A. S. Hoenshel and R. Mittra EMC Lab Pennsylvania State University University Park, PA 16802
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Platform Tolerance of RFID Platform Tolerance of RFID Antennas and their Antennas and their Performance Enhancement with Performance Enhancement with Artificial Magnetic Artificial Magnetic Conductors Conductors A. S. Hoenshel and R. Mittra EMC Lab Pennsylvania State University University Park, PA 16802
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A Parametric Study on the Platform Tolerance of RFID Antennas and their Performance Enhancement with Artificial Magnetic Conductors. A. S. Hoenshel and R. Mittra EMC Lab Pennsylvania State University University Park, PA 16802. Electronic Toll Collection Access Control Animal Tracking - PowerPoint PPT Presentation
Transcript of A. S. Hoenshel and R. Mittra EMC Lab Pennsylvania State University University Park, PA 16802
A Parametric Study on the Platform A Parametric Study on the Platform Tolerance of RFID Antennas and their Tolerance of RFID Antennas and their
Performance Enhancement with Performance Enhancement with Artificial Magnetic ConductorsArtificial Magnetic Conductors
A. S. Hoenshel and R. MittraEMC Lab
Pennsylvania State University University Park, PA 16802
RFID Antenna ApplicationsRFID Antenna Applications
Electronic Toll Collection
Access Control Animal Tracking Inventory Control Tracking Runners in
Races!
RFID Antenna RFID Antenna Design ChallengesDesign Challenges
Small Size Planar UHF Frequency Allocation
– Europe 866-869 MHz– North America 902-928 MHz
Impedance Matching– ASIC Chip: High
Capacitive Value, Small Resistive Value
Environmental Conditions
Scope of PresentationScope of Presentation
Mounting Materials• Cardboard (r=2.5)
• Glass with No Loss(r=3.8)
• Glass with Loss(r=2.5) and Loss Tangent 0.002
• Plastic (r=4.7)
Performance Enhancement using Artificial Magnetic Conductors (AMCs)
Two Planar-Inverted F-Antenna Designs
Antenna Parameters InvestigatedAntenna Parameters Investigated Characteristic
Impedance– Power
3-Dimensional Radiation Patterns
Maximum Directivity
22)(4
asas
sa
XXRR
RRP
where Zwhere Zaa = R = Raa + j X + j Xa a is the antenna impedanceis the antenna impedance
and Zand Zss = R = Rss + j X + j Xs s is the source impedanceis the source impedance
radP
UD max
max
4
where Uwhere Umaxmax is the radiation intensity is the radiation intensity
in maximum direction in maximum direction and Pand Pradrad is the total radiated power is the total radiated power
* Source: Constantine A. Balanis. Antenna Theory, Analysis and Design, New Jersey, (Third Edition) John Wiley and Sons.
* *
ASIC Chip:
Zc=10-j160 [] at 867 MHz
Zc=10-j150 [] at 915 MHz
Zc=10-j145 [] at 940 MHz
62mm
51mm
= 2.35 3mm
5mm
•Dual-band Frequency Operation
•Gap Dimension and Stub Dimension Used to Tune
•Platform Tolerance
•Dominating Horizontal Current Distribution
Open-Ended Stub PIFA Open-Ended Stub PIFA DesignDesign
* Source: M. Hirvonen, K. Jaakkola, P. Pursula, and J. Saily, “Dual-Band Platform Tolerant Antennas for Radio-Frequency Identification,” IEEE Trans. Antennas Propag., vol. 54, no. 9, pp. 2632 - 2637, Sept. 2006.
