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Dr. Florian Ramian Characterization and Compensation of Non-Linear Effects in Components

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Page 1: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Dr. Florian Ramian

Characterization and Compensation of Non-Linear

Effects in Components

Page 2: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Agenda

ı Introduction: What Is a Non-Linear Device

ı Characterization of Non-Linear Devices

Characterization Parameters

Traditional CW level swept measurement

Modulated Measurement

ı Compensation of Linear and Non-Linear Effects

Equalizer

Digital Predistortion (DPD)

ı Summary

A&D Symposium 216.03.2017

Page 3: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Introduction

ı What is a non-linear device?

16.03.2017 A&D Symposium 3

DUT

Page 4: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Agenda

ı Introduction: What Is a Non-Linear Device

ı Characterization of Non-Linear Devices

Characterization Parameters

Traditional CW level swept measurement

Modulated Measurement

ı Compensation of Linear and Non-Linear Effects

Equalizer

Digital Predistortion (DPD)

ı Summary

A&D Symposium 416.03.2017

Page 5: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Characterization of Non-Linear Devices

Characterization Parametersı Distortion: AM/AM,

AM/PM

ı Gain

ı Compression

16.03.2017 A&D Symposium 5

Page 6: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Characterization of Non-Linear Devices

CW Stimulusı Measurement of amplitude dependent effects sweep input amplitude

ı Level swept CW signal

16.03.2017 A&D Symposium 6

Page 7: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Measurement Instruments

ı VNA

ı Signal Generator / Signal Analyzer

16.03.2017 A&D Symposium 7

CW Measurement

Modulated Measurement

Page 8: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Modulated Measurements

DistortionCW distortion

measurement

describes DUT

behavior, but

does not indicate

whether the DUT

will distort the

modulated signal

significantly

16.03.2017 A&D Symposium 8

Stimulus: Ramp

AM/AM is a line as expected

Line Width: Memory Effect

Stimulus: Modulated signal

AM/AM is a “cloud”

Page 9: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Modulated Measurements

Gain Measurementı Gain at specified frequency / level can be precisely measured with CW

Gain @ 2 GHz / 0 dBm input level: 17.9 dB

ı But: a real word signal looks like this

16.03.2017 A&D Symposium 9

Page 10: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Modulated Measurements

Gain Measurementı Measurement on a modulated signal is equivalent to multiple gain measurements across

the input power range

16.03.2017 A&D Symposium 10

Page 11: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Modulated Measurements

Principle

16.03.2017 A&D Symposium 11

VSG

(play

waveform)

VSA

(capture RF

signal)RF connection

Data / Control Connection (LAN)

DSP

Reference

signal (Ref)

Measured signal

(Meas)

DUT

Page 12: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Measurement Principle (DSP)

A&D Symposium 12

DSP

Reference

signal (Ref)

Measured

signal (Meas)

Sync

Synchronized

Meas signal

Compare

Gain,

Distortion,

EVM, …

16.03.2017

Reference

signal (Ref)

Page 13: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Modulated Measurements

All Characterization Results from a Single Measurement

16.03.2017 A&D Symposium 13

ACLR

Distortion

Numeric

Results,

modulation

accuracy:

• EVM

• I/Q

Imbalance

• …

Page 14: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Modulated Measurements

Modulation Accuracyı EVM Measurement based on a sample-by-

sample comparison

ı Depending on oversampling and distortion

of DUT, EVM may differ from demodulation

EVM measurements

16.03.2017 A&D Symposium 14

Page 15: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Agenda

ı Introduction: What Is a Non-Linear Device

ı Characterization of Non-Linear Devices

Characterization Parameters

Traditional CW level swept measurement

Modulated Measurement

ı Compensation of Linear and Non-Linear Effects

Equalizer

Digital Predistortion (DPD)

ı Summary

A&D Symposium 1516.03.2017

Page 16: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Compensation of Linear and Non-Linear Effects

ı Frequency response

ı Non-linear effects

16.03.2017 A&D Symposium 16

Page 17: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Compensation of Frequency Response

Equalizerı Frequency response can be compensated by a filter, often referred to as “equalizer”

ı Flattened magnitude / phase vs. frequency

16.03.2017 A&D Symposium 17

Equalizer

Page 18: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Compensation of Non-Linearities

Digital Predistortion (DPD)

16.03.2017 A&D Symposium 18

DPD

EVM

ACLR

Page 19: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Model Based DPD

Characterization of DUT

16.03.2017 A&D Symposium 19

Apply (inverse) model to signal, i.e. in the

TX chipset

DUT

DUT

TX Chipset

𝑧−1 𝑛BB

Inverse

Page 20: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Waveform Based DPD

DPD on Individual Samples

16.03.2017 A&D Symposium 20

ı Each sample is predistorted to a

new value

ı Since each sample is individually

predistorted, any memory effect

can be compensated

samples of equal level may have

different predistorted levels

compensation is limited to

measured bandwidth

Original Signal

Measured Signal

Predistorted Signal

Page 21: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Waveform Based DPD

Iterative Approach

Measure

Compensate each individual

sample

Upload new WV to SigGen

16.03.2017 A&D Symposium 21

DUT

Page 22: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Agenda

ı Introduction: What Is a Non-Linear Device

ı Characterization of Non-Linear Devices

Characterization Parameters

Traditional CW level swept measurement

Modulated Measurement

ı Compensation of Linear and Non-Linear Effects

Equalizer

Digital Predistortion (DPD)

ı Summary

A&D Symposium 2216.03.2017

Page 23: Characterization and Compensation of Non-Linear Effects in … · 2017. 3. 24. · Summary ıLinear and non-linear effects contribute significantly to signal quality ıNon-linear

Summary

ı Linear and non-linear effects contribute significantly to signal quality

ı Non-linear effects may vary significantly, depending on the stimulus (input signal)

ı Characterization of these effects is vital to understand limitations to system design

ı With effects understood, compensation methods can be contemplated

ı R&S FSW-K18 Amplifier Measurement Personality characterizes signal and evaluated

different compensation methods

16.03.2017 A&D Symposium 23