
on-body wireless communications in healthcare monitoring was also analysed and
presented. The radar absorbing material (RAM) property of the AgHT was investigated
and highlighted using CST simulation software, as no measurement facilities were
available. The transparent UWB antenna in lieu of the inherent absorbent property of
the AgHT material is thus able to exhibit stealth characteristics, a feature that would be much desired in military communications. Introduction of a novel method of connecting the co-axial connector to the feed of the antenna to improve gain and efficiency of transparent polymer based antennas and the development of a UWB antenna that maintains its Omni-directional characteristic instead of becoming directional on an amorphous silicon solar cell are presented as some of the contributions for this research work. Some preliminary analysis on the impact of glass on UWB antennas for video transmission and how to improve transmission is presented. The ability of the conductive part of the antenna radiator to be used as a RF and microwave harvester and how it can further add value to a transparent UWB antenna is presented by way of experimental data. Finally yet importantly, this thesis presents some insight into how transparent
antennas may be used in Green Technology Buildings to provide an integrated solution
for both wireless communications and energy harvesting as part of the future work.
Improvement to the aesthetics of the external appearance of residential buildings
through the integration of transparent satellite dish onto solar panels on rooftops is also discussed and illustrated as part of this future work
Experimental characterization of the radio channel for systems with large bandwidth and multiple antennas
[SPA] Cada dĂa son necesarias comunicaciones mejores y mĂĄs eficientes, con mayores anchos de banda y mayores tasas de transferencias de datos. Por un lado los sistemas de mĂșltiples antenas, MIMO, surgieron como una tĂ©cnica para optimizar el uso de la potencia y el espectro. Por otro lado, los sistemas Ultra-Wideband, UWB, han ganado recientemente el interĂ©s de la comunidad cientĂfica por su gran ancho de banda combinado con su baja potencia de transmisiĂłn. A la hora de diseñar y testear nuevos dispositivos de comunicaciones inalĂĄmbricas, es esencial poseer un conocimiento preciso del canal de propagaciĂłn por el que se propagan dichas señales. Esta tesis, se basa en el modelado del canal de propagaciĂłn para sistemas de gran ancho de banda y mĂșltiples antenas desde un punto de vista experimental. Primeramente se presentan las mejoras y desarrollos realizados en el ĂĄmbito de los sistemas de medida del canal, dado que es necesario disponer de equipos adecuados y precisos para realizar adecuadas medidas del canal. Seguidamente, se analiza el canal MIMO-UWB en interiores. Se realiza un anĂĄlisis en profundidad de varios parĂĄmetros, especialmente parĂĄmetros de una antena como las pĂ©rdidas de propagaciĂłn, el factor de polarizaciĂłn cruzada o la dispersiĂłn del retardo. Finalmente, la tesis particulariza el anĂĄlisis del canal en un entorno especial como es el caso de tĂșneles. Se realiza un anĂĄlisis experimental de parĂĄmetros de una antena como multi antena para luego evaluar las prestaciones que pueden brindar varias tĂ©cnicas de diversidad como es en el dominio de la frecuencia, la polarizaciĂłn, el espacio o el tiempo.[ENG] Wireless communications have become essential in our society [Rappaport, 1996], [Parsons, 2000]. Nowadays, people need to be connected everywhere and at any time, and demand faster and enhanced communications every day. New applications requires higher data rates and, therefore, higher bandwidths. On the one hand, Multiple-Input Multiple-Output (MIMO) systems were proposed as one solution to achieve higher data rates and optimize the use of the spectrum. On the other hand, more recently, systems with an ultra large bandwidth, and particularly Ultra-Wideband (UWB) systems, have gained the interest of the scientific community. Such interest is owing to the extremely high data rates offered and its possible coexistence with existing systems due to the its low transmitted power. However, this improvement in mobile communications involves the development and testing of new wireless communications systems. Precise knowledge of the radio channel is an essential issue to design this new devices and, thus, reach such improvement in wireless communications. In general, the modeling of the radio channel can be undertaken in two main ways: Theoretically, where the channel is characterized by means of simulations and theoretical approaches. - Experimentally, where the radio channel is characterized by means of the analysis of measurements carried out in real scenarios. This thesis is mainly focused on the experimental characterization of the radio channel for systems with large bandwidth and multiple antennas (MIMO). However, characterizing experimentally the MIMO wideband channel implies the availability of adequate and accurate channel sounders.Universidad PolitĂ©cnica de CartagenaUniversitĂ© des Sciences et Technologies de Lille (USTL)Programa de doctorado en TecnologĂas de la InformaciĂłn y Comunicacione
Design of an Ultra-wideband Radio Frequency Identification System with Chipless Transponders
The state-of-the-art commercially available radio-frequency identification (RFID) transponders are usually composed of an antenna and an application specific integrated circuit chip, which still makes them very costly compared to the well-established barcode technology. Therefore, a novel low-cost RFID system solution based on passive chipless RFID transponders manufactured using conductive strips on flexible substrates is proposed in this work. The chipless RFID transponders follow a specific structure design, which aim is to modify the shape of the impinged electromagnetic wave to embed anidentification code in it and then backscatter the encoded signal to the reader.
