Improved Algorithm for MIMO Antenna Measurement

7/28/2019 Improved Algorithm for MIMO Antenna Measurement

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SRANT Lab., Korea Maritime University

A Study on Improved Algorithm for

MIMO Antenna Measurement

Thanh-Ngon Tran

Supervisor: Professor Kyeong-Sik Min

SRANT Laboratory, Korea Maritime University

November, 2006

Master Thesis


2/24

SRANT Lab., Korea Maritime University 2

Contents

Chapter 1: Introduction

Chapter 2: Algorithm of antenna measurement

software with noise reduction

Chapter 3: Measurement of key parameters of

MIMO antenna Chapter 4: Design of multi-band MIMO test-bed

Chapter 5: Conclusion


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Introduction (1)

Cordless phone

Voice

Wireless LAN

High Data rate

Home/office systems

Multi-media

Voice/Data

Mobile phone

Single

Antenna

Single

Antenna

Single/Multiple

Antenna

Multiple

Antenna

Antenna development vs.

Antenna measurement

system

Chapter 1


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Introduction (2) The goal and limitation

The goal: Develop measurement software & system

for MIMO antenna & channel measurement.

Apply the

improved mea.software for

MIMO ant. mea.

Improve

single antennameasurement

software

Design 22MIMO testbed

for MIMO

measurement

Futureworks

Diversities,

Correlation,

Mutual Coupling

Gain,2D/3D pattern,

Polarization,

w/ Filter algorithm

Direct up/downconverters,

Software structure

and algorithm

MIMOantenna and

channel

characterizat

ion

(1) (2) (3) ()Steps:

Chapter 1


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Single antenna measurement system

EL-AZ

PositionerPositioner

Controller

Microwave

Receiver

CW Signal

Generator

Directional

Coupler

Frequency

Converter

Polarization

Positioner

Computer

Linear

Polarization

Antenna

Antenna

Under

Test

GPIB GPIBMicrowaveAmplifier

Chapter 2


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Previous Software vs. New Software

There are two

independent programs Gain

Radiation Pattern

This program is not

divided in specificfunctions

Simple structure

When there are

changes, wholeprogram have to bechanged

Chapter 2

Ref.: Young-Hwan Park, A study on construction of antenna measurement

environment, Master Thesis, Korea Maritime University, Feb. 2005

The program can be modified easily when equipment is changed.

4 measurement functions: gain, 2D and 3D pattern, polarization.

New algorithm for noise reduction


7/24SRANT Lab., Korea Maritime University 7

Software algorithmChapter 2

Layer 4

Graphic userinterface

Layer 3

Data processing

Layer 2

Equipment

interface

Layer 1

GPIB interface of

computer (DLL)

Layer 1

GPIB interface of

Equipment

Equipment

processor

GPIB

Equipment

CommandsCommand sets

in text file

Software structure

Enter measurement

parameters (layer 4)

Start measurement

Process input parameters

(layer 3)

Send commands to

equipments and receive

data (layer 2&1)

Process measurement data

(layer 3)

Display data (layer 4)

End

Software flowchart



TX-RX Antenna in anechoic chamber

TX Ant

AUT

4m

Chapter 2

For experimentalmeasurement:

TX Ant.: Horn antenna, 1-

18 GHz

RX Ant.: Helical antenna,

~ 3 GHz

Distance: ~4 meter



Measurement Results with filter algorithm

Original Signal (pattern)

Measured by conventional

measurement system

Filtered Signal (pattern)

Measured and processed real-time

by noise reduction algorithm

Chapter 2

-100-95-90-85-80-75-70-65-60-55

-50

0 50 100 150 200 250 300 350

Angle (degree)

PowerLevel(dB)

Time 1

Time 2

-100-95-90-85-80-75-70-65-60-55-50

0 50 100 150 200 250 300 350

Angle (degree)

PowerLevel(dB)Signalprocessing

algorithm



Noise Reduction Algorithm

Combination of time and space mean filter

Noise in measurement system is Additive WhiteGaussian Noise (AWGN)

Mean filter is suitable for removing AWGN

d[j-1]

d[j-W/2]

d[j]d[j+1]

d[j+W/2]

Angle[degree]

Power

[dB]

