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					 Technical seminar
 Safety Issues on Electromagnetic Radiations and
 Batteries of Mobile Communication Devices

 Specific Absorption Rate Evaluation Methods
     of Wireless Communication Devices

 Dr. Chan Kwok Hung, Brian
 Research Fellow, City University of Hong Kong
 EMC Consultant, CityU Professional Services Ltd.
 Secretary, IEEE EMC Hong Kong Chapter

 Email: brian_chan@ieee.org                                             5 December 2009



                                                                                          1
                                         Hong Kong Chapter   Hong Kong Chapter




                                 Outline
• Introduction
   – Wireless Communication Device, SAR, Standards

• SAR Evaluation Methods
   – Numerical Method
   – Experimental Method
        • Limitations
        • Future works



                                                                                          2
                     Introduction
           Wireless Communication Device
    Product                                                                                             System
  • Mobile Phone                                                                                  • GSM / CDMA
                                                                                                        – 900MHz

  • PDA Phone                                                                                     • PCS
                                                                                                        – 1.8GHz
                                                                                                  • 3G (WCDMA / CDMA2000)
  • Smart Phone                                                                                         – 1.9 & 2.1 GHz
                                                                                                  • Bluetooth
  • Netbook                                                                                             – 2.4 GHz
                                                                                                  • Wifi
                                                                                                        – 2.4 and 5.8 GHz
  • Notebook




                  Introduction
        Mobile Phone Usage in Hong Kong

Number of Mobile Phone                                                        7
Customer in Aug 2009                                                                 Post-paid SIM
                                                                              6
                         N u m b e r o f C u s to m e r s ( M i l l i o n )




                                                                                     Pre-paid SIM
Post‐paid SIM                                                                 5      3G
 6.24 Million
                                                                              4
Pre‐paid SIM
 5,68 Million                                                                 3

                                                                              2
3G
 3,24 Million                                                                 1

                                                                              0
                                                                                  2000    2001   2002   2003   2004   2005   2006    2007   2008   A ug
                                                                                                                                                   2009
 More concern on human safety
                                                                                                                                    Source: OFTA
 using wireless communication device!!
                 Introduction
       Specific Absorption Rate (SAR)
  • Definition
     – the estimation of radiated energy absorbed in
       human body             σ | E |2
     – Equation:       SAR =              [W/kg]
                                     ρ
                  σ : conductivity, ρ : density, and E : E-field
  • SAR induced in human head is mainly depends on
    the level of E-field radiated by mobile phone
Region -       Reference cited                    SAR limit
Country
 Europe     ICNIRP Guidelines 1998       2.0 W/Kg over 10g of tissue

  US        American Standard ANSI       1.6 W/Kg over 1g of tissue
                  C95.1:1999




                        Outline
• Introduction
  – Wireless Communication Device, SAR, Standards

• SAR Evaluation Methods
  – Numerical Method
  – Experimental Method
       • Limitations
       • Future works



                                                                   6
               SAR Evaluation Methods
                 Numerical Methods
•Maxwell’s Equations
                     r
       r          ∂H
  ∇ × E = −µ
                   ∂t
                     r
     r       r     ∂E
 ∇ × H = σE + ε
                   ∂t
Methods:                              Form of Maxwell’s Example of
Full 3-D EM simulation                Equation          Software
Finite-Difference Time-Domain Method Differential      Zeland Fidelity,
                              (FDTD)                   XFDTD
Finite Element Method         (FEM)   Matrix           HFSS
Finite Integration Method     (FIM)   Integral         CST




                    Numerical Methods
                     EM Simulations
• Applications
    – Microwave circuits and components
        • Amplifier, Filter, Transmission line, Coaxial
          cable, …
    – EMC and EMI structures
        • Shielding, Meshes and Apertures…
    – Other high-speed and high-frequency circuitry
        • CAT cable, Waveguide, PBG, …
    – Wireless/RF antennas
        • Monopole, Helix, Patch, …
          Parameters: Frequency / Return Loss /
          Antenna Pattern / Gain / SAR
                                                                          8
                         Example of Mobile Antenna in
                             Numerical Modeling
                     For walkie‐Talkie                               Common and Practical External and
                                                                     Internal Mobile Antenna




                        Monopole                                           Helical                                  Patch




           Example of Human Head Modeling in
                  Numerical Modeling


 Head
 Model

                                   Cubical                                       Spherical                                          Realistic
Modeling
Complexity
                                      Simple                                            Simple                                        Complex
Previous              Iyania et al. [1]                                 Moneda et al. [2]                                Heterogeneous
Studies               -Flat-plane solid phantom                         -including a pair of                             -Scan by MRI
                      -Measure accurate SAR                             eyeballs                                         Homogeneous
                                                                                                                         -IEEE std. 1528

