The Effects of Non-linear Distortion in Radio Systems · 1 As Telecomunicações para a Presente D...

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1As Telecomunicações para a Presente Década (4 de Abril 2001) – Nuno Borges de Carvalho

The Effects of Non-linear Distortion in Radio Systems

Nuno Borges de Carvalho

Departamento de Electrónica e TelecomunicaçõesUniversidade de Aveiro

E-mail: [email protected]


? The radio transmission reception chain? Transmission Blocks

? Reception Blocks

? The Non-linear Distortion and its effects on Modulated Signals

? The reasons of non-linear distortion

? Non-linear distortion sources

SummarySummary

2


?Modulated signals characteristics? Commercially used modulation techniques

? GMSK (Gaussian Minimum Shift Keying)

? QPSK (Quadrature Phase Shift Keying)

? 8-PSK (8 Phase Shift Keying)

? QAM (Quadrature Amplitude Modulation)

? The effects of non-linear distortion on modulated signals

? The Power Amplifier? Non-linear distortion figures of merit

? Non-linear distortion mechanisms

? Measuring non-linear distortion

SummarySummary


? How to minimize the non-linear distortion effects? Linearization techniques

? Frequency Hopping

?Bibliography

SummarySummary

3


The radio transmission/reception chain


The radio transmission reception chainThe radio transmission reception chain

ProcessamentoBanda Base Modulação UP-Conversion

BB IF RF

EncriptaçãoIntrodução de correctores de erro

AmplitudeFaseFrequência

Deslocação em frequência

0 1 0 1 0 1 0 1

Transmission

ProcessamentoBanda Base

DesmodulaçãoDownConversion

BBIFRF




0 1 0 1 0 1 0 1

Reception

4


ProcessamentoBanda Base Modulação UP-Conversion

BB IF RF




0 1 0 1 0 1 0 1

OL

PA

IN OUT

?2

GeradorRFM

apea

dor




DesmodulaçãoDownConversion

BBIFRF




0 1 0 1 0 1 0 1

OL

AMP

PI F

LNA

GAi(r)

RF IF

Pr Lcabo(r)

Linband(r) GLNA

Lconv(r)

L inband(r) GAMP

?2

GeradorRF

Des

map

eado

r


5


The Non-linear Distortion and its effects on Modulated Signals


The NonThe Non--linear Distortion and its effects on Modulated Signalslinear Distortion and its effects on Modulated Signals

The reasons of non-linear distortion

Sources of non-linear distortion

How to measure them?

6


GSM GSM 1800 UMTS

IMD due to Even Order

Distortion Real ProblemsDistortion Real ProblemsGSM900-GSM1800 and GSM-UMTS Interference

The reasons of non-linear distortion (Mobile Radio System)



GSM

Odd Order

Distortion Real ProblemsDistortion Real ProblemsIn-band GSM-GSM and UMTS-UMTS Interference

The reasons of non-linear distortion (Mobile Radio System)


7


DAC

DAC

090

Synt.osc? 0

DC DC ? 0 ? 0




BB0 1 0 1 0 1 0 1

Modulação

IF

1 0 1 0 1

ProcessamentoBanda Base Desmodulação

B B IF

Não Linearidade

1 0 1 0 1 1 ? 1 ? 1

1 1 1 1 1 1 1 1

?

The reasons of non-linear distortion (ASK – Amplitude Shift Keying)


8


Linear y=kxx y

Non Linear y=kx+k2x2+..

x y

Output signal is proportional to its input


The reasons of non-linear distortion

Output signal is not proportional to its input


Non-linear distortion sources

• On every devices where its output it is not proportional to its input:

? Active Elements

? Passive Elements, when operated in its saturation zone

? Incorrect connections, for example bad connections


9


PA

Pin Pout

Typically the main non-linear distortion sources are attributed to amplifiers: power amplifiers at the transmission and low-noise amplifiers at the reception.And also to mixers that are inherently non-linear.


Non-linear distortion sources


Modulated signals characteristics

10


Commercially used modulation formats:

GSM – GMSK

EDGE – 8 - PSK

UMTS – QPSK

TV-Digital – QAM

Modulated signals characteristicsModulated signals characteristics


? 0

? 0

GMSK

QPSK

? 0

8-PSK

? 0

QAM


11


Envelope constant modulation formats are more immune to the non-linear distortion, nevertheless they are less spectral efficient.



How to evaluate a modulation format from the non-linear distortion point of view:

Peak to Average Ratio

Constellation Diagram

Error Vector Magnitude


12


GMSK – Gaussian Minimum Shift Keying

? ? ? ? ? ?tfTtthtmtf

Ttthtmts c

bGaussQc

bGaussIi ???? 2sen

2sen)()(2cos

2cos)()( ???

????

?????

????

??