Space Mean FilterTime Mean Filter

2

2

][1

][

Wi

Wij

jdW

iD

N

j

jtidN

iD1

],[1

][

d[i-1]

d[i, tj]

d[i+1]

Angle[degree]

Power

[dB]

d[i, tj+1]

Time

[ms]

d[i, tj+1]

d[i, tj+N]

],[],[],[ jjj tintiDtid

Measured

Power

Expected

Power

Noise

Chapter 2



MIMO antenna measurement

Metal box, PDA-size with 4 IFA antennas

(PDA: Personal Data Assistant)

(a) Front view (b) Inside view

Measure and

evaluate:

Diversities: pattern,polarization.

Pattern correlation.

Mutual coupling.

Chapter 3

#1

#2 #3

#4

z

y

x

This EUT is chosen

because it is: One of MIMO appli-

cation.

Elements have differ-

ent polarization, pattern,

gain, coupling



Pattern (gain) diversityChapter 3

-30

-25

-20

-15

-10

-5

0

5

-30

-25

-20

-15

-10

-5

0

5

0

30

60

90

120

150

180

210

240

270

300

330

Element #1

Element #2

Element #3

Element #4

-30

-25

-20

-15

-10

-5

0

5

-30

-25

-20

-15

-10

-5

0

5

0

30

60

90

120

150

180

210

240

270

300

330

Element #1

Element #2

Element #3

Element #4

-30

-25

-20

-15

-10

-5

0

5

-30

-25

-20

-15

-10

-5

0

5

0

30

60

90

120

150

180

210

240

270

300

330

Element #1

Element #2

Element #3

Element #4

Gain of antenna elements

on x-y planeGain of antenna elements

on x-z planeGain of antenna elements

on y-z plane

x

yz

x

z

y

#4 is the best choice#3 is the best choice #1 is the best choice

#2 is thebest choice

Maximum gain of EUT antenna elements on three planes is about 6 dBi (y-z plane).

In any direction, there is at least one element with high gain. Difference between the

highest and lowest gain is higher than 3 dB at any direction.

Conclusion: This difference of gain pattern shows good gain diversity.



-40

-35

-30

-25

-20

-15

-10

-40

-35

-30

-25

-20

-15

-10

0

30

60

90

120

150

180

210

240

270

300

330

E-theta

E-phi

-40

-35

-30

-25

-20

-15

-10

-40

-35

-30

-25

-20

-15

-10

0

30

60

90

120

150

180

210

240

270

300

330

E-theta

E-phi

-40

-35

-30

-25

-20

-15

-10

-40

-35

-30

-25

-20

-15

-10

0

30

60

90

120

150

180

210

240

270

300

330

E-theta

E-phi

-40

-35

-30

-25

-20

-15

-10

-40

-35

-30

-25

-20

-15

-10

0

30

60

90

120

150

180

210

240

270

300

330

E-theta

E-phi

Polarization diversityChapter 3

Element #1 and #4: linear horizontal polarization.

Element #2 and #3: linear vertical polarization.

Conclusion: Good the polarization diversity.

Element #1, x-z plane

XPD = 22dB @ 178oElement #4, x-z plane

XPD = 20dB @ 183oElement #2, x-y plane

XPD = 20dB @ 89oElement #3, x-y plane

XPD = 20dB @ 268o

dBcrossdBcocross

co

EEE

E

XPD

log20E

co andE

cross areco-polarization and

cross-polarization

components of E-

field, respectively.

x

yz

x x

y z

x



Pattern Correlation

Elements

x-y plane x-z plane y-z plane x-y plane x-z plane y-z plane

#1 and #2 0.103 0.426 0.022 0.331 0.222 0.175

#1 and #3 0.152 0.481 0.260 0.071 0.131 0.269

#1 and #4 0.100 0.616 0.352 0.382 0.607 0.073

#2 and #3 0.486 0.822 0.198 0.107 0.847 0.027

#2 and #4 0.196 0.616 0.085 0.186 0.118 0.244

#3 and #4 0.147 0.543 0.270 0.110 0.343 0.139

E E

Chapter 3

359

0

359

0

222

211

359

0

2211

)][()][(

)][)(][(

i i

ic

EiEEiE

EiEEiE

-40

-35

-30

-25

-20

-15

-10

-40

-35

-30

-25-20

-15

-10

0

30

60

90

120

150

180

210

240

270

300

330

E-theta

E-phi

-40

-35

-30

-25

-20

-15

-10

-40

-35

-30

-25

-20

-15

-10

0

30

60

90

120

150

180

210

240

270

300

330

E-theta

E-phi

x

y

x

y

Element #2, x-y plane Element #3, x-y plane



Mutual Coupling Measurement

Frequency (GHz)

