Linearization of power amplifiers by
`means of digital predistortion
`
`Linearisierung von Leistungsverst¨arkern mittels
`digitaler Vorverzerrung
`
`Der Technischen Fakult¨at der
`
`Universit¨at Erlangen-N¨urnberg
`
`zur Erlangung des Grades
`
`Doktor-Ingenieur
`
`vorgelegt von
`
`Nazim Ceylan
`
`Erlangen - 2005
`
`PETITIONERS EXHIBIT 1010
`Page 1 of 156
`
`

`

`Als Dissertation genehmigt von
`
`der Technischen Fakult¨at der
`
`Universit¨at Erlangen-N¨urnberg
`
`Tag der Einreichung:
`Tag der Promotion:
`Dekan:
`Berichterstatter:
`
`07.04.2005
`17.10.2005
`Prof. Dr. Alfred Leipertz
`Prof. Dr. Robert Weigel
`Prof. Dr. Christian Sch¨affer
`
`PETITIONERS EXHIBIT 1010
`Page 2 of 156
`
`

`

`Kurzfassung
`
`In der neuen Generation von Mobilfunksystemen (WCDMA, CDMA2000, EDGE)
`werden Modulationsformate implementiert, die das jeweilige Frequenzspektrum ef-
`fizient ausnutzen. Die Schl¨usselvoraussetzung daf¨ur ist eine hohe Linearit¨at des Leis-
`tungsverst¨arkers (PA). Diese Komponente des Senders weist zudem den h¨ochsten Leis-
`tungsverbrauch auf, so dass sie neben den Anforderungen an die Linearit¨at auch ¨uber
`einen hohen Wirkungsgrad verf¨ugen muss. Dieser Umstand ist besonders bei batteriebe-
`triebenen Systemen von grosser Bedeutung.
`
`Das Ziel, einen PA mit hoher Linearit¨at und gleichzeitig hohem Wirkungsgrad zu en-
`twerfen f¨uhrt zu Anforderungen, die sich gegenseitig ausschlieen, so dass ein Kompro-
`miss zwischen Wirkungsgrad und Linearit¨at eingegangen werden muss. Die Arbeit-
`spunkte von PA’s werden gew¨ohnlich in einem Bereich weit unterhalb der S¨attigung
`(back-off) betrieben, um die Spezifikationen bez¨uglich ihrer Linearit¨at einzuhalten,
`welche aber auf einen niedrigen Wirkungsgrad hinausf¨uhrt. Eine m¨ogliche L¨osung
`ist es, PAs in der N¨ahe des S¨attigungsbereiches zu betreiben, wo sie einen hohen
`Wirkungsgrad haben. Ihre Eigenschaften bzgl. der Linearit¨at werden dann durch Lin-
`earisierungsverfahren verbessert.
`
`Es gibt verschiedene Linearisierungsmethoden f¨ur PA, die im Wesentlichen durch die
`Oberbegriffe Feedback, Feedforward und Vorverzerrung klassifiziert werden k¨onnen.
`Im Rahmen dieser Dissertation wird das weite Feld der Linearisierung von PA auf die
`Untersuchung sog. ”Look-up-Table” (LUT) basierter ged¨achtnisloser digitaler Vorverz-
`errung (MDP) eingeschr¨ankt. Dieses Verfahren wird favorisiert, da der PA f¨ur die hohen
`Anforderungen der Leistungsf¨ahigkeit dimensioniert werden und gleichzeitig ihre Lin-
`earit¨at mit der MDP unabh¨angig davon verbessert werden kann. Im Weiteren wird
`es im digitalen Basisband realisiert und ist vorteilhaft aufgrund seiner hohen Leis-
`tungsf¨ahigkeit, der Einfachheit, dem niedrigen Leistungsverbrauch, der Zuverl¨assigkeit,
`der Flexibilit¨at, den niedrigen Kosten und der Gr¨osse. Diese Kombination ergibt eine
`flexible Designmethode, um PA mit guter Linearit¨at und gleichzeitig gutem Wirkungs-
`grad zu entwerfen.
`
`Digitale Vorverzerrung ist daf¨ur bekannt, eine Linearisierungsmethode mit hohem Leis-
`tungsverbrauch und komplizierter Linearisierungsverfahren zu sein, die man in Basis-
`stationen anwendet, wo ¨ausserst hohe Anforderungen an die Linearit¨at gestellt werden.
`Studien zu MDP zeigten, dass diese Methode auch f¨ur Mobilstationen anwendbar ist
`und eine signifikante Linearit¨atsverbesserung erreicht werden kann.
`
`Die haupts¨achlichen Leistungen dieser Arbeit sind:
`• Eine genaue und einfache PA-Charakterisierungsmethode wird vorgeschlagen. Die
`Zahl der erforderlichen Analogbestandteile der herk¨ommlichen Methode wird re-
`duziert, und ein in Systemsimulationen verwendbares Verhaltensmodell wird er-
`stellt [1, 2].
`
`i
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`