This dissertation comprises a multidisciplinary research encompassing the design of low-cost chipless RFID transponders with a novel frequency coding technique, unlike usually disregarded in literature, this approach considers the communication channel effects and assigns a unique frequency response to each transponder. Hence, the identification codes are different enough, to reduce the detection error and improve their automatic recognition by the reader while working under normal conditions. The chipless RFID transponders are manufactured using different materials and state-of-the-art mass production fabrication processes, like printed electronics. Moreover, two different reader front-ends working in the ultra-wideband (UWB) frequency range are used to interrogate the chipless RFID transponders. The first one is built using high-performance off-theshelf components following the stepped frequency modulation (SFM) radar principle, and the second one is a commercially available impulse radio (IR) radar.
Finally, the two readers are programmed with algorithms based on the conventional minimum distance and maximum likelihood detection techniques, considering the whole transponder radio frequency (RF) response, instead of following the commonly used approach of focusing on specific parts of the spectrum to detect dips or peaks. The programmed readers automatically identify when a chipless RFID transponder is placed within their interrogation zones and proceed to the successful recognition of its embedded identification code. Accomplishing in this way, two novel fully automatic SFM- and IRRFID readers for chipless transponders. The SFM-RFID system is capable to successfully decode up to eight different chipless RFID transponders placed sequentially at a maximum reading range of 36 cm. The IR-RFID system up to four sequentially and two simultaneously placed different chipless RFID transponders within a 50 cm range.:Acknowledgments
Abstract
Kurzfassung
Table of Contents
Index of Figures
Index of Tables
Index of Abbreviations
Index of Symbols
1 Introduction
1.1 Motivation
1.2 Scope of Application
1.3 Objectives and Structure
Fundamentals of the RFID Technology
2.1 Automatic Identification Systems Background
2.1.1 Barcode Technology
2.1.2 Optical Character Recognition
2.1.3 Biometric Procedures
2.1.4 Smart Cards
2.1.5 RFID Systems
2.2 RFID System Principle
2.2.1 RFID Features
2.3 RFID with Chipless Transponders
2.3.1 Time Domain Encoding
2.3.2 Frequency Domain Encoding
2.4 Summary
Manufacturing Technologies
3.1 Organic and Printed Electronics
3.1.1 Substrates
3.1.2 Organic Inks
3.1.3 Screen Printing
3.1.4 Flexography
3.2 The Printing Process
3.3 A Fabrication Alternative with Aluminum or Copper Strips
3.4 Fabrication Technologies for Chipless RFID Transponders
3.5 Summary
UWB Chipless RFID Transponder Design
4.1 Scattering Theory
4.1.1 Radar Cross-Section Definition
4.1.2 Radar Absorbing Materialâs Principle
4.1.3 Dielectric Multilayers Wave Matrix Analysis
4.1.4 Frequency Selective Surfaces
4.2 Double-Dipoles UWB Chipless RFID Transponder
4.2.1 An Infinite Double-Dipole Array
4.2.2 Double-Dipoles UWB Chipless Transponder Design
4.2.3 Prototype Fabrication
4.3 UWB Chipless RFID Transponder with Concentric Circles
4.3.1 Concentric Circles UWB Chipless Transponder
4.3.2 Concentric Rings UWB Chipless RFID Transponder
4.4 Concentric Octagons UWB Chipless Transponders
4.4.1 Concentric Octagons UWB Chipless Transponder Design 1
4.4.2 Concentric Octagons UWB Chipless Transponder Design 2
4.5 Summary
5. RFID Readers for Chipless Transponders
5.1 Background
5.1.1 The Radar Range Equation
5.1.2 Range Resolution
5.1.3 Frequency Band Selection
5.2 Frequency Domain Reader Test System
5.2.1 Stepped Frequency Waveforms
5.2.2 Reader Architecture
5.2.3 Test System Results
5.3 Time Domain Reader
5.3.1 Novelda Radar
5.3.2 Test System Results
5.4 Summary
Detection of UWB Chipless RFID Transponders
6.1 Background
6.2 The Communication Channel
6.2.1 AWGN Channel Modeling and Detection
6.2.2 Free-Space Path Loss Modeling and Normalization
6.3 Detection and Decoding of Chipless RFID Transponders
6.3.1 Minimum Distance Detector
6.3.2 Maximum Likelihood Detector
6.3.3 Correlator Detector
6.3.4 Test Results
6.4 Simultaneous Detection of Multiple UWB Chipless Transponders
6.5 Summary
System Implementation
7.1 SFM-UWB RFID System with CR-Chipless Transponders