5.0 5.1 5.2 5.3 5.4 5.5

Mutualco

upling(dB)

-40

-35

-30

-25

-20

-15

-10C12

C13

C14

C23

Chapter 3

MW Receiver &

Freq. converter

EUT



MIMO TestbedChapter 4

Block diagram of

22 MIMO testbed FPGA:APEX-

20K600

Output

CPU: SH-4(SH7750)

OS:

NetSBD

Analog

(RF)

DACI/O

DAC:DAC904

FPGA:

APEX-

20K600

Input

Direct Up-converter

1

Direct Up-

converter

2

TX Ant. 1

TX Ant. 2

I1

I2

Q1

Q2

TCP/IP

Network

FPGA:

APEX-

20K600

Output

CPU: SH-4(SH7750)

OS:

NetSBD

Analog

(RF)

ADCI/O

ADC:SPT7938

FPGA:

APEX-

20K600

Input

DirectDown

converter 1

Direct

Down

converter 2

RX Ant. 1

RX Ant. 2

I1

I2

Q1

Q2

Windows PC

Brains Co. - DA System

Brains Co. - AD System

Freq.: 1.85.8 GHz

Use direct-conversion

technique for analog RF

circuits

RF analog circuits are

coupled with DSP algorithm



RX - Design of Down-converter

FPGA:

APEX-

20K600

Output

CPU: SH-4(SH7750)

OS:

NetSBD

Analog

(RF)

DACI/O

DAC:DAC904

FPGA:

APEX-

20K600

Input

Direct Up-converter

1

Direct Up-

converter

2

TX Ant. 1

TX Ant. 2

I1

I2

Q1

Q2

TCP/IP

Network

FPGA:

APEX-

20K600

Output

CPU: SH-4(SH7750)

OS:

NetSBD

Analog

(RF)

ADCI/O

ADC:SPT7938

FPGA:

APEX-

20K600

Input

DirectDown

converter 1

Direct

Down

converter 2

RX Ant. 1

RX Ant. 2

I1

I2

Q1

Q2

Windows PC



Design the wide bandwidth direct

down-conversion receivers by: Combine the analog front-end

circuit with base-band DSP

Freq.: 1.8 5.8 GHz

Analog

front-end

Baseband

DSP

Bandwidth is

Wider

RF LNA

I

Q

Quadrature

down-converter

90 LO

A

B

LPF

LPF

A/D

A/D

DSP

xLO,I(t) = cos(2pfC t)

xLO,Q (t) = gsin(2pfC t + )

xI(t)

xQ(t)

Analog

front endcircuit is

simpler

LORF

Q

12

3

Phase shifterMixer

Baseband Amp.

Power div. I

Chapter 4



0.00

0.20

0.40

0.60

0.801.00

1.20

1.40

1.60

1.80

2.00

1.6 2.0 2.4 2.8 3.2 3.6 4.0 4.4 4.8 5.2 5.6 6.0

Frequency (GHz)

Amplitude

Imbalance

Simulation

Measurement

5%

amplitude

imbalance

Imbalance parameters

-90.00

-70.00

-50.00

-30.00

-10.00

10.00

30.00

50.00

70.00

90.00

1.6 2.0 2.4 2.8 3.2 3.6 4.0 4.4 4.8 5.2 5.6 6.0

Frequency (GHz)

PhaseImbalance(degree) Simulation

Measurement

Conventional

bandwidth: 0.25 GHz

(5o

imbalance)

Chapter 4


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RX - I/Q signalsChapter 4

Lissajuos graph of the I and Q signal at 1.8 GHz

V_Q (Volts)

Measured sig.

Processed sig.

Reference sig.