`

`• Der LUT basierte MDP ist im Stande, den Senderwirkungsgrad in WCDMA und
`EDGE Mobilstationen bedeutsam zu verbessern. Die Methode ist dazu f¨ahig, die
`in einem WCDMA-System maximal erreichbare lineare Ausgangsleistung um 2
`dB und den durchschnittlichen System-Wirkungsgrad um 20% zu verbessern, im
`Vergleich zu einem System ohne Vorverzerrung [3]. Der verwendete PA ist f¨ur ein
`TDMA - System dimensioniert. In EDGE ist eine Verbesserung der linearen Aus-
`gangsleistung von 3.5 dB zu verzeichnen und der Wirkungsgrad an der maximal
`erreichbaren Ausgangsleistung wird von 15% auf 23% erh¨oht mit einem vorhan-
`denen GSM PA [2]. Die ben¨otigten Modifizierungen in vorhandenen Systemen
`wurden bestimmt, um MDP zu implementieren.
`• Eine neue LUT Adressierungsmethode wird vorgeschlagen, die den Leistungsver-
`brauch im MDP reduzieren kann [4]. Das ist n¨utzlich in Sendern, die ihre Basis-
`bandsignale in kartesischer Form haben.
`• Es wird gepr¨uft, ob dass LUT basierte MDP dazu f¨ahig ist, die Linearit¨at der
`hocheffizienten Senderarchitektur Envelope-Elimination and Restoration (EER)
`in EDGE Mobilstationen mit PAs in S¨attigung zu verbessern. Spezifikationen
`werden erf¨ullt f¨ur Ausgangsleistungsniveaus von 20 bis 29.5 dBm mit nur einer
`Netzspannungsabstimmung. Durch zus¨atzliche Bias-Modulation kann die System-
`leistung weiter verbessert werden.
`
`ii
`
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`

`

`Abstract
`
`In new generation mobile communication systems (WCDMA, CDMA2000, EDGE),
`where spectrum efficient linear modulation formats are used, power amplifier (PA)
`linearity is a key requirement. On the other hand the PA is one of the most power
`consuming components in a mobile communication system. Therefore its power added
`efficiency (PAE) and linearity must be simultaneously high especially in battery oper-
`ated handsets. However, normally a compromise between PAE and linearity has to be
`accepted in a design. PAs are usually operated with a back-off in order to fulfill linear-
`ity specifications, which in turn results in lower power efficiency. One possible solution
`is to operate PAs near to saturation where they are highly nonlinear but efficient, and
`linearize them by using some external circuitry.
`
`There are different PA linearization methods available which can be classified mainly
`as feedback, feedforward and predistortion. This thesis deals mainly with look-up table
`(LUT) based memoryless digital predistortion (MDP) realized in digital baseband due
`to its high performance, simplicity, low power consumption, reliability, flexibility, low
`cost and size. It is attractive because the PA can be designed for high efficiency and
`the linearity can be improved independently with MDP. The combination of both gives
`design flexibility for achieving good linearity and efficiency at the same time. Although
`digital predistortion is known to be a high power consuming and complicated lineariza-
`tion method applicable in base stations where extremely high linearity is required, the
`studies on MDP showed that with a careful design it is also applicable in handsets
`resulting in significant linearity improvement.
`
`The main achievements of this thesis are:
`• An accurate and simple PA characterization method is proposed. The number of
`required analog components in the conventional measurement setup is reduced
`and a behavioral model based on large signal S-parameters usable in system
`simulations is generated [1, 2].
`• The LUT based MDP is able to improve the transmitter efficiency significantly
`in WCDMA and EDGE handsets. The method is proved to be capable of increas-
`ing the maximum achievable linear output power by 2 dB and average system
`efficiency by 20% compared to without predistortion case in WCDMA using an
`available linear PA designed for TDMA [3]. In EDGE the improvement in linear
`output power is 3.5 dB and the efficiency at maximum linear output power is in-
`creased from 15% to 23% using an available GSM PA [2]. Required modifications
`in available systems are determined in order to implement the system.
`• A novel LUT addressing method capable of reducing power consumption in MDP
`systems is proposed [4]. It is useful in transmitters having baseband signals in
`Cartesian form.
`
`iii
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`

