Ultra Wide Band Antennas Ultra Wide Band Antennas Edited by Xavier Begaud Series Editor Pierre-Noël Favennec First published 2011 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc. Adapted and updated from Les antennes Ultra Large Bande published 2010 in France by Hermes Science/Lavoisier © LAVOISIER 2010 Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address: ISTE Ltd John Wiley & Sons, Inc. 27-37 St George’s Road 111 River Street London SW19 4EU Hoboken, NJ 07030 UK USA www.iste.co.uk www.wiley.com © ISTE Ltd 2011 The rights of Xavier Begaud to be identified as the author of this work have been asserted by him in accordance with the Copyright, Designs and Patents Act 1988. Library of Congress Cataloging-in-Publication Data Antennes ultra large bande. English Ultra wide band antennas / edited by Xavier Begaud. p. cm. Rev. papers of the autumn school, GDR Ondes, organized in Valence, Oct. 2006. Includes bibliographical references and index. ISBN 978-1-84821-232-9 (hardback) 1. Ultra-wideband antennas--Congresses. I. Begaud, Xavier. II. Title: Ultra-wideband antennas. TK7871.67.U45A5813 2010 621.382'4--dc22 2010038273 British Library Cataloguing-in-Publication Data A CIP record for this book is available from the British Library ISBN 978-1-84821-232-9 Printed and bound in Great Britain by CPI Antony Rowe, Chippenham and Eastbourne. Cover photo: created by Atelier Isatis, Dijon, France Table of Contents Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix Chapter 1. Applications of Ultra Wide Band Systems. . . . . . . . . . . . . . 1 Serge HÉTHUIN and Isabelle BUCAILLE 1.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2. UWB regulation: a complex context . . . . . . . . . . . . . . . . . . . . . 2 1.2.1. UWB regulation in the USA . . . . . . . . . . . . . . . . . . . . . . . 2 1.2.2. UWB regulation in Europe . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2.3. UWB regulation in Japan . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2.4. Emission mask in the United States, Europe and Japan . . . . . . . 7 1.3. Formal Ultra Wide Band types . . . . . . . . . . . . . . . . . . . . . . . . 8 1.3.1. Ultra Wide Band Impulse Radio (UWB-IR) . . . . . . . . . . . . . . 8 1.3.2. OFDM-ultra wide band (UWB-OFDM) . . . . . . . . . . . . . . . . 12 1.4. Non-formal ultra wide band types . . . . . . . . . . . . . . . . . . . . . . 14 1.4.1. Ultra wide band frequency hopping (UWB-FH) . . . . . . . . . . . . 14 1.4.2. Chirp Ultra Wide Band (UWB-FM) . . . . . . . . . . . . . . . . . . . 17 1.5. Comparison between the different Ultra Wide Band techniques . . . . . 20 1.6. Typical UWB-OFDM applications . . . . . . . . . . . . . . . . . . . . . . 21 1.6.1. Peripheral connection to a PC . . . . . . . . . . . . . . . . . . . . . . 21 1.6.2. High speed applications in large structures with optical fiber backbone . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 1.6.3. High speed UWB in a harsh indoor environment . . . . . . . . . . . 26 1.6.4. High speed UWB combined with other technologies . . . . . . . . . 27 1.7. Specialized UWB-OFDM applications . . . . . . . . . . . . . . . . . . . 28 1.7.1. Last mile radio applications . . . . . . . . . . . . . . . . . . . . . . . . 28 1.7.2. Information and video streaming applications . . . . . . . . . . . . . 29 1.8. Typical applications of the Impulse Radio UWB, UWB-FH and UWB-FM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 vi Ultra Wide Band Antennas 1.8.1. Professional geo-localization . . . . . . . . . . . . . . . . . . . . . . . 30 1.8.2. Geolocalization for private individuals . . . . . . . . . . . . . . . . . 31 1.9. Impact on the antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Chapter 2. Radiation Characteristics of Antennas . . . . . . . . . . . . . . . . 33 Xavier BEGAUD 2.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 2.1.1. What is an antenna and how can we define it? . . . . . . . . . . . . . 36 2.1.2. Where does antenna radiation come from? . . . . . . . . . . . . . . . 37 2.2. How can we characterize an antenna? . . . . . . . . . . . . . . . . . . . . 37 2.2.1. Plane wave and polarization . . . . . . . . . . . . . . . . . . . . . . . 38 2.3. Radiation fields and radiation power . . . . . . . . . . . . . . . . . . . . . 40 2.3.1. Radiation fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 2.3.2. Radiation power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 2.3.3. The radiation pattern, the phase center . . . . . . . . . . . . . . . . . 41 2.3.4. Directive gain, directivity . . . . . . . . . . . . . . . . . . . . . . . . . 43 2.3.5. Radiation impedance and radiation resistance . . . . . . . . . . . . . 46 2.4. Gain, efficiency and effective aperture . . . . . . . . . . . . . . . . . . . . 