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Progress in Compact Antennas Edited by Laure Huitema Progress in Compact Antennas D3pZ4i & bhgvld, Dennixxx & rosea (for softarchive) Edited by Laure Huitema Stole src from http://avaxho.me/blogs/exLib/ Published by AvE4EvA Copyright © 2014 All chapters are Open Access distributed under the Creative Commons Attribution 3.0 license, which allows users to download, copy and build upon published articles even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. After this work has been published, authors have the right to republish it, in whole or part, in any publication of which they are the author, and to make other personal use of the work. Any republication, referencing or personal use of the work must explicitly identify the original source. As for readers, this license allows users to download, copy and build upon published chapters even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. Notice Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher. No responsibility is accepted for the accuracy of information contained in the published chapters. The publisher assumes no responsibility for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained in the book. Publishing Process Manager Technical Editor AvE4EvA MuViMix Records Cover Designer Published: 10 September, 2014 ISBN-10 9535117238 ISBN-13 978-9535117230 C ontents Preface Chapter 1 Compact Antennas — An overview by L. Huitema and T. Monediere Chapter 2 Anten nas for Body Centric Wireless Communications at Millimeter Wave Frequencies by Nacer Chahat, Maxim Zhadobov and Ronan Sauleau Chapter 3 Low Cost Compact Multiband Printed Monopole Antennas and Arrays for Wireless Communications by Qi Luo, Jose Rocha Pereira and Henrique Salgado Chapter 4 Miniature Antenna with Frequency Agility by L. Huitema and T. Monediere Chapter 5 Active Compact Antenna for Broadband Applications by Y. Taachouche, M. Abdallah, F. Colombel, G. Le Ray and M. Himdi Chapter 6 All-Dielectric Optical Nanoantennas by Alexandr E. Krasnok, Pavel A. Belov, Andrey E. Miroshnichenko, Arseniy I. Kuznetsov, Boris S. Luk’yanchuk and Y uri S. Kivshar Chapter 7 Building Partial Discharge Signal Wireless Probes by Fabio Viola and Pietro Romano Preface Compact antennas are a subject of growing interest from industry and scientific community to equip wireless communicating objects. The need for high performance small antennas and RF front ends is the challenge for future and next generation mobile devices. This book brings the body of knowledge on compact antennas into a single comprehensive volume. It is designed to meet the needs of electrical engineering and physics students to the senior undergraduate and beginning graduate levels, and those of practicing engineers. Chapter 1 Compact Antennas — An overview L. Huitema and T. Monediere Additional information is available at the end of the chapter 1. Introduction Antenna size reduction is restricted by fundamental physical limits [1-3], in terms of trade-off between radiation performances and impedance bandwidth. Miniaturization of devices leads to the reduction of antennas which becomes one of the most important challenges [4]. Limi‐ tations in terms of bandwidth and efficiency suggest an analysis with respect to fundamental limits [5]. Although interests are often focused on the impedance bandwidth, many studies deal with the radiation quality factor Q. Some papers [6] have been concluded that the impedance bandwidth BW equals 1/Q. The minimum Q value reachable by an infinitesimal electric dipole, or similarly by the azimuthally symmetric TM spherical mode, has been 10 investigated thoroughly. Hansen and Best [7] have shown that the lower bound on Q, deriving from Chu’s analysis, is depending on the expense of efficiency as shown by the equation: ( 1 1 ) Q =η + lb (ka)3 ka where a is the minimum radius of the sphere enclosing the antenna and k is the wave number (k=2π/λ). The Figure 1 shows that it is very difficult to have a wide bandwidth (low Q-factor), while reaching a good efficiency for miniature antennas (k.a around 0.2). Thus, the miniaturization of antennas implies them to suffer of both limited efficiency and low bandwidth. Since many years the scientific literature addresses some approaches concerning miniaturiza‐ tion techniques. The goal is to decrease the electrical size of the radiating element. This chapter will draw up a survey of compact antennas in practical settings and the most common miniaturization techniques listed below: 2 Progress in Compact Antennas 105  = 100% antenna 104 antenna = 50%  = 20% antenna 103  = 2% antenna Q r o t102 c a f y tila101 u Q 100 10-1 10-2 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 k.a Figure 1. Quality factor according to the antenna dimensions and efficiencies • Folded configurations [8-10] • Surface etching techniques [11-14] • Shorting walls or pins [15-16] • The use of high dielectric constant materials or magneto-dielectric materials [17-22]. • Loading the radiating element with active components [23-26]. • Creation of hybrid modes with particular boundary conditions in dielectric resonator antennas. It allows choosing their resonance frequencies (for multiband or wide impedance bandwidth) [27]. We will start this chapter by detailing wire antennas. Indeed, after explaining the classical dipole antenna, we will show how to miniaturize this kind of antennas based on shape design such as bending, folding and meandering. The second part will detail planar antennas. We will see the impact of materials properties under the patch antenna hat, i.e. dielectric or magneto-dielectric materials. Then, planar miniature antennas will be shown, e.g. Planar Inverted F Antenna (PIFA) and monopolar wirepatch antenna. The third part will exhibit Dielectric Resonator Antennas and how to use this kind of antennas for low frequency band application while having compact sizes. Finally, the last part will summary all the antennas presented in this chapter, while showing their main settings.