`• It is verified that LUT based MDP is able to improve the linearity of highly
`efficient transmitter architecture envelope elimination and restoration (EER) in
`EDGE handsets which uses highly efficient saturated power amplifiers. Specifica-
`tions are fulfilled for 20 to 29.5 dBm output power levels by modulating just the
`supply voltage. The performance can be improved further using additional bias
`modulation.
`
`iv
`
`PETITIONERS EXHIBIT 1010
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`

`

`Contents
`
`1 Introduction
`
`1.1 Outline of the thesis
`
`. . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`2 Power amplifiers
`
`2.1 Power amplifier fundamentals
`
`. . . . . . . . . . . . . . . . . . . . . . .
`
`2.1.1 Gain and output power . . . . . . . . . . . . . . . . . . . . . . .
`
`2.1.2 Linearity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`2.1.3 Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`2.1.4 Back-off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`2.1.5 Matching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`2.2 Amplifier classes
`
`. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`2.2.1 Class A amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`2.2.2 Class B amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`2.2.3 Class AB amplifiers . . . . . . . . . . . . . . . . . . . . . . . . .
`
`2.2.4 Class C amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`2.2.5 Class D amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`2.2.6 Class E amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`2.2.7 Class F amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`2.3 Amplifier topologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`2.3.1
`
`Single-ended power amplifiers . . . . . . . . . . . . . . . . . . .
`
`2.3.2 Differential power amplifiers . . . . . . . . . . . . . . . . . . . .
`
`2.3.3 Balanced power amplifiers . . . . . . . . . . . . . . . . . . . . .
`
`2.4
`
`Investigated power amplifiers
`
`. . . . . . . . . . . . . . . . . . . . . . .
`
`3 Mobile communications
`
`3.1 Digital modulation formats . . . . . . . . . . . . . . . . . . . . . . . . .
`
`3.1.1 Amplitude shift keying (ASK) . . . . . . . . . . . . . . . . . . .
`
`v
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`1
`
`2
`
`4
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`4
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`4
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`4
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`8
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`10
`
`11
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`12
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`13
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`14
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`15
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`17
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`17
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`18
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`19
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`20
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`3.1.2 Phase shift keying (PSK) . . . . . . . . . . . . . . . . . . . . . .
`
`3.1.3 Quadrature amplitude modulation (QAM) . . . . . . . . . . . .
`
`3.1.4 Gaussian minimum shift keying (GMSK) . . . . . . . . . . . . .
`
`3.2 Cellular systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`3.2.1 GSM/EDGE . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`3.2.2 WCDMA/CDMA2000 . . . . . . . . . . . . . . . . . . . . . . .
`
`4 RF transmitters
`
`4.1 Transmitter architectures . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`4.1.1 Direct conversion (homodyne) architecture . . . . . . . . . . . .
`
`4.1.2 Two-step conversion (heterodyne) architecture . . . . . . . . . .
`
`4.1.3 Modulation loop . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`4.1.4 Polar modulator . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`4.2 Nonlinear transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`4.3 Linear transmitters . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`4.3.1 Linear transmitter with linear PA . . . . . . . . . . . . . . . . .
`
`4.3.2 Envelope elimination and restoration (EER) / Polar transmitter
`(PTx)
`. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`4.3.3 Polar loop transmitter (PLTx) . . . . . . . . . . . . . . . . . . .
`
`4.3.4 Envelope Follower . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`4.3.5 Power Tracking . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`5 Power amplifier linearization methods
`
`5.1 Feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`5.1.1 RF feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`5.1.2 Polar loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`5.1.3 Cartesian loop . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`5.2 Feedforward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`5.3 Predistortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`5.3.1 Analog predistortion . . . . . . . . . . . . . . . . . . . . . . . .
`
`5.3.2 Digital predistortion . . . . . . . . . . . . . . . . . . . . . . . .
`
`5.4 Memoryless digital predistortion (MDP)
`
`. . . . . . . . . . . . . . . . .
`
`5.4.1 Look-up table (LUT) based predistortion . . . . . . . . . . . . .
`
`5.4.2 Polynomial predistorter
`
`. . . . . . . . . . . . . . . . . . . . . .
`
`5.4.3 Effects of system imperfections
`
`. . . . . . . . . . . . . . . . . .
`
`5.5 Predistortion of PAs with memory . . . . . . . . . . . . . . . . . . . . .
`
`24
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`26
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`26
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`27
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`