•Mounting Materials
•Dimensions
•900 mm x 900 mm
•(4 x 4 )
•Thickness=13 mm
•Cardboard (r=2.5)
•Glass(r=3.8)
•Plastic(r=4.7)
•Tag Dimension
•62 mm x 51 mm
Open-Ended Stub PIFA Open-Ended Stub PIFA DesignDesign
62mm
51mm
= 2.35 3mm
5mm
Impedance Impedance [867/915 MHz] [867/915 MHz]
Open-Ended Stub PIFA DesignOpen-Ended Stub PIFA Design
Real Impedance
0
50
100
150
200
250
300
850 858 865 873 880 888 895 903 910 918 925 933
Frequency [MHz]
No Material Cardboard Glass Plastic
Imaginary Impedance
0
50
100
150
200
250
300
850 858 865 873 880 888 895 903 910 918 925 933
Frequency [MHz]
No Material Cardboard Glass Plastic
Power Power Open-Ended Stub Open-Ended Stub PIFA DesignPIFA Design
Power (867 MHz)
Power (915 MHz)
Power (940 MHz)
No Material 83.49 64.92 74.07
Cardboard(r=2.5) 54.53 86.28 80.5
Amount Increased -28.96 21.36 6.43
No Material 83.49 64.92 74.07
Glass (r=3.8) 54.81 80.72 72.9
Amount Increased -28.68 15.8 -1.17
No Material 83.49 64.92 74.07
Plastic (r=4.7) 58.3 85.72 72
Amount Increased -25.19 20.8 -2.07
*Design Goal: Power > 40% at Selected Frequencies
Radiation [867 MHz]Radiation [867 MHz]Open-Ended Stub PIFA DesignOpen-Ended Stub PIFA Design
No Material Cardboard
Glass Plastic
DirectivityDirectivity Open-Ended Stub PIFA Design Open-Ended Stub PIFA Design
Directivity at 867 MHz [dB]
Directivity at 915 MHz [dB]
Directivity at 940 MHz [dB]
No Material 2.2637 2.6293 2.7450
Cardboard(r=2.5) 2.8511 3.1605 3.6968
Amount Increased
0.5874 0.5313 0.9518
No Material 2.2637 2.6293 2.7450
Glass(r=3.8) 3.8117 4.4925 5.9277
Amount Increased
1.5480 1.8632 3.1826
No Material 2.2637 2.6293 2.7450
Plastic(r=4.7) 4.7619 5.3194 6.1712
Amount Increased
2.4983 2.6901 3.4261
Inductively-Coupled Feed Loop PIFA DesignInductively-Coupled Feed Loop PIFA Design
•Dual-band Frequency Operation Achieved
•Gap dimension between loop and radiators is used to tune
•Platform Tolerance
•Reduced Current on Ground Plane
ASIC Chip:
Zc=10-j150 [] at 915 MHz
Zc=10-j145 [] at 940 MHz
Inductively-Coupled Feed Loop PIFA DesignInductively-Coupled Feed Loop PIFA Design
•Mounting Materials
•Dimensions
•200 mm x 200 mm
•( x )
•Thickness=5 mm
•Cardboard (r=2.5)
•Glass with No Loss(r=3.8)
•Glass with Loss(r=2.5) and Loss Tangent 0.002
•Tag Dimension
•54 mm x 45 mm
Impedance Impedance Inductively-Coupled Feed Loop PIFAInductively-Coupled Feed Loop PIFA
Impedance (Before Optimization)
020406080
100120140160180200
0.83 0.85 0.87 0.89 0.91 0.93 0.95 0.97 0.99 1.01 1.03
Frequency [GHz]
Imaginary No Material Imaginary Cardboard Imaginary No Loss Imaginary Glass with Loss
Real No Material Real Cardboard Real Glass with Loss Real No Loss
Impedance Impedance Inductively-Coupled Feed Loop PIFAInductively-Coupled Feed Loop PIFA
Impedance (Optimized)
0
20
40
60
80
100
120
140
160
180
200
0.83 0.85 0.87 0.89 0.91 0.93 0.95 0.97 0.99 1.01 1.03
Frequency [GHz]
Imaginary No Material Imaginary Cardboard Imaginary Glass No Loss Imaginary Glass With Loss
Real No Material Real Cardboard Real Glass No Loss Real Glass With Loss
Power Before and After Optimization Power Before and After Optimization Inductively-Coupled Feed Loop PIFA Inductively-Coupled Feed Loop PIFA
Power (915 MHz) [%] Power (940 MHz) [%]
Free Space 86.09 41.45
Cardboard 16.29 6.5
Cardboard Optimized 61.19 31.69
Free Space 86.09 41.45
Glass 24.06 9.48
Glass Optimized 56.59 69.36
Free Space 86.09 41.45
Glass with Loss 11.65 23.81
Glass with Loss Optimized 61.6 52.55
*Design Goal: Power > 40% at Selected Frequencies
Directivity & Radiation Directivity & Radiation Inductively Coupled Feed Loop PIFAInductively Coupled Feed Loop PIFA
Directivity at 915 MHz[dB]
Directivity at 940 MHz[dB]
No Material 5.4033 5.1851
Cardboard (r=2.5) 5.3529 4.6835
