Frequency reconfigurable tapered slot antennas for wideband narrowband and multiband applications

Presented in this thesis are reconfigurable tapered slot antennas for wideband-narrowband and wideband-multiband reconfigurations. The presented approaches give benefits in reducing the interference level at the receiver. These reconfigurations enable RF front end to have better flexibility in wireless communication systems. After compiling considerable research on previous similar schemes in the literature, five new reconfigurable tapered slot antennas are presented and discussed, in order to contribute to the present state of knowledge in the field. Firstly, a wideband to narrowband reconfiguration is proposed by using a switched feed technique. The second design integrates wideband and multiband operations using a resonator technique. This antenna is capable of wideband, dual-band and triple-band functionalities. In the third design, a wide to multiband operation is achieved by using an internal loading technique. This is done by feeding the tapered slot antenna with a coplanar waveguide (CPW) to slot-line transition feed incorporating matching stub. The fourth design is a wide and a multiband antenna using dual port technique. The advantage of using this technique enables it to operate wideband and multiband function simultaneously. The fifth and final approach is the best proposed design. The design shows an improved structure of wideband tapered slot antenna that can switch to multiband slot dipole antenna using single port. The main advantage of this design is that multiband (single, dual and triple) operations are easily obtained and have shown to be more flexible in obtaining different operating frequency bands. The design has adopted in and out part of the antenna technique to achieve the frequency reconfiguration. The superiority of the proposed design over the other designs is stable radiation pattern in almost all different operating modes. The wideband frequency range is from 1-3.7 GHz. The resonance frequency of the single-band is at 2.4 GHz. In the dual-band, the resonance frequency of the first band is at 2.1 GHz, while the second resonance frequency is at 3.2 GHz. The low, mid and high resonance frequencies of the triple-band are at 1.5 GHz, 2.5 GHz, and 3.3 GHz, respectively. This design supports applications such as Global System for Mobile Communication (GSM), Universal Mobile Telecommunications System (UMTS), Wireless Fidelity (WiFi), Wireless Local Area Network (WLAN), Worldwide Interoperability for Microwave Access (WiMAX) and Long-Term Evolution (LTE) bands

Wideband reconfigurable antennas

The work described in this thesis concerns the combining of wideband and reconfigurable narrow band functionality into a single antenna. This concept may be useful in reducing size and to give flexibility to a wireless terminal to operate in several different modes. The approach also offers additional pre-filtering to the front-end, which reduces the interference levels at the receiver, giving them a significant advantage over fixed non reconfigurable transceivers. Wideband-narrowband reconfiguration is potentially useful for future wireless communications such as software defined radio and cognitive radio, since they may employ wideband sensing and reconfigurable narrowband communications. Five novel reconfigurable antennas are presented. One is a switchable log periodic patch array and four are Vivaldi antennas with various forms of reconfiguration. The log periodic is reconfigured by placing switches between the patches and the feed line whilst the Vivaldi antenna has switched resonators controlling the current in the edges of the tapered slots. Wideband to various narrowband functions, wideband with a tunable band rejection having a very wide tuning ratio, and combined three function wide, narrow and tunable band rejection in a single antenna are demonstrated. Prototypes are presented with PIN diode switches, varactors, fixed capacitor or hard wire switches. Measured and simulated results with a very good agreement are presented, thus verifying the proposed concepts.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

New frequency reconfigurable antennas for wide frequency range tuning

Frequency reconfigurable antennas are becoming a compelling solution for the increasing demand of higher antenna capabilities, since they can operate at tunable narrow frequency bands while rejecting the undesirable signals from other bands. The aim of this project is to develop new designs for frequency reconfigurable antennas that can work across a wide frequency range (from 1 GHz up to 6 GHz) while maintaining stable radiation pattern and polarisation as required by the industry sponsors. A Vivaldi antenna is considered as the basis for a frequency reconfigurable design as it maintains the radiation characteristics in its operating band. Dual-band, tri-band and quad-band switched reconfigurable designs are proposed and analysed. These antennas are electronically-tuned using RF switches which adjust the impedance to reconfigure the operating band of the antenna. A prototype is tested in an anechoic chamber obtaining good performance. However, as the switches lead to several challenges, such as the effect of bias lines and the excessive insertion losses, a new approach is taken. State-of-the-art technologies are studied and fluid antennas are introduced. Current developments show that liquid antennas can have radiation efficiencies up to 90 % and conductivities close to copper, which makes them a good candidate to fulfil the requirements of this project. A hybrid Vivaldi antenna with an ionised water switch is proposed and a prototype tested. By introducing ionised water into a specific point of the feed line the operating frequency of the antenna is adjusted. The replacement of RF switches for electronically-controlled fluids brings high flexibility, suppression of the bias lines impact, dynamic adjustment and continuous frequency tuning compared to conventional antenna systems

