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Mobile Antenna Systems Handbook

Third Edition

Kyohei Fujimoto

Editor

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Library of Congress Cataloging-in-Publication Data

A catalog record for this book is available from the U.S. Library of Congress.

British Library Cataloguing in Publication Data

A 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 Street

Norwood, 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 1

1.1 Introduction 1

1.2 Trends 9

1.2.1 Mobile Systems 13

1.2.2 Increasing Information Flow 15

1.2.3 Propagation 151.3 Modern Mobile Antenna Design 15

1.4 Objectives of This Book 19

References 22

Chapter 2 Essential Techniques in Mobile Antenna Systems Design 25

2.1 Mobile Communication Systems 25

2.1.1 Technologies in Mobile Communications 25

2.1.2 Frequencies Used in Mobile Systems 31

2.1.3 System Design and Antennas 33

2.2 Fundamentals in Land Mobile Propagation 34

2.2.1 Propagation Problems in Land Mobile Communications 34

2.2.2 Multipath Propagation Fundamentals 36

2.2.3 Classification of Multipath Propagation Models: NB, WB, and

UWB 38

2.2.4 Spatio-Temporal Propagation Channel Model 40

2.2.5 Relation Between Space Correlation Characteristics and Space

Diversity Effect 44

2.2.6 Propagation Modeling for OFDM 47

2.2.7 Propagation Studies for UWB 50

References 51

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Chapter 3 Advances in Mobile Propagation Prediction Methods 55

3.1 Introduction 55

3.2 Macrocells 55

3.2.1 Definition of Parameters 57

3.2.2 Empirical Path Loss Models 58

3.2.3 Physical Models 65

3.2.4 Comparison of Models 76

3.2.5 Computerized Planning Tools 76

3.2.6 Conclusions 77

3.3 Microcells 78

3.3.1 Dual-Slope Empirical Models 79

3.3.2 Physical Models 81

3.3.3 Nonline-of-Sight Models 86

3.3.4 Microcell Propagation Models: Discussion 92

3.3.5 Microcell Shadowing 93


3.4 Picocells 93

3.4.1 Empirical Models of Propagation Within Buildings 94

3.4.2 Empirical Models of Propagation into Buildings 97

3.4.3 Physical Models of Indoor Propagation 101

3.4.4 Constitutive Parameters for Physical Models 105

3.4.5 Propagation in Picocells: Discussion 105

3.4.6 Multipath Effects 106


3.5 Megacells 108

3.5.1 Shadowing and Fast Fading 110

3.5.2 Local Shadowing Effects 111

3.5.3 Empirical Narrowband Models 113

3.5.4 Statistical Models 115

3.5.5 Physical-Statistical Models for Built-Up Areas 122

3.5.6 Wideband Models 131

3.5.7 Multisatellite Correlations 131

3.5.8 Overall Mobile-Satellite Channel Model 133

3.6 The Future 134

3.6.1 Intelligent Antennas 134

3.6.2 Multidimensional Channel Models 135

3.6.3 High-Resolution Data 135

3.6.4 Analytical Formulations 135

3.6.5 Physical-Statistical Channel Modeling 136

3.6.6 Real-Time Channel Predictions 136

3.6.7 Overall 136

References 137

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Chapter 4 Antennas for Base Stations 141