47 2.4.1. Gain and efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 2.4.2. Receive antenna effective aperture . . . . . . . . . . . . . . . . . . . . 48 2.5. Budget link, transfer function . . . . . . . . . . . . . . . . . . . . . . . . . 49 2.6. Equivalent circuits of the antennas . . . . . . . . . . . . . . . . . . . . . . 51 2.7. Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 2.8. Example of characterization: the triangular probe antenna in F . . . . . 52 2.8.1. Description of the structure . . . . . . . . . . . . . . . . . . . . . . . . 53 2.8.2. Impedance matching . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 2.8.3. Radiation patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 2.8.4. Optimization of the antenna . . . . . . . . . . . . . . . . . . . . . . . . 58 Chapter 3. Representation, Characterization and Modeling of Ultra Wide Band Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Christophe ROBLIN 3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 3.2. Specificities of UWB antennas: stakes and representation . . . . . . . . 62 3.2.1. Context and requirements of an effective and complete representation . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 3.2.2. Transfer function in transmission . . . . . . . . . . . . . . . . . . . . 64 3.2.3. Transfer function in reception, reciprocity . . . . . . . . . . . . . . . 71 3.2.4. Transfer function and “conventional” quantities . . . . . . . . . . . 75 3.2.5. Elements on the measurement of transfer functions in the frequency domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 3.3. Temporal behavior, distortion . . . . . . . . . . . . . . . . . . . . . . . . . 77 Table of Contents vii 3.4. Distortion and ideality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 3.5. Performance characterization: synthetic indicators . . . . . . . . . . . . 82 3.5.1. Energy gain and mean realized gain (MRG) . . . . . . . . . . . . . . 83 3.5.2. Synthetic indicators of distortion . . . . . . . . . . . . . . . . . . . . . 86 3.6. Parsimonious representation by development of singularities and spherical modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 3.6.1. The singularity expansion method . . . . . . . . . . . . . . . . . . . . 95 3.6.2. Spherical mode expansion method (SMEM) . . . . . . . . . . . . . . 98 3.6.3. Parametric model with very high order reduction . . . . . . . . . . . 102 3.6.4. Examples of processing of measured ATF . . . . . . . . . . . . . . . 103 Chapter 4. Experimental Characterization of UWB Antennas . . . . . . . . 113 Christophe DELAVEAUD 4.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 4.2. Measurements of the characteristics of radiation . . . . . . . . . . . . . . 114 4.2.1. Basic concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 4.2.2. Frequency methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 4.2.3. Time domain method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 4.3. Measurements of the electric characteristics . . . . . . . . . . . . . . . . 156 4.3.1. Preamble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 4.3.2. Frequency domain measurements . . . . . . . . . . . . . . . . . . . . 157 4.3.3. Time domain measurements . . . . . . . . . . . . . . . . . . . . . . . 159 Chapter 5. Overview of UWB Antennas . . . . . . . . . . . . . . . . . . . . . . 163 Nicolas FORTINO, Jean-Yves DAUVIGNAC, Georges KOSSIAVAS and Xavier BEGAUD 5.1. Classification of UWB antennas . . . . . . . . . . . . . . . . . . . . . . . 163 5.2. Frequency independent antennas . . . . . . . . . . . . . . . . . . . . . . . 164 5.2.1. Equiangular antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 5.2.2. Log-periodic antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 5.2.3. Techniques of frequency-independent antennas performance improvement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 5.3. Elementary antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 5.3.1. The biconical antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 5.3.2. The discone antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 5.3.3. The bowtie antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 5.3.4. Planar monopoles antennas . . . . . . . . . . . . . . . . . . . . . . . . 181 5.3.5. Performance improvement techniques of elementary UWB antennas . . . . . . . . . . . . . . . . . . . . . . . . . . 190 5.3.6. Directive elementary antennas . . . . . . . . . . . . . . . . . . . . . . 195 5.3.7. Antennas with progressive transition . . . . . . . . . . . . . . . . . . 196 5.3.8. Horn antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 viii Ultra Wide Band Antennas 5.4. Miniaturization of UWB antennas . . . . . . . . . . . . . . . . . . . . . . 202 5.4.1. General principles of antenna miniaturization . . . . . . . . . . . . . 