`6 Memoryless digital predistortion for terminals
`
`6.1 Power amplifier characterization . . . . . . . . . . . . . . . . . . . . . .
`
`6.2 Application of MDP in EDGE . . . . . . . . . . . . . . . . . . . . . . .
`
`6.2.1
`
`System performance
`
`. . . . . . . . . . . . . . . . . . . . . . . .
`
`6.2.2 Quantization analysis . . . . . . . . . . . . . . . . . . . . . . . .
`
`6.2.3 Effects of antenna mismatch . . . . . . . . . . . . . . . . . . . .
`
`6.2.4 Required system modifications . . . . . . . . . . . . . . . . . . .
`
`78
`
`79
`
`87
`
`89
`
`93
`
`95
`
`97
`
`6.3 Application of MDP in WCDMA . . . . . . . . . . . . . . . . . . . . . 101
`
`6.4 MDP for PAs with DC-DC converters . . . . . . . . . . . . . . . . . . . 105
`
`6.5 Symbol addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
`
`6.6 MDP implemented as open- and closed-loop . . . . . . . . . . . . . . . 115
`
`6.6.1 Open-loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
`
`6.6.2 Closed-loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
`
`6.7 Application of MDP in polar transmitter concept
`
`. . . . . . . . . . . . 120
`
`6.7.1 PA characterization . . . . . . . . . . . . . . . . . . . . . . . . . 120
`
`6.7.2
`
`System performance
`
`. . . . . . . . . . . . . . . . . . . . . . . . 123
`
`7 Conclusions
`
`125
`
`7.1 Future work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
`
`Bibliography
`
`128
`
`vii
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`

`Acknowledgements
`
`I would like to express my deep appreciation to my advisor Prof. Dr. Robert Weigel
`for his guidance and support throughout the study.
`
`The work presented was supported by Infineon Technologies AG, department for RFICs,
`Munich. I would like to gratefully acknowledge the help, comments and guidance re-
`ceived from Dr. Jan-Erik M¨uller. I am also grateful to Stefan Beyer, Dr. Volker Thomas
`and Josef Fenk for making this study at Infineon possible.
`
`I would like to express my thanks to Dr. Andreas Holm, Dr. Winfried Bakalski and Nick
`Shute for critical reading of the manuscript and informative discussions. My gratitude
`also goes to Peter Pfann and Dr. Alexander Zenzinger for valuable discussions and help
`during the measurements. Further I want to thank my friends ¨Ozhan Koca, Caglayan
`Erdem, Krzysztof Kitlinski and Martin Simon for their help and motivating discussions
`with them.
`
`Finally, I would like to thank my wife Esra for her understanding and valuable support
`and my parents for their encouragement during my PhD studies.
`
`viii
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`

`

`List of Abbreviations
`
`AC
`ACI
`ACPR
`ACPR I
`ACPR II
`ADC
`ADS
`AM
`ASK
`BALUN
`BER
`BPF
`BPSK
`BS
`CDMA
`CMOS
`Cp
`DAC
`DC
`DP
`DPCCH
`DPDCH
`DSP
`DSSS
`DUT
`EDGE
`EER
`EVM
`FDD
`FDMA
`FM
`FPGA
`GMSK
`GSM
`I
`Iq
`IMD
`IMP
`IC
`IF
`LAN
`
`Alternating Current
`Adjacent Channel Interference
`Adjacent Channel Power Ratio
`Adjacent Channel Power Ratio
`Alternate Channel Power Ratio
`Analog-to-Digital Converter
`Advanced Design System
`Amplitude Modulation
`Amplitude Shift Keying
`BALanced to Unbalanced
`Bit Error Rate
`Band-Pass Filter
`Binary Phase Shift Keying
`Base Station
`Code Division Multiple Access
`Complementary Metal Oxide Semiconductor
`Output power capability
`Digital-to-Analog Converter
`Direct Current
`Digital Predistortion
`Dedicated Physical Control CHannel
`Dedicated Physical Data CHannel
`Digital Signal Processing
`Direct Sequence Spread Spectrum
`Device Under Test
`Enhanced Data for Gsm Evolution
`Envelope Elimination and Restoration
`Error Vector Magnitude
`Frequency Division Duplex
`Frequency Division Multiple Access
`Frequency Modulation
`Field Programmable Gate Array
`Gaussian Minimum Shift Keying
`Global System for Mobile communications
`Current
`Quiescent current
`InterModulation Distortion
`InterModulation Product
`Integrated Circuit
`Intermediate Frequency
`Local Area Networking
`
`ix
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`