4.1 Basic Techniques for Base Station Antennas 141

4.1.1 System Requirements 141

4.1.2 Types of Antennas 143

4.1.3 Radio Zone Design 144

4.1.4 Diversity 146

4.2 Design and Practice of Japanese Systems 151

4.2.1 Multiband Antennas 151

4.2.2 Remote Beam Tilting System 157

4.2.3 Antennas for Radio Blind Areas 158

4.2.4 Antennas for CDMA Systems 164

4.3 Adaptive Antenna Systems 170

4.3.1 Personal Handy Phone System 170

4.3.2 W-OAM 172

4.3.3 i-Burst System 173

4.3.4 Experimental System of Adaptive Array for WCDMA 175

4.3.5 Experimental System of Adaptive Array for CDMA2000

1xEV-DO 176

4.4 Design and Practice II (European Systems) 177

4.4.1 Antenna Configurations 179

4.4.2 Antenna Solutions 187

4.4.3 Antenna Units 195

4.4.4 Antenna Development Trends 203

References 208

Chapter 5 Antennas for Mobile Terminals 213

5.1 Basic Techniques for Mobile Terminal Antennas 213

5.1.1 General 213

5.1.2 Brief Historical Review of Design Concept 215

5.1.3 Modern Antenna Technology 217

5.2 Design and Practice of Antennas for Handsets I 219

5.2.1 Some Fundamental Issues 220

5.2.2 Various Multiband Antenna Concepts 226

5.2.3 Antenna Integration and Some Practical Issues 239

5.2.4 The Multichannel Antenna Applications 245

5.2.5 Human Body Interaction with Terminal Antennas and Some

Measurement Methods 257

5.3 Design and Practice of Antennas for Handsets 266

5.3.1 Multiband and Broad Band Antenna Technologies 268

5.3.2 Diversity Antenna Technologies 274

5.3.3 Antenna Technologies Mitigating Human Body Effect 287

5.3.4 Antenna Technologies for Reducing SAR 298

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5.3.5 Technique of Omitting Balun 304

5.3.6 Technology of Downsizing PIFA 307

5.4 Evaluation of Antenna Performance 309

5.4.1 Measurement Method Using Optical Fiber 309

References 313

Chapter 6 Radio Frequency Exposure and Compliance Standards for Mobile

Communication Devices 321

6.1 Introduction 322

6.2 Physical Parameters 322

6.3 Types of RF Safety Standards 323

6.4 Exposure Standards 325

6.4.1 ICNIRP 326

6.4.2 IEEE C95.1-2005 328

6.4.3 Similarities and Differences Between the 1998 ICNIRP

Guidelines and IEEE C95.1-2005 330

6.4.4 Regulations Based on Older Standards 330

6.5 Compliance Standards 333

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

IEC 62209-1 333

6.5.2 Other Standards Related to Mobile Communication 339

6.6 Discussion and Conclusions 339

References 341

Chapter 7 Applications of Modern EM Computational Techniques: Antennas

and Humans in Personal Communications 343


7.2 Definition of Design Parameters for Handset Antennas 347

7.2.1 Absorbed Power and Specific Absorption Rate 347

7.2.2 Directivity and Gain 348

7.2.3 Antenna Impedance and S11 348

7.3 Finite-Difference Time-Domain Formulation 349

7.4 Eigenfunction Expansion Method 351

7.4.1 EEM Implementation 351

7.4.2 Hybridization of the EEM and MoM 352

7.5 Results Using EEM 353

7.5.1 Human Head Model 353

7.5.2 EM Interaction Characterizations 354

7.5.3 Effects of Size of the Head Model: Adult and Child 358

7.5.4 Comparison Between Homogeneous and Multilayered Spheres 360

7.5.5 Vertical Location of Antennas 361

7.5.6 Comparison with EEM and FDTD 364

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7.5.7 Anatomical Head Versus Spherical Head 368

7.5.8 Directional Antennas 370

7.5.9 High-Frequency Effect 372

7.6 Results Using the FDTD Method 376

7.6.1 Tissue Models 376

7.6.2 Input Impedance and the Importance of the Hand Position 378

7.6.3 Gain Patterns 383

7.6.4 Near Fields and SAR 384

7.7 Assessment of Dual-Antenna Handset Diversity Performance 389

7.7.1 Dual-Antenna Handset Geometries 390

7.7.2 Simulated Assessment of Diversity Performance 390

7.7.3 Experimental Assessment of Diversity Performance 392

7.7.4 Results 394

References 396

Chapter 8 Digital TV Antennas for Land Vehicles 399

8.1 Reception Systems 399

8.1.1 Digital Television Services in Japan 399

8.1.2 Problems of Mobile Reception 400

8.1.3 Diversity Reception Methods 4008.1.4 Demonstration 402

8.2 Digital Television Antennas 405

8.2.1 Quarter Glass Antenna for a Van 405

8.2.2 Thin Antenna 407

8.2.3 Omnidirectional Pattern Synthesis Technique for a Car 408

8.2.4 Antennas Currently on the Market 410

References 415

Chapter 9 Antennas for the Bullet Train 4179.1 Introduction 417

9.2 Train Radio Communication Systems 418

9.3 Antenna Systems 419

9.3.1 LCX Cable 419

9.3.2 Train Antenna 421

References 425

Chapter 10 Antennas for ITS 427

10.1 General 427

10.2 Antenna Design 429

10.2.1 Communication Beam Coverage 429

10.2.2 Antenna Fundamental Design 431

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10.2.3 Microstrip Antenna Design 435