Ultrawideband and Multi-state Reconfigurable Antennas with Sum and Difference Radiation Patterns

Pattern diversity is a term used to describe the operation of several antenna elements working together to produce multiple different radiation patterns with the aim of improving the quality and reliability of a communications system. One useful implementation of pattern diversity considers sum and difference radiation patterns which can be exploited to extend high-gain space coverage and tackle multipath fading. The conventional forms of such pattern diversity antennas are generally working at a single or multiple narrowband frequencies and are designed for specific applications. Hence, generating sum and difference pattern diversity in wide range of frequencies requires the development of new pattern diversity antenna designs. Ultrawideband and frequency reconfigurable designs of pattern diversity antennas are desirable to help reduce the cost and increase the flexibility in applications of pattern diversity antennas. These two types of performances constitute the principal parts of this thesis. The first part of this thesis deals with the challenges of designing ultrawideband Vivaldi antennas with sum and difference radiation patterns. When two Vivaldi antennas are placed next to each other, two mutually exclusive phenomena of grating lobe generation at the highest end of frequency and mutual coupling at the lowest end of frequency will define the bandwidth. Hence, to enhance the bandwidth, the separation between the antenna elements is reduced, which delays the grating lobes generation, and the coupling at lower frequencies is mitigated by introducing an asymmetry in the design of each Vivaldi antenna element. It is shown that this method can be extended to multi-element Vivaldi antennas for higher gain. Next, the bandwidth is further enhanced by adding two vertical metal slabs between the antenna elements improving the isolation at lower frequencies. The proposed antennas use commercially available couplers as feeding networks. As a potential replacement for couplers, an out-of-phase power divider with unequal power division is also proposed. In the second part of this thesis, the pattern diversity function is combined with multistate frequency-reconfigurable filtering functions in a series of novel designs. In the first proposed design, two quasi-Yagi-Uda antennas are used for pattern diversity, while two switchable and reconfigurable bandpass-to-bandstop filters are used to excite the antenna elements. The whole system is excited by an external commercially available rat-race coupler. In a next step, this design is modified to attain wideband, tunable bandpass, and tunable bandstop operations while obviating the need for an external coupler by using three antenna elements excited by a switchable power divider. In another implementation, the filtering functions is extended to dual-band independently tunable bandpass and bandstop to excite wideband antennas. While all the former designs featured E-plane pattern diversity, in another design aiming at increasing space coverage, a switchable patch antennas with sum and difference radiation patterns in both E- and H-plane of the antenna is designed.Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 202

Comparative Analysis of Integrated Wideband/Narrow Band Antenna for Cognitive Radio Applications

Cognitive radio is an inventive system to wireless technologies in which radios are designed with an astonishing level of intelligence and agility. This handles the available spectrum in an expedient manner to avoid spectrum scarcity. The cognitive radio antenna consists of integrated wideband and narrow band antenna in same substrate which is taxing task. A UWB antenna is pondered for the wide band operation which has the bandwidth of 7.5 GHz respectively is used for sensing vacant slots in the spectrum. For narrowband antenna the frequency and pattern reconfigurable antenna is usually suggested which is used for transmission of data through the vacant slots from the outcomes of sensing antenna. In this paper the various cognitive radio antennas are investigated in tremendously