`

`LNA
`LO
`LPF
`LUT
`MDP
`MMIC
`MSK
`OBO
`OQPSK
`OSR
`PA
`PAE
`PAR
`PBO
`PFD
`Pin
`PLL
`PLTx
`PM
`Pmax
`Pout
`Psat
`PSK
`PTx
`QAM
`QPSK
`RF
`RAM
`RMS
`RRC
`SAW
`SDM
`SF
`SMIQ
`SNR
`TDD
`TDMA
`UMTS
`V
`VCO
`VSWR
`WCDMA
`1G
`2G
`2.5G
`3G
`
`Low Noise Amplifier
`Local Oscillator
`Low-Pass Filter
`Look-Up Table
`Memoryless Digital Predistortion
`Monolithic Microwave Integrated Circuit
`Minimum Shift Keying
`Output Back-Off
`Offset Quadrature Phase Shift Keying
`OverSampling Ratio
`Power Amplifier
`Power Added Efficiency
`Peak-to-Average Ratio
`Peak Back-Off
`Phase-Frequency Detector
`Input Power
`Phase-Locked Loop
`Polar Loop Transmitter
`Phase Modulation
`Maximum Power
`Output Power
`Saturated Output Power
`Phase Shift Keying
`Polar Transmitter
`Quadrature Amplitude Modulation
`Quadrature Phase Shift Keying
`Radio Frequency
`Random Access Memory
`Root Mean Square
`Root Raised Cosine
`Surface Acoustic Wave
`Sigma-Delta Modulator
`Spreading Factor
`Signal generator from Rohde & Schwarz
`Signal-to-Noise Ratio
`Time Division Duplex
`Time Division Multiple Access
`Universal Mobile Telecommunications System
`Voltage
`Voltage Controlled Oscillator
`Voltage Standing Wave Ratio
`Wideband Code Division Multiple Access
`1st Generation
`2nd Generation
`2.5th Generation
`3rd Generation
`
`x
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`

`Chapter 1
`
`Introduction
`
`Products in the area of mobile communications became very important in our daily
`life in the last decade and it seems that their importance will increase further. Manu-
`facturers try to improve their products by adding new features and services to increase
`the number of subscribers. This forces them to use new system topologies, reduce
`power consumption, increase system integration in order to increase the battery life
`and reduce the size and cost of the products.
`
`Higher number of subscribers and new services require wider spectrum bandwidths
`which is not easily available due to current fixed spectrum allocations. The solution is
`to use spectrum efficient modulation schemes as in 2.5th and 3rd generation (2.5G, 3G)
`mobile communication systems such as EDGE (Enhanced Data for GSM Evolution)
`and UMTS (Universal Mobile Telecommunications System) in Europe. In 2nd genera-
`tion (2G) systems such as GSM (Global System for Mobile Communications) the phase
`of the carrier is modulated and its envelope is kept constant whereas in the 2.5G and
`3G systems the amplitude of the carrier (signal envelope) is also modulated. This is
`the reason for increase in spectrum efficiency (transmitted bits/Hz) compared to 2G
`systems.
`
`New generation mobile communication systems are very sensitive to nonlinearities in
`their transmitter paths because their signals have fluctuating envelopes. The nonlin-
`earity in a transmitter is mostly due to the PA at the end of the chain. Therefore the
`PA is operated with some back-off in order to obtain desired linearity. This makes the
`PA operate with low power efficiency which is not the case in the phase modulated
`constant envelope 2G systems. If the system linearity requirements are stringent, then
`the efficiency is worse because the PA must be operated with more back-off. Since PA is
`one of the most power consuming components in a mobile communication transmitter,
`every small change in its efficiency has a significant effect on overall system efficiency
`and therefore talk time. This is very important especially in battery operated mobile
`terminals. Moreover in low efficient systems a significant part of the power is disipated
`as heat which may cause high case temperatures.
`
`The linearity requirement in a transmitter path makes the design of PAs difficult be-
`cause it must be linear and at the same time highly efficient. Linearization techniques
`can be applied to improve the linearity, decrease the required amount of back-off and
`hence increase the efficiency of PAs. There are different types of linearization techniques
`
`1
`
`PETITIONERS EXHIBIT 1010
`Page 13 of 156
`
`

