Mobile Antenna Systems Handbook - Semantic Scholar · Chapter 2 Essential Techniques in Mobile Antenna Systems Design 25 2.1 Mobile Communication Systems 25 2.1.1 Technologies in

Mobile Antenna Systems Handbook

Third Edition

Kyohei Fujimoto

Editor

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Library of Congress Cataloging-in-Publication DataA catalog record for this book is available from the U.S. Library of Congress.

British Library Cataloguing in Publication DataA catalogue record for this book is available from the British Library.

ISBN-13: 978-1-59693-126-8

Cover design by Igor Valdman

2008 ARTECH HOUSE, INC.685 Canton StreetNorwood, MA 02062

All rights reserved. Printed and bound in the United States of America. No part of this book may bereproduced or utilized in any form or by any means, electronic or mechanical, including photocopying,recording, or by any information storage and retrieval system, without permission in writing from thepublisher.

All terms mentioned in this book that are known to be trademarks or service marks have beenappropriately capitalized. Artech House cannot attest to the accuracy of this information. Use of a termin this book should not be regarded as affecting the validity of any trademark or service mark.

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Contents

Preface to the Third Edition xvii

Chapter 1 Importance of Antennas in Mobile Systems and Recent Trends 11.1 Introduction 11.2 Trends 9

1.2.1 Mobile Systems 131.2.2 Increasing Information Flow 151.2.3 Propagation 15

1.3 Modern Mobile Antenna Design 151.4 Objectives of This Book 19References 22

Chapter 2 Essential Techniques in Mobile Antenna Systems Design 252.1 Mobile Communication Systems 25

2.1.1 Technologies in Mobile Communications 252.1.2 Frequencies Used in Mobile Systems 312.1.3 System Design and Antennas 33

2.2 Fundamentals in Land Mobile Propagation 342.2.1 Propagation Problems in Land Mobile Communications 342.2.2 Multipath Propagation Fundamentals 362.2.3 Classification of Multipath Propagation Models: NB, WB, and

UWB 382.2.4 Spatio-Temporal Propagation Channel Model 402.2.5 Relation Between Space Correlation Characteristics and Space

Diversity Effect 442.2.6 Propagation Modeling for OFDM 472.2.7 Propagation Studies for UWB 50

References 51

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Chapter 3 Advances in Mobile Propagation Prediction Methods 553.1 Introduction 553.2 Macrocells 55

3.2.1 Definition of Parameters 573.2.2 Empirical Path Loss Models 583.2.3 Physical Models 653.2.4 Comparison of Models 763.2.5 Computerized Planning Tools 763.2.6 Conclusions 77

3.3 Microcells 783.3.1 Dual-Slope Empirical Models 793.3.2 Physical Models 813.3.3 Nonline-of-Sight Models 863.3.4 Microcell Propagation Models: Discussion 923.3.5 Microcell Shadowing 933.3.6 Conclusions 93

3.4 Picocells 933.4.1 Empirical Models of Propagation Within Buildings 943.4.2 Empirical Models of Propagation into Buildings 973.4.3 Physical Models of Indoor Propagation 1013.4.4 Constitutive Parameters for Physical Models 1053.4.5 Propagation in Picocells: Discussion 1053.4.6 Multipath Effects 1063.4.7 Conclusions 108

3.5 Megacells 1083.5.1 Shadowing and Fast Fading 1103.5.2 Local Shadowing Effects 1113.5.3 Empirical Narrowband Models 1133.5.4 Statistical Models 1153.5.5 Physical-Statistical Models for Built-Up Areas 1223.5.6 Wideband Models 1313.5.7 Multisatellite Correlations 1313.5.8 Overall Mobile-Satellite Channel Model 133

3.6 The Future 1343.6.1 Intelligent Antennas 1343.6.2 Multidimensional Channel Models 1353.6.3 High-Resolution Data 1353.6.4 Analytical Formulations 1353.6.5 Physical-Statistical Channel Modeling 1363.6.6 Real-Time Channel Predictions 1363.6.7 Overall 136

References 137

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Chapter 4 Antennas for Base Stations 1414.1 Basic Techniques for Base Station Antennas 141

4.1.1 System Requirements 1414.1.2 Types of Antennas 1434.1.3 Radio Zone Design 1444.1.4 Diversity 146

4.2 Design and Practice of Japanese Systems 1514.2.1 Multiband Antennas 1514.2.2 Remote Beam Tilting System 1574.2.3 Antennas for Radio Blind Areas 1584.2.4 Antennas for CDMA Systems 164

4.3 Adaptive Antenna Systems 1704.3.1 Personal Handy Phone System 1704.3.2 W-OAM 1724.3.3 i-Burst System 1734.3.4 Experimental System of Adaptive Array for WCDMA 1754.3.5 Experimental System of Adaptive Array for CDMA2000

1xEV-DO 1764.4 Design and Practice II (European Systems) 177

4.4.1 Antenna Configurations 1794.4.2 Antenna Solutions 1874.4.3 Antenna Units 1954.4.4 Antenna Development Trends 203

References 208

Chapter 5 Antennas for Mobile Terminals 2135.1 Basic Techniques for Mobile Terminal Antennas 213

5.1.1 General 2135.1.2 Brief Historical Review of Design Concept 2155.1.3 Modern Antenna Technology 217

5.2 Design and Practice of Antennas for Handsets I 2195.2.1 Some Fundamental Issues 2205.2.2 Various Multiband Antenna Concepts 2265.2.3 Antenna Integration and Some Practical Issues 2395.2.4 The Multichannel Antenna Applications 2455.2.5 Human Body Interaction with Terminal Antennas and Some

Measurement Methods 2575.3 Design and Practice of Antennas for Handsets 266

5.3.1 Multiband and Broad Band Antenna Technologies 2685.3.2 Diversity Antenna Technologies 2745.3.3 Antenna Technologies Mitigating Human Body Effect 2875.3.4 Antenna Technologies for Reducing SAR 298

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5.3.5 Technique of Omitting Balun 3045.3.6 Technology of Downsizing PIFA 307

5.4 Evaluation of Antenna Performance 3095.4.1 Measurement Method Using Optical Fiber 309

References 313

Chapter 6 Radio Frequency Exposure and Compliance Standards for MobileCommunication Devices 321

6.1 Introduction 3226.2 Physical Parameters 3226.3 Types of RF Safety Standards 3236.4 Exposure Standards 325

6.4.1 ICNIRP 3266.4.2 IEEE C95.1-2005 3286.4.3 Similarities and Differences Between the 1998 ICNIRP

Guidelines and IEEE C95.1-2005 3306.4.4 Regulations Based on Older Standards 330

6.5 Compliance Standards 3336.5.1 Main Features of IEEE 1528-2003 (Including 1528a-2005) and

IEC 62209-1 3336.5.2 Other Standards Related to Mobile Communication 339

6.6 Discussion and Conclusions 339References 341

Chapter 7 Applications of Modern EM Computational Techniques: Antennasand Humans in Personal Communications 343

7.1 Introduction 3437.2 Definition of Design Parameters for Handset Antennas 347

7.2.1 Absorbed Power and Specific Absorption Rate 3477.2.2 Directivity and Gain 3487.2.3 Antenna Impedance and S11 348

7.3 Finite-Difference Time-Domain Formulation 3497.4 Eigenfunction Expansion Method 351

7.4.1 EEM Implementation 3517.4.2 Hybridization of the EEM and MoM 352

7.5 Results Using EEM 3537.5.1 Human Head Model 3537.5.2 EM Interaction Characterizations 3547.5.3 Effects of Size of the Head Model: Adult and Child 3587.5.4 Comparison Between Homogeneous and Multilayered Spheres 3607.5.5 Vertical Location of Antennas 3617.5.6 Comparison with EEM and FDTD 364

