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Design and Linearization of Energy Efficiency Power Amplifier in Nonlinear OFDM Transmitter for LTE-5G Applications. Simulation and measurements of energy efficiency power amplifier in the presence of nonlinear OFDM transmitter system and digital predistortion based on Hammerstein-Wiener method
This research work has made an effort to understand a novel line of radio frequency
power amplifiers (RFPAs) that address initiatives for efficiency enhancement and
linearity compensation to harmonize the fifth generation (5G) campaign. The objective
is to enhance the performance of an orthogonal frequency division multiplexing-long
term evolution (OFDM-LTE) transmitter by reducing the nonlinear distortion of the
RFPA.
The first part of this work explores the design and implementation of 15.5 W class AB
RF power amplifier, adopting a balanced technique to stimulate efficiency enhancement
and redeeming exhibition of excessive power in the transmitter. Consequently, this work
goes beyond improving efficiency over a linear RF power amplifier design; in which a
comprehensive investigation on the fundamental and harmonic components of class F
RF power amplifier using a load-pull approach to realise an optimum load impedance
and the matching network is presented. The frequency bandwidth for both amplifiers was
allocated to operate in the 2.620-2.690 GHz of mobile LTE applications.
The second part explores the development of the behavioural model for the class AB
power amplifier. A particular novel, Hammerstein-Wiener based model is proposed to
describe the dynamic nonlinear behaviour of the power amplifier. The RF power amplifier
nonlinear distortion is approximated using a new linear parameter approximation
approach. The first and second-order Hammerstein-Wiener using the Normalised Least
Mean Square Error (NLMSE) algorithm is used with the aim of easing the complexity of
filtering process during linear memory cancellation. Moreover, an enhanced adaptive
Wiener model is proposed to explore the nonlinear memory effect in the system. The
proposed approach is able to balance between convergence speed and high-level
accuracy when compared with behavioural modelling algorithms that are more complex
in computation.
Finally, the adaptive predistorter technique is implemented and verified in the OFDM
transceiver test-bed. The results were compared against the computed one from
MATLAB simulation for OFDM and 5G modulation transmitters. The results have
confirmed the reliability of the model and the effectiveness of the proposed predistorter.Fundacão para a Ciência e a Tecnologia, Portugal, under
European Union’s Horizon 2020 research and innovation programme ... grant agreement H2020-MSCA-ITN- 2016 SECRET-722424
I also acknowledge the role of the National Space Research and Development Agency (NASRDA)
Sokoto State Government
Petroleum Technology Trust Fund (PTDF
Novel power amplifier design using non-linear microwave characterisation and measurement techniques
This thesis, addresses some aspects of the well-known, problem, experienced by designer of
radio frequency power amplifiers (RFPA): the efficiency/linearity trade-off. The thesis is
focused on finding and documenting solution to linearity problem than can be used to
advance the performance of radio frequency (RF) and microwave systems used by the
wireless communication industry. The research work, this was undertaken by performing a
detailed investigation of the behaviour of transistors, under complex modulation, when
subjected to time varying baseband signals at their output terminal: This is what in this thesis
will be referred to as “baseband injection”. To undertake this study a new approach to the
characterisation of non-linear devices (NLD) in the radio frequency (RF) region, such as
transistors, designated as device-under-test (DUT), subjected to time varying baseband
signals at its output terminal, was implemented. The study was focused on transistors that are
used in implementing RF power amplifiers (RFPA) for base station applications. The nonlinear
device under test (NL-DUT) is a generalisation to include transistors and other nonlinear
devices under test. Throughout this thesis, transistors will be referred to as ‘device’ or
‘radio frequency power amplifier (RFPA) device’. During baseband injection investigations
the device is perturbed by multi-tone modulated RF signals of different complexities. The
wireless communication industry is very familiar with these kinds of devices and signals.