10.2.4 Communication Coverage 441

10.2.5 Multiple Reflections 442

10.3 Field Strength in Communication Area 443

10.3.1 Multiple Reflections from Canopies 443

10.3.2 Mitigation Using an Absorber at the ETC Gate 444

10.3.3 Propagation in DSRC Coverage 448

10.3.4 Data Rate of DSRC 450

10.4 Antennas for DSRC 453

10.5 Applications for DSRC 453

References 457

Chapter 11 Antennas for Mobile Satellite Systems 459


11.2 System Requirements for Vehicle Antennas 461

11.2.1 Mechanical Characteristics 461

11.2.2 Electrical Characteristics 461

11.2.3 Propagation Problems 465

11.3 Omnidirectional Antennas for Mobile Satellite Communications 467

11.3.1 Overview 467

11.3.2 Quadrifilar Helical Antenna 467

11.3.3 Crossed-Drooping Dipole Antenna 468

11.3.4 Patch Antenna 469

11.4 Directional Antennas for Mobile Satellite Communications 470

11.4.1 Antennas for INMARSAT 470

11.4.2 Directional Antennas in the ETS-V Program 481

11.4.3 Airborne Phased Array Antenna in the Domestic Satellite

Phone Program 489

11.4.4 Directional Antennas in the MSAT Program 490

11.4.5 Directional Antennas in the Ku-Band CBB Program 495

11.5 Antenna Systems for GPS 498

11.5.1 General Requirements for GPS Antennas 498

11.5.2 Quadrifilar Helical Antennas 502

11.5.3 Microstrip Antennas 504

11.6 Multiband Antennas for Future GPS/ITS Services 507

11.6.1 Slot Ring Multiband Antenna for Future Dual Bands (L1, L2)

GPS 507

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

11.7 Satellite Constellation Systems and Antenna Requirements 523

11.7.1 Constellation Systems and Demands on Antenna Design 523

11.7.2 Handset Antennas for Satellite Systems 526

References 538

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Chapter 12 UWB Antennas 543

12.1 UWB Systems: Introduction 543

12.2 Requirements for UWB Antennas 544

12.2.1 Basic Principle of UWB Antennas 544

12.2.2 Modeling and Structure of Feeding Points 545

12.2.3 Current Distributions of Circular Disc Monopole Antenna 549

12.3 Characteristics of Popular UWB Antennas 551

12.3.1 Three-Dimensional UWB Antennas 552

12.3.2 Planar UWB Antennas 555

12.3.3 CPW Feed 557

12.3.4 Multilayer Technologies 561

12.3.5 Band-Rejection for Coexistence with Other Wireless Systems 562

12.4 Wire-Structured UWB Antennas and Wire-Grid Modeling Simulation 565

12.4.1 High Efficiency Moment Method 565

12.5 UWB Antennas in Specific Wireless Environments 567

12.5.1 UWB Antennas Used in Unlicensed and Autonomous

Wireless Environments 567

12.5.2 Measurements of Multipath Propagation Environments for

UWB Antennas 568

12.5.3 Transmission Characteristics of UWB Antennas and Effects of

the Human Body 569

12.5.4 UWB Antennas Near the Human Body 574

12.6 UWB Antenna Evaluation Indexes 576

12.7 UWB Antenna Measurements 577

12.7.1 Radiation Pattern Measurements 577

12.7.2 Impedance Measurements 578

12.7.3 Scale Model Measurements 579

12.7.4 Impedance Measurements with Two Coaxial Cables 580

12.8 Integrated Antenna Design Approach Based on LSI Technology 583

12.9 Radio Wave Resource Sharing with Technology Leadership and the

Role of the Antenna 583

References 584

Chapter 13 Antennas for RFID 589

13.1 The Characteristics of an RFID System 589

13.1.1 What Is RFID? 589

13.1.2 Operating Frequencies 591

13.1.3 Operating Principles 592

13.1.4 Read Range 595

13.2 Reader Antennas 596

13.2.1 Fixed Reader 596

13.2.2 Mobile Reader 599

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13.3 Tag Antennas 605

13.3.1 Structure of a Tag Antenna 605

13.3.2 Impedance Matching 607

13.3.3 Tags on Metallic Surface 609

13.3.4 Bandwidth-Enhanced Tag Antennas 611

13.3.5 SAW Tags 612

13.4 Measurement of Tag Antennas 612

13.4.1 Measurement of the Tag Antenna Impedance 613

13.4.2 Read Range Measurement 614

13.4.3 Efficiency Measurement 615

References 616

Chapter 14 Multiple-Input Multiple-Output (MIMO) Systems 619


14.2 Diversity in Wireless Communications 620

14.2.1 Time Diversity 620

14.2.2 Frequency Diversity 621

14.2.3 Space Diversity 622

14.3 Multiantenna Systems 623

14.4 MIMO Systems 624

14.5 Channel Capacity of the MIMO Systems 627

14.6 Channel Known at the Transmitter 628

14.6.1 Water-Filling Algorithm 629

14.7 Channel Unknown at the Transmitter 629