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7.5.7 Anatomical Head Versus Spherical Head 3687.5.8 Directional Antennas 3707.5.9 High-Frequency Effect 372

7.6 Results Using the FDTD Method 3767.6.1 Tissue Models 3767.6.2 Input Impedance and the Importance of the Hand Position 3787.6.3 Gain Patterns 3837.6.4 Near Fields and SAR 384

7.7 Assessment of Dual-Antenna Handset Diversity Performance 3897.7.1 Dual-Antenna Handset Geometries 3907.7.2 Simulated Assessment of Diversity Performance 3907.7.3 Experimental Assessment of Diversity Performance 3927.7.4 Results 394

References 396

Chapter 8 Digital TV Antennas for Land Vehicles 3998.1 Reception Systems 399

8.1.1 Digital Television Services in Japan 3998.1.2 Problems of Mobile Reception 4008.1.3 Diversity Reception Methods 4008.1.4 Demonstration 402

8.2 Digital Television Antennas 4058.2.1 Quarter Glass Antenna for a Van 4058.2.2 Thin Antenna 4078.2.3 Omnidirectional Pattern Synthesis Technique for a Car 4088.2.4 Antennas Currently on the Market 410

References 415

Chapter 9 Antennas for the Bullet Train 4179.1 Introduction 4179.2 Train Radio Communication Systems 4189.3 Antenna Systems 419

9.3.1 LCX Cable 4199.3.2 Train Antenna 421

References 425

Chapter 10 Antennas for ITS 42710.1 General 42710.2 Antenna Design 429

10.2.1 Communication Beam Coverage 42910.2.2 Antenna Fundamental Design 431

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10.2.3 Microstrip Antenna Design 43510.2.4 Communication Coverage 44110.2.5 Multiple Reflections 442

10.3 Field Strength in Communication Area 44310.3.1 Multiple Reflections from Canopies 44310.3.2 Mitigation Using an Absorber at the ETC Gate 44410.3.3 Propagation in DSRC Coverage 44810.3.4 Data Rate of DSRC 450

10.4 Antennas for DSRC 45310.5 Applications for DSRC 453References 457

Chapter 11 Antennas for Mobile Satellite Systems 45911.1 Introduction 45911.2 System Requirements for Vehicle Antennas 461

11.2.1 Mechanical Characteristics 46111.2.2 Electrical Characteristics 46111.2.3 Propagation Problems 465

11.3 Omnidirectional Antennas for Mobile Satellite Communications 46711.3.1 Overview 46711.3.2 Quadrifilar Helical Antenna 46711.3.3 Crossed-Drooping Dipole Antenna 46811.3.4 Patch Antenna 469

11.4 Directional Antennas for Mobile Satellite Communications 47011.4.1 Antennas for INMARSAT 47011.4.2 Directional Antennas in the ETS-V Program 48111.4.3 Airborne Phased Array Antenna in the Domestic Satellite

Phone Program 48911.4.4 Directional Antennas in the MSAT Program 49011.4.5 Directional Antennas in the Ku-Band CBB Program 495

11.5 Antenna Systems for GPS 49811.5.1 General Requirements for GPS Antennas 49811.5.2 Quadrifilar Helical Antennas 50211.5.3 Microstrip Antennas 504

11.6 Multiband Antennas for Future GPS/ITS Services 50711.6.1 Slot Ring Multiband Antenna for Future Dual Bands (L1, L2)

GPS 50711.6.2 Microstrip Multiband Antennas for GPS, VICS, and DSRC 517

11.7 Satellite Constellation Systems and Antenna Requirements 52311.7.1 Constellation Systems and Demands on Antenna Design 52311.7.2 Handset Antennas for Satellite Systems 526

References 538

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Chapter 12 UWB Antennas 54312.1 UWB Systems: Introduction 54312.2 Requirements for UWB Antennas 544

12.2.1 Basic Principle of UWB Antennas 54412.2.2 Modeling and Structure of Feeding Points 54512.2.3 Current Distributions of Circular Disc Monopole Antenna 549

12.3 Characteristics of Popular UWB Antennas 55112.3.1 Three-Dimensional UWB Antennas 55212.3.2 Planar UWB Antennas 55512.3.3 CPW Feed 55712.3.4 Multilayer Technologies 56112.3.5 Band-Rejection for Coexistence with Other Wireless Systems 562

12.4 Wire-Structured UWB Antennas and Wire-Grid Modeling Simulation 56512.4.1 High Efficiency Moment Method 565

12.5 UWB Antennas in Specific Wireless Environments 56712.5.1 UWB Antennas Used in Unlicensed and Autonomous

Wireless Environments 56712.5.2 Measurements of Multipath Propagation Environments for

UWB Antennas 56812.5.3 Transmission Characteristics of UWB Antennas and Effects of

the Human Body 56912.5.4 UWB Antennas Near the Human Body 574

12.6 UWB Antenna Evaluation Indexes 57612.7 UWB Antenna Measurements 577

12.7.1 Radiation Pattern Measurements 57712.7.2 Impedance Measurements 57812.7.3 Scale Model Measurements 57912.7.4 Impedance Measurements with Two Coaxial Cables 580

12.8 Integrated Antenna Design Approach Based on LSI Technology 58312.9 Radio Wave Resource Sharing with Technology Leadership and the

Role of the Antenna 583References 584

Chapter 13 Antennas for RFID 58913.1 The Characteristics of an RFID System 589

13.1.1 What Is RFID? 58913.1.2 Operating Frequencies 59113.1.3 Operating Principles 59213.1.4 Read Range 595

13.2 Reader Antennas 59613.2.1 Fixed Reader 59613.2.2 Mobile Reader 599

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13.3 Tag Antennas 60513.3.1 Structure of a Tag Antenna 60513.3.2 Impedance Matching 60713.3.3 Tags on Metallic Surface 60913.3.4 Bandwidth-Enhanced Tag Antennas 61113.3.5 SAW Tags 612

13.4 Measurement of Tag Antennas 61213.4.1 Measurement of the Tag Antenna Impedance 61313.4.2 Read Range Measurement 61413.4.3 Efficiency Measurement 615

References 616

Chapter 14 Multiple-Input Multiple-Output (MIMO) Systems 61914.1 Introduction 61914.2 Diversity in Wireless Communications 620

14.2.1 Time Diversity 62014.2.2 Frequency Diversity 62114.2.3 Space Diversity 622

14.3 Multiantenna Systems 62314.4 MIMO Systems 62414.5 Channel Capacity of the MIMO Systems 62714.6 Channel Known at the Transmitter 628

14.6.1 Water-Filling Algorithm 62914.7 Channel Unknown at the Transmitter 629

14.7.1 Alamouti Scheme 63014.8 Diversity-Multiplexing Trade-Off 63114.9 MIMO Under an Electromagnetic Viewpoint 632

14.9.1 Case Study 1 63414.9.2 Case Study 2 63514.9.3 Case Study 3 63514.9.4 Case Study 4 63914.9.5 Case Study 5 641

14.10 Conclusions 643References 644

Chapter 15 Smart Antennas 64715.1 Definition 64715.2 Why Smart Antennas? 64915.3 Introduction 65015.4 Background 652