Also familiar to the industry are the effects that arise when these kind of signal perturb these
devices, such as inter-modulation distortion and linearity, power consumption/dissipation and
efficiency, spectral re-growth and spectral efficiency, memory effects and trapping effects.
While the concept of using baseband injection to linearize RFPAs is not new the
mathematical framework introduced and applied in this work is novel. This novel approach
NOVEL POWER AMPLIFIER DESIGN USING NON-LINEAR MICROWAVE CHARACTERISATION AND MEASUREMENT TECHNIQUES CARDIFF UNIVERISTY - UK
ABSTRACT vi
has provided new insight to this very complex problem and highlighted solutions to how it
could be a usable technique in practical amplifiers.
In this thesis a very rigorous and complex investigative mathematical and measurement
analysis on RFPA response to applied complex stimulus in a special domain called the
envelope domain was conducted. A novel generic formulation that can ‘engineer’ signal
waveforms by using special control keys with which to provide solution to some of the
problems highlighted above is presented.
The formulation is based on specific background principles, identified from the result of both
mathematical theoretical analysis and detailed experimental device characterisation
OFDM based air interfaces for future mobile satellite systems
This thesis considers the performance of OFDM in a non-linear satellite channel and mechanisms for overcoming the degradations resulting from the high PAPR in the OFDM signal in the specific satellite architecture. It was motivated by new S-DMB applications but its results are applicable to any OFDM system via satellites. Despite many advantages of OFDM, higher PAPR is a major drawback. OFDM signals are therefore very sensitive to non-linear distortion introduced by the power amplifiers and thus, significantly reduce the power efficiency of the system, which is already crucial to satellite system economics. Simple power amplifier back-off to cope with high OFDM PAPR is not possible. Two transmitter based techniques have been considered: PAPR reduction and amplifier linearization.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Behavioral modeling and FPGA implementation of digital predistortion for RF and microwave power amplifiers
With the high interest in digital modulation techniques which are very sensitive to the PA nonlinearity, modern wireless communication systems require the usage of linearization techniques to improve the linear behavior of the RF power amplifier. The powerful and cheap digital processing technology makes the digital predistortion (DPD) a competitive candidate for the linearization of the PA. This thesis introduces the basic principle of DPD, its implementation on FPGA and the adaptive DPD system.
The linearization of 4 PAs with DPD technique has been introduced: for the hybrid class AB PA operating at 2.6 GHz with a WiMAX testing signal, 33.7 dBm average power, 29.6 % drain efficiency, 13 dB ACPR and 9 dB NMSE improvement have been obtained; for the hybrid Doherty PA operating at 3.4 GHz with an I/Q testing signal, 35.0 dBm average power, 36.8 % drain efficiency, 12 dB ACPR and 13 dB NMSE improvement have been obtained; for the MMIC class AB PA operating at 7 GHz with an I/Q testing signal, 29.4 dBm average power, 25.7 % drain efficiency, 12 dB ACPR and 12 dB NMSE improvement have been obtained; for the two-stage PA operating at 24 GHz with an I/Q testing signal, 23.5 dBm average power, more than 14.0 % drain efficiency, 11 dB ACPR and 11 dB NMSE improvement have been obtained. The DPD algorithm has been implemented on FPGA with two methods based on LUT and a direct structure with only adders and multipliers. The block RAM on the FPGA board is chosen as the table in the LUT methods. The linearization performance for these three methods is similar. The test PA is the hybrid Doherty PA mentioned above and the test signal is the I/Q signal with 7.4 dB PAPR. 35.1 dBm average power, 36.8 % efficiency, 11 dB ACPR and 11 dB NMSE improvement have been obtained. The cost of logic resources for the direct structure method is the largest with 1,172 flip-flops, while the number of flip-flops for the two LUT methods are 263 and 583, respectively.