14.7.1 Alamouti Scheme 630

14.8 Diversity-Multiplexing Trade-Off 631

14.9 MIMO Under an Electromagnetic Viewpoint 632

14.9.1 Case Study 1 634

14.9.2 Case Study 2 635

14.9.3 Case Study 3 635

14.9.4 Case Study 4 639

14.9.5 Case Study 5 641

14.10 Conclusions 643

References 644

Chapter 15 Smart Antennas 647

15.1 Definition 647

15.2 Why Smart Antennas? 649


15.4 Background 652

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15.5 Beam Forming 653

15.5.1 Minimum Mean Square Error 655

15.5.2 Minimum Variance Distortionless Response 656

15.6 Direct Data Domain Least Squares (D3

LS) Approaches to Adaptive

Processing Based on a Single Snapshot of Data 659

15.6.1 Eigenvalue Method 662

15.6.2 Forward Method 663

15.6.3 Backward Method 665

15.6.4 Forward-Backward Method 666

15.7 Simulations 667

15.8 Conclusion 671

References 671

Appendix A Glossary 675

A.1 Catalog of Antenna Types 675

A.1.1 Linear Antennas 676

A.1.2 Material Loading 678

A.1.3 Planar Antenna 679

A.1.4 Broadband and Multiband Antennas 680

A.1.5 Balance-Unbalance Transforming 681

A.1.6 Arrays and Diversity Systems 681

A.1.7 Recent Innovative Concepts 682

References 682

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

A.2 Land Mobile Systems 704

A.2.1 Automobiles 704

A.2.2 Portable Equipment 711

A.2.3 Trains 718

A.2.4 Base Stations 719

A.2.5 Satellite Systems 723

A.2.6 UWB 727

A.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 energy

has a rich history going back almost a century. Although much of the earlier work was

carried out as a matter of scientific curiosity, since the mid-1950s the majority of the

research has been focused on filling gaps in the knowledge-base regarding safety in order

to develop rational radio frequency (RF) safety standards and guidelines to protect against

established adverse health effects in humans. Members of the public and RF workers

continue to raise questions about the safety of new RF technologies, including radar, radio

and television broadcasting facilities, microwave ovens, point-to-point microwave radio,

and satellite communications systems. The most recent concern is the safety of mobile

and portable telephones and their base stations. Consequently, much of the bioeffects

research carried out during the past 15 years is specific to conditions relative to exposure

to portable telephones. The results of this research are used to ensure that contemporary

safety guidelines and standards adequately protect the public and the worker, or if changes

are 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 to

protect against harmful effects associated with RF exposure, and (2) conformance (or

compliance) standards that describe protocols to ensure that RF-emitting devices, such as

portable 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 energy

frequently 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 of

RF power at which mobile and portable wireless communication devices operate may be

as low as a few mW for a Bluetooth device; a fraction of a watt for a mobile phone; up

to 7W for two-way mobile radios; several tens of watts for mobile radio systems installed

in motor vehicles; and up to 100W, or more, for certain mobile telephone and two-way

radio 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 higher

exposures, especially to important organs such as the brain and eyes, because of their

proximity to the callers body during normal use. Although exposure from base station

antennas is far less than that from handheld devices, the public appears to be more

concerned about the safety of base stations. Sound, science-based safety standards help

to 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 types

of standards that address the safety of mobile communication devices are described

specifically safety standards that recommend limits to protect against harmful effects

associated with RF exposure, and conformance (or compliance) standards that describe

protocols to ensure that RF-emitting devices comply with the safety standards. For purposes

of this chapter, the frequency range of interest is 30 MHz to 6 GHz, which includes the

frequencies most commonly used for mobile communications.

