seminar ppt
DESCRIPTION
SAR REDUCTION IN MOBILE PHONES USING PIFA WITH EBG STRUCTURETRANSCRIPT
SAR Reduction In Mobile Phones
Using PIFA With EBG Structure
PRESENTED BY
Athira.D.Nair
S7 ECE
Roll No : 14
LBSITW
2
OUTLINE
Introduction
SAR
PIFA
EBG Structure
Structure
Optimization
Characteristics (After optimization)
Return loss
Radiation pattern
Total Radiated power (TRP)
SAR
Conclusion
References
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INTRODUCTION Health risk in mobile usage
Need to reduce SAR
SAR (Specific Absorption Rate) Power absorbed per mass of the tissue (Unit :- W/kg)
Measurement – Taking average over small volume (1g/10g tissue)
σ – Sample electrical conductivity E - RMS electric field ρ - Sample density
Must not exceed exposure guidelines
Techniques to reduce SAR Optimizing antenna geometry Use of ferrite PIFA with EBG structure
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PIFA (Planar Inverted F – Antenna)
• Consists of :-
Ground plane
Top plate
Shorting strip
Feed wire
Features:-
Compact
Omni directional radiation pattern
High gain for both states of polarization
Reduced SAR
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Electromagnetic Band Gap (EBG) Structure
Small scale periodic structures
Prevent propagation of EM waves in specified frequency band
High surface impedance
Suppress propagation of surface waves
Stop band characteristics (in PCS): control radiation characteristics
Enhanced antenna performance
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PROPOSED STRUCTURE
• Consists of:-
Antenna (PIFA)
EBG cells
PCB layer
All connected to ground plane
Side view Top view
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PROPOSED STRUCTURE ….. cntd
Antenna (PIFA) :-
• Operate at PCS band (1.85 – 1.91GHz)
• Located on the underside of mobile phone
EBG Structure :-
Placed between PCB & PIFA
Control the radiations of EM waves towards body
Via – less EBG structure selected (simple & less SAR)
Consists of EBG unit cell
PCB:-
• Consists of active circuits, power lines, battery etc
• Eg:- FR4
EBG unit cell
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OPTIMIZATION
SIMULATION & MEASUREMENT
Simulation• Microwave studio based on 3-D FIT EM
simulator Measurement System
• MR900-W SAR
• Uses SAM head phantom• Consists of :
• Head equivalent liquid (Er = 40, σ = 1.4)
• Shell
• Test device (mobile) at distance 3mm
• Antenna location :
• X-Y plane, orientation – Z-axis
• Probe measures E–fields in head phantom
• Computer system calculates SAR values
Head Phantom
MR900-W SAR Measurement System
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OPTIMIZATION …. cntd
Parameter study of structure is done
Antenna bandwidth fixed under (-10dB) return loss
1. Vertical length (L) of EBG unit cell
• Vertical length (L) decreases Number of EBG cells increases
• More EBG cells in limited space SAR value reduced
• Optimized value of L= 3mm
SAR Values With Parameter L
EBG unit cell
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OPTIMIZATION …. cntd
2. Antenna height (Ha); Antenna position fixed
• Ha –> 3 – 3.5mm , SAR reduced
• Optimized value of Ha = 3.14mm
SAR values with Parameter Ha SAR Values With Parameter
Ha
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OPTIMIZATION …. cntd
3. Antenna position (T); Antenna height(Ha) fixed (3.14mm)
• Position between antenna & EBG structure asymmetrical
• Optimized value of T = 8mm
SAR Values With Parameter T
SAR values with parameter T
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CHARACTERISTICS Return loss :-
• Loss of signal power due to reflection
• RL(dB) = 20 log10(1 / )
• Less for proposed structure
• Satisfies PCS transmitting band for VSWR < 3
Return loss of the proposed antenna
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CHARACTERISTICS ….. cntd
Radiation pattern :-
• Spatial distribution of radiation as a function of angle
• Reduced radiation pattern in user’s direction
Simulated Radiation Pattern - Proposed Antenna Measured Radiation Pattern - Proposed Antenna
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CHARACTERISTICS ….. cntd
Total Radiated power (TRP) :-
• Power radiated by the antenna
• Should meet criteria of mobile communication service vendors
• Greater for proposed antenna (increased antenna gain)
TRP Values
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CHARACTERISTICS ….. cntd
SAR :-
• SAR reduced by 31% at center frequency
SAR Values
SAR DISTRIBUTION MAP
Conventional PIFA
Proposed PIFA
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CONCLUSION
Presented a novel scheme for SAR reduction
Radiation towards body reduced
Reduction in SAR value
Antenna performance maintained
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REFERENCES
Sang il Kwak, Dong-Uk Sim, and Jong Hwa Kwon, “Design of Optimized Multilayer PIFA With the EBG Structure for SAR Reduction in Mobile Applications,” IEEE Transactions On Electromagnetic Compatibility, Vol. 53, No. 2, May 2011.
Design of Multilayer PIFA based on an EBG structure for SAR reduction in mobile Applications - Sang il Kwak, Dong-Uk Sim, Jong Hwa Kwon and Je Hoon Yun.
D. Sivenpiper, L. Zhang, R. F. Broas, N. G. Alexopoulos, and E. Yablonovitch, “High-impedance electromagnetic surface with a forbidden frequency band,” IEEE Trans Microw. Theory Tech., vol. 47, no. 11, pp. 2059–2074, Nov. 1999.
Effects of Ferrite Sheet Attachment to Portable Telephone in Reducing Electromagnetic Absorption in Human Head - Jianqing Wangt Osamu F’ujiwarat Tasuku Takagi.
Z. Duan, D. Linton, W. Scanlon, and G. Conway, “Improving wearable slot antenna performance with EBG structures,” in Proc. Loughborough Antennas and Propag. Conf., Mar. 2008, pp. 173–176.
Thank You