ceramic antennas for small form factors
TRANSCRIPT
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© 2007, Ethertronics
Advances in High-Performance Ceramic Antennas
for Small-Form-Factor, Multi-Technology Devices
© 2007, Ethertronics
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© 2007, Ethertronics 2
Presentation outline
• Market Requirements Driving Multiple
Antenna Integration & Thinner Packages
• Antenna Design Requirements
• Advantages of Ethertronics IMD Technology
• GPS Antenna Comparison Testing
• Dual frequency products
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Trend: Multiple Antennas per Phone
Main Cellular
Bluetooth
GPS
WiFi
-
500,000
1,000,000
1,500,000
2,000,000
2,500,000
3,000,000
3,500,000
4,000,000
2005 2006 2007 2008 2009 2010
U n i t V o
l u m
e
WiFi
GPS
Bluetooth
Main Cellular
Source – Gartner
• Common to have 2-4antennas per phone
• Most popular
features withhighest attach rates
– Bluetooth - 50%
– GPS - 25%
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Trend: Smaller Handsets – Less Volume
• Thin phone trend is accelerating
– Volumes decreasing ~10% per year– Ultra Thin handsets are challenging
• Utilize ~50% of the average volume
55 cubic cm75 cubic cm71 cubic cm 56 cubic cm
Avg PhoneVolume
2004 131 cu.cm
2005 122 cu.cm
2006 106 cu.cm
Ultra Thin 55 cu.cm
Source: Current Analysis
Industry Trendline
Cell Phone Volumes
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Design Challenges
• Overall device size shrinking
– More antennas in less space
– Maximum component heightunder 2.5mm for Ultra models
• More parasitic elements
– Speakers, cameras, flex…
• Less quality real estate
– More I/O connectors on side of the board
• Antenna collocation
– Diversity or different applications
– Example: Bluetooth and WiFi integration
Cell antenna
WLAN antenna
BT antenna
WCDMA antenna
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Antenna Requirements
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Benchmark Dual Band Performance
• Typical antenna
specifications:Better than 10 dB
Return Loss
Better than 20 dB
Isolation
• Benchmark phone
required 25 dB of
isolation to meetOEM performance
specificationsGPS Bluetooth
Return
Loss
Isolation
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Antenna Volume Theory
• Wheeler & Mc Lean provided the basic insights for
identifying the real effective volume of embedded antennas
• Wheeler’s Formula
• Given constraints on design space, how should one compare
two antennas when their “antenna mode volume” will
become altered as part of the mechanical design?– How close is the nearest metal object?
– Should coupling effects and consequences be considered?
( )3wavelengthradiovolumemodeantenna
K f
Δf ×=
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Antenna Requirements
• Smaller antennas in close proximity
– With high efficiency – above 40% threshold
– Well-controlled radiation – resist performance changes
(good for customer as well as designer)– Immunity to other frequencies or diversity antennas
• GPS separation from UMTS-1700, sharing of 2.4 GHz
• How to achieve ideal performance:– Decrease interaction between antennas
– Decrease interaction between phone elements
– Minimize antenna ground dependence
Isolation
SelectivityKey Factors
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Isolation Drives Overall Performance
Isolation describes how an antenna
interacts with its surrounding.
How can isolation be improved ?
By shaping the antenna’s near field away
from the perturbations and the absorbers.
Superior isolation allows:
- better efficiency- easier integration
- semi-standardized products
ET antenna isolation: 2mmfor 0.3% frequency shift
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IMD Provides Superior Isolation
• ET IMD antennas are more tolerant of interfering objects– Hand placement and head significantly impact performance
• GPS signal strength improved by staying on frequency
Isola t i on Test Result s
- GPS Internal antenna example-very sensitive to freq. shift
- IMD antennas stay on frequency
even with interference from
other objects – e.g., hand
Return-Loss ChartBefore / After Hand Placement
Any current flow on the board becomes
a part of the antenna radiating mechanism.
When touched, the characteristics of the antenna change.
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GPS Antenna Comparisons(following vendors recommendations)
• Highest efficiency does not tell entire story– Important to also study the frequency component of antenna’s efficiency
• Selectivity – ability to reject the frequencies outside its range
Antenna Selectivi ty
0
10
20
30
40
50
60
70
80
90
100
1500 1525 1550 1575 1600 1625 1650 1675 1700
frequency, MHz
e f f i c i e n c y ,
%
Ethertronics
Sample 1
Sample 2
Sample 3
Problem Area
Overlap with UMTS,
AWS Band
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Ceramic
GPS AntennaTest Bed
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Several Variables to Consider
• The antenna may require ground plane removal
• It will excite some of the board, but how much?