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15.5 Beam Forming 65315.5.1 Minimum Mean Square Error 65515.5.2 Minimum Variance Distortionless Response 656

15.6 Direct Data Domain Least Squares (D3LS) Approaches to AdaptiveProcessing Based on a Single Snapshot of Data 65915.6.1 Eigenvalue Method 66215.6.2 Forward Method 66315.6.3 Backward Method 66515.6.4 Forward-Backward Method 666

15.7 Simulations 66715.8 Conclusion 671References 671

Appendix A Glossary 675A.1 Catalog of Antenna Types 675

A.1.1 Linear Antennas 676A.1.2 Material Loading 678A.1.3 Planar Antenna 679A.1.4 Broadband and Multiband Antennas 680A.1.5 Balance-Unbalance Transforming 681A.1.6 Arrays and Diversity Systems 681A.1.7 Recent Innovative Concepts 682

References 682A.1.8 Key to Symbols and Acronyms Used in Sections A.2 to A.3 703

A.2 Land Mobile Systems 704A.2.1 Automobiles 704A.2.2 Portable Equipment 711A.2.3 Trains 718A.2.4 Base Stations 719A.2.5 Satellite Systems 723A.2.6 UWB 727A.2.7 RFID 729

A.3 Typical Antenna Types and Their Applications 732

Acronyms and Abbreviations 735

List of Contributors 739

Index 747

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Chapter 6

Radio Frequency Exposure andCompliance Standards

for Mobile Communication Devices

C-K. Chou and Ron Petersen

The study of the biological effects associated with exposure to electromagnetic energyhas a rich history going back almost a century. Although much of the earlier work wascarried out as a matter of scientific curiosity, since the mid-1950s the majority of theresearch has been focused on filling gaps in the knowledge-base regarding safety in orderto develop rational radio frequency (RF) safety standards and guidelines to protect againstestablished adverse health effects in humans. Members of the public and RF workerscontinue to raise questions about the safety of new RF technologies, including radar, radioand television broadcasting facilities, microwave ovens, point-to-point microwave radio,and satellite communications systems. The most recent concern is the safety of mobileand portable telephones and their base stations. Consequently, much of the bioeffectsresearch carried out during the past 15 years is specific to conditions relative to exposureto portable telephones. The results of this research are used to ensure that contemporarysafety guidelines and standards adequately protect the public and the worker, or if changesare necessary. Two types of standards directly related to the safety of mobile communica-tion devices are described in this chapter: (1) safety standards that recommend limits toprotect against harmful effects associated with RF exposure, and (2) conformance (orcompliance) standards that describe protocols to ensure that RF-emitting devices, such asportable telephones, comply with the safety standards.

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6.1 INTRODUCTION

Public awareness of the dramatic increase in the number of systems that emit RF energyfrequently leads to questions about safety. For example, during the past few decades,questions have arisen about the safety of radar, radio and television broadcasting facilities,microwave ovens, point-to-point microwave radio, and satellite communications systems,and most recently, mobile and portable telephones and their base stations. The range ofRF power at which mobile and portable wireless communication devices operate may beas low as a few mW for a Bluetooth device; a fraction of a watt for a mobile phone; upto 7W for two-way mobile radios; several tens of watts for mobile radio systems installedin motor vehicles; and up to 100W, or more, for certain mobile telephone and two-wayradio base stations. Even though they operate at lower power than base station and vehicle-mounted mobile radio antennas, handheld devices have the potential for producing higherexposures, especially to important organs such as the brain and eyes, because of theirproximity to the caller’s body during normal use. Although exposure from base stationantennas is far less than that from handheld devices, the public appears to be moreconcerned about the safety of base stations. Sound, science-based safety standards helpto allay the fears of those who approach the RF safety issue with an open mind.

In this chapter, the relevant parameters used to assess exposure, and the typesof standards that address the safety of mobile communication devices are described—specifically safety standards that recommend limits to protect against harmful effectsassociated with RF exposure, and conformance (or compliance) standards that describeprotocols to ensure that RF-emitting devices comply with the safety standards. For purposesof this chapter, the frequency range of interest is 30 MHz to 6 GHz, which includes thefrequencies most commonly used for mobile communications.

6.2 PHYSICAL PARAMETERS

Radio frequencies are loosely defined as frequencies between 3 kHz and 300 GHz—thatis, frequencies below the infrared region of the electromagnetic spectrum. Because thephoton energy associated with an RF electromagnetic wave is far below that required toremove an electron from an atom (ionization), RF exposure is characterized as nonionizingradiation, as is infrared radiation, visible light, and the longer ultraviolet wavelengths.The physical interaction of RF energy with biological material is complex, often resultingin highly nonuniform distributions of the induced electric (E) and magnetic (H) fieldsand the induced current density within the object regardless of the uniformity of theexternal exposure fields. The internal fields are related to a dosimetric quantity, calledspecific absorption rate (SAR), which was first proposed by the National Council onRadiation Protection and Measurements in 1981 [1], and defined as the time derivativeof the incremental energy absorbed by (dissipated in) an incremental mass contained ina volume of a given density and is expressed in W/kg. The internal electric field strength,


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induced current density, and SAR are related to the physical and electrical properties ofthe absorbing object by the following equations:

SAR =��

E 2 W/kg (6.1)

E = ��

SAR�1/2

V/m (6.2)

J = (��SAR )1/2 A/m (6.3)

where E is the root-mean-square value of the induced electric field strength (V/m) intissue, J is the current density (A/m2) in tissue, � is the tissue density (kg/m3), and � isthe dielectric conductivity of the tissue (S/m).

In a tutorial on RF dosimetry, Chou et al. [2] discuss the relationship between SARand the characteristics of the incident field and the geometrical and electrical propertiesof the absorbing object. SAR patterns, whole-body averaged SAR, and methods for themeasurement of peak SAR, are also discussed. (Details for the measurement of peak SARfor mobile phones and other portable devices are described in Section 6.5.)

In order to determine the thresholds for harmful effects and develop exposure limitsto protect against such effects, it is necessary to know the magnitude and distribution ofthe SAR within the exposed object. The SAR depends not only on the properties of theincident field, including the magnitudes of E and H (or equivalent power density); it alsodepends on the dielectric properties, geometry, size, and orientation of the exposed object,the polarization and frequency of the incident fields, the source configuration, exposureenvironment, and time-intensity factors. Figure 6.1 shows the parameters associated withhuman exposure to RF energy.

6.3 TYPES OF RF SAFETY STANDARDS

There are three types of RF standards related to human safety. The first type is the‘‘safety’’ standard, which sets limits to protect against harmful effects associated withRF exposure. Currently two recognized international organizations develop RF safetystandards and guidelines. One, now called the Institute of Electrical and ElectronicsEngineers (IEEE) International Committee on Electromagnetic Safety (ICES) TechnicalCommittee 95, has a history of RF safety standard activities that traces back to the late1950s. The first RF safety standard was published by this committee in 1966 [4]; fourrevisions have been published since then—the latest in 2006 [5]. This committee develops


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Figure 6.1 External and internal physical parameters of human exposure to RF energy. (Modified from Guy[3].)

standards through an open consensus process that is transparent at every level; that is,the committee is open to anyone with an expressed material interest, the meetings areopen, and meeting records are posted on the Internet. A total of 130 members representing24 countries were involved with developing the latest revision of this standard (IEEEC95.1-2005) [5], including members of government, academia, industry and the generalpublic. (See Petersen [6] for a detailed historical record.) In 2006, this standard wasapproved by the American National Standards Institute and is recognized as an AmericanNational Standard (ANSI/IEEE C95.1-2006).