6.2 PHYSICAL PARAMETERS

Radio frequencies are loosely defined as frequencies between 3 kHz and 300 GHzthat

is, frequencies below the infrared region of the electromagnetic spectrum. Because the

photon energy associated with an RF electromagnetic wave is far below that required to

remove an electron from an atom (ionization), RF exposure is characterized as nonionizing

radiation, as is infrared radiation, visible light, and the longer ultraviolet wavelengths.

The physical interaction of RF energy with biological material is complex, often resulting

in highly nonuniform distributions of the induced electric (E) and magnetic (H) fields

and the induced current density within the object regardless of the uniformity of the

external exposure fields. The internal fields are related to a dosimetric quantity, called

specific absorption rate (SAR), which was first proposed by the National Council on

Radiation Protection and Measurements in 1981 [1], and defined as the time derivative

of the incremental energy absorbed by (dissipated in) an incremental mass contained in

a 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 of

the absorbing object by the following equations:

SAR =

E

2W/kg (6.1)

E= SAR1/2

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) in

tissue, J is the current density (A/m2

) in tissue, is the tissue density (kg/m3

), and is

the dielectric conductivity of the tissue (S/m).

In a tutorial on RF dosimetry, Chou et al. [2] discuss the relationship between SAR

and the characteristics of the incident field and the geometrical and electrical properties

of 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 SAR

for mobile phones and other portable devices are described in Section 6.5.)

In order to determine the thresholds for harmful effects and develop exposure limits

to protect against such effects, it is necessary to know the magnitude and distribution of

the SAR within the exposed object. The SAR depends not only on the properties of the

incident field, including the magnitudes of E and H (or equivalent power density); it also

depends on the dielectric properties, geometry, size, and orientation of the exposed object,

the polarization and frequency of the incident fields, the source configuration, exposure

environment, 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 with

RF exposure. Currently two recognized international organizations develop RF safety

standards and guidelines. One, now called the Institute of Electrical and Electronics

Engineers (IEEE) International Committee on Electromagnetic Safety (ICES) Technical

Committee 95, has a history of RF safety standard activities that traces back to the late

1950s. The first RF safety standard was published by this committee in 1966 [4]; four

revisions have been published since thenthe 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 are

open, and meeting records are posted on the Internet. A total of 130 members representing

24 countries were involved with developing the latest revision of this standard (IEEE

C95.1-2005) [5], including members of government, academia, industry and the general

public. (See Petersen [6] for a detailed historical record.) In 2006, this standard was

approved by the American National Standards Institute and is recognized as an American

National Standard (ANSI/IEEE C95.1-2006).

The second international organization that develops RF safety guidelines is the

International Commission on Non-Ionizing Radiation Protection (ICNIRP), which consists

of 14 elected members from various government organizations and academia (but no

members representing commercial interests). The ICNIRP guidelines, developed mostly

in closed forums, are endorsed and promoted globally by the World Health Organization

for 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. Similarities

and differences in the recommendations from IEEE and ICNIRP are presented in Section

6.4.3.

The second type of standard is the product standard which recommends methodolo-

gies for ensuring products comply with the safety standards. The committees that develop

international 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); IEC

TC-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 to

readily ensure that their products comply with these or similar requirements. The goal is

to provide unambiguous procedures that yield repeatable results (e.g., similar to the

procedure for certifying compliance of microwave ovens). In addition to standards for

measuring the peak SAR associated with handheld mobile telephones, TC-34 is in the

process of developing product standards for vehicle-mounted antennas, as well as for

other devices using both measurement and numerical techniques [8]. Recent collaboration

between ICES TC-34 and IEC TC-106 led to the development of the product standard

for 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 associated

with RF energy. Examples of this type of standard include compatibility standards (e.g.,

standards for limiting electromagnetic interference with electronic equipment on aircraft

or in medical environments). Compatibility standards, developed by the American National

Institute 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 adopted

by various agencies and organizations throughout the world. The first RF exposure standard

published in the United States (USAS C95.1-1966) [4] limited RF-induced heating of the

body. 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, dosimetry

studies revealed that the interaction of RF energy with biological bodies is extremely

complex, and a frequency-independent limit over a broad frequency range is unrealistic.