Amount Increased -0.0504 -0.5016
Directivity at 915 MHz[dB]
Directivity at 940 MHz[dB]
No Material 5.4033 5.1851
Glass No Loss (r=3.8) 5.3148 5.1188
Amount Increased -0.0885 -0.0663
Directivity at 915 MHz[dB]
Directivity at 940 MHz[dB]
No Material 5.4033 5.1851
Glass With Loss (r=2.5) and loss 0.002
5.2634 5.1851
Amount Increased -0.1399 0
867 MHz No Material
867 MHz Cardboard
Performance Enhancement with Artificial Performance Enhancement with Artificial Magnetic ConductorsMagnetic Conductors
PEC Ground– Reflects Half the Radiation
Gain can be increased by 3 dB
– Image Currents Can Cancel Currents in Antenna
Limitation on distance between ground and radiating elements (/4)
– Reflection Coefficient of -1
PMC Ground– Image Currents In Phase with
Original Currents PMC is reflective Low Profile Antennas
– High Impedance Surface Current is filtered at selected
frequencies so tangential magnetic field is small while electric field is still large
Suppression of Surface Waves=>Minimizes Backlobe
– Reflection Coefficient of +1
Fabrication of AMCsFabrication of AMCs
Configuration of AMC
GA Input
Parameter Output
FSS LayerFSS Layer
FSS Unit Cell
/2 x /2 FSS Layer
Reflection Phase Crosses 0 at 939 MHz
Directivity Directivity AMCAMC
Directivity [dB]
867 MHz 940 MHz
PEC Ground
4.0235 4.1707
AMC Ground
4.6120 4.9485
Increased 0.5885
Directivity [dB]
915 MHz 940 MHz
PEC Ground
4.3255 3.8399
AMC Ground
5.6650 4.7566
Increased 1.3395 0.9167
Open-Ended Stub PIFA
Inductively-Coupled Feed Loop PIFA
0.7778
Radiation [867 MHz]Radiation [867 MHz]AMCAMC
Open Ended Stub PIFA
Inductively Coupled PIFAPEC
PEC
AMC
AMC
Optimization Optimization Open-Ended Stub PIFA DesignOpen-Ended Stub PIFA Design
Impedance Stub 2.8
0
50
100
150
200
250
850 855 860 865 870 875 880 885 890 895 900 905 910 915 920 925 930 935 940 945 950
Frequency [MHz]
[]
Imaginary Gap 2.6 Imaginary Gap 2.5 Imaginary Gap 2.4 Imaginary Gap 2.2 Imaginary Gap 2.1
Real Gap 2.6 Real Gap 2.5 Real Gap 2.4 Real Gap 2.2 Real Gap 2.1
Optimization Optimization Open-Ended Stub PIFA Design Open-Ended Stub PIFA Design
STUB 2.8 Imaginary 867 MHz []
Real 867 MHz []
Power 867 MHz [%]
Gap 2.6 157.45 40.29 63.56
Gap 2.5 142.94 3.55 29.90
Gap 2.4 153.95 26.54 77.39
Gap 2.2 131.14 2.66 10.70
Gap 2.1 128.29 2.69 9.23
Note: 915 MHz and 940 MHz were not able to be sufficiently matched.
*Design Goal: Power > 40% at Selected Frequencies
Dimension [mm]
Imaginary 915 MHz
[]
Real 915 MHz
[]
Imaginary 940 MHz
[]
Real 940 MHz
[]
Power 915 MHz
[%]
Power 940 MHz
[%]
8.90 164.15 0.07 169.24 3.27 0.92 17.11
9.10 164.23 0.06 170.52 4.52 0.78 20.97
9.20 162.70 0.24 166.82 1.47 3.64 9.68
9.25 166.60 2.98 171.89 0.51 26.83 2.44
9.30 158.90 0.14 163.86 1.29 3.11 10.70
9.40 163.04 0.13 167.28 4.80 1.90 26.83
9.50 163.52 0.17 168.06 4.42 2.34 23.91
Optimization Optimization Inductively-Coupled Feed Loop PIFA DesignInductively-Coupled Feed Loop PIFA Design
*Design Goal: Power > 40% at Selected Frequencies
Work in ProgressWork in Progress
16 mm x 16 mm Unit Cell 6 x 6 Unit Cells for /2 x /2 FSS
30 mm x 30 mm Unit Cell 3 x 3 Unit Cells for /2 x /2 FSS
SummarySummary
Open-Ended Stub PIFA Design showed to be platform tolerant in numerous cases
– Each case was thoroughly examined Inductively-Coupled Feed Loop PIFA was very sensitive to platform
– An optimization was done for each mounting material The AMC ground plane did improve the directivity and reduce the
backlobe for both antenna cases An optimization needed to be done using the AMC for both antenna
cases because the impedance was altered significantly in each case The Open-Ended Stub Design was optimized to sufficient operation
but the Inductively-Coupled Feed Loop PIFA could not be tuned for sufficient operation
