rf power amplifiers for wireless communications - Lirias - KU Leuven

255 Pages·2008·10.12 MB·English

KATHOLIEKE UNIVERSITEIT LEUVEN
FACULTEIT INGENIEURSWETENSCHAPPEN
DEPARTEMENT ELEKTROTECHNIEK (ESAT)
AFDELING ESAT-TELEMIC
Kasteelpark Arenberg 10, B-3001 Leuven (Heverlee), België
RF POWER AMPLIFIERS
FOR WIRELESS COMMUNICATIONS
Promotors: Proefschrift voorgedragen tot
Prof. Dr. Ir. B. Nauwelaers het behalen van het doctoraat
Prof. Dr. Ir. D. Schreurs in de ingenieurswetenschappen
door
Ir.ManuelAugustoYarlequéMedina
June 2008

KATHOLIEKE UNIVERSITEIT LEUVEN
FACULTEIT INGENIEURSWETENSCHAPPEN
DEPARTEMENT ELEKTROTECHNIEK (ESAT)
AFDELING ESAT-TELEMIC
Kasteelpark Arenberg 10, B-3001 Leuven (Heverlee), België
RF POWER AMPLIFIERS
FOR WIRELESS COMMUNICATIONS
Jury: Proefschrift voorgedragen tot
Prof. Dr. Ir.- Arch. H. Neuckermans, het behalen van het doctoraat
voorzitter in de ingenieurswetenschappen
Prof. Dr. Ir. B. Nauwelaers, promotor
Prof. Dr. Ir. D. Schreurs, promotor door
Prof. Dr. Ir. A. Barel (VUB)
Prof. Dr. Ir. P. Wambacq (VUB/IMEC) Ir.ManuelAugustoYarlequéMedina
Prof. Dr. Ir. R. Mertens
(KULeuven/IMEC)
Prof. Dr. Ir. D. Vanhoenacker-Janvier
(UCL)
Prof. Dr. Ir. P. Colantonio
(Università di Roma Tor Vergata,
Italy)
U.D.C. 621.3.049.77
Wet. Depot : D/2008/7515/66
ISBN 978-90-5682-957-5
June 2008
©Katholieke Universiteit Leuven - Faculteit Ingenieurswetenschappen
Arenbergkasteel, B-3001 Leuven (Heverlee), België
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All rights reserved. No part of the publication may be reproduced in any form by
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publisher.
Wet. Depot : D/2008/7515/66
ISBN 978-90-5682-957-5
Acknowledgment
A journey of a thousand miles begins with one step. This has been a very
longjourney,longerthanIexpected. Nevertheless,ithasbeenanenrichingexpedition
with new experiences and challenges. I would not have reached this point without
the help and support of the people I met on this quest and the friends from here and
all over the world and my family in Peru.
WhileIamwritingdowntheselines,itisrainingheavily,whichissomehowarecurring
feature in Belgium. Despite this being disturbing, particularly to Latin people, rain
stirs up in me joyful memories. My friends and I playing football in the rain, totally
soaked,fallingdownovertheartificialgrassthatwasmorewaterthangrassandeach
fall a shower! Even more amazing, we played in the snow as well. It was a unique
experience,runningandjumpingoverthicksnow,kickingthesnowinsteadoftheball
and doing our best to try to defeat the opposite team. But overall, we had lots of
fun.
First, I would like to thank the support of the SBA scholarship program of the KU
Leuven,whichprovidedmewiththefacilitiesandresourcestostart,pursueandfinish
my doctoral studies. My thanks are due to my home university in Peru, Pontificia
UniversidadCatólicadelPerú. Inaddition,IwouldliketothanktheformerEuropean
NetworkofExcellence(NoE)TARGET,whichallowedmetorealizefruitfulscientific
interchanges with other European universities related to my research area.
Above all, I would like to thank God because He chose this place (Leuven-Heverlee)
for me. He knew that here I would find everything I needed to carry out this project
andrealizemydream; thevibrantscholarlyatmosphere, thefriends, thechurchcom-
munity, the sports facilities, the forest, the castle, nature replete with birds. No, I do
not think He forgot anything.
I would like to thank my two promoters, Professors Dominique Schreurs and Bart
Nauwelaers for all the academic and extra-academic assistance.
Dominique Schreurs, who was also my office mate, provided me with abundant sci-
entific information, which was valuable for my research. Likewise, she introduced
me to academics from other European universities, which was of high importance for
i
the development of this investigation. Additionally, she managed to proofread all my
papers, and even exceeding her own time, did a thorough revision and correction of
my thesis manuscript. Her open and cheerful character contrasts with my reserved
and shy personality. I remember that she broke up my silence many times to chat
for a while, which turned out to be very refreshing and this frequently ended up in
laughter. I want to express my deep gratitude to her for all this.
BartNauwelaers,whowithhissmartadviceandrefinedsenseofhumor,relievedsome
ofthetensemomentsduringthecourseofthisresearch. Irememberparticularlythat
afterstayingworkingatthefacultyovertheChristmasandNewYearholidays, Iwas
feelingexhaustedanddown,thenhecametomyofficetogreetmeandhisenthusiasm
and cheer changed my mood completely and recharged my energy. Furthermore, he
providedmewithallthenecessarymeanstocontinuemyresearchwhenthetimeand
the resources had expired. For all this and also for making time in his very tight
agenda to proofread my thesis, I am very grateful to him.
I would like to thank my research group Telemic for providing me with assistance
from the very beginning and during the course of this adventure, in particular to
my colleagues Dave Trappeniers and Ilja Ocket and the secretary Ann Deforce. A
very special acknowledgment to the former Telemicer Peter Delmotte, his technical
assistance and clever ideas were fundamental for this investigation. Additionally, I
want to express my gratitude to my colleague Maciej Myslinski for his important
collaboration on the execution of the measurements. On the other hand, I am also
grateful to all the technicians of the ESAT mechanical and electronics workshop, in
particular, to Ms. Noella Gaethofs for her sympathy and patience during the whole
device mounting process.
This part of the acknowledgment crosses the Belgian borders and goes to the Uni-
versity of Rome Tor Vergata. I want to express my gratitude to professors Franco
Giannini and Paolo Colantonio, for their invaluable assistance and guidance during
mystayintheirinstitution. IhavetotrulyconfessthattheexperienceIgainedthere
allowed me to clearly mark the path to follow for the final development of this inves-
tigation. Additionally, I would like to express my very warm thanks to my Italian
colleaguesRocco,Augusto,Antonio,PatrickandMarcofortheircompanyandfriend-
ship during my stay there. Finally, my gratitude to Professor Iltcho Angelov from
the University of Chalmers, Sweden, without his support, the essential non-linear
modeling task would not have been finished successfully.
I am also very grateful to all the members of my examination committee for realizing
a thorough revision of the manuscript and providing me with important insights and
remarks that improved the contents and quality of this final manuscript.
During the first years of my doctorate, I had the constant support (although she was
in Peru) of Ms. LiliAna Mendoza. I want to express my gratitude to her for all her
understanding, friendship and comforting. She had a lot of faith that I would finish
this work and always expressed it so that I would not forget it. I am grateful to her
for this.
ii
With the risk of forgetting someone’s name, I would like to express my apprecia-
tion and gratitude to all the international friends I met on this journey: Aude (from
France), Sonja (from Germany), Onur (from Turkey), Javier (from Spain), Roberto
(from Mexico), Oscar, Jairo, Don Jairo and Elizabeth (from Colombia), Claudia,
Daniela, Sandra (from Chile), Diego, Mauricio, Marcelo (from Bolivia), Luis (from
Ecuador), Els, Sandra, Ellen, Joke and Bart (from Belgium). I am thankful to my
compatriots and friends Josefina, Romina, Antonio, Fernando, Luis, and Javier. Ad-
ditionally,IwanttothankmyfriendsGeertandChris,fromtheconditioningtraining
class, Wouter, Julian and Sebastian from Football Leuven, and finally from my danc-
ing class, I would like to thank Rommy, Katrien, Sandy and Ives. And overall, I
would like to express my gratitude to all these friends whose names I cannot recall,
for a strange and unfair reason, at this moment, but I am sure that they were utterly
important and I am indebted to them.
I would also like to express my profound gratitude and acknowledgment to three
special people. To Ms. Maria Adela, for her friendship, company, special attention
and caring for me at every moment. To Ms. Isabel Fernandez, for her determined
and opportune counseling. And to Ms. Vina Vaswani, for her invaluable friendship
and support as well as for all the transcendental talks and advice.
A special thanks to my parents and my brothers. Despite the distance, they always
made me feel that I was with them in Peru. One of my brothers often liked to joke
that I was calling up from a public telephone in Lima, very close to home, and that I
would suddenly show up. The telephone talks with my mum were always comforting
and cheering. I believe I received the persevering and stubborn character from her,
without which it would have been hard to finish this job.
Finally,Iwanttoreservetheselastlinestomydearestlove; tothislong-awaitedand
unrevealed love that I endeavor to find. I am not sure yet if you were already in my
dreams or whether you somehow accompanied me all this time without me realizing.
However, I have to thank you for being this last motivation and driving force that
ultimately took me to the end of this journey. Gracias Amor Mio.
Manuel Yarlequé
Leuven, June 2008
iii