4,3,2,1 0 2

)1(2cos2

)( ??????

??? ?

???? iTtitfTE

ts scs

sQPSK

QPSK – Quadrature Phase Shift Keying


13


3? /8, 8-PSK – 8 Phase Shift Keying shifted 3? /8

8,7,6,5,4,3,2,1 0 83

4)1(2cos

2)( ????

??

??? ???? iTtitf

TE

ts scs

sQPSK ?

??



QAM – Quadrature Amplitude Modulation

? ? ? ?tftpE

AE

tftpE

AE

ts cp

iip

cp

iip

i ???? 2sen)(2

sen2

2cos)(2

cos2

)( ???

????

???

??

????

??


14


CDMA 2000 GSM



Constellation diagram modifications

Non-linear effects on 16 QAM


15


The Power Amplifier


How to measure the amplifier non-linear distortion?

1. Linear systems extension:Excite the system with a sinusoid (1 tone)

2. Excite the system with two tones

3. Excite the system with multi tone signals

4. Excite the system with continuous narrow band white Gaussian noise

The Power AmplifierThe Power Amplifier

16


Power Amplifier Figures of Merit• Gain• Maximum Output power, P1dB• Efficiency• IP3(distortion) PA

Pin Pout

y[v(t)]=a1v(t)+a2v(t)2+a3v(t)3

Linear model:

y[v(t)]=a1v(t)

Non-linear model:



Power Amplifier•1 tone Excitation

PA

Pin Pout

y[v(t)]=a1v(t)+a2v(t)2+a3v(t)3Non-linear model:

? ? ? ?? ?)11()11()11(3)11(33

13

)11(2)11(221

2)11()11(1

1

338

242

)(

??????????????

??????????????

????

??????

tjtjtjtj

tjtjtjtj

eeeeXa

eeXa

eeXa

ty

? ? ? ? ? ?? ?11111111 2

)( ??????? ?????? tjtj eeXtsenXtv


17


12

34

56

7

Pout (dBm)

-100

-80

-60

-40

-20

0

20

Frequency (GHz)

Signal Generator

f=2.2GHzLPF ATEN. DUT Spectrum

Analyser




PA

Pin Pout

12

34

56

7

Pout (dBm)

-100

-80

-60

-40

-20

0

20

Frequency (GHz)



18


PA

Pin Pout

12

34

56

7

Pout (dBm)

-100

-80

-60

-40

-20

0

20

Frequency (GHz)




PA

Pin Pout

12

34

56

7

Pout (dBm)

-100

-80

-60

-40

-20

0

20

Frequency (GHz)



19


PA

Pin Pout

AM/AM Characteristic AM/PM Characteristic

6

7

8

9

1 0

1 1

1 2

1 3

1 4

-50 -40 -30 -20 -10 0 1 0 2 0

Pin [dBm]

Gai

n [d

B]

1dB




PA

Pin Pout

y[v(t)]=a1v(t)+a2v(t)2+a3v(t)3Non-linear model:

? ? ? ?

22

coscos)()22()22(

2

)11()11(

1

222111

?????????????? ??

??

?????????tjtjtjtj ee

Xee

X

tXtXtx

? ? ? ?? ?

? ?? ? ?? ??? ?? ? ?? ?? ??)122122()122122()122122()122122()11()11(2

21

)212212()212212()212212()212212()22()22(2

2

1

)22()22()22(3)22(332

)11()11()11(3)11(331

3

)2121()2121()2121()2121(21

)22(2)22(222

)11(2)11(221

2

)22()22(2

)11()11(1

1

333366

333366

33338

224

2)(

?????????????????????????????????????

?????????????????????????????????????

????????????????????????????

??????????????????????????????

??????????????

??????????????

??????

???????

?????????

?????

???????

?????

ttjttjttjttjtjtj

ttjttjttjttjtjtj

tjtjtjtjtjtjtjtj

ttjttjttjttj

tjtjtjtj

tjtjtjtj

eeeeeeXX

eeeeeeXX

eeeeXeeeeXk

eeeeXX

eeXeeXk

eeXeeXk

ty



20


f0 2f0 3f0 4f0 5f0 6f0

f=2.19GHz LPF

ATEN. DUT Spectrum Analyser

f=2.21GHzLPF

?