7.2 IR-UWB RFID System with COD1-Chipless Transponders
7.3 Summary
Conclusion and Outlook
References
Publications
Appendix A
RCS Calculation
Measurement Setups
Appendix B
Resistance and Skin Depth Calculation
Appendix C
List of Videos
Test Videos
Consortium Videos
Curriculum Vita
Analysis and design of antennas for wireless communications using modal methods
El diseño de antenas para los nuevos sistemas de comunicaciones inalĂĄmbricas ha suscitado un creciente interĂ©s en los Ășltimos años. El principal objetivo de esta Tesis Doctoral es la propuesta de un mĂ©todo general de diseño de antenas para sistemas de comunicaciones inalĂĄmbricas que proporcione una visiĂłn fĂsica del proceso de diseño. Para alcanzar este objetivo, se propone el uso de un mĂ©todo basado en la descomposiciĂłn modal de la corriente en la superficie del cuerpo conductor. Los modos tienen la ventaja de proporcionar una visiĂłn mĂĄs fĂsica del comportamiento radiante de la antena, asĂ como informaciĂłn muy Ăștil para la optimizaciĂłn de la geometrĂa de la antena y para la selecciĂłn del mecanismo Ăłptimo de alimentaciĂłn y su localizaciĂłn.
En la Tesis se realizarĂĄ una revisiĂłn de los diferentes mĂ©todos modales disponibles, asĂ como de los parĂĄmetros mĂĄs importantes a tratar cuando se trabaja con soluciones modales. AdemĂĄs, se investigarĂĄ un mĂ©todo para obtener expresiones cerradas para las corrientes superficiales en objetos conductores planos abiertos. Como se verĂĄ, los objetos planos con formas canĂłnicas se pueden interpretar en muchas ocasiones como deformaciones de objetos tridimensionales cuyas superficies coinciden con las de algunos de los sistemas de coordenadas curvilĂneas. De esta forma, se obtendrĂĄn expresiones cerradas para los modos vectoriales en un disco conductor circular y una tira plana infinita. Estas funciones se propondrĂĄn como funciones base de dominio completo en problemas mĂĄs complejos que incluyan este tipo de superficies planas.
Los modos de corriente definidos a partir de las funciones de onda vectoriales son de naturaleza compleja, lo que dificulta en ocasiones su uso para el diseño de antenas. Por el contrario, la TeorĂa de los Modos CaracterĂsticos proporciona una descomposiciĂłn de la corriente total en la superficie de un cuerpo conductor de forma arbitraria en un conjunto de modos reales, cuyos diagramas de radiaciĂłn son ortogonalesAntonino Daviu, E. (2008). Analysis and design of antennas for wireless communications using modal methods [Tesis doctoral no publicada]. Universitat PolitĂšcnica de ValĂšncia. https://doi.org/10.4995/Thesis/10251/2188Palanci
Autonomous smart antenna systems for future mobile devices
Along with the current trend of wireless technology innovation, wideband, compact size,
low-profile, lightweight and multiple functional antenna and array designs are becoming more
attractive in many applications. Conventional wireless systems utilise omni-directional or
sectored antenna systems. The disadvantage of such antenna systems is that the
electromagnetic energy, required by a particular user located in a certain direction, is radiated
unnecessarily in every direction within the entire cell, hence causing interference to other
users in the system. In order to limit this source of interference and direct the energy to the
desired user, smart antenna systems have been investigated and developed. This thesis
presents the design, simulation, fabrication and full implementation of a novel smart antenna
system for future mobile applications.
The design and characterisation of a novel antenna structure and four-element liner array
geometry for smart antenna systems are proposed in the first stage of this study. Firstly, a
miniaturised microstrip-fed planar monopole antenna with Archimedean spiral slots to cover
WiFi/Bluetooth and LTE mobile applications has been demonstrated. The fundamental
structure of the proposed antenna element is a circular patch, which operates in high
frequency range, for the purpose of miniaturising the circuit dimension. In order to achieve a
multi-band performance, Archimedean spiral slots, acting as resonance paths, have been
etched on the circular patch antenna. Different shapes of Archimedean spiral slots have been
investigated and compared. The miniaturised and optimised antenna achieves a bandwidth of
2.2GHz to 2.9GHz covering WiFi/Bluetooth (2.45GHz) and LTE (2.6GHz) mobile standards.