The second international organization that develops RF safety guidelines is theInternational Commission on Non-Ionizing Radiation Protection (ICNIRP), which consistsof 14 elected members from various government organizations and academia (but nomembers representing commercial interests). The ICNIRP guidelines, developed mostlyin closed forums, are endorsed and promoted globally by the World Health Organizationfor adoption by national governments. Most countries in the world adopt the basic restric-tions or derived limits of either the ICNIRP guidelines or the IEEE standard. Similaritiesand differences in the recommendations from IEEE and ICNIRP are presented in Section6.4.3.

The second type of standard is the product standard which recommends methodolo-gies for ensuring products comply with the safety standards. The committees that developinternational product standards for mobile communications devices are IEEE ICES Techni-cal Committee 34 (TC-34) and International Electrotechnical Commission (IEC) TC-106.TC-34 is a relatively new committee established in 1995 (compared with ICES TC-95,


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which was established as an American Standards Association Committee in 1960); IECTC-106 was established in 2000. Although TC-34 and TC-95 are both ICES committees,the TC-34 product standard for mobile telephones IEEE 1528-2003 [7] is used for determin-ing compliance with TC-95 and ICNIRP recommendations to allow manufacturers toreadily ensure that their products comply with these or similar requirements. The goal isto provide unambiguous procedures that yield repeatable results (e.g., similar to theprocedure for certifying compliance of microwave ovens). In addition to standards formeasuring the peak SAR associated with handheld mobile telephones, TC-34 is in theprocess of developing product standards for vehicle-mounted antennas, as well as forother devices using both measurement and numerical techniques [8]. Recent collaborationbetween ICES TC-34 and IEC TC-106 led to the development of the product standardfor hand-held devices IEC 62209-1 [9], which is harmonized with IEEE 1528-2003.

The third type of RF safety standard protects against indirect effects associatedwith RF energy. Examples of this type of standard include compatibility standards (e.g.,standards for limiting electromagnetic interference with electronic equipment on aircraftor in medical environments). Compatibility standards, developed by the American NationalInstitute of Standards, International Standard Organization, Consumer Electronics Associa-tion and others, are not discussed further in this chapter.

6.4 EXPOSURE STANDARDS

As early as the mid-1950s, recommendations to limit exposure to RF energy were adoptedby various agencies and organizations throughout the world. The first RF exposure standardpublished in the United States (USAS C95.1-1966) [4] limited RF-induced heating of thebody. The recommended exposure limit was 100 W/m2 averaged over any 0.1-hr interval;the applicable frequency range was 10 MHz to 100 GHz. In the mid-1970s, dosimetrystudies revealed that the interaction of RF energy with biological bodies is extremelycomplex, and a frequency-independent limit over a broad frequency range is unrealistic.The third revision of the 1966 standard (American National Standards Institute ANSIC95.1-1982) [10] incorporated dosimetry, which resulted in frequency-dependent limitsbased on whole-body-averaged and peak spatial-average SAR (to address localized expo-sure). In 1986, the National Council on Radiation Protection and Measurements (NCRP)adopted the 1982 ANSI standard as the upper tier for occupational exposure, but addedan additional safety factor of 5 for a lower tier for exposure of the public [11]. The uppertier includes a 10-fold safety factor; the lower tier has an additional factor of 5 (i.e., atotal safety factor of 50 below the threshold for effects considered adverse). The IEEECommittee adopted this approach, and the revision of the 1982 C95.1 standard (IEEEC95.1-1991) [12] also contains two tiers, as does the 1998 ICNIRP guidelines [13].Although the ICNIRP guidelines and the 1991 IEEE standard are based on limiting thewhole-body-averaged SAR to the same values of 0.4 and 0.08 W/kg for the upper andlower tiers, respectively, the peak spatial-average SAR limits differ, both in magnitude


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and in averaging volume. This discrepancy caused confusion for the general public, extraburdens for manufacturers, and discordance among the regulators. During the revisionprocess that led to IEEE C95.1-2005 [5], consideration was given to harmonizing with theICNIRP guidelines where scientifically justifiable. An important issue that was addressed isthe peak SAR limits which are now essentially identical in the new IEEE standard andICNIRP guidelines. The 1998 ICNIRP guidelines and IEEE C95.1-2005 are detailed inthe following sections.

6.4.1 ICNIRP

The most recent ICNIRP guidelines, approved in November 1997, were published in 1998[13]. As in the case of the ANSI and IEEE committees, the ICNIRP guidelines are basedon studies reporting established adverse health effects. In agreement with the rationale ofC95.1-1991, ICNIRP also found that the relevant established effects are surface effectsat the lower frequencies (e.g., electrostimulation, shocks and burns) and effects associatedwith tissue heating at the higher frequencies. Although a number of in vitro studies werereviewed, the focus was on in vivo studies. Epidemiological studies of reproductiveoutcome and cancer were reviewed but because of the lack of adequate exposure assessmentand inconsistency of results, these studies were found to be of little use for establishingscience-based exposure criteria. Studies reporting athermal effects, including ‘‘windoweffects’’ [e.g., effects associated with ELF amplitude modulated (AM) RF fields] werealso considered, but ICNIRP concluded: ‘‘Overall, the literature on athermal effects ofAM electromagnetic fields is so complex, the validity of reported effects so poorlyestablished, and the relevance of the effects to human health is so uncertain, that it isimpossible to use this body of information as a basis for setting limits on human exposureto these fields’’ [13]. The more recent review of the literature by IEEE led to the followingconclusions regarding low-level effects: ‘‘Despite more than 50 years of RF research,low-level biological effects have not been established. No theoretical mechanism has beenestablished that supports the existence of any effect characterized by trivial heating otherthan microwave hearing. Moreover, the relevance of reported low-level effects to healthremains speculative and such effects are not useful for standard setting’’ [5, p. 82].

Standard-setting organizations (e.g., ANSI, IEEE) and organizations that developrecommendations and guidelines (e.g., NCRP and ICNIRP) have all determined that SARis the appropriate dosimetric parameter over the broad whole-body resonance region andalso found that the most reliable and sensitive indicator of potential harm was behavioraldisruption, with a threshold SAR of 4 W/kg. A safety factor of 10 was incorporated forexposures in the workplace, and an additional factor of 5 for exposure of the generalpublic yielding maximum whole-body-average SAR values of 0.4 and 0.08 W/kg, respec-tively (called basic restrictions). In addition, basic restrictions in terms of peak spatial-average SAR of 10 and 2 W/kg averaged over any 10-g contiguous tissue are recommendedfor localized exposure. The ICNIRP peak spatial-average SAR values are based on the


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thresholds of cataract formation in rabbit eyes (about 10g) with safety factors of 10 and50. The ICNIRP limits for high-peak, low-average-power pulsed fields are based onthe evoked auditory response (microwave hearing [14, 15]) whereas the correspondingC95.1-1991 and C95.1-2005 limits are based on the stun-effect in small animals (witha suitable margin of safety) [16]. That is, while ICNIRP considers ‘‘microwavehearing’’ a harmful effect, it is not considered an adverse effect in the C95.1-2005 standard[5, pp. 81–82].