A new adaptive algorithm has been proposed in this thesis for the adaptive DPD system. This new algorithm improves the performance in extracting the model parameters in complex number domain. With the experimental data from a combined class AB PA, the final accuracy of the model extracted by the new algorithm has been improved from -20 dB to about -40 dB and the converge speed is faster
Caracterização, modelação e compensação de efeitos de memória lenta em amplificadores de potência baseados em GAN HEMTS
Gallium nitride (GaN) high-electron-mobility transistors (HEMTs) have
emerged as the most compelling technology for the transmission of highpower
radio-frequency (RF) signals for cellular mobile communications and
radar applications. However, despite their remarkable power capabilities, the
deployment of GaN HEMT-based RF power amplifiers (PAs) in the mobile
communications infrastructure is often ruled out in favor of alternative siliconbased
technologies. One of the main reasons for this is the pervasiveness of
nonlinear long-term memory effects in GaN HEMT technology caused by thermal
and charge-trapping phenomena. While these effects can be compensated
for using sophisticated digital predistortion algorithms, their implementation
and model-extraction complexity—as well as the power necessary for
their real-time execution—make them unsuitable for modern small cells and
large-scale multiple-input multiple-output transceivers, where the power necessary
for the linearization of each amplification element is of great concern.
In order to address these issues and further the deployment of high-powerdensity
high-efficiency GaN HEMT-based RF PAs in next-generation communications
and radar applications, in this thesis we propose novel methods for
the characterization, modeling, and compensation of long-term memory effects
in GaN HEMT-based RF PAs. More specifically, we propose a method
for the characterization of the dynamic self-biasing behavior of GaN HEMTbased
RF PAs; multiple behavioral models of charge trapping and their implementation
as analog electronic circuits for the accurate real-time prediction
of the dynamic variation of the threshold voltage of GaN HEMTs; a method
for the compensation of the pulse-to-pulse instability of GaN HEMT-based
RF PAs for radar applications; and a hybrid analog/digital scheme for the
linearization of GaN HEMT-based RF PAs for next-generation communications
applications.Os transístores de alta mobilidade eletrónica de nitreto de gálio (GaN HEMTs)
são considerados a tecnologia mais atrativa para a transmissão de sinais
de radiofrequência de alta potência para comunicações móveis celulares e
aplicações de radar. No entanto, apesar das suas notáveis capacidades de
transmissão de potência, a utilização de amplificadores de potência (PAs)
baseados em GaN HEMTs é frequentemente desconsiderada em favor de
tecnologias alternativas baseadas em transístores de silício. Uma das principais
razões disto acontecer é a existência pervasiva na tecnologia GaN
HEMT de efeitos de memória lenta causados por fenómenos térmicos e de
captura eletrónica. Apesar destes efeitos poderem ser compensados através
de algoritmos sofisticados de predistorção digital, estes algoritmos não são
adequados para transmissores modernos de células pequenas e interfaces
massivas de múltipla entrada e múltipla saída devido à sua complexidade
de implementação e extração de modelo, assim como a elevada potência
necessária para a sua execução em tempo real. De forma a promover a
utilização de PAs de alta densidade de potência e elevada eficiência baseados
em GaN HEMTs em aplicações de comunicação e radar de nova geração,
nesta tese propomos novos métodos de caracterização, modelação,
e compensação de efeitos de memória lenta em PAs baseados em GaN
HEMTs. Mais especificamente, nesta tese propomos um método de caracterização
do comportamento dinâmico de autopolarização de PAs baseados
em GaN HEMTs; vários modelos comportamentais de fenómenos de captura
eletrónica e a sua implementação como circuitos eletrónicos analógicos para
a previsão em tempo real da variação dinâmica da tensão de limiar de condução
de GaN HEMTs; um método de compensação da instabilidade entre
pulsos de PAs baseados em GaN HEMTs para aplicações de radar; e um
esquema híbrido analógico/digital de linearização de PAs baseados em GaN
HEMTs para comunicações de nova geração.Programa Doutoral em Telecomunicaçõe
Efficient solid state power amplifiers: power combining and highly accurate AM/AM and AM/PM behavioural models with application to linearisation
Radio Frequency (RF) Power Amplifiers (PAs) are a major contributor to modern communication
systems, both in terms of being an enabling technology as well as having
the most impact on overall system availability, linearity and power consumption. In
order to achieve the most optimum system outcome there needs to be an appropriate
method for selecting the most suitable RF PA design approach, as well as being able to
select the most appropriate RF PA output device, based on a range of varying requirements,
specifications and technologies. The ability to perform these tasks quickly, with
improved accuracy, using existing available device data, with minimal or no further
device testing and from a range of existing and emerging technologies would provide
RF PA designers with significant benefits.