`

`Chapter 1.
`
`Introduction
`
`2
`
`which can be classified under three main groups: feedback, feedforward and predistor-
`tion. In this thesis a LUT based MDP system is investigated which is simple, low power
`consuming, reliable, flexible, having low cost and size, and applicable to handset (also
`called terminal) PAs achieving significant performance improvement.
`
`In todays mobile communication systems the overall system performance is important.
`This means the individual integrated circuits (IC) must not necessarily have very high
`performance but the systems composed of these ICs and embedded within an adequate
`architectural approach require high performance in terms of linearity and efficiency.
`This makes digital predistortion (DP) attractive because the PA can be designed for
`high efficiency and the linearity can be improved with DP. The combination of both
`gives design flexibility for achieving good linearity and efficiency at the same time. The
`additional efforts for the processor benefit in the long term from a fast and continuous
`improvement in digital IC technology, as its performance benefits from device scaling.
`Power consumption decreases, achievable clock frequency increases and digital ICs are
`more flexible and robust compared to analog ICs. DP is a promising linearization
`technique because in future more and more tasks will be done in digital domain much
`more easily.
`
`1.1 Outline of the thesis
`
`In chapter 2 PAs are considered in general. The fundamental terms such as gain,
`linearity, efficiency etc. are explained, different PA classes and topologies are considered.
`The PAs used for the work are listed.
`
`Chapter 3 explains 2G, 2.5G and 3G mobile communication systems GSM, EDGE,
`CDMA2000 (Code Division Multiple Access 2000) and WCDMA (Wideband CDMA).
`Their system capacity, advantage and disadvantages are mentioned and their specifi-
`cations especially in terms of adjacent channel power ratio and error vector magnitude
`are explained, the effects of PA nonlinearities are discussed.
`
`Various transmitter architectures are described in chapter 4 with respect to their ben-
`efits and drawbacks for future high efficient terminal transmitter architectures. These
`are nonlinear transmitters as in GSM, linear transmitters as in EDGE, WCDMA or
`CDMA2000 and polar transmitter which is able to handle both linear and nonlinear
`systems at the same time.
`
`Linearization methods are explained in detail throughout chapter 5. They can be clas-
`sified mainly as feedback, feedforward and predistortion systems, where various im-
`plementation types (polar, cartesian, digital, analog) are possible. DP systems having
`the capability to correct memory effects are complex and may be applicable in base
`stations. MDP has a good performance in terminal PAs due to small memory effects
`and it has been observed to be simple, low power consuming, reliable, flexible, having
`low cost and low size. This chapter concentrates on predistortion and explains it in
`detail.
`
`In chapter 6 static and dynamic PA AM/AM and AM/PM characterization methods
`are compared. Application of MDP in EDGE and WCDMA terminals using linear mode
`
`PETITIONERS EXHIBIT 1010
`Page 14 of 156
`
`

`

`Chapter 1.
`
`Introduction
`
`3
`
`PAs is investigated. Required system modifications in available systems and possible
`efficiency improvement with a DC-DC converter are also investigated. A new addressing
`method useful in transmitters with Cartesian form baseband signals is proposed and
`tested successfully. Also some novel open- and closed-loop MDP implementations usable
`in terminal applications are proposed. Moreover the application of MDP in EER is
`investigated.
`
`Chapter 7 concludes the thesis and points out possible future work for implementing
`the proposed method in mobile communication systems.
`
`PETITIONERS EXHIBIT 1010
`Page 15 of 156
`
`