Table 6.1 shows the basic restrictions (SAR) of the ICNIRP guidelines for frequen-cies between 100 kHz to 10 GHz, both for occupational and for general-public exposure.Table 6.2 lists the derived limits (reference levels) for the incident fields. While compliancewith the reference levels ensures that the basic restrictions are met, because of the conserva-tism built into the reference levels, exceeding the reference levels does not mean that the

Table 6.11998 ICNIRP Basic Restrictions

Whole Body Local SAR Local SARAvg. SAR (Head and Trunk) (Limbs)

Exposure Group Frequency W/kg W/kg W/kg

Occupational 100 kHz to 10 GHz 0.4 10 (10g) 20 (10g)General Population 100 kHz to 10 GHz 0.08 2 (10g) 4 (10g)

Source: [13].

Table 6.21998 ICNIRP Reference Levels

Frequency E Field (V/m) H Field (A/m) Power Density (W/m2)

Occupational3 to 65 kHz 610 24.40.065 to 1 MHz 610 1.6/f1 to 10 MHz 610/f 1.6/f10 to 400 MHz 61 0.16 10400 to 2,000 MHz 3f 1/2 0.008f 1/2 f /402 to 300 GHz 1.37 0.36 50

General Population3 to 150 kHz 87 50.15 to 1 MHz 87 0.73/f1 to 10 MHz 87/f 1/2 0.73/f10 to 400 MHz 28 0.073 2400 to 2,000 MHz 1.375f 1/2 0.0037f 1/2 f /2002 to 300 GHz 61 0.16 10

Source: [13].


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basic restrictions are exceeded. For additional details of ICNIRP recommendations, referto the ICNIRP guidelines [13].

6.4.2 IEEE C95.1-2005

IEEE C95.1-2005 was approved on October 5, 2005, and published on April 19, 2006.The purpose of this standard is to provide recommendations to protect against establishedadverse effects to human health associated with exposure to RF electric, magnetic, andelectromagnetic fields over the frequency range of 3 kHz to 300 GHz [5]. This revision(of C95.1-1991) is based on an evaluation of the scientific literature through 2003 (althoughthe literature cutoff date was December 2003, several papers published in 2004 and 2005were included), including those studies that involve low-level exposures where increasesin temperature could not be measured or were not expected. New insights gained fromimproved experimental and numerical methods and a better understanding of the effectsof acute and chronic RF electromagnetic field exposures of animals and humans areincluded. A lack of credible scientific and medical reports showing adverse health effectsfor RF exposures at or below corresponding exposure limits in past standards supportsthe protective nature of this standard. Above 100 kHz, the limits are designed to protectagainst adverse health effects resulting from tissue heating, the only established mechanismrelating to adverse effects of exposure to RF energy at these frequencies. For the firsttime, guidance on the necessity of an RF exposure control program (e.g., recommendationsin IEEE C95.7-2005 [17]) is included.

The C95.1 standard consists of normative sections, including an overview of thedocument (scope, purpose, and introduction), references, definitions, and recommenda-tions, as well as informative sections. The informative sections include seven annexes;the first three explain the revision process, summary of the literature, and rationale of therevision; the fourth provides examples of practical applications; and the last three annexesare glossary, literature database, and bibliography. Refer to the standard [5] for details,especially on the literature summary of about 1,300 peer-reviewed papers (Annex B) andthe rationale (Annex C).

6.4.2.1 Recommendations

The recommendations are expressed in terms of basic restrictions (BRs) and maximumpermissible exposure (MPE) values (sometimes called reference levels or investigationlevels). The BRs are limits on internal fields, SAR, and current density; the MPEs, derivedfrom the BRs, are limits on external fields and on induced and contact currents. Therecommendations are intended to apply to all human exposures except for exposure ofpatients by, or under the direction of, physicians and medical professionals.


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Basic Restrictions

The whole-body-average BRs shown in Table 6.3 for frequencies between 100 kHz and3 GHz protect against established adverse health effects associated with heating of thebody during whole-body exposure. Consistent with the approach used in the prior standardsand the ICNIRP guidelines, a traditional safety factor of 10 has been applied to theestablished SAR threshold of 4 W/kg for such effects, yielding an SAR of 0.4 W/kgaveraged over the whole body. In the absence of an RF safety program, the BRs of thelower tier (action levels) may also be used for the general public. Applied to membersof the general public, the lower tier provides more assurance that continuous, long-termexposure of all individuals in the population will be without risk of adverse effects. TheBRs in terms of peak spatial-average SAR shown in Table 6.3 protect against excessivetemperature rise in any part of the body that might result from localized or nonuniformexposure.

As the frequency increases above 3 GHz, the power deposition becomes moresuperficial and SAR less meaningful. To account for the shallow penetration depth at thehigher frequencies, the BRs are expressed in terms of incident power density and areidentical to the derived limits (MPEs). Although exposure at or near these values maybe accompanied by a slight sensation of warmth, this effect is not considered adverse.

Maximum Permissible Exposure Values

The derived limits (MPEs) in terms of equivalent power density, considered appropriatefor all human exposure, are shown in Figure 6.2. (For detailed information on averagingtime, refer to Table 6.4 and [5].)

6.4.2.2 RF Safety Programs

Throughout the RF spectrum, the BRs and MPEs apply to exposure of people (i.e.,compliance is determined by whether exposures of people to RF fields, currents, and

Table 6.3Basic Restrictions for Frequencies Between 100 kHz and 3 GHz

Persons in ControlledAction Level Environments SARSAR (W/kg) (W/kg)

Whole-body exposure (Whole-body Average) 0.08 0.4Localized exposure (Local peak spatial-average) 2a 10a

Localized exposure (Extremitiesb and pinnae) 4a 20a

aAveraged over any 10g of tissue (defined as a tissue volume in the shape of a cube).bThe extremities are the arms and legs distal from the elbows and knees, respectively.Source: [5].


330

Figure 6.2 IEEE C95.1-2005 [5] MPEs for the upper and lower tiers in the frequency band 100 kHz to 300GHz, as compared to reference levels in ICNIRP guidelines [13].

voltages exceed the applicable values). Where there may be access to RF fields, currents,and/or voltages that exceed the lower tier (action level) BRs and MPEs of IEEEC95.1-2005, an RF safety program such as detailed in IEEE Std C95.7-2005 [17] can beimplemented to ensure that exposures do not exceed the MPEs or BRs for the upper tier(persons in a controlled environment).

6.4.3 Similarities and Differences Between the 1998 ICNIRP Guidelines and IEEEC95.1-2005

Table 6.4 compares various parameters of the 1998 ICNIRP guidelines with the correspond-ing parameters of C95.1-2005. This comparison indicates that while the two documentsare similar, there are some differences between the two that suggests a need for continuedharmonization efforts to achieve one global standard.