Signal Generator 1

Signal Generator 2




PA

Pin Pout

-70

-60

-50

-40

-30

-20

-10

0

10

-60 -40 -20 0 2 0 40 6 0

f-2GHz (MHz)

dBm Nonlinear Distortion

OutputLinearSignals

Nonlinear Distortion



21


PA

Pin Pout

-180

-160

-140

-120

-100

-80

-60

-40

-20

0

20

40

-60 -50 -40 -30 -20 -10 0 10

Pin (dBm)

Pou

t (dB

m)

Pout (2w1-w2) Pout (w1)

1dB slope 3dB slope

IP3

IMR2




PA

Pin Pout

IP3 – 3rd Order Intercept Point

P1dB – 1 dB Compression Point

IMD – Intermodulation Distortion

IMR – Intermodulation Ratio

Two tone figures of merit:



22


PA

Pin Pout

? 0? 0

Spectral Regrowth

Power Amplifier•Multi-tone excitation•Gaussian Noise Excitation



? 0

? 0

ACPR – Adjacent Channel Power Ratio

LPF

ATEN. DUTAnalisador

de Espectros

Oscilador Local

(f GHz)

Filtro Passa Baixo para a Banda Base

X

Amplificador altamente linear

Modulador AM

Gerador de Ruído


23


-80

-70

-60

-50

-40

-30

-20

-1000 -800 -600 -400 -200 0 200 400 600 800 1000Freq-2GHz [KHz]

Pout

[dB

m]

Measured NPR

Measured Output Power

NPR – Noise Power Ratio



CCPR – Co-channel Power Ratio

?

25dB

HPA

ATT

1-11dB(CAL)

DUT

VNG


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CCPR – Co-channel Power Ratio

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-1000 -800 -600 -400 -200 0 200 400 600 800 1000

Freq-2GHz [dBm]

Pout

[dB

m]

Measured CCPR

Measured Output Power

Residual signal



How to minimize the non-linear distortion effects

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How to minimize the non-linear distortion effects?

How to minimize the nonHow to minimize the non--linear distortion effectslinear distortion effects

Amplifier Linearization? Pre distortion? Feed-back? Feed-Forward? ????

Frequency Hopping (mobile radio systems)


Amplifier Distortion (Pre Distortion)


Pre-DistortionAmplifier

Pin

PA

Pout

26


Amplifier Distortion (Feed-Back)


PA

PinPout

Auxiliary Amplifier

+

? ?A

tKdtKxtyKA

AKtdtAxK

ty

tytxtx Kty

ty tdtAxty rer

)()()(;

)()()(

)()()(;)(

)();()()(

???????

??

?????


Amplifier Distortion (Feed-Forward)


PA

PinPout

-Aten(A)

+

AuxiliaryAmplifier(A)

27


Frequency Hopping


Interfered ChannelInterferer Channel

Channel afterthe jump infrequency

Interfered channelAfter the jump infrequency

1 2

2’


Bibliography

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BibliographyBibliography ((Nonlinear Distortion Nonlinear Distortion and and MeasurementMeasurement))

MAAS, S., Nonlinear Microwave Circuits, Artech House, Inc., Norwood, MA, 1988.

CARVALHO, N. B., and PEDRO, J. C.: “Multi-Tone Intermodulation Distortion Performance of 3rd Order Microwave Circuits”. 1999 IEEE Intern. Microwave Theory and Tech. Symposium, pp.763-766, Anaheim, June 1999.

PEDRO, J. C., and CARVALHO, N. B.: “On the Use of Multi-Tone Techniques for Assessing RF Components’ Intermodulation Distortion”. IEEE Trans. on Microwave Theory and Techniques, December 1999, MTT-47, (12), pp.2393-2402.

PEDRO, J. C., and CARVALHO, N. B. Carvalho, “A Novel Set-up for Co -Channel Distortion Ratio Evaluation”, 2000 IEEE Intern. Microwave Theory and Tech. Symposium, pp. 1851-1854, Boston, June 2000.

PEDRO, J. C. and CARVALHO, N. B. Carvalho, “Sistema de Medida de Distorção Não Linear Co -Canal”, Portuguese Patent Pending, nº 102 521.

KRIKORIAN, N.: “Bridge Method for Measuring Amplitude Intermodulation Distortion”, RF Design, March 1995, pp.30-34.

SEIDEL, H.: “A Feedforward Experiment Applied to an L-4 Carrier System Amplifier”, IEEE Trans. on Communications, June 1971, COM-19, (3), pp.320-325.

PEDRO, J. C., and CARVALHO, N. B.: ”Evaluating Co-Channel Distortion ratio in Microwave Power Amplifiers”, IEEE Trans. on Microwave Theory and Techniques, in press.


BibliographyBibliography ((Modulation TechniquesModulation Techniques))

Mischa Schwartz, “Information, Transmission, Modulation and Noise”, Mc-Graw Hill, 1990. Fugin Xiong, “Digital Modulation Techniques”, Artech House Publishers, 2000.Theodore S. Rappaport, “Wireless Communications – Principles & Practice”, Prentice Hall 1996.Seyed Hamidreza Jamali, Le-Ngoc Tho, “Coded-modulation Techniques for Fading Channels“, Kluwer Academic Press, 1994.

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QuestionsQuestions

Questions?

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