Table of Contents

Preface

Chapter 1. Electromagnetic Environment

1.1. Electromagnetic radiation sources

1.2. Electromagnetic fields

1.3. Bibliography

Chapter 2. From Measurement to Control of Electromagnetic Waves using a Near-field Scanning Optical Microscope

2.1. Introduction

2.2. Principle of the measurement using a local probe

2.3. Measurement of the electromagnetic field distribution inside nanophotonic components

2.4. Measuring the amplitude and phase in optical near-field

2.5. Active optical near-field microscopy

2.6. Conclusion

2.7. Acknowledgements

2.8. Bibliography

Chapter 3. Meteorological Visibility Measurement: Meteorological Optical Range

3.1. Introduction

3.2. Definitions

3.3. Atmospheric composition

3.4. Atmospheric effects on light propagation

3.5. Units and scales

3.6. Measurement methods

3.7. Visibility perturbation factors

3.8. Applications

3.9. Appendix – optical contrast and Koschmieder's law

3.10. Glossary

3.11. Bibliography

Chapter 4. Low Coherence Interferometry

4.1. Introduction

4.2. Phase measurement

4.3. Metrology considerations

4.4. Applications

4.5. Conclusion

4.6. Bibliography

Chapter 5. Passive Remote Sensing at Submillimeter Wavelengths and THz

5.1. Introduction

5.2. Submillimeter – THz low noise heterodyne receivers

5.3. Submillimeter – THz applications for astronomy and astrophysics

5.4. Submillimeter – THz remote-sensing applications to aeronomy and planetology

5.5. Conclusion

5.6. Acknowledgements

5.7. Bibliography

Chapter 6. Exposimetry – Measurements of the Ambient RF Electromagnetic Fields

6.1. Introduction

6.2. Definitions

6.3. Interactions of the electromagnetic fields with biological tissues and medical risks

6.4. Exposure limit values

6.5. Electromagnetic environment to be measured

6.6. Measurement equipment

6.7. Measurements

6.8. Control stations and uninterrupted electromagnetic measurements: towards a 3D electromagnetic land register

6.9. Appendix 1 – some field measurements

6.10. Appendix 2 – principal characteristics of mobile communication systems

6.11. Bibliography

Chapter 7. Ambient RF Electromagnetic Measurements in a Rural Environment

7.1. Introduction

7.2. Measurement set-up

7.3. Operating mode

7.4. Different studies

7.5. Measurements results

7.6. Electrical field strength

7.7. Conclusion

7.8. Acknowledgements

7.9. Bibliography

Chapter 8. Radio Mobile Measurement Techniques

8.1. Introduction

8.2. Field strength measurements

8.3. Measurement of the impulse response

8.4. Measurement of directions of arrival

8.5. WiFi measurements in a home environment (field strength, data rate)

8.6. Conclusion

8.7. Glossary

8.8. Acknowledgments

8.9. Bibliography

Chapter 9. Dosimetry of Interactions Between the Radioelectric Waves and Human Tissues – Hybrid Approach of the Metrology

9.1. Introduction

9.2. Evaluation of the power absorber for the tissues

9.3. Experimental evaluation of the specific absorption rate (SAR)

9.4. SAR evaluation in biological tissues

9.5. Variability, representativeness and uncertainty

9.6. Conclusions

9.7. Bibliography

Chapter 10. Measurement for the Evaluation of Electromagnetic Compatibility

10.1. Introduction

10.2. General aspects of EMC measurement

10.3. Emissivity and radiated immunity testing

10.4. Efficiency and limitations of EMC measurement techniques

10.5. Mode-stirred reverberation chambers

10.6. Electromagnetic near-field measurement techniques applied to EMC

10.7. Conclusions and future prospects

10.8. Bibliography

Chapter 11. High Precision Pulsar Timing in Centrimetric Radioastronomy

11.1. Introduction

11.2. Ultra-stable clocks to the limits of the Galaxy

11.3. Dispersion by the interstellar medium

11.4. Instrumentation used to study pulsars

11.5. Swept local oscillator dedispersion

11.6. Filterbank dedispersion

11.7. Real-time coherent dedispersion

11.8. The coherent pulsar instrumentation installed at Nançay

11.9. Conclusion

11.10. Bibliography

Chapter 12. Long Baseline Decameter Interferometry between Nançay and LOFAR

12.1. Introduction

12.2. Observations

12.3. Analysis

12.4. Conclusions and perspectives

12.5. Acknowledgements

12.6. Bibliography

List of Authors

Index

First published 2010 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.