6.4.4 Regulations Based on Older Standards

In the United States, the Federal Communications Commission (FCC), in 1996, adopteda combination of the IEEE C95.1-1991 and NCRP 1986 exposure criteria to regulate RF


331

Table 6.4Comparison of the 1998 ICNIRP Guidelines [13] with the IEEE C95.1-2005 Standard [5] over the

Frequency Range Where the Predominant Interaction Mechanism Is Tissue Heating

Parameter ICNIRP IEEE C95.1-2005

Frequency range ∼ 100 kHz to 300 GHz ∼ 100 kHz to 300 GHzRecognition of whole-body Yes YesresonanceIncorporation of dosimetry Yes Yes(SAR)Database of experimental Large Very large (∼ 1,300 citations)literatureMost significant biological Behavioral disruption Behavioral disruptionendpoint (associated with ∼ 1°C core (associated with ∼ 1°C core

temperature rise) temperature rise)Whole-body-averaged SAR 1–4 W/kg ∼ 4 W/kgassociated with behavioraldisruptionLimiting whole-body-averaged 0.4 W/kg (occupational) 0.4 W/kg (controlledSAR 0.08 W/kg (general public) environment)

—Applicable frequency range 100 kHz to 10 GHz 0.08 W/kg (action level)100 kHz to 3 GHz

Peak spatial-average SAR 10 W/kg (occupational) 10 W/kg (controlled(localized exposure) 2 W/kg (general public) environment)

—Averaging volume 10g of contiguous tissue 2 W/kg (action level)—Averaging time 6 minutes (occupational) 10g of tissue in the shape of a

6 minutes (general public) cube6 minutes (controlledenvironments)30 minutes (action level)

Limits for extremities 20 W/kg (limbs) 20 W/kg (extremities and—Upper tier 4 W/kg (limbs) pinnae)—Lower tier 100 kHz < f ≤ 10 GHz 4 W/kg (extremities and pinnae)—Applicable frequency range 100 kHz < f ≤ 3 GHz

Averaging time ( f > 100 kHz) 6 minutes ( f ≤ 10 GHz) 6 minutes ( f ≤ 3 GHz) then—Upper tier decreasing to 10 seconds at 300 decreasing to 10 seconds at 300—Lower tier GHz GHz)

6 minutes ( f ≤ 10 GHz) 6 min (3 kHz ≤ f ≤ 1.34 MHz).decreasing to 10 seconds at 300 E2 and H 2 have differentGHz averaging times for 1.34 MHz <

f ≤ 100 MHz but both are equalto 30 minutes at 100 MHz. For100 MHz < f ≤ 5 GHz theaveraging time is 30 minutesand then decreases to 10seconds at 300 GHz.

Induced and contact current 40 mA (limb currents) 90 mA (each foot)limits 20 mA (limb current) 45 mA (each foot)

—Upper tier 100 kHz ≤ f ≤ 110 MHz 100 kHz ≤ f ≤ 110 MHz—Lower tier—Applicable frequency range


332

Table 6.4 (continued)Comparison of the 1998 ICNIRP Guidelines [13] with the IEEE C95.1-2005 Standard [5] over the

Frequency Range Where the Predominant Interaction Mechanism Is Tissue Heating

Parameter ICNIRP IEEE C95.1-2005

Special criterion for modulated No NofieldsSpecific limits for high-peak, Yes. Based on evoked auditory Yes. Based on the stun-effectlow-average-power pulses response (‘‘microwave

hearing’’)RF safety program Not specifically Yes. IEEE C95.7-2005. The

BRs and MPEs of the lower tier(action level) are linked to anRF safety program to mitigateagainst exposures that couldexceed the BRs and MPEs ofthe upper tier

Source: [6].

exposures from transmitting equipment (including mobile communications) [18]. Thebasic restrictions for the whole body exposure is the same as those of ICNIRP and IEEEC95.1-2005, but the peak SAR is 1.6 and 8 W/kg averaged over any 1g of tissue forexposure in controlled environments (occupational exposure) and general-public exposure,respectively. The MPEs are shown in Table 6.5.

Table 6.5FCC Limits for Maximum Permissible Exposure (MPE)

Frequency (MHz) E Field (V/m) H Field (A/m) Power Density* (W/m2)

Exposure in Controlled Environments (Occupational)0.3 to 3 614 1.63 10003 to 30 1842/f 4.89/f 2 9000/f 2

30 to 300 61.4/f 0.163 10300 to 1,500 — — f /301500 to 100,000 — — 50

Exposure in Uncontrolled Environments (General Population)0.3 to 1.34 614 1.63 10001.34 to 30 824/f 2.19/f 1800/f30 to 300 27.5 0.073 2300 to 1,500 — — f /1501,500 to 100,000 — — 10

*Plane-wave equivalent power density.Source: [19].


333

At the time this chapter was prepared, the FCC had not taken an action to issue aNotice of Proposed Rule Making for public comment in order to initiate the process forrevising the above limits based on the new IEEE C95.1-2005 Standard or any other RFsafety recommendations.

6.5 COMPLIANCE STANDARDS

Several standards are used to ensure that various products (e.g., mobile phones and basestations) comply with contemporary safety standards, guidelines, and national regulations.For whole body exposures, compliance with the MPEs (reference levels) can be determinedby measuring the incident fields using commercially available survey meters, or similardevices, following the protocols described in standards such as IEEE C95.3-2002 [20].For near field exposures from specific devices, particularly handheld and portable devices,determination of the SAR is usually required. In 1996, IEEE Standards CoordinatingCommittee 34 (now IEEE ICES TC-34) began drafting a standard that specifies measure-ment protocols for certifying that mobile phones meet peak spatial-average SAR require-ments. The result of this effort is IEEE 1528-2003 [7] and 1528a-2005 [21]. The EuropeanCommittee for Electrotechnical Standardization (CENELEC) published a similar standard(EN50361) in July 2001 [22]. Because of minor differences between the two standards(e.g., the values for some tissue simulant parameters for certain frequencies), some productsare required to be tested twice, once for the European and Australian markets and oncefor other parts of the world. This duplication emphasized the need for a globally harmonizedtest method. This issue was resolved with the publication of IEC 62209-1 [9] which isharmonized with IEEE 1528-2003 and replaces the CENELEC standard (EN50361).

6.5.1 Main Features of IEEE 1528-2003 (Including 1528a-2005) and IEC 62209-1

IEEE ICES TC-34 Subcommittee 2 and IEC TC-106 Project Team 62209 share commonmembership and goals for harmonized international standards for the measurement ofpeak SAR for mobile phones intended for use when placed next to the head. As a result,both the IEEE standards (1528-2003 and 1528a-2005) and IEC 62209-1 are technicallyidentical. These standards specify measurement protocols designed to allow various labora-tories to perform SAR measurements in a consistent manner. Included is a standardphantom model with specified size and shape, specific liquid compounds for tissue simula-tion, standard calibration techniques for E-field probes, and phone positioning require-ments. Some of the salient features of the two standards are described below. For detailsof the SAR measurement protocol, the reader should refer to the original standards: IEEE1528-2003 [7]; IEEE 1528a-2005 [21]; and IEC 62209-1 [9].


334

SAR Measurement System

Figure 6.3 shows a typical SAR measurement system used to perform SAR measurementin a head phantom. The system consists of an E-field probe, dc voltage amplifiers, high-impedance cables connecting the amplifier outputs to a personal computer, a controllingrobot, a simulated tissue phantom, and a holder assembly for placing the phone withrespect to the phantom. The robot holding the probe scans the entire exposed volume ofthe phantom in order to evaluate the three-dimensional field distribution. The entire system,including the E-field probe, is calibrated in a controlled laboratory environment in eachtissue equivalent liquid at the appropriate operating frequency.

Figure 6.3 Mobile phone SAR measurement system showing robot-controlled electric field probe for SARmeasurement in a head phantom exposed to a mobile phone at the left ear.