The third revision of the 1966 standard (American National Standards Institute ANSI

C95.1-1982) [10] incorporated dosimetry, which resulted in frequency-dependent limits

based 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 added

an additional safety factor of 5 for a lower tier for exposure of the public [11]. The upper

tier includes a 10-fold safety factor; the lower tier has an additional factor of 5 (i.e., a

total safety factor of 50 below the threshold for effects considered adverse). The IEEE

Committee adopted this approach, and the revision of the 1982 C95.1 standard (IEEE

C95.1-1991) [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 the

whole-body-averaged SAR to the same values of 0.4 and 0.08 W/kg for the upper and

lower 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, extra

burdens for manufacturers, and discordance among the regulators. During the revision

process that led to IEEE C95.1-2005 [5], consideration was given to harmonizing with the

ICNIRP guidelines where scientifically justifiable. An important issue that was addressed is

the peak SAR limits which are now essentially identical in the new IEEE standard and

ICNIRP guidelines. The 1998 ICNIRP guidelines and IEEE C95.1-2005 are detailed in

the 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 based

on studies reporting established adverse health effects. In agreement with the rationale of

C95.1-1991, ICNIRP also found that the relevant established effects are surface effects

at the lower frequencies (e.g., electrostimulation, shocks and burns) and effects associated

with tissue heating at the higher frequencies. Although a number of in vitro studies were

reviewed, the focus was on in vivo studies. Epidemiological studies of reproductive

outcome and cancer were reviewed but because of the lack of adequate exposure assessment

and inconsistency of results, these studies were found to be of little use for establishing

science-based exposure criteria. Studies reporting athermal effects, including window

effects [e.g., effects associated with ELF amplitude modulated (AM) RF fields] were

also considered, but ICNIRP concluded: Overall, the literature on athermal effects of

AM electromagnetic fields is so complex, the validity of reported effects so poorly

established, and the relevance of the effects to human health is so uncertain, that it is

impossible to use this body of information as a basis for setting limits on human exposure

to these fields [13]. The more recent review of the literature by IEEE led to the following

conclusions regarding low-level effects: Despite more than 50 years of RF research,

low-level biological effects have not been established. No theoretical mechanism has been

established that supports the existence of any effect characterized by trivial heating other

than microwave hearing. Moreover, the relevance of reported low-level effects to health

remains speculative and such effects are not useful for standard setting [5, p. 82].

Standard-setting organizations (e.g., ANSI, IEEE) and organizations that develop

recommendations and guidelines (e.g., NCRP and ICNIRP) have all determined that SAR

is the appropriate dosimetric parameter over the broad whole-body resonance region and

also found that the most reliable and sensitive indicator of potential harm was behavioral

disruption, with a threshold SAR of 4 W/kg. A safety factor of 10 was incorporated for

exposures in the workplace, and an additional factor of 5 for exposure of the general

public 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 recommended

for 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 and

50. The ICNIRP limits for high-peak, low-average-power pulsed fields are based on

the evoked auditory response (microwave hearing [14, 15]) whereas the corresponding

C95.1-1991 and C95.1-2005 limits are based on the stun-effect in small animals (with

a suitable margin of safety) [16]. That is, while ICNIRP considers microwave

hearing a harmful effect, it is not considered an adverse effect in the C95.1-2005 standard

[5, pp. 8182].

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 compliance

with 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 6.1

1998 ICNIRP Basic Restrictions

Whole Body Local SAR Local SAR

Avg. 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 6.2

1998 ICNIRP Reference Levels

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

)

Occupational

3 to 65 kHz 610 24.40.065 to 1 MHz 610 1.6/ f

1 to 10 MHz 610/ f 1.6/f

10 to 400 MHz 61 0.16 10

400 to 2,000 MHz 3f1/2

0.008f1/2

f/40

2 to 300 GHz 1.37 0.36 50

General Population

3 to 150 kHz 87 5

0.15 to 1 MHz 87 0.73/ f

1 to 10 MHz 87/ f1/2

0.73/f

10 to 400 MHz 28 0.073 2

400 to 2,000 MHz 1.375f1/2

0.0037f1/2

f/200

2 to 300 GHz 61 0.16 10

Source:[13].