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:

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© ISTE Ltd 2010

The rights of Frédérique de Fornel and Pierre-Noël Favennec to be identified as the authors of this work have been asserted by them in accordance with the Copyright, Designs and Patents Act 1988.

Library of Congress Cataloging-in-Publication Data

Measurements using optic and RF waves / edited by Frédérique de Fornel, Pierre-Noël Favennec.
     p. cm.
   Includes bibliographical references and index.
   ISBN 978-1-84821-187-2
   1.  Electromagnetic measurements. 2.  Frequencies of oscillating systems--Measurement. 3.  Radio meteorology. 4. Radio astronomy. I. Fornel, Frédérique de, 1953- II. Favennec, Pierre-Noël.
   QC661.M467 2010
   681′.25--dc22

2009041736

British Library Cataloguing-in-Publication Data
A CIP record for this book is available from the British Library
ISBN 978-1-84821-187-2

Preface

The extent of measurements centered on electromagnetism largely exceeds traditional characterization of the electromagnetic fields. It can apply to domains as varied as nanotechnologies, telecommunications, meteorology, geolocalization, radioastronomy, health, biology, etc.

Measurement must follow the evolution of technologies. Note, for example, the strong development of radio and optical techniques. It is necessary to learn how to characterize these waves, which are increasingly powerful and propagate in increasingly complex media. These controlled waves also become a formidable tool for measurement, making it possible to consider high performance measurements giving time, distance, spectroscopic characterization, etc.

Regarding the multiplicity of controlled radio transmissions added to the different multiple sources that we call electromagnetic noises, there are naturally, increasingly pressing safety environment requirements, applied as standards and increasingly severe thresholds resulting in the development of more precise metrology in electromagnetism and methods of continuously improved measurements.

Measurement has a societal requirement that leads to the establishment and respect of recommendations and standards, which are intended for the information of companies and also to preserve public health. Specialists must encourage the development of a true metrological culture. This culture must give professionals and citizens the ability to properly analyze the very high quantity of data currently provided.

Science and measurement techniques in electromagnetism are very broad fields, as our electromagnetic environment covers all frequencies and wavelengths through distances from nanometers to light-years (described in Chapter 1). During the writing of this book we had to make some choices to limit the extent of this volume, while considering multiple facets of the topic. Thus we sweep the entire electromagnetic spectrum, from several hertz to terahertz; with optics, we consider distances ranging from nanometers to light-years; before extending towards the various measurement techniques using electromagnetic waves for various applications.

Chapter 2 written by Lalouat et al. concerns measurement to control electromagnetic waves using a near-field scanning optical microscope. The development of nanotechnologies and particularly nanophotonics involves new tools working within the nanometric scale. Optical near field techniques opens an interesting avenue for measurement within the nanometric scale, but also for controlling the electromagnetic field within nanometric dimensions and at last for designing new optical functions.

Visibility, the possibility of seeing at a certain distance is necessary in many fields such as meteorology, optical wireless communications, road safety or maritime, etc. Measurement of visibility, determined by the atmosphere transparency is described by Sizun and Al Naboulsi. In Chapter 3 they describe the measuring instruments dedicated to this determination — such as the transmissiometer and the diffusiometer — as well as the applicability covered by these visibility measurements.

Low coherence interferometry, discussed in Chapter 4 by Chapeleau et al., enables the measurement of phase and chromatic dispersion. This interferometric technique finds applications in the characterization of standard optical fibers, microstructured fibers and doped fibers, Bragg networks and optical planar circuits. In addition to the optical characteristics of the analyzed objects, interferometry makes it possible to reach, by rebuilding, other parameters such as the local temperature or deformation fields.

All the observations in millimeter-length, submillimeter waves and THz provide significant information for the study of atmospheric chemistry (ground, planets), astrochemistry (molecular clouds, star formation, study of galaxies, comets) and cosmology. In Chapter 5, Gérard Beaudin presents the new instrumental techniques for passive remote sensing at submillimeter waves and THz, which made it possible to obtain observations never achieved until now. The future significant projects for astronomy, aeronomy and planet exploration, will profit advantageously from these new technological developments.

In-situ measurements of the electromagnetic fields remain a difficult problem and it was necessary to give a reliable metrology that is accepted by all. In Chapter 6 Favennec develops exposimetry, i.e. techniques to measure human exposure to the electromagnetic field. Measurement of the fields lies within the scope of the field level checks with respect to the limitations of the field levels imposed on the territory.

