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A Compact Tri-Polarization Antenna for MIMO Communication Systems

Yoshio KARASAWA & M. SHINOZAWA

Advanced Wireless Communication research Center (AWCC)

Univ. Electro-Communications (UEC Tokyo)

EMTS2007, OttawaJuly 27-28, 2007

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Contents of Presentation

1. MIMO Channel and its Capacity

2. Tri-Polarization Antenna

3. Hand-Made Radio Echoic Chamber

(Creation of Multipath-rich Environment)

4. Performance Characteristics

5. Conclusions

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MIMO Technologies

Tx signal Rx signal

Radiowave propagation

Tx arrayEncoding with time and space domain

Rx arrayDecoding with time and space domain

Multi-path propagation

Information theory and coding theory

Adaptive array and adaptive signalprocessing

MIMOcovers wide technical areas

Applications are from W-LAN to next-generation mobile wireless systems.

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Tx Rx

TX array

Eigen path #1

#2

#3

#4

RX array

Path profile (indoor)

MIMO Propagation Channel Model

Equivalent circuit modelbased on SVD

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Average Channel Capacity in iid Rayleigh Fading Environment

λλλγ dpN

mC unord

t

)(1log 0

201 ⎟⎟⎠

⎞⎜⎜⎝

⎛+= ∫

∞

⎟⎟⎠

⎞⎜⎜⎝

⎛+≈ λγ

tNm 0

2 1log

⎟⎠⎞

⎜⎝⎛ +=

mNm r0

2 1log γ

0CNr≈

( ) };1;1log{ 0020 rt NNC =>>+≡ γγ

Channel capacity is approximately proportional to the number of antennas when

(since <λ> = NtNr/m)

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Increase of Channel Capacity

Use of Dual-Polarization BranchesUse of Triple-Polarization Branches

Compact MIMO Antenna

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(H)(V)

HV

HV

Dual-Polarization antenna

Z

Z

(Z)

Triple-Polarization antenna

The tri-polarization antenna acts as a three-element MIMO antenna in the case of multipath-rich environment

N.K. Das et al., IEEE VTC2004 Fall, LA, Sep. 27-29, 2004.

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3×3 single-pol. MIMO

3×3 tri-pol. MIMO

Compare

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Antenna Element

4/λ

H Z V

V

HZ

4 cm

(5 GHz)

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Creation of a Multipath-Rich Environment

Radio Echoic Chamber (Reverberation Chamber)as a Reference Environment

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Handmade Radio Echoic Chamber(Reverberation Chamber)

4m

2m

2m

Hutch

The chamber is enclosed with 20 aluminum plates (1mx2m plate)

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Radio-Echoic Chamber

Creation of an ideal multipath-rich environment

2m 4m

2m

The chamber is enclosed with 20 aluminum plates (1mx2m plate)

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Measurement of Propagation Characteristics

1m

NetworkAnalyzer

5GHz Band Dipole Antennas

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Measured Propagation Characteristicsin frequency and spatial domains

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-60 -50 -40 -30 -2010

-3

10-2

10-1

100

Received power (dB)

Cum

ulat

ive

prob

abili

ty

0 1 2 3 4-60

-55

-50

-45

-40

-35

-30

-25

-20

Delay (ms)

Pow

er (

dB)

5000 5020 5040 5060 5080 5100-60

-55

-50

-45

-40

-35

-30

-25

-20

Frequency (MHz)

Rec

eive

d po

wer

(dB

)

Tx pol . – Rx pol.V-V

στ = 430ns

Rayleighdist.

Measured Characteristics of Radio-Echoic Chamber

The characteristics are well represented by an outdoor multipath-rich environment!!

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-50 -45 -40 -35 -30 -25 -20

0

0.2

0.4

0.6

0.8

1

Received power when Tx power is 0dB [dB]

Cum

ulat

ive

prob

abili

ty

Radio Echoic Chamber(Multipath-rich environment)

ZV

Rx pol: Horizontal (H)

H H H

Z H

V H

CDF of Received Power for H-H, V-H, and Z-H

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-20 -15 -10 -5 0 5 100

0.2

0.4

0.6

0.8

1

Eigen value: λ1 [dB]

Cum

ulat

ive

prob

abili

ty

1 x 1(V-V)

2 x 2(V, H - V, H)

3 x 3(V, H, Z - V, H, Z)

The largest eigenvalue for multiple polarizations

(measured in a radio echoic chamber)

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1 10

0

0.2

0.4

0.6

0.8

1

Channel capacity [bit/s/Hz]

Cum

ulat

ive

prob

abili

ty

SNR=10dB

SNR=20dB

A B C D

A B C D

CDF of Channel Capacity

A: single pol. (1x1)

B: dual-pol. (2x2)

C: tri-pol. (3x3)

D: 3-antenna array(3x3)

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0

5

10

15

20

SNR = 10dBSNR = 20dB

Cha

nnel

cap

acity

(b/

s/H

z)

Case: A B C D

Average channel capacity when using multiple polarizations

A: single-pol. (V-V: 1x1)

B: dual-pol (V,H-V,H: 2x2)

C: tri-pol (V,H,Z-V,H,Z: 3x3)

D: three single-pol. antennas

by three single-pol. antennas

(V,V,V-V,V,V: 3x3)

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Conclusions

-Tri-polarization antenna, which is one of very compact antennas, showed a nearly the same performance of 3x3 single-pol MIMO array in multipath-rich environment.

We will evaluate the performance of the antenna in actual environments (both indoors and outdoors).

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Thank you very muchfor your kind attention!