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Phantom Model

To simulate the human head, both committees agreed to use the dielectric property valuesof Gabriel et al. [23]. Table 6.6 lists the dielectric properties of the equivalent head tissueat various frequencies based on a plane-wave analysis [24]. The dielectric constant is theaverage of all head tissues, and the conductivity is the larger of the 1g or 10g averagecalculated effective conductivity. Formulas for liquid head tissue phantoms for the variousfrequency bands are included in the IEEE and IEC standards. The dielectric constant andconductivity are required to be within 5% of the target values at the specified frequencies,excluding instrument error, and must be checked periodically to ensure compliance. Themeasured dielectric properties of the liquid at the device operating frequencies should beused in SAR calculations instead of the target values shown in Table 6.6.

The U.S. Army head model (90% adult male head dimensions and shape) [25] wasadopted by both committees from which a hairless specific anthropomorphic mannequin(SAM) of the head was constructed. Figure 6.4 shows the side view of SAM with earstructure and marking lines. The ear protrusion of the Army head model (28 mm) wasreduced to 4 mm to simulate the compression of the ear during mobile phone use. Thisspacing brings the phone close to the head and provides results that are relevant to theexposure of the population with smaller ears, such as children. The SAM shell is madeof fiberglass with a thickness no greater than 2 mm at the site of measurement, exceptat the ear. The relative dielectric constant of the shell is less than 5 and the conductivityless than 0.01 S/m. A 4-mm lossless spacer plus the 2-mm shell thickness at the ear canalis used to simulate the ear. All dimensions are specified in a CAD file.

Right and left head models, obtained by bisecting the fiberglass SAM shell, arenecessary because the asymmetric location of the antenna in many phones results in

Table 6.6Dielectric Properties of the Equivalent Head Tissue for Frequencies Between 300 and 3,000 MHz

Frequency (MHz) Relative Dielectric Constant (�r ) Conductivity (�) (S/m)

300 45.3 0.87450 43.5 0.87835 41.5 0.90900 41.5 0.97

1,450 40.5 1.201,800 40.0 1.401,900 40.0 1.401,950 40.0 1.402,000 40.0 1.402,450 39.2 1.803,000 38.5 2.40

Source: [7, 9].


336

Figure 6.4 Side view of the SAM phantom head showing the ear and marking lines BM and NF.Intersection RE is the ear reference point (ERP). (Source: [7].)

different SAR distributions on each side of the head. The models are filled with the correctliquid mixture simulating head tissue at the desired frequency. The liquid is 15 ± 0.5 cmin depth measured at the ear canal, which is approximately equivalent to the distancebetween the ears of the phantom.

Measurement Procedures

Figure 6.5 is a flow chart of the SAR testing protocol. E-field measurements are takenat a reference point where the fields are above the noise level (e.g., 10 mm above the earreference point) to monitor power changes during the testing. This measurement is con-ducted after placing the mobile phone in operation with a fully charged battery. The insidesurface of the SAM phantom immediately adjacent to the phone is scanned. If the peakoccurs at the border of the area, the scan is repeated using an enlarged area when possible.A volumetric scan known as a zoom scan is then conducted at the location of the peakof the area scan, and the peak spatial-average SAR is calculated. These steps are repeatedif the peak spatial-average SAR touches any side of the zoom scan volume. At the endof the zoom scan, the field is measured again at the initial power measurement reference


337

Figure 6.5 Flow chart of SAR testing procedures. (Source: [9].)


338

point. If the power has changed by more than 5%, it is recommended that the measurementsbe repeated.

In Step 1, the above scan evaluation is conducted at the center frequency of thedevice under test at two positions on each side of the head with the antenna fully extendedand with it retracted (if applicable), and all operational modes (i.e., AMPS, TDMA,CDMA, and so forth). The two positions are ‘‘cheek touch’’ and ‘‘15° tilt.’’ Figure 6.6shows the two positions. The second position (15° tilt) is achieved by positioning thephone at the cheek touch position and then pivoting the device outwards by 15° with thetop of the phone against the pinna. When positioning the phones against the head, thecoordinates of two types of phones are as shown in Figure 6.7. Point A on the phone ispositioned against the ear reference point on the SAM phantom, and the centerline of thephone (line AB) is lined up with the back-to-mouth (BM) line on the phantom. In Step2, the same evaluation is repeated with the phone operating at a frequency at the highend of its frequency range and again at a frequency at the low end with the phone placedat the side of the phantom and the position that resulted in the largest peak spatial-averageSAR. The last step is to examine the data and determine the maximum spatial peak SAR,which is the largest value found in Steps 1 and 2. The time needed for a complete testof a new multimode phone for compliance can be up to several weeks.

Figure 6.6 ‘‘Cheek’’ and ‘‘touch’’ positions of the mobile phone on the left side of the phantom. (Source:[7].)


339

Figure 6.7 Handset vertical and horizontal reference lines and reference points A, B on two example devicetypes. (Source: [7].)

6.5.2 Other Standards Related to Mobile Communication

Many contemporary communication devices now use frequencies above 3 GHz, andtherefore, IEEE ICES TC-34 is developing a second amendment to IEEE 1528 to extendthe frequency range from 3 to 6 GHz. TC-34 is also developing standards for assessingcompliance of mobile phones and radios using numerical techniques. These include astandard specifying the general requirements for using the finite difference time domain(FDTD) method for SAR calculations, a standard specifying the specific requirements forFDTD modeling of vehicle mounted antennas, and a standard for FDTD modeling ofmobile phone exposure.

Through a liaison arrangement with IEEE ICES, IEC Project Team 62209 is devel-oping Part 2 of the 62209 standard for testing two-way radios, palmtop terminals, desktopterminals, body-worn devices including accessories, as well as multiple transmitters (30MHz to 6 GHz). Another IEC Project Team 62232 is drafting a standard for characterizingthe RF electromagnetic environment near base stations used for mobile radio communica-tion.

6.6 DISCUSSION AND CONCLUSIONS

Many government agencies throughout the world have adopted regulations that ensuredevices used for mobile communications are safe. Such regulations are generally basedon the basic restrictions and derived limits (reference levels, MPEs) found in consensus


340

standards and guidelines that protect against adverse effects associated with exposure toRF energy. The collective credible evidence on which these standards and guidelines arebased has not demonstrated that exposure to RF energy at levels at or below the basicrestrictions and derived limits can affect biological systems in a manner that might leadto, or augment, any health effect. Moreover, both the ICNIRP guidelines and IEEEstandards are living documents—once a standard is approved, work begins on assessingthe evolving database of relevant scientific literature to ensure that the limits continue tobe valid (i.e., the surveillance and evaluation of the RF bioeffects literature is continuous).If any new adverse effect is established that would require a change in the current limits,the standard can be promptly revised or amended to reflect these changes. Althoughwhole-body-averaged and peak spatial-average SAR have been the accepted dosimetricquantities for almost three decades, replacing the latter with temperature increase wasdiscussed during development of the 2005 IEEE standard and is being explored as apossibility for the next revision. The rationale for using temperature rather than peak SARis based on the literature showing that adverse health effects of RF exposure are associatedwith significant temperature increases in the body. Dosimetry studies are now in progressto identify the relationship between temperature rise and peak spatial-average SAR forfuture consideration.

In order to ensure that such devices comply with the safety standards and guidelines,compliance standards have been developed by international committees (e.g., IEEE ICES,IEC, and CENELEC). These product/compliance standards identify specific protocols toensure that test methods used throughout the world are consistent. One set of such standardsspecifies uniform SAR test methods, which are utilized by mobile phone manufacturersto demonstrate that their products comply with the requirements of the safety standards.

