mimo antenna performance for handsets and data terminals[1]
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Page 1
MIMO Antenna Performance for Handsets and Data Terminals
November 2008
Confidential and Proprietary Ethertronics, Inc © 2008
Page 2
Company Profile: Ethertronics
Main CellularAntenna
BluetoothCeramic Antenna
WLAN a/b/gCeramic Antenna
GPS Ceramic Antenna
Media antenna
Leading embedded antenna provider for mobile devices
– Global top-tier customers
Global design locations– Close to major wireless customer design teams– 180+ employees; 80% engineering – Design centers in San Diego, Shanghai, Seoul,
Taipei, and SwedenInnovative antenna technology & patent strategy
– Over 40 patents– Proprietary design software
Diverse, cost-effective, high volume manufacturing
– ISO 9001 and 14001 certified– Over 100M units shipped
Award winning– Deloitte Awards in 2007 & 2008
• #1, #5 in San Diego for technology companies• #9 in USA for wireless companies
– Inc. 500 List in 2007 & 2008• #52 for fastest growing private companies in USA• #8 for fastest growing private Telecom companies in
USA
Cellular Main Antennas
Bluetooth Antennas
GPSAntennas
WLANAntennas
800, 1900 MHz
900, 1800 MHz
1700, 2100 MHz
2.4 GHz 1.5 GHz 2.4, 4.9 GHz
5.2, 5.8 GHz
Mobile Phones
CDMA, GSM, TDMA, iDEN, WCDMA
Headsets, PCs, PDA’s
Tracking, e911Access Points, Home Networks, PC Cards
Low FreqAntennasFM Radio
DVB-H
MediaFLO
Mobile Phones
Portable Media Players
Page 3
SummaryStudy of passive antennas for MIMO applications– Important antenna parameters for MIMO applications– Examples of antenna performance at 2.5 GHz. And 3.5 GHz. (the easy part
…)– Measured antenna performance data at 700 MHz.
• Reference to classical monopoles• PIFA antennas• IMD antennas
– Integration of multi-frequency antenna (700-PCS) in a phoneFree space measurements and hand effect
– Pattern correlation calculation
Alternative approach: active antennas– Antenna null-steering technique to provide multiple pattern states for
improved performance
Page 4
Important Antenna Characteristics
1. Efficiency = radiated power____
power delivered to antenna input
takes into account: mismatch loss
losses in the antenna
losses in the surroundings
2. Isolation is a measure of how much an antenna couples to adjacent antennas and/or components
3. Selectivity is the ability of an antenna to provide out of band rejection and is defined by the frequency behavior of the antenna efficiency
4. Correlation coefficient in a multi-antenna system is a measure of the correlation between antennas, i.e. how different are the antennas in terms of radiation pattern characteristics
Page 5
Benchmark of MIMO Antenna Performance: 3.5 GHz
Antenna 1 Antenna 2
Performance of two antenna solution at 3.5 GHz on 33mm by 45mm circuit board
-35
-30
-25
-20
-15
-10
-5
0
3400 3450 3500 3550 3600 3650 3700 3750 3800
Frequency (MHz)
Ret
urn
Loss
dBFully populated circuit board and plastic
housing
3.5 GHz is an easy pick as the size of the antenna and wavelength lend themselves to easy integration
0%
10%
20%
30%
40%
50%
60%
70%
3400 3450 3500 3550 3600 3650 3700 3750 3800Frequency (MHz)
Effic
ienc
y (%
)
Dimensions
• PCB 33mm*45mm
• Antenna 5mm x 3mm x 1.3mm
Good efficiencyGood isolation
Page 6
Benchmark of MIMO Antenna Performance: 2.5 GHz
Performance of two antenna solution at 2.5 GHz on 33mm by 45mm circuit board
-20
-15
-10
-5
0
2450 2500 2550 2600 2650 2700 2750Frequency (MHz)
Ret
urn
Loss