For radiomobile communications, the propagation wave channel depends on the environment which is urban, rural, mountainous, etc. In Chapters 7 and 8, Sizun et al. present radiomobile measurement techniques, with particular focus on method choices according to the applications concerned and the need for analysis and modeling. Among the useful techniques specific to mobility, we see measurements in narrow band, impulse response measurements, angles of arrival and rates of transmission measurements.

With the explosion of mobile telephony into the world, dosimetry of the radio wave interactions with biological tissues has made significant progress in recent years. However, direct measurement of the absorptive powers of human tissues is limited by the heterogenity of tissues and the intrusive aspect of this approach. Taking account of significant progress in the field of electromagnetic simulators, a hybrid approach associating measurements and simulation was developed by Joe Wiart and Man Faï Wong (Chapter 9) and is applied to the dosimetry of the interactions in the head of portable telephones users. This hybrid approach, nevertheless, remains confronted with the variability of morphology and the representativeness of the digital models used.

Electromagnetic compatibility measurement of the electronic systems is fundamental. In Chapter 10, Besnier et al. gives a progress report on the current stakes of this type of measurement at the time when it plays an increasingly significant role in the development and homologation of electronic systems, whose complexity is increasing in a number of industrial products. The principles, the characteristics and the limits of certain current procedures are presented while emphasizing measurements of radiated emissivity and radiated immunity. The development of two recent measurement methods are presented because they offer new prospects for the electromagnetic measurement of compatibility: reverberating room with mode mixing and measurement in the near-field.

Chapter 11 written by Ismaël Cognard covers high precision pulsar timing in centimetric radioastronomy. This chapter presents instrumentations specific to 1.4 GHz for ultra-precise timing of radio impulses. A review of the techniques used to reach precise details of timing of a few hundred nanoseconds is proposed, accompanied by results obtained from Nançay's radio telescope.

In radioastronomy, interferometry appears as a new technique of observation. Thus, in Chapter 12, Zarka presents long baseline decameter interferometry. The Jupiter observations carried out simultaneously at Nançay and in Holland (700 km away), confirm this feasibility and the reliability of the suggested method.

We are quite conscious that this book on science and measurement techniques in electromagnetism does not cover all the fields and in particular that of quantum metrology; however it does enable us to form a well informed opinion about the variety of techniques and the methods available:

– to measure the characteristics of electromagnetic waves, in terms of local field, power and phase for a broad field of frequencies;

– for the metrology of physical quantity such as distance, time, optical range, etc., using the properties of electromagnetic waves;

– to find new approaches for new requirements for electromagnetic measurements in complex structured media such as biologic tissues.

Pierre-Noël FAVENNEC
Institute Télécom, Paris
and URSI-France

Frédérique DE FORNEL
University of Burgundy, Dijon

Chapter 1

Electromagnetic Environment¹

1.1. Electromagnetic radiation sources

In his environment, man is subjected to radiations due to various electromagnetic fields. These fields are either of natural origin, or of domestic or industrial origins. In the following, we present this electromagnetic environment by separating the optical irradiations (i.e. low wavelengths) from the radio frequency (RF) irradiations (i.e. long wavelengths).

1.1.1. Optical sources

Light can be regarded either as an electromagnetic wave or as a beam of photons (phôs or photos = light). Thus, when frequencies ν of the electromagnetic waves are increasing (and thus the wavelengths λ are decreasing), energies of the photons Ephoton are also increasing (E = h ν, h being Planck's constant).

1.1.1.1. Solar radiation

Energy from the Sun, produced by thermonuclear reaction, is emitted in space in the form of electromagnetic waves. This solar energy reaching the Earth drives almost every known physical and biological energy cycle in Earth's system.

The Sun is a giant fusion reactor, located 150 million km from Earth, radiating 2.3 billion times more energy than the energy that strikes the Earth — which itself is more energy in a hour than the entire human civilization directly uses in a year. Our Sun is the largest known energy resource in the solar system. Near the Earth at the top of the Earth's atmosphere, every square meter receives 1.366 kW of solar radiation. To reach the ground, this luminous energy must cross the Earth's atmosphere at a thickness that depends on the slope of the rays of the sun compared to the horizon. The average value of the vertical thickness of the atmosphere is equal to 7.8 km under normal conditions. In fact, various components of the solar radiation are received at the ground level:

– direct radiation coming from the Sun to be diffused or emitted back by the obstacles;

– diffuse radiation by different gases present in the atmosphere;

– the albedo which is the part of the radiation reflected by the ground (intensified by snow).

The total radiation is the sum of these three components, and the average illumination, in clear air, is equal to 1,000 W/m (100 mW/cm). By taking account of the weather, season and day-night cycles the usable mean energy is reduced to less than an average of 250 W/m.

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