– the board itself could become the antenna
• What about board placement, and distance to nearest
interferers, eg a shield can, or a battery
• We developed a test bed, focusing on the isolation,
selectivity, efficiency and position of the antenna
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Shield Can Separation Test
• Several Tests utilizingmetal can as interferer
– Measure changes in:• Efficiency
• Center frequency
– At 3 distances• 3, 6 and 9mm apart
• Calculate Volume/Area
– Device size• Footprint & placement
– Real antenna volume• Interaction with can
• Keep-out zone is 3D
shield can
separation
3mm
6mm
9mm
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Efficiency Lowered by Shield Can
• Sample 1, significantly impacted
• Broadband antenna has best performance
• All samples above 40% efficiency threshold in free space
Efficiency
0
10
20
30
40
50
60
70
80
90
100
0 3 6 9 12 15
shield can distance, mm
e f f i c i e n c y ,
%
Ethertronics
Sample 1Sample 2
Sample 3
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Frequency Shifted by Shield Can
• Sample 1 significantly impacted• High-efficiency, broadband sample 2 survives shift’s impact
• IMD antenna stays rock solid on frequency
Frequency Shift
0
25
50
75
100
125
150
0 3 6 9 12 15
shield can distance, m m
f r e q u e n c y s h i f t , M H z Ethertronics
Sample 1
Sample 2
Sample 3
Efficiency
15%
70%
40%60%
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Board Position Test Set up
• How often is the best
antenna location where
one has space to place it?
• Determine how muchnormal performance can
vary from the specified
best case…
Position 4
Position 3
P o s i t i o n
1
P o s
i t i o n
2
Board Area
40mm x 80mm
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Typical GPS Antenna Performance
• Average from 3 best positions out of 4 tested
• Samples 1 & 2 show a 5~10% drop from peak efficiency
• IMD stayed consistent across all three locations
Average Per for mance - 3 locat ions
0
10
20
30
40
50
60
70
80
90
100
1525 1550 1575 1600 1625
frequency, MHz
e f f i c i e n c y ,
%
Ethert ronics - Avg Bes t 3
Sam ple 1 - Avg Bes t 3
Sam ple 2 - Avg Bes t 3
Sam ple 3 - Location 3 only
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“Worst Case” Performance
• Two antennas still above 40% threshold– Broadband antenna Sample 2 vs IMD Dual Band, Dual Feed
• IMD antenna decreased efficiency by 25% vs >50%+ by all others
Wor st Perform ance - Single Location
0
10
20
30
40
50
60
70
80
90
100
1525 1550 1575 1600 1625
fre quenc y, MHz
e f f i c i e n c y ,
%
Ether tro nics - Pos it ion 1
Sam ple 1 - Pos it ion 3
Sam ple 2 - Pos it ion 2
Sam ple 3 - Pos it ion 2
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Summary of Test Results
• Simple Volume test provided valuable
insights on efficiency and freq shifts
• Two antennas excelled throughout
– Ethertronics and Broadband Sample #2
• Design Tradeoffs include:
– Keep Out and Ground restrictions
– Cost & Space needed for Filters
Samples 1 & 2
ET & Sample 3
Keep-out
AreaW1
L1
H
L2
W2
Circuit Board
Antenna
L1 W1 H G r o u
n d C l e
a r a n
c e ( G C )
T o t a l P
C B A r e a
S h i e l d
C a n
O f f s
e t
R e a l
P C B
A r e a
A n t e
n n a ' s
V o l u m
e
M e a
s u r e d E f
f i c i e
n c y
Observations
Samp le 1 10 3 4 3 96 9 336 1,344 65% Limited Isolation from its environment; significant perf changes
Samp le 2 20 3 4 0 60 3 156 624 77% High Gain, but poor GPS band selectivity; need BPFSamp le 3 8 2 1.5 2 48 3 70 105 46% Low Efficiency, stable performance, single location usage
ET BT & GPS 14 4 1.3 1 80 3 140 182 68% Steady performance under all conditions; thinnest package
ET GPS onl y 10 4 1.3 1 60 3 112 146 68% Best efficiency to volume ratio
all measurements in mm , sq mm, or cu mm
Area = (L1 + 2x GC) x (W1 + GC) Use L2 and W2
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New Antenna Up To Market Challenges
• Phone real estate as pricey as Paris
– So combining functions is mandatory
– Yet antennas prefer separation for isolation
• Perform a Best of Performance Criteria Review
– Compact Size, Great Isolation & Freq Stability
– Flexible implementation without sacrificing gain
• ET’s IMD dual band, dual feed antenna products
– GPS and Bluetooth sampling now
– PCS Diversity, WiFi, WiMAX and others in testing
4.5mm gap
Quad Band Antenna
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Next Generation of Ceramic Antennas
• Leverages underlying
IMD technology
• Dual Band, Dual Feed
– Ideal implementation
• Peak Efficiency
– GPS over 68%
– Bluetooth over 50%
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One Antenna Outperforms Two…
• Ceramic version
improves key resultsby approx 4 dB
– GPS isolation
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Conclusion
• Smaller and more complex phone designs make
antenna design more challenging.
• IMD technology allows smaller designs and better
performance in densely populated volumes.
• IMD’s isolation and selectivity allow integration of
multiple antennas in a single ceramic block.
• Ceramic IMD antennas demonstrate ideal
characteristics for next-generation products.