dBAntenna placement and orientation not optimal
for best isolation
2.5 GHz is still above the frequency band (~1500 MHz) which is the limit of size integration for flexibility in small format
Antenna 1
Antenna 2
Dimensions
• PCB 33mm*45mm
• Antenna 5mm x 3mm x 1.3mm
0%
10%
20%
30%
40%
50%
60%
2450 2500 2550 2600 2650 2700 2750Frequency (MHz)
Effic
ienc
y (%
)
Good efficiencyGood isolation
Page 7
Monopoles in different positions
-25
-20
-15
-10
-5
0
660 680 700 720 740 760
Frequency(MHz)
Retu
rn L
oss
(dB
)
Antenna 1Antenna 2Isolation
-4.8 dB
0%
10%
20%
30%
40%
50%
60%
70%
660 680 700 720 740 760
Frequency (MHz)
Effic
inec
y
Antenna 1
Antenna 2
38%
33%
Dimensions
• PCB 50mm*100mm
• Antenna 97mm
0%
10%
20%
30%
40%
50%
60%
70%
660 680 700 720 740 760
Frequency (MHz)
Effic
inec
y
Antenna 1
Antenna 2
48%52%
Good efficiencyPoor isolation
Difficult to integrate with otherantennas on small
ground plane
External
-25
-20
-15
-10
-5
0
660 680 700 720 740 760
Frequency(MHz)
Retu
rn L
oss
(dB)
Antenna 1Antenna 2Isolation
-5.5 dB
Dimensions
• PCB 50mm*100mm
• Antenna 48mm*12mm*8mm
Position 2
Page 8
PIFA in different positions
Dimensions
• PCB 50mm*100mm
• Antenna 47mm*23mm*8mm
-25
-20
-15
-10
-5
0
660 680 700 720 740 760
Frequency(MHz)
Retu
rn L
oss
(dB)
Antenna 1Antenna 2Isolation
-12 dB
0%
10%
20%
30%
40%
50%
60%
70%
660 680 700 720 740 760
Frequency (MHz)
Effi
cine
cy
Antenna 1
Antenna 2 47%
16%
Poor efficiencyAverage isolation
Difficult to integrate with otherantennas on small
ground plane
Position 1
-25
-20
-15
-10
-5
0
640 660 680 700 720 740
Frequency(MHz)
Retu
rn L
oss
(dB
)
Antenna 1Antenna 2Isolation
-4.6 dB
0%
10%
20%
30%
40%
50%
60%
70%
640 660 680 700 720 740
Frequency (MHz)
Effi
cine
cy
Antenna 1
Antenna 2 47%
35%
Dimensions
• PCB 50mm*100mm
• Antenna 47mm*23mm*8mm
Position 2
Page 9
IMD antennas in different positions
Antenna #1
Antenna #2
0%
10%
20%
30%
40%
50%
60%
70%
660 680 700 720 740 760Frequency (MHz)
Effic
inec
y
Antenna 1
Antenna 2 52%
28%
-25
-20
-15
-10
-5
0
660 680 700 720 740 760Frequency(MHz)
Ret
urn
Loss
(dB
)
Antenna 1Antenna 2Isolation
-15.4 dB
-25
-20
-15
-10
-5
0
660 680 700 720 740 760
Frequency(MHz)
Retu
rn L
oss
(dB
) Antenna 1Antenna 2Isolation
-7.4 dB
0%
10%
20%
30%
40%
50%
60%
70%
660 680 700 720 740 760
Frequency (MHz)
Effi
cine
cy
Antenna 1
Antenna 235%
33%
Dimensions
• PCB 50mm*100mm
• Antenna 40mm*10mm*7mm
Average efficiencyGood isolation
Position 2Dimensions
• PCB 50mm*100mm
• Antenna 40mm*10mm*7mm
Position 1
less dependent on ground
plane dimensions
Page 10
Correlation Data
Correlation coefficient for IMD antennas at position 1 and external monopoles
Low correlation can be achieved for moderate bandwidths
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
660 680 700 720 740 760
Frequency (MHz)
Cor
rela
tion
Coe
ffici
ent
Position 1, IMD
External Monopole
Page 11
Summary of 700 MHz Data
Antenna position and orientation is critical for good isolation
Isolation more difficult to achieve at 700 MHz bands
Configuration Isolation Best Efficiency Worst Efficiency
52% 28%
33%
16%
35%
48%
33%
35%
47%
47%
52%
38%
Correlation coefficient
Position 1, IMD -15.4dB 0.17
0.12
0.22
0.12
0.11
0.15
Position 2, IMD -7.4dB
Position 2, Pifa -4.6dB
External monopoles -4.8dB
Position 2,Monpoles -5.5dB
Position 1, Pifa -12dB
Best Configuration
Page 12
Simulations: Correlation Coefficient
3D EM simulations performed using CST to verify measured results
Position 1, IMD antennas
Correlation coefficient
Simulation: 0.18