Dual Port Antenna Combining Sensing and Communication Tasks for Cognitive Radio

Dynamic spectrum access has been proposed asthe effective solution to overcome the spectrum scarcity issue,supported by cognitive radio technology. Sensing and communicationfunctions are both the most important tasks in cognitiveradio systems. In this paper, an antenna system combiningsensing and communication tasks is proposed to be integratedinto cognitive radio front-ends. Sensing task is performed bythe means of an ultra-wideband quasi-omnidirectional antenna.Whilst the communication task is ensured by using a narrowbandantenna. Both antennas have been designed on the same layer ofa FR4 substrate, for manufacturing cost constraint. Therefore,the isolation between them must take into consideration. Themeasured mutual coupling of less than -18dB is achieved overthe whole impedance bandwidth. The proposed sensing antennacovers a wide range frequency bands ranging from 2 to 5.5GHz.While the communication antenna operates at 2.8GHz, and byadding inductors to the antenna, the resonant frequency canbe tuned from 2.6 to 2.7GHz. The whole antenna system wasdesigned, fabricated, and tested. Measurement and simulationresults prove the feasibility of the proposed structure for cognitiveradio applications

Reconfigurable and multi-functional antennas

This thesis describes a research into multi-frequency and filtering antennas. Several novel antennas are presented, each of which addresses a specific issue for future communication systems, in terms of multi-frequency operation, and filtering capability. These antennas seem to be good candidates for implementation in future multiband radios, cognitive radio (CR), and software defined radio (SDR). The filtering antenna provides an additional filtering action which greatly improves the noise performance and reduces the need for filtering circuitry in the RF front end. Two types of frequency reconfigurable antennas are presented. One is tunable left-handed loop over ground plane and the second is slot-fed reconfigurable patch. The operating frequency of the left handed loop is reconfigured by loading varactor diodes whilst the frequency agility in the patch is achieved by inserting switches in the coupling slot. The length of the slot is altered by activating the switches. Compact microstrip antennas with filtering capabilities are presented in this thesis. Two filtering antennas are presented. Whilst the first one consists of three edge-coupled patches, the second filtering antenna consists of rectangular patch coupled to two hairpin resonators. The proposed antennas combine radiating and filtering functions by providing good out of band gain suppression

Novel and Compact Reconfigurable Antennas for Future Wireless Applications

PhDThe development of reconfigurable antennas is considered to be very promising in modern and future communication systems. Reconfigurable antennas have made use of many reconfiguration techniques that are centred upon switching mechanisms such as p-i-n diodes or MEMS. Other techniques such as optical switches, mechanical structure changing or the ability to change the permeability or permittivity of smart substrate materials have also been used. Reconfigurable antennas have created new horizons for many types of applications especially in Cognitive Radio, Multiple Input Multiple Output Systems, personal communication systems, satellites and many other applications. Cognitive Radio is one of the potential wireless applications that may place severe demands on RF systems designers and particularly antenna designers, when it comes to providing exible radio front-ends capable of achieving the set objectives of the technology. The aim of this work is to investigate possible roles that different categories of reconfigurable antenna can play in cognitive and smart radio. Hence, the research described in this thesis focuses on investigating some novel methods to frequency-reconfigure compact ultra-wideband antennas to work in different bands; this will offer additional filtering to the radio front-end. In the ultra-wideband mode, the antenna senses the spectrum for available bands with less congestion and interference and hence decides on the most suitable part to be reconfigured to, allowing reliable and efficient communication links between the radio devices. Ultra-wideband antenna with reconfigurable integrated notch capability is also demonstrated to provide further enhancement to interference rejection and improve the overall communication link. Furthermore, the design of novel pattern and polarisation reconfigurable antennas will be also investigated to assist Cognitive Radio through spatial rather than frequency means. An ultimate target for this research is to combine different degrees of reconfiguration into one compact, state of the art antenna design that meets the growing demand of cognitive and smart radio devices for more intelligent and multi-functional wireless devices within the personal area network domains and beyond

2009 Index IEEE Antennas and Wireless Propagation Letters Vol. 8

This index covers all technical items - papers, correspondence, reviews, etc. - that appeared in this periodical during the year, and items from previous years that were commented upon or corrected in this year. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author\u27s name. The primary entry includes the coauthors\u27 names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author\u27s name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index

2008 Index IEEE Transactions on Control Systems Technology Vol. 16

This index covers all technical items - papers, correspondence, reviews, etc. - that appeared in this periodical during the year, and items from previous years that were commented upon or corrected in this year. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author\u27s name. The primary entry includes the coauthors\u27 names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author\u27s name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index