MIMO Antenna Performance for Handsets and Data Terminals[1]

MIMO Antenna Performance for Handsets and Data Terminals

November 2008

Confidential and Proprietary Ethertronics, Inc © 2008

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

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

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

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

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

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)


-5.5 dB

Dimensions

• PCB 50mm*100mm

• Antenna 48mm*12mm*8mm

Position 2

PIFA in different positions

Dimensions

• PCB 50mm*100mm


-25

-20

-15

-10

-5

0

660 680 700 720 740 760

Frequency(MHz)

Retu

rn L

oss

(dB)


-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

)


-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


Position 2

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

)


-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


Average efficiencyGood isolation

Position 2Dimensions

• PCB 50mm*100mm


Position 1

less dependent on ground

plane dimensions

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

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

Simulations: Correlation Coefficient

3D EM simulations performed using CST to verify measured results

Position 1, IMD antennas


Simulation: 0.18

Measured: 0.17

External monopoles


Simulation: 0.06

Measured: 0.11

Antenna 1 Antenna 2

Antenna 1 Antenna 2

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

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

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 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



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



Phantom Head/ HandAntenna 1

Phantom Head/ HandAntenna 2

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

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

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

MIMO Antenna Performance for Handsets and Data Terminals[1]

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