Measured: 0.17
External monopoles
Correlation coefficient
Simulation: 0.06
Measured: 0.11
Antenna 1 Antenna 2
Antenna 1 Antenna 2
Page 13
Simulations: Isolation
Position 1, IMD Antennas External MonopolesIsolation IsolationSimulation: -18.5 dB Simulation: -4.8 dBMeasured: -15.4 dB Measured: -4.8 dB
-4.8 dB
Simulation
-18.5 dB
Isolation
Simulation
Isolation
Page 14
Dual frequency antennas: 700/1700
IMD at 700MHz and DCS (same feed)
Transition from bare ground plane to populated circuit board shows an improvement in isolation and degradation in efficiency
Next step in design process would be to improve antenna efficiencies
Page 15
Dual Frequency Antenna: Measured Data
-25
-20
-15
-10
-5
0
1600 1650 1700 1750 1800 1850
Frequency (MHz)
Ret
urn
Loss
Phantom Head/ Hand Antenna 1(High Band)Phantom Head/ Hand Antenna 2(High Band)Phantom Head/ Hand Isolation(High Band)Free Space Antenna 1 (High Band)
Free Space Antenna 2 (High Band)
Free Space Isolation (High Band)
-25
-20
-15
-10
-5
0
650 670 690 710 730 750
Frequency (MHz)
Ret
urn
Loss
(dB
)
Free Space Antenna 1
Free Space Antenna 2
Free Space Isolation
Phantom Head/ HandAntenna 1 Phantom Head/ HandAntenna 2 Phantom Head/ HandIsolation
0%
10%
20%
30%
40%
50%
60%
70%
1700 1750 1800 1850
Frequency (MHz)
Effi
cien
cy
Free Space Antenna 1 (High Band)
Free Space Antenna 2 (High Band)
Phantom Head/ Hand Antenna 1(High Band)Phantom Head/ Hand Antenna 2(High Band)
0%
10%
20%
30%
40%
50%
60%
70%
650 670 690 710 730 750
Frequency (MHz)
Effic
ienc
y
Free Space Antenna 1
Free Space Antenna 2
Phantom Head/ HandAntenna 1
Phantom Head/ HandAntenna 2
Page 16
Active antenna solutionActive antennas being developed will provide improvements in MIMO antenna applications;
– null-steering technique provides a variable radiation pattern from a single driven antenna which translates into improved antenna gain
The data shown below is measured TRP data from a null-steering antenna tested in a production handset 1900 MHz., TRP data for two antenna modes
This antenna technique can be implemented at 700 MHz. band to provide pattern diversity for Tx and Rx functions
Page 17
Conclusion/Wish List700 MHz MIMO antenna scheme applied to a handset more challenging not only from size point of view but also flexibility of placement of 2 antennas.
Recommended antenna performance data for link budget calculations:– Antenna gain (ave.): -5 dBi / -8 dBi (ant 1/ ant 2) or -7 dBi for both– Isolation: -12 dB– Correlation coefficient: 0.2
Wish List
1. Antenna requirements for two antenna MIMO system in 700 MHz. band
2. Better definition on first generation LTE mobile UE product sizes;
- volume of device
- circuit board dimensions
- volume allocated for antennas
3. Involve the antenna suppliers early on to be able to compromise the performances
Page 18
How to Evaluate the Diversity Performance
Correlation coefficient– Use 3D radiation patterns
• An environment where the polarizations are mutually uncorrelated and with uniform probability distributions of arriving angles and cross polarization ratio XPR=1
Correlation coefficient = 1 patterns are identical
Correlation coefficient = 0 patterns are completely de-correlated
Correlation coefficient < 0.3 is usually desired
S. Blanch, J. Romeu, I. Corbella, “Exact presentation of antenna system diversity performance from input parameter description”, Electr. Lett., Vol. 39, no. 9, pp. 705-707, May 2003
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