The investigations and research provided in this thesis consider a range of existing and
emerging RF PA technologies and power combining methods and compares them via
a new selection and design methodology developed in this thesis. The new methodology
builds on modern design and statistical approaches including manufacturing
options that enable an appropriate technology to be selected for Solid State Power Amplifier
(SSPA) design. In addition to hard design specifications, the current thesis also
considers less tangible specifications, such as graceful degradation, time tomarket and
ease of use, as well as alternative design approaches, such as fuzzy logic approaches.
With a suitable technology approach determined, a selection of a suitable RF output
device(s) is considered. As the demand for new communication services continues
to increase, requiring tighter specifications and reduced product delivery time scales,
then the ability to accurately and quickly compare available RF PA devices from a
range of device technologies or devices from different manufacturers, at both the system
and component level, makes such a selection paramount. In this thesis, simplememoryless
(AmplitudeModulation/AmplitudeModulation (AM/AM) only) and
Quasi-Memoryless (QM) Behavioural Models (BMs) (AM/AM combined with Amplitude
Modulation/Phase Modulation (AM/PM)) are reviewed, extended and improved
upon, with up to 20 dB Normalised Mean Squared Error (NMSE) modelling
improvement achieved over a range of technologies, allowing effective RF PA device selection using these newly developed simple and fast models. This thesis uses recent
existing accurate and powerful semi-physical memoryless BMs, suited to RF PA
devices, and develops and extends their use for QM modelling. The trade-off from
the improvement in the overall accuracy is some further simple processing steps. Furthermore,
this thesis also provides a comparison of other models, presented in the
literature. The improved simple RF PA device models and extension techniques presented
in this thesis show, via simulation and measurement, that the new models are
suitable for use over a wide range. Lineariser improvements, linked to the accuracy
improvements of the proposed models of this thesis, are also investigated, showing
further benefits from this research.
Physically based simple QM BMs are also used to model thermal and bias network
memory effects, which are becomingmore relevant tomodern communication services
that use wider bandwidths, enabling the impacts of RF PA device memory effects to be
determined and compared.