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basic restrictions are exceeded. For additional details of ICNIRP recommendations, refer

to 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 established

adverse effects to human health associated with exposure to RF electric, magnetic, and

electromagnetic 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 2005

were included), including those studies that involve low-level exposures where increases

in temperature could not be measured or were not expected. New insights gained from

improved experimental and numerical methods and a better understanding of the effects

of acute and chronic RF electromagnetic field exposures of animals and humans are

included. A lack of credible scientific and medical reports showing adverse health effects

for RF exposures at or below corresponding exposure limits in past standards supports

the protective nature of this standard. Above 100 kHz, the limits are designed to protect

against adverse health effects resulting from tissue heating, the only established mechanismrelating to adverse effects of exposure to RF energy at these frequencies. For the first

time, guidance on the necessity of an RF exposure control program (e.g., recommendations

in IEEE C95.7-2005 [17]) is included.

The C95.1 standard consists of normative sections, including an overview of the

document (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 the

revision; the fourth provides examples of practical applications; and the last three annexes

are 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) and

the rationale (Annex C).

6.4.2.1 Recommendations

The recommendations are expressed in terms of basic restrictions (BRs) and maximum

permissible exposure (MPE) values (sometimes called reference levels or investigation

levels). The BRs are limits on internal fields, SAR, and current density; the MPEs, derived

from the BRs, are limits on external fields and on induced and contact currents. The

recommendations are intended to apply to all human exposures except for exposure of

patients 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 the

body during whole-body exposure. Consistent with the approach used in the prior standards

and the ICNIRP guidelines, a traditional safety factor of 10 has been applied to the

established SAR threshold of 4 W/kg for such effects, yielding an SAR of 0.4 W/kg

averaged over the whole body. In the absence of an RF safety program, the BRs of the

lower tier (action levels) may also be used for the general public. Applied to members

of the general public, the lower tier provides more assurance that continuous, long-term

exposure of all individuals in the population will be without risk of adverse effects. The

BRs 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 nonuniform

exposure.

As the frequency increases above 3 GHz, the power deposition becomes more

superficial and SAR less meaningful. To account for the shallow penetration depth at the

higher frequencies, the BRs are expressed in terms of incident power density and are

identical to the derived limits (MPEs). Although exposure at or near these values may

be 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 appropriate

for all human exposure, are shown in Figure 6.2. (For detailed information on averaging

time, 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 6.3

Basic Restrictions for Frequencies Between 100 kHz and 3 GHz

Persons in Controlled

Action Level Environments SAR

SAR (W/kg) (W/kg)

Whole-body exposure (Whole-body Average) 0.08 0.4

Localized 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].

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Figure 6.2 IEEE C95.1-2005 [5] MPEs for the upper and lower tiers in the frequency band 100 kHz to 300

GHz, 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 IEEE

C95.1-2005, an RF safety program such as detailed in IEEE Std C95.7-2005 [17] can be

implemented 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 IEEE

C95.1-2005

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 documents

are similar, there are some differences between the two that suggests a need for continued

harmonization 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, adopted

a combination of the IEEE C95.1-1991 and NCRP 1986 exposure criteria to regulate RF

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Table 6.4

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

Frequency range 100 kHz to 300 GHz 100 kHz to 300 GHz

Recognition of whole-body Yes Yesresonance

Incorporation of dosimetry Yes Yes

(SAR)

Database of experimental Large Very large ( 1,300 citations)

literature

Most significant biological Behavioral disruption Behavioral disruption

endpoint (associated with 1C core (associated with 1C coretemperature rise) temperature rise)

Whole-body-averaged SAR 14 W/kg 4 W/kg

associated with behavioral

disruption

Limiting whole-body-averaged 0.4 W/kg (occupational) 0.4 W/kg (controlled

SAR 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) cube

6 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 GHzAveraging 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 H2

have different

GHz averaging times for 1.34 MHz

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