`

`Chapter 2
`
`Power amplifiers
`
`2.1 Power amplifier fundamentals
`
`PAs are devices used to amplify signals in order to obtain high signal powers neces-
`sary for transmission via a propagation medium. They are indispensable in wireless
`communications. The following section is a brief introduction of some fundamantal PA
`features.
`
`2.1.1 Gain and output power
`
`In mobile communications each system has its specifications which must be fulfilled.
`Obtaining output powers high enough for various applications is a very important task
`achieved by PAs. In general the information signal is first modulated and upconverted,
`and then sent to a PA. This input is multiplied with a gain factor and the desired output
`power is obtained. Gain is handled in dB and power in dBm throughout this thesis. Fig.
`2.1 (a) and (b) show example PA output and gain versus input power characteristics
`of a linear PA respectively. PA output versus input power characteristics shown in fig.
`2.1 (a) is also called AM/AM characteristics of the PA
`
`As it can be seen from the figures the gain is constant for low input powers and it
`reduces with approaching its saturation region. Saturation region is easily visible from
`the output power curve where the output power stays constant with further increase of
`the input power. In the fig. 2.1 (a) 1 dB compression point is also shown, which refers
`to the output power level at which the amplifier’s transfer characteristics deviates
`from the ideal one by 1 dB [5]. This is a widely used measure of amplifier linearity
`revealing roughly which linear output power value is achievable with the device under
`test (DUT).
`
`2.1.2 Linearity
`
`Linearity is one of the key issues in PAs used in new generation mobile communication
`systems [5, 6]. The linearity of a PA is easily visible in its gain and phase characteristics.
`
`4
`
`PETITIONERS EXHIBIT 1010
`Page 16 of 156
`
`

`

`Chapter 2. Power amplifiers
`
`5
`
`1 dB
`
`-25
`
`-20
`
`-15
`
`-10
`
`-5
`
`0
`
`5
`
`10
`
`Pin (dBm)
`(a)
`
`24
`
`21
`
`18
`
`15
`
`91
`
`2
`
`6
`
`28
`
`26
`
`24
`
`22
`
`20
`
`18
`
`16
`
`Pout (dBm)
`
`Gain (dB)
`
`-25
`
`-20
`
`-15
`
`-10
`
`-5
`
`0
`
`5
`
`10
`
`Pin (dBm)
`(b)
`
`Figure 2.1: (a) Output power and (b) gain characteristics of a PA.
`
`If an amplifier has a constant gain and phase response for an input power region, then
`the amplifier is said to be linear for this region. Fig. 2.2 (a) and (b) show typical and
`desired amplifier gain and phase characteristics respectively. Solid lines are gain and
`phase characteristics of a memoryless PA and dashed lines indicate the ideally linear
`PA gain and phase characteristics. In general after reaching a relatively high output
`power value the amplifier gain decreases gradually with increasing input power because
`the PA reaches its saturation point. Phase nonlinearity increases also with increasing
`input power. Amplifier phase characteristics shown in fig. 2.2 (b) is also called as
`AM/PM characteristics. The other way of determining PA nonlinearity is using second
`and third order intercept points. The advantage is that it is a fixed quantity from which
`the distortion level at a particular operating point may be predicted [5].
`
`There are some conventional analog techniques used to design linear PAs by optimizing
`linearity and efficiency through bias and matching adjustments [7, 8]. However, these
`analog techniques have their limits and achieving a highly linear gain and phase re-
`sponse simultaneously is very difficult. Currently these methods are widely used and
`achievable performance is close to its limits. Therefore some other sophisticated solu-
`tions are necessary to solve the problem.
`
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`
`

`

`Chapter 2. Power amplifiers
`
`6
`
`Gain
`Linear gain
`
`-25
`
`-20
`
`-15
`
`-10
`
`-5
`
`0
`
`5
`
`10
`
`Pin (dBm)
`(a)
`
`Phase response
`
`Linear phase
`response
`
`-25
`
`-20
`
`-15
`
`-10
`
`-5
`
`0
`
`5
`
`10
`
`Pin (dBm)
`(b)
`
`28
`
`26
`
`24
`
`22
`
`20
`
`18
`
`16
`
`-36
`
`-38
`
`-40
`
`-42
`
`-44
`
`-46
`
`Gain (dB)
`
`Phase (deg)
`
`Figure 2.2: Nonlinear and ideally linear PA (a) gain and (b) phase characteristics.
`
`The reason why the linearity is so important is the varying signal envelopes in spec-
`trum efficient modulation types used in new generation mobile communication systems
`[5]. If signals have constant envelopes like in FM (Frequency Modulation) or GMSK
`(Gaussian Minimum Shift Keying) then PA linearity is not an important issue because
`the instantaneous input power stays constant and therefore there are no gain and phase
`variations for a specific operation point. However, if the signal envelope varies, then the
`instantaneous input power changes continuously. As a result the signal at the PA output
`is distorted if the amplifier gain and phase response are not linear. This distortion can
`be measured in terms of IMD (Intermodulation Distortion), ACPR (Adjacent Channel
`Power Ratio) or EVM (Error Vector Magnitude) [6]. Fig. 2.3 (a) and (b) show possible
`degradation of PA output ACPR (for WCDMA) and EVM due to its nonlinearity. If
`a two-tone signal is applied to a nonlinear device, then a large number of harmonics
`and IMPs (Intermodulation Products) are generated depending on the nonlinearity
`degree of the device. The odd-order IMPs (3rd, 5th, 7th, etc) are the most important
`ones because they fall into the neighborhood of the main signal and therefore not easily
`filterable. The most commonly used measure of IMD is the ratio of the largest IMP
`to the amplitude of one of the two equal tones [5]. ACPR is caused by IMPs falling in
`
`PETITIONERS EXHIBIT 1010
`Page 18 of 156
`
`