V_

I(V

olts)

Frequency: 1.8 GHz

Amp. imbalance: 0.898

Phase imbalance: -75.74

degree


V_Q (Volts)

Measured sig.

Processed sig.

Reference sig.

V_

I(V

olts)

Frequency: 4.0 GHz


Phase imbalance: -13.25

degree


V_Q (Volts)

Measured sig.

Processed sig.

Reference sig.

V_

I(V

olts)

Frequency: 5.6 GHz


Phase imbalance: 44.50

degree

I

Q

A/D

A/D

xI(t)

xQ(t)

+

cos1

g

cos

sin

DSP

'Iz

'Qz


20/24


TX - Design of Up-converter

FPGA:

APEX-

20K600

Output

CPU: SH-4(SH7750)

OS:

NetSBD

Analog

(RF)

DACI/O

DAC:DAC904

FPGA:

APEX-

20K600

Input

Direct Up-converter

1

Direct Up-

converter

2

TX Ant. 1

TX Ant. 2

I1

I2

Q1

Q2

TCP/IP

Network

FPGA:

APEX-

20K600

Output

CPU: SH-4(SH7750)

OS:

NetSBD

Analog

(RF)

ADCI/O

ADC:SPT7938

FPGA:

APEX-

20K600

Input

DirectDown

converter 1

Direct

Down

converter 2

RX Ant. 1

RX Ant. 2

I1

I2

Q1

Q2

Windows PC



RF AMP

I

Q

Quadrature

up-converter

90LO

A

B

LPF

LPF

D/A

D/A

DSP

xLO,I(t) = cos(2pfLO t)

xLO,Q (t) =gsin(2pfLO t + )

xI(t)

xQ(t)

LPF

Analog front-end circuit is coupled with DSP algorithm to

compensate the imbalance characteristics of analog circuit (as in

down converter).

LO leaky is controlled by bias voltage on MIXER chips.Measurement setup

Up converter circuit

LORF

QPhase shifterMixer

Power

combiner

I

Chapter 4

Ch 4


21/24


Leaky signal suppression

RF AMP

I

Q

Quadrature

up-converter

90LO

A

B

LPF

LPF

D/A

D/A

DSP


xLO,Q (t) =gsin(2p fLO t + )

xI(t)

xQ(t)

LPF

fLO + f0fLO f0 fLO fLO + f0fLO f0 fLO

Desired

signal

Desired

signal

Sideband

leakageCarieer

leakageCarieer

leakage

Sideband

leakage

Spectrum of output signal before and after imbalance compensation

Suppressed

by

controlling

amplitude

and phase

coefficient

Suppressed

by

controlling

bias voltage

on MIXER

chips

Chapter 4

Ch t 4


22/24


Measurement results of output spectrum

RF AMP

I

Q

Quadrature

up-converter

90LO

A

B

LPF

LPF

D/A

D/A

DSP


xLO,Q(t) =gsin(2pfLO t + )

xI(t)

xQ(t)

LPF

Spectrum of

output signal

without I/Q

imbalance

compensationat 3.0 GHz

Spectrum of

output signal

with I/Q

imbalance


I-Channel: 0.402VDC + 0.142Vac, phase = 0o

Q-Channel: 0.308VDC + 0.150Vac, phase = 112.3

o

Spectrum of

output signal

without I/Q

imbalance


Spectrum of

output signal

with I/Q

imbalance


I-Channel: 0.239VDC + 0.120Vac, phase = 0o

Q-Channel: 0.638VDC + 0.122Vac, phase = 73.9

o

Chapter 4


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Conclusion and future study

Development of measurement software & system for

MIMO antenna & channel measurement is dividedinto 3 steps with the good experiments results:

Improve single antenna measurement software:

Gain, 2D/3D pattern, polarization with noise reduction.

Apply the improved measurement software for MIMO

antenna measurement:

Diversities, Correlation, Mutual Coupling.

Design 22 MIMO testbed for MIMO measurement. Direct up/down converter, system design.

Future study: Develop algorithm for MIMO

antenna and channel characterization.


24/24

SRANT Lab Korea Maritime University 24

THANK YOU FOR YOUR ATTENTION!

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Improved Algorithm for MIMO Antenna Measurement