Abstract
The most recent standards for wireless communications have resorted to the Orthog-
onal Frequency Division Multiplexing (OFDM) technique to reduce channel impair-
ments. Multipath fading and intersymbol interference (ISI) can be limited by using
multiple orthogonal sub-carriers. Nevertheless this OFDM signal exhibits large in-
stantaneous signal amplitudes compared to its average values. This compels the use
of linear amplifiers working with several dB backoff with respect to their 1 dB com-
pression point (P1dB). In this way, the entire OFDM signal is amplified linearly;
however at the cost of a very poor efficiency. This increases the energy consumption
and reduces operating time per battery charge of mobile terminals. Hence, providing
linear amplification with high efficiency has become one of the major challenges for
current RF amplifier design for wireless communications.
Severaltechniquesareunderresearchtotacklethisproblem. Thesetechniquescanbe
classified as linearity and efficiency oriented techniques. Predistortion, feedforward
and feedback techniques are examples of the first kind of technique. They mainly
correct the inherent distortion of the amplifier by providing an inversion function of
theamplifierorbycomparisonwiththeoriginalinputsignal. Examplesofthesecond
type of technique are dynamic biasing, dynamic load and Envelope Elimination and
Restoration (EER), which basically vary the bias or load of the amplifier according
to the input signal.
This PhD-thesis has focused on Doherty amplifiers (dynamic load technique) and
high efficiency class-E amplifiers (main amplifier in EER) applied to WiMAX at 3.5
GHz. In the design process of these amplifiers, the concept of equivalent capacitance
is introduced and applied successfully. Measurements of the designed Doherty ampli-
fier confirm the potential benefits of this technique in terms of overall efficiency and
linearity in comparison with legacy class-AB amplifier. Nonetheless, this design task
is not possible without a reliable and sturdy device model. Hence, the task of con-
structing a non-linear model for a GaAs HEMT device was undertaken in this thesis,
whichgavefineresults. Theconjunctionofthisreliablemodelwiththeequivalentca-
pacitance concept has made possible the contemporization of aged design techniques
to face the stringent requirements of modern wireless communications.
v