1.   Iyama, et al. “Novel SAR measurement system using flat‐plane solid phantom,” 6th Inter. Symposium on AP and EM Theory, pp. 638‐641, Oct. 2003.
2.   Moneda et al. “Radio‐wave exposure of the human head: analytical study based on a versatile eccentric spheres model including a brain core and a pair of
     eyeballs,” IEEE Transactions on Biomedical Engineering, vol. 50, no. 6, pp. 667‐676, Jun. 2003.
                 Example of FDTD Simulation
   900MHz Helical Antenna
   and realistic phantom

Boundary condition : PML
 Grid Size : 2 mm3
                                                                 Length of
    Grid Size : 0.2 mm3                                          each cell
                                                                 0.2-1mm




                                                                             294 grids
                                                                   Length
 σ=5x    107                                      εr = 41.5        of each
                                                  σ = 0.99         cell
                                                                   2mm
σ = 3.84 x 107

                              164
                                  gr   ids                          ids
                                                              164 gr




                      SAR Evaluation
                     Numerical Methods
 Advantage                               Disadvantage
 • Inexpensive compare to                • Time-consuming to model
   measurement                              complex structure
 • Can obtain the all SAR                    – Human Head and DUT
   distribution in each locations        • Cannot simulate wideband
 • Automatic                               frequencies

 Limitations                             Applications
 • Depends on computer                   • Research & Development
    specifications                       • Pre-compliance
     – CPUs speed                        • Education
     – Memory
     SAR Measurement Standards
EUROPE
• BS EN 62209 Series - Human exposure to radio frequency fields
  from hand-held and body-mounted wireless communication devices.
  Human models, instrumentation, and procedures.
     – BS EN 62209-1:2006 , Status: Current
         • Part 1: Procedure to determine the specific absorption rate (SAR) for hand-
           held devices used in close proximity to the ear (frequency range of 300
           MHz to 3 GHz)
     – BS EN 62209-2 , Status: Draft for public comment
         • Part 2. Procedure to determine the specific absorption rate (SAR) for
           mobile wireless communication devices used in close proximity to
           the human body (frequency range of 30 MHz to 6 GHz)

US
• IEEE Std 1528 - 2003 , Status: Current
     – IEEE Recommended Practice for Determining the Peak Spatial-Average Specific
       Absorption Rate (SAR) in the Human Head from Wireless Communications
       Devices - Measurement Techniques

                                                                                    13




EN62209-1 & IEEE 1528 Standards
• SAR Measurement system

   – Phantom

   – Electronic measurement instrumentation

   – Scanning system

   – Device holder
                                                                                    14
                       SAR Measurement
                           Phantom
  • Specifications
      –   Shape
      –   Size
      –   Phantom shell material
      –   Tissue-equivalent liquid
          properties

     Name:
     Specific
     Anthropomorphic
     Mannequin

      or we can call him “SAM”!!




          Compliance SAR Measurement
                 system in CityU
Support EN62209‐1 &
Draft EN62209‐2
Standards                                Probe

  Connect to
  Computer for
  SAR Calculation
                                         Phantom
Device Under
Test ‐
Mobile Phone                             Device
                                         Holder
Measurement
Flow Chart
• Mobile Phone
   – GSM / PCS / 3G
         • Max. Power
         • Flip/ non-filp phone
         • Lower, Middle,
           Upper Channel
 • Phantom
    – Left, Right
         • Touch /
           Titled


 • System
    –   Reference
    –   2D / 3D scan
    –   Measurement
    –   Data processing,
        SAR calculation.




        Positioning of Mobile Phone
 Position             Side View   Front View   Top View


  Touch




  Tilted


Comparison                Same    Different!   Different!
        Example of compliance SAR
           Measurement Result
• Device Name
  – sxxx exxxxxxx k8xxx
• Frequency
  – 1800.00 MHz
• Channel
  – Middle
• Max. Transmit Power
  –1W
• Result
  – Compliance




   Pre-Compliance SAR Measurement
           System in CityU
• Bench top system
  Advantage
  1) Faster
  2) Smaller
  3) Cheaper
       Isotropic E-field probe
    Measured data sent
    to PC by optical fibre                              Mobile
                           Pre-amplifier                phone

           Sealed glass sphere              Stand for
                 Tissue Liquid             the sphere
                  SAR Evaluation
               Experimental Methods
Advantage                          Disadvantage
• Faster than simulation           • Expensive
• Independent of the complexity    • Require to change simulating
  of DUT                              liquid when measuring other
• Can obtain the all SAR              frequencies
  distribution in each locations

Limitations                        Applications
• High maximum expanded            • Pre-Compliance Test
   uncertainty, up to 30%          • Compliance Test
• Homogenous Phantom
• Cannot perform wideband
   frequencies at once




More Topics on SAR in Future


   Base Station
    (drafting)
                                                           Vehicle

                            Aircraft




       Ship                  Elevator
         Systems: RFID, EAS, SRD, etc……………
‐THE END‐



Thank you!
             23

				
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