202 5.4.2. Miniaturization problems of UWB antennas . . . . . . . . . . . . . . 203 5.4.3. Miniaturization techniques applicable to UWB antennas . . . . . . 204 5.5. UWB antennas for surface penetrating radars. . . . . . . . . . . . . . . . 206 5.5.1. Presentation of SPR UWB technologies . . . . . . . . . . . . . . . . 206 5.5.2. Design of antennas for SPR radars . . . . . . . . . . . . . . . . . . . . 207 Chapter 6. Antenna-Channel Joint Effects in UWB . . . . . . . . . . . . . . . 213 Alain SIBILLE 6.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 6.2. Recalls on the UWB radio channel . . . . . . . . . . . . . . . . . . . . . . 214 6.3. Impact of the channel on the performance of UWB systems . . . . . . . 218 6.4. Effective antenna performance in an ideal channel . . . . . . . . . . . . 220 6.4.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 6.4.2. Radiation patterns for various architectures . . . . . . . . . . . . . . 221 6.5. Effective performance of non-directional antennas in dispersive channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 6.5.1. Gain calculation for non-ideal antennas . . . . . . . . . . . . . . . . . 225 6.5.2. Results on measured channels . . . . . . . . . . . . . . . . . . . . . . 231 6.6. Effective performance of directional antennas in dispersive channels . 233 6.7. Factorization of antenna patterns . . . . . . . . . . . . . . . . . . . . . . . 235 6.8. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 APPENDICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 Appendix A. Reciprocity of the Antennas in Reception and Transmission Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 A.1. Reciprocity applied to waveguides . . . . . . . . . . . . . . . . . . . . . . 243 A.2. Reciprocity applied to the passive antennas in transmission and reception . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 Appendix B. Method of the Stationary Phase . . . . . . . . . . . . . . . . . . . 253 Acronyms and Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 List of Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 Preface Ultra wide band (UWB) has received a great amount of interest since the decision by the US Federal Communications Commission (FCC) in February 2002 authorizing the emission of very low power spectral density in a bandwidth going from 3.1 to 10.6 GHz. This technique of radio transmission consists of using signals whose spectrum is spread out over a wideband of frequencies, typically from about 500 MHz to several GHz. It was formerly used for military and radar applications, then transposed a few years ago to telecommunications, thus causing a growing interest within the scientific community and industry. This spectral availability makes it possible to consider the wideband communications and also leads to a fine space resolution for the radars. However, the current restrictions of the regulatory agencies on the emission power level limit the range of the UWB communications to a few meters for high data rates and up to a few hundred meters for low data rates. UWB technology thus seems naturally well positioned for short range communications (WLAN, WPAN), offering an alternative at the same time of low cost and low consumption to the existing standards in these networks. The acronym UWB gathers two standardized but distinct technologies today. The first is founded on the emission of impulses of very short duration; this is the mono-band or impulse radio approach. The second approach is based on the use of multiple simultaneous carriers where the bandwidth is subdivided into several sub- bands (multi-band approach).The modulation used in each sub-band is the OFDM (Orthogonal Frequency Division Multiplexing). The advantages and disadvantages of the mono- and multi-band approaches are delicate questions and have been the subject of debate by many regulatory agencies. A particularly important question is the minimization of the interference to the emission and reception of the UWB system. x Ultra Wide Band Antennas The multiple band approach is particularly interesting because the carrier frequencies can be suitably selected to avoid interferences with narrow band-based systems. This offers more flexibility but requires an additional layer of control in the physical layer. UWB signals in the impulse technique require very good RF components (very short switching time) and a greater accuracy of synchronization. UWB systems can then be developed at a relatively low cost. Contrary to the multi-band approach which is based on techniques which are tested and available already, the architecture of a telecommunication system in impulse mode has involved many developments and in particular has required the installation of new definitions. The antenna does not