Then a four-element linear antenna array geometry utilising the planar monopole elements
with Archimedean spiral slots has been described. All the relevant parameters have been
studied and evaluated. Different phase shifts are excited for the array elements, and the main
beam scanning range has been simulated and analysed.
The second stage of the study presents several feeding network structures, which control
the amplitude and phase excitations of the smart antenna elements. Research begins with the
basic Wilkinson power divider configuration. Then this thesis presents a compact feeding
network for circular antenna array, reconfigurable feeding networks for tuning the operating
frequency and polarisations, a feeding network on high resistivity silicon (HRS), and an ultrawide-band
(UWB) feeding network covering from 0.5GHz to 10GHz. The UWB feeding
network is used to establish the smart antenna array system.
Different topologies of phase shifters are discussed in the third stage, including ferrite
phase shifters and planar phase shifters using switched delay line and loaded transmission line
technologies. Diodes, FETs, MMIC and MEMS are integrated into different configurations.
Based on the comparison, a low loss and high accurate Hittite MMIC analogue phase shifter
has been selected and fully evaluated for this implementation. For the purpose of impedance
matching and field matching, compact and ultra wideband CPW-to-Microstrip transitions are
utilised between the phase shifters, feeding network and antenna elements. Finally, the fully
integrated smart antenna array achieves a 10dB reflection coefficient from 2.25GHz to
2.8GHz, which covers WiFi/Bluetooth (2.45GHz) and LTE (2.6GHz) mobile applications. By
appropriately controlling the voltage on the phase shifters, the main beam of the antenna array
is steered ±50° and ±52°, for 2.45GHz and 2.6GHz, respectively. Furthermore, the smart
antenna array demonstrates a gain of 8.5dBi with 40° 3dB bandwidth in broadside direction,
and has more than 10dB side lobe level suppression across the scan.
The final stage of the study investigates hardware and software automatic control systems
for the smart antenna array. Two microcontrollers PIC18F4550 and LPC1768 are utilised to
build the control PCBs. Using the graphical user interfaces provided in this thesis, it is able to
configure the beam steering of the smart antenna array, which allows the user to analyse and
optimise the signal strength of the received WiFi signals around the mobile device.
The design strategies proposed in this thesis contribute to the realisation of adaptable and
autonomous smart phone systems
ULTRA-WIDEBAND MICROSTRIP ANTENNA ENHANCED PERFORMANCE USING METAMATERIAL
Antenna engineering is very important in the development of communication systems and the requirements for low profile antennas that cover a wide spectrum of frequencies increase the number of researches in this field. Accordingly, scientists have focused on UWB microstrip antennas that cover the range from 3.1 GHz to 10.6 GHz but others concentrate on enhancing its performance using a special type of materials called metamaterials.
The main objective of this work is to enhance frequency bandwidth, antenna gain, and radiation pattern for the UWB circular microstrip antenna by employing the Split Ring Resonator (SRR) technique, which is one type of metamaterial.
Circular and square split-ring resonators are investigated as an enhancement method after studying their characteristics. Multiple techniques are also applied to these two structures prior to being implemented at the antennaâs backside including different SRR schematics such as the SRR position with respect to the ground, inner and outer ring rotation, positive and negative rotation angle, number of SRR units, SRR size, SRR design, in addition to using the complementary SRR. Furthermore, two techniques are combined together in some designs to observe how the antennaâs performance will be affected. The proposed techniques rely on the variation in capacitance and inductance which will affect the resonant frequency of the SRR unit cell. Then some SRR Schematics were implemented in the proposed circular antenna design to test the functionality within WiFi frequencies 2.4 GHz and 5 GHz. The enhancement can be summarized in increasing antenna bandwidth and transmitting or rejecting specific frequency bands. The results of the study reveal an enhancement in circular antenna performance. UWB circular antenna with elliptical rings has a frequency bandwidth between 3.5 GHz to 9 GHz and a maximum gain of around 5 dB; during the enhancement process using the previously mentioned techniques, the frequency bandwidth increased to cover the range from 2.2 GHz to 9.8 GHz along with some bands rejection. It was noted that some rejected bands have shifted to higher frequencies when applying inner or outer ring rotation. To emphasize this, WiFi frequencies 2.4 GHz and 5GHz are inspected by using the suitable size of S-SRR to decide which frequency to reject or transmit depending on the communication applications.
The outcomes of this work should assist in designing antennas with SRR depending on required communication applications and operating frequencies
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