1,721,033 research outputs found
Design and Implementation of Reconfigurable and MIMO Antennas for Future Heterogeneous Wireless Systems
No full textThe recent progress in electronics and communication technologies has driven the unprecedented demand for multi-functional wireless communication in most single wireless devices. However, employing the limited spectrum effectively on communication equipment poses a key design challenge, as most antennas often suffer from bandwidth limitations and restricted frequency rarge. Onekey approach to overcome this problem without significantly affecting the antenna size is to apply antenna tuneability and reconfigurability. This is achieved by electronically changing some properties of the antenna usually by loading the reactive loading of the resonator by means of active electronic elements including varactor diode or PIN diode with extra circuitry.
The main objective of this research is to design and investigate low-profile antennas for heterogeneous wireless systems using the antenna reconfigurability concept through tuning and/or using the MIMO antenna techniques. The research focuses on antenna design and implementation to cover various wireless standards and applications within the electromagnetic spectrum including UMTS (1.92-2.17 GHz), Cognitive Radio such as WLAN and WiMAX (2.4GHz), Wi-Fi (5.2GHz), 5G (600MHz - 6GHz) and MBAN applications. A family of compact microstrip printed reconfigurable antennas for various cognitive radio applications is presented. Effects of various slots on the antenna performance are also investigated, and the final version was reconfigured across a broad frequency range (1.5 - 2.4 GHz)
Furthermore, four new variants of the miniaturised hexagonal-shaped monopole printed antennas for different UWB applications are proposed. Prototypes of the four versions are fabricated and compared to establish their results. Two reconfigurable rejection bands are introduced to avoid anticipated interference with other systems working within the UWB range.
Finally, a novel low-profile four-element MIMO antenna was designed and fabricated to operate at the 2.4 GHz ISM band. both measurements and simulation results revealed strong agreement. Furthermore, the designed antenna was also tested on human tissues, with acceptable results when compared to its performance in free space. it is proved to be a good fit for wireless, mobile communications, medical systems and WBAN applications.Libyan Ministry of Higher Education.Subtitle: Simulation and Measurement of Reconfigurable Antennas for Cognitive Radio, UWB Applications, Investigation of Antenna Gain and Efficiency, Frequency Tuneable Range, Antenna Radiation Performance and Antenna Design Optimization using Parametric Studies as well as using MIMO antenna for wireless body area network
Recent Advances in Antenna Design for 5G Heterogeneous Networks
Full text linkThe aim of this book is to highlight up to date exploited technologies and approaches in terms of antenna designs and requirements. In this regard, this book targets a broad range of subjects, including the microstrip antenna and the dipole and printed monopole antenna. The varieties of antenna designs, along with several different approaches to improve their overall performance, have given this book a great value, in which makes this book is deemed as a good reference for practicing engineers and under/postgraduate students working in this field. The key technology trends in antenna design as part of the mobile communication evolution have mainly focused on multiband, wideband, and MIMO antennas, and all have been clearly presented, studied and implemented within this book. The forthcoming 5G systems consider a truly mobile multimedia platform that constitutes a converged networking arena that not only includes legacy heterogeneous mobile networks but advanced radio interfaces and the possibility to operate at mm wave frequencies to capitalize on the large swathes of available bandwidth. This provides the impetus for a new breed of antenna design that, in principle, should be multimode in nature, energy efficient, and, above all, able to operate at the mm wave band, placing new design drivers on the antenna design. Thus, this book proposes to investigate advanced 5G antennas for heterogeneous applications that can operate in the range of 5G spectrums and to meet the essential requirements of 5G systems such as low latency, large bandwidth, and high gains and efficiencies
Compact MIMO antenna array design for wireless applications
No full textDesign of compact handset antennas to exploit two techniques to increase capacity in mobile systems is reported. Firstly, the use of noise-like signals spread over a very wide frequency band, known as ultrawideband; secondly, MIMO (multiple-input multiple-output) transmission. Methods of achieving MIMO through spatial diversity require array antenna elements to be separated by significant fractions of a wavelength, giving a relatively bulky structure: an alternative is to exploit multiple polarisations in the signal pathways. This requires antenna elements responding principally to each of the orthogonal polarisations and these can be closely located, enabling integration into a mobile handset. The designs presented are very compact and amenable to production by modern printing methods
Recent Advances in Antenna Design for 5G Heterogeneous Networks
No full textThe aim of this book is to highlight up to date exploited technologies and approaches in terms of antenna designs and requirements. In this regard, this book targets a broad range of subjects, including the microstrip antenna and the dipole and printed monopole antenna. The varieties of antenna designs, along with several different approaches to improve their overall performance, have given this book a great value, in which makes this book is deemed as a good reference for practicing engineers and under/postgraduate students working in this field. The key technology trends in antenna design as part of the mobile communication evolution have mainly focused on multiband, wideband, and MIMO antennas, and all have been clearly presented, studied and implemented within this book. The forthcoming 5G systems consider a truly mobile multimedia platform that constitutes a converged networking arena that not only includes legacy heterogeneous mobile networks but advanced radio interfaces and the possibility to operate at mm wave frequencies to capitalize on the large swathes of available bandwidth. This provides the impetus for a new breed of antenna design that, in principle, should be multimode in nature, energy efficient, and, above all, able to operate at the mm wave band, placing new design drivers on the antenna design. Thus, this book proposes to investigate advanced 5G antennas for heterogeneous applications that can operate in the range of 5G spectrums and to meet the essential requirements of 5G systems such as low latency, large bandwidth, and high gains and efficiencies
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
5G Optical Sensing Technologies
No full textThis chapter describes the future network architecture in 5G communication systems and the development of fiber optic sensors to provide not just only secure but also reliable access for the new mobile communication systems. In case of fiber optic sensors, measurement is employed by sensing either intensity or phase change in one or more lights beams. The use of optical fibers as the main backbone of most communication systems including the 5G network can efficiently and cost effectively help in transferring large amounts of information from point to point. The chapter covers optical fiber based sensors and pays particular attention to optical fiber network physical security solutions. It presents three types of optical fiber sensor technologies: optical time domain reflectometer based sensor, MFI and fiber Bragg grating sensor. The chapter discusses performance parameters and design considerations
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Investigation, design and implementation of frequency tuneable antennas for mobile handset and UWB applications. Simulation and measurement of tunable antennas for handheld mobile handsets and UWB system, investigations of frequency tuneable range, antenna radiation performance and antenna design optimisation using parametric studies
No full textGeneral Secretariat of Education and Scientific Research, Libya.The only available copy is the print version kept in the J.B.Priestley Library for reference
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