escape these changes and we will show that this interface between the propagation channel and the architecture of the transmitters/receivers must add other time-domain radiation characteristics to optimize the transmission and the reception of impulses. These characteristics naturally come to complement and not replace the conventional ones, making it possible to qualify the antennas. This is the method which we retained in this work; starting from the usual parameters necessary for characterization of the antennas in the spectral domain, we added to these the suitable definitions in the time domain. We will not consider the radiation characteristics which will not be used during the antenna design in time domain. We will thus look at the frequency and time-domain characteristics, by specifying each time the joint and specific definitions. This book, dedicated specifically to UWB antennas, provides the electromagnetic foundations to students and presents state of arts for engineers and researchers. The reader will notice some absences: the IRA (Impulse Radiating Antenna) and specialized UWB smart antennas which could not be detailed within the scope of this book. This book is one of the fruits of the autumn school, GDR1 Ondes, on UWB organized in October 2006 in Valence (France). Its role was to present the fundamental aspects, measurement, processing and architectures of UWB systems. The large majority of the authors of this book were already “on board” and took an active part in the GDR Ondes Working group “Ultra Large-Bande, Communications Hauts-Débits, Contrôle et Commande” (Ultra Wide Band, High Data Rates Communications, Remote and Control). Finally, the book is a summary of French work recognized at an international level on a subject which, still today, produces several hundred scientific articles 1. GDR ONDES 2451, created on 1st January 2002 by the CNRS, has the role of being an indispensible center for all specialists in electromagnetism, optics and photonics and acoustics. Preface xi every year. The chapters were written by academic and institutional researchers and industrial specialists in the field. This book is composed of six chapters. Chapter 1 presents the definitions and the regulatory aspects of the UWB. A classification then a comparison of UWB approaches is proposed. The chapter is closed by a presentation of UWB target applications on fields as varied as broadband communications in multiple environments and geolocalization. Chapter 2 defines the radiation characteristics of the antennas usually used in the frequency domain. It is a restricted, rather than an exhaustive, presentation of the characteristics which will be then used throughout the book. Special attention has been brought to the validity of the definitions in the time and frequency domains. An example of a directive UWB antenna is then proposed to illustrate the characteristics defined in the chapter. Chapter 3 enriches the conventional characterization of the antennas. Through a functional approach, we define concepts, objects of reference and indicators appropriate for the analysis of time domain behavior of UWB antennas. In particular, we focus on the phenomenon of signal distortion and on the concept of an ideal antenna. Because of the significant amount of data (experimental or simulated) to be handled and analyzed, various indicators of performance are then proposed making it possible to synthesize information to better expose the behaviors and imperfections, in order to more easily compare the antennas. Then a parametric modeling approach based on drastic order reduction closes the chapter. Chapter 4 provides the necessary complement to the two preceding chapters and presents the experimental characterization methods allowing the validation of any design. The first part of this chapter takes the logic of the book, describing antenna radiation measurements in the spectral domain then the methods developed for the time domain characterization of UWB antennas. The methods presented are detailed and specificities of the instrumentation are also described. Measurements of a compact UWB antenna make it possible to illustrate the preceding definitions. The chapter is concluded by the measurement methods of the electric characteristics of the inputs of the antennas. Chapter 5 is devoted to a panorama of existing antennas with matching impedance characteristics on very wide bandwidths and to some techniques making it possible to improve their performances. The frequency-independent antennas which present the property to be dimensioned identically at all the frequencies are initially detailed. Then, the elementary antennas with a widened shape are also described, in particular for UWB communications. Directive antennas, then antennas