The authors have participated in the development of both the safety (exposure) andcompliance (measurement) standards. During committee deliberations that led to IEEEC95.1-2005, the focus was on conservatism; during deliberations on the compliancestandards, the focus was on precision. Worst-case assumptions were always considered.While it is always a good practice to make precise and accurate measurements, there isa trade-off when assessing compliance of a device with limits having large built-in safetymargins. That is, whether or not a product meets a specified limit is a compliance issue—not a safety issue. An unrealistic focus on precision causes one to lose sight of the objective(i.e., ‘‘can’t see the forest for the trees’’). The objective should be agreement on a realisticcompliance method and international harmonization.

Harmonized standards provide triple wins to all involved. First, consumers gain theprotection of an internationally recognized safety standard and have equal access toproducts and services that are available to consumers elsewhere in the world. Second,regulators gain the framework for a consistent approach to regulation that is in agreementwith the recommendations of the WHO, the ITU, and the WTO. Third, industry gains bydeveloping and manufacturing products to widely accepted international standards and,once tested for compliance, can make those products available around the world in aconsistent and timely manner.


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REFERENCES

[1] NCRP, ‘‘Radiofrequency Electromagnetic Fields—Properties, Quantities and Units, Biophysical Interac-tion, and Measurements,’’ NCRP Report No. 67, National Council on Radiation Protection and Measure-ments, Bethesda, MD, 1981.

[2] Chou, C. K., et al., ‘‘Radio Frequency Electromagnetic Exposure: A Tutorial Review on ExperimentalDosimetry,’’ Bioelectromagnetics, Vol. 17, 1996, pp. 195–208.

[3] Guy, A. W., ‘‘Dosimetry Associated with Exposure to Non-Ionizing Radiation: Very Low Frequency toMicrowaves,’’ Health Phys., Vol. 53, 1987, pp. 569–584.

[4] USAS C95.1-1966, Safety Level of Electromagnetic Radiation with Respect to Personnel, United Statesof America Standards Institute.

[5] IEEE C95.1-2005, ‘‘IEEE Standard for Safety Levels with Respect to Human Exposure to Radio FrequencyElectromagnetic Fields, 3 kHz to 300 GHz.’’

[6] Petersen, R. C., ‘‘Radiofrequency/Microwave Safety Standards,’’ in RF Dosimetry Handbook, P. Chadwick,(project leader), 2007, Chapter 6, available at http://www.emfdosimetry.org/petersen/Radiofrequency_Safety_Standards.html.

[7] IEEE 1528-2003, ‘‘IEEE Recommended Practice for Determining the Peak Spatial-Average SpecificAbsorption Rate (SAR) in the Human Head from Wireless Communications Devices: Measurement Tech-niques.’’

[8] Osepchuk, J. M., and R. C. Petersen, ‘‘Safety and Environmental Issues,’’ in The RF and MicrowaveHandbook, M. Golio, (ed.), Boca Raton, FL: CRC Press LLC, 2007.

[9] IEC 62209-1, ‘‘Human Exposure to Radio Frequency Fields from Hand-Held and Body-Mounted WirelessCommunication Devices—Human Models, Instrumentation, and Procedures—Part 1: Procedure to Deter-mine the Specific Absorption Rate (SAR) for Hand-Held Devices used in Close Proximity to the Ear(Frequency Range of 300 MHz to 3 GHz),’’ International Electrotechnical Commission, Geneva, 2005.

[10] ANSI C95.1-1982, ‘‘American National Standard Safety Levels with Respect to Human Exposure to RadioFrequency Electromagnetic Fields, 300 kHz to 100 GHz.’’

[11] NCRP, ‘‘Biological Effects and Exposure Criteria for Radiofrequency Electromagnetic Fields,’’ Report86, National Council on Radiation Protection and Measurements, Bethesda, MD, 1986.

[12] IEEE C95.1-1991, ‘‘IEEE Standard for Safety Levels with Respect to Human Exposure to Radio FrequencyElectromagnetic Fields, 3 kHz to 300 GHz.’’

[13] ICNIRP (International Commission on Non-Ionizing Radiation Protection), ‘‘Guidelines for LimitingExposure to Time-Varying Electric, Magnetic, and Electromagnetic Fields (Up to 300 GHz),’’ HealthPhysics, Vol. 74, 1998, pp. 494–522.

[14] Chou, C. K., A. W. Guy, and R. Galambos, ‘‘Auditory Perception of Radio-Frequency ElectromagneticFields (80th Review and Tutorial Paper),’’ J. of Acoustic Society of America, Vol. 71, No. 6, 1982,pp. 1321–1334.

[15] Elder, J. A., and C. K. Chou, ‘‘Auditory Response to Pulsed Radiofrequency Energy,’’ Bioelectromagnetics,Vol. 24, Supplement 6, 2003, pp. S162–S173.

[16] Guy, A. W., and C. K. Chou, ‘‘Effects of High-Intensity Microwave Pulse Exposure on Rat Brain,’’ Rad.Sci., Vol. 17, No. 5S, 1982, pp. 169S–178S.

[17] IEEE C95.7-2005, ‘‘Recommended Practice for Radio Frequency Safety Programs.’’[18] Federal Communication Commission, 47 CFR Parts 1, 2, 15, 24 and 97, ‘‘Guidelines for Evaluating the

Environmental Effects of Radiofrequency Radiation,’’ August 6, 1996.[19] Federal Communications Commission, Office of Engineering and Technology, OET Bulletin 65, Edition

97-01, Washington, D.C., August 1997.[20] IEEE C95.3-2002, ‘‘Recommended Practice for Measurements and Computations of Radio Frequency

Electromagnetic Fields with Respect to Human Exposure to Such Fields, 100 kHz–300 GHz.’’


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[21] IEEE 1528a-2005, ‘‘IEEE Recommended Practice for Determining the Peak Spatial-Average SpecificAbsorption Rate (SAR) in the Human Head from Wireless Communications Devices: Measurement Tech-niques—Amendment 1: CAD File for Human Head Model (SAM Phantom).’’

[22] EN50361-2001, ‘‘Basic Standard for the Measurement of Specific Absorption Rate Related to HumanExposure to Electromagnetic Fields from Mobile Phones (300 MHz–3 GHz),’’ European Committee forElectrotechnical Standardisation, (CENELEC), Brussels.

[23] Gabriel, S., R. W. Lau, and C. Gabriel, ‘‘The Dielectric Properties of Biological Tissues: 2. Measurementin the Frequency Range 10 Hz to 20 GHz,’’ Phys. Med. Biol., Vol. 41, No. 11, 1996, pp. 2251–2269.

[24] Drossos, A., V. Santomaa, and N. Kuster, ‘‘The Dependence of Electromagnetic Energy Absorption UponHuman Head Tissue Composition in the Frequency Range of 300–3000 MHz,’’ IEEE Trans. on MicrowaveTheory and Techniques, Vol. 48, No. 11, 2000, pp. 1988–1995.

[25] Gordon, C. C., et al., ‘‘1988 Anthropometric Survey of U.S. Army Personnel: Methods and SummaryStatistics,’’ Technical Report NATICK/TR-89/044, U.S. Army Natick Research, Development and Engi-neering Center, Natick, MA, September 1989.


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