`

`Chapter 2. Power amplifiers
`
`7
`
`Alternate
`Ch. Left
`
`Adjacent
`Ch. Left
`
`Main
`Ch.
`
`Adjacent
`Ch. Right
`
`Alternate
`Ch. Right
`
`PA Input
`
`PA Output
`
`0
`
`-20
`
`-40
`
`-60
`
`-80
`
`-100
`
`-120
`
`Power, dBm
`
`-140
`-12.5
`
`-7.5
`
`-2.5
`2.5
`Freq, MHz
`
`7.5
`
`12.5
`
`20
`
`0
`
`-20
`
`-40
`
`-60
`
`-80
`
`Power, dBm
`
`-100
`-12.5
`
`-7.5
`
`-2.5
`2.5
`Freq, MHz
`(a)
`
`7.5
`
`12.5
`
` I
`
`Actual
`
`Error
`Vector
`
`Intended
`
`Q
`
`(b)
`
`Figure 2.3: Effects of PA nonlinearity on (a) ACPR for a WCDMA signal and (b) EVM
`[9].
`
`the signal neighborhood in the case of complex modulated signals composed of a lot
`of spectral components. It is defined as the ratio of the distortion signal power falling
`in the adjacent channels to the carrier power (main channel power) in dB [9]. In fig.
`2.3 (a) PA input and output signals are compared. Under ideal conditions PA output
`is a shifted version of the input in the vertical direction by an amount equal to PA
`gain. However, the PA output in fig. 2.3 (a) has some unwanted distortion elements
`
`PETITIONERS EXHIBIT 1010
`Page 19 of 156
`
`

`

`Chapter 2. Power amplifiers
`
`8
`
`in the neighbor channels indicating PA nonlinearity. ACPR is a very critical issue in
`mobile communications. A transmitter must fulfill the specifications and not to disturb
`dedicated neighbor channels because they are usually used by other transmitters.
`
`EVM can be defined as the distance between the desired and actual signal vectors
`(error vector), normalized to a fraction of the signal amplitude [9]. In fig. 2.3 (b) the
`degradation in output signal phasor is shown which corresponds the signal constellation.
`The actual value of the constellation point can deviate from the ideal one significantly
`depending on PA nonlinearity. EVM can be defined for each symbol k as
`|E(k)|
`N(cid:2)
`|S(k)|2
`
`(cid:1)
`
`EVM(k) =
`
`(2.1)
`
`k=1
`
`1 N
`
`where E(k) is the error vector for symbol k, S(k) is the ideal signal vector of the
`symbol k and N is the number of symbols. Root-mean-square (RMS) value of EVM for
`a number of symbols is a widely used measure of system linearity and it can be defined
`as
`
`(cid:1)
`(cid:1)
`
`EV MRM S =
`
`N(cid:2)
`N(cid:2)
`
`k=1
`
`|E(k)|2
`
`|S(k)|2
`
`(2.2)
`
`k=1
`
`EVM is an inband distortion causing high bit error rates during reception of the trans-
`mitted data. Therefore EVM specifications must also be fulfilled in order to have proper
`communication.
`
`2.1.3 Efficiency
`
`Efficiency is another key issue in mobile communications [6, 10], especially for battery
`operated mobile terminals. It has two widely used definitions, drain (or collector) effi-
`ciency and PAE (Power Added Efficiency). Drain efficiency is the ratio of output radio
`frequency (RF) power to input DC power
`
`η = PoutRF /PDC
`
`(2.3)
`
`and PAE is the overall efficiency obtained by subtracting input drive power from output
`RF power and divide it by input DC power [9].
`PAE = (PoutRF − Pdrive)/PDC
`
`(2.4)
`
`If the gain of a PA is high then its drain efficiency and PAE