The feasibility of the developed models and improvements are also utilised in the simulation
of a low cost RF PA lineariser. With the trend to smaller localised low cost
and power RF mobile wireless repeater cells being away from larger more expensive
and complex hardware, used to perform linearisation, this thesis presents a trade-off
between complexity and linearisation performance and demonstrates, through modelling
and simulation, that 8-10 dB improvement in linearisation performance is achievable
with the use of the newly developed models.Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 201
Machine Learning Meets Communication Networks: Current Trends and Future Challenges
The growing network density and unprecedented increase in network traffic, caused by the massively expanding number of connected devices and online services, require intelligent network operations. Machine Learning (ML) has been applied in this regard in different types of networks and networking technologies to meet the requirements of future communicating devices and services. In this article, we provide a detailed account of current research on the application of ML in communication networks and shed light on future research challenges. Research on the application of ML in communication networks is described in: i) the three layers, i.e., physical, access, and network layers; and ii) novel computing and networking concepts such as Multi-access Edge Computing (MEC), Software Defined Networking (SDN), Network Functions Virtualization (NFV), and a brief overview of ML-based network security. Important future research challenges are identified and presented to help stir further research in key areas in this direction
High-Power Microwave/ Radio-Frequency Components, Circuits, and Subsystems for Next-Generation Wireless Radio Front-Ends
As the wireless communication systems evolve toward the future generation, intelligence will be the main signature/trend, well known as the concepts of cognitive and software-defined radios which offer ultimate data transmission speed, spectrum access, and user capacity. During this evolution, the human society may experience another round of `information revolution\u27. However, one of the major bottlenecks of this promotion lies in hardware realization, since all the aforementioned intelligent systems are required to cover a broad frequency range to support multiple communication bands and dissimilar standards. As the essential part of the hardware, power amplifiers (PAs) capable of operating over a wide bandwidth have been identified as the key enabling technology. This dissertation focuses on novel methodologies for designing and realizing broadband high-power PAs, their integration with high-quality-factor (high-Q) tunable filters, and relevant investigations on the reliabilities of these tunable devices. It can be basically divided into three major parts:
1.Broadband High-Efficiency Power Amplifiers. Obtaining high PA efficiency over a wide bandwidth is very challenging, because of the difficulty of performing broadband multi-harmonic matching. However, high efficiency is the critical feature for high-performance PAs due to the ever-increasing demands for environmental friendliness, energy saving, and longer battery life. In this research, novel design methodologies of broad-band highly efficient PAs are proposed, including the first-ever mode-transferring PA theory, novel matching network topology, and wideband reconfigurable PA architecture. These techniques significantly advance the state-of-the-art in terms of bandwidth and efficiency.
2.Co-Design of PAs and High-Q Tunable Filters. When implementing the intelligent communication systems, the conventional approach based on independent RF design philosophy suffers from many inherent defects, since no global optimization is achieved leading to degraded overall performance. An attractive method to solve these difficulties is to co-design critical modules of the transceiver chain. This dissertation presents the first-ever co-design of PAs and tunable filters, in which the redundant inter-module matching is entirely eliminated, leading to minimized size & cost and maximized overall performance. The saved hardware resources can be further transferred to enhance system functionalities. Moreover, we also demonstrate that co-design of PAs and filters can lead to more functionalities/benefits for the wireless systems, e.g. efficient and linear amplification of dual-carrier (or multi-carrier) signals.
3.High-Power/Non-Linear Study on Tunable Devices. High-power limitation/power handling is an everlasting theme of tunable devices, as it determines the operational life and is the threshold for actual industrial applications. Under high-power operation, the high RF voltage can lead to failures like tuners\u27 mechanical deflections and gas discharge in the small air spacing of the cavity. These two mechanisms are studied independently with their instantaneous and long-term effects on the device performance. In addition, an anti-biased topology of electrostatic RF MEMS varactors and tunable filters is proposed and experimentally validated for reducing the non-linear effect induced by bias-noise. These investigations will enlighten the designers on how to avoid and/or minimize the non-ideal effects, eventually leading to longer life cycle and performance sustainability of the tunable devices
Nonlinear Characterization and Modeling of Radio-Frequency Devices and Power Amplifiers with Memory Effects
Despite the fast development of telecommunications systems experienced during the last two decades, much progress is expected in the coming years with the introduction of new solutions capable of delivering fast data-rates and ubiquitous connectivity. However, this development can only happen through the evolution of radio-frequency systems, which should be capable of working at high-power and high-speed. At the same time, the power dissipation of these systems should be minimized. In this dissertation, methods for the characterization and modeling of transistors and power amplifiers are presented, along with the necessary nonlinear measurements techniques. In particular, dynamic electrical effects, originated by the properties of the semiconductor materials and by the system configurations, are investigated. Consequently, these phenomena, which cannot be ignored to obtain the wanted performance, are empirically identified and included in models for Gallium Nitride (GaN) transistors and power amplifiers driven by a dynamic voltage supply