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1
Tallmarken, Manne. "Digital Predistortion for Broadcast FM repeaters." Thesis, KTH, Signalbehandling, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-53778.
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This thesis presents the design and implementation of a memoryless and adaptive digital predistorter used to linearize a power amplier. Specically, it deals with the implementation of a so-called constantgain predistorter, based on a lookup table, on a digital signal processing board built around an FPGA. The board also has two analog-to-digital converters, two digital-to-analog converters and a PIC microcontroller. By means of a high speed USB interface, input/output data to/from the system can be captured and sent to a PC. The adaptation of the constant-gain predistorter is implemented in Matlab by means of comparing the input and output data. When a new lookup table is ready, it is sent to the board for an update. By stimulating the system with a two-tone signal with center frequency of 162:5 MHzand tone spacing of1 MHz , the third order intermodulation product (IM3) was decreased by28 dB. By stimulating the system with an IS95 CDMA signal with center frequency of 162 :5 MHzand channel width of1:3 MHz , the power of the distortion right next to the channel edges were decreased by 24:7 dB.
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Waegemans, R. "Digital electronic predistortion for optical communications." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/20007/.
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The distortion of optical signals has long been an issue limiting the performance of communication systems. With the increase of transmission speeds the effects of distortion are becoming more prominent. Because of this, the use of methods known from digital signal processing (DSP) are being introduced to compensate for them. Applying DSP to improve optical signals has been limited by a discrepancy in digital signal processing speeds and optical transmission speeds. However high speed Field Programmable Gate Arrays (FPGA) which are sufficiently fast have now become available making DSP experiments without costly ASIC implementation possible for optical transmission experiments. This thesis focuses on Look Up Table (LUT) based digital Electronic Predistortion (EPD) for optical transmission. Because it is only one out of many possible implementations of EPD, it has to be placed in context with other EPD techniques and other distortion combating techniques in general, especially since it is possible to combine the different techniques. Building an actual transmitter means that compromises and decisions have to be made in the design and implementation of an EPD based system. These are based on balancing the desire to achieve optimal performance with technological and economic limitations. This is partly done using optical simulations to asses the performance. This thesis describes a novel experimental transmitter that has been built as part of this research applying LUT based EPD to an optical signal. The experimental transmitter consists of a digital design (using a hardware description language) for a pair of FPGAs and an analogue optical/electronic setup including two standard DAC integrated circuits. The DSP in the transmitter compensated for both chromatic dispersion and self phase modulation. We achieved transmission of 10.7 Gb/s non-return-to-zero (NRZ) signals with a +4 dBm launch power over 450 km keeping the required optical-signal-to-noise-ratio (OSNR) for a bit-error-rate of 2x10^{-3} below 11 dB. In doing so we showed experimentally, for the first time, that nonlinear effects can be compensated with this approach and that the combination of FPGA-DAC is a viable approach for an experimental setup.
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Karlsson, Robert. "Digital predistortion of semi-linear power amplifier." Thesis, Linköping University, Department of Electrical Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2617.
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In this thesis, a new way of using predisortion for linearization of power amplifiers is evaluated. In order to achieve an adequate power level for the jamming signal, power amplifiers are used in military jamming systems. Due to the nonlinear characteristic of the power amplifier, distortion will be present at the output. As a consequence, unwanted frequencies are subject to jamming. To decrease the distortion, linearization of the power amplifier is necessary.
In the system of interest, a portion of the distorted power amplifier output signal is fed back. Using this measurement, a predistortion signal is synthesized to allow suppression of the unwanted frequency components. The predistortion signal is updated a number of times in order to achieve a good outcome. Simulations are carried out in Matlab for testing of the algorithm.
The evaluation of the new linearization technique shows promising results and that good suppression of distortion components is achieved. Furthermore, new predistortion features are possible to implement, such as predistorsion in selected frequency bands. However, real hardware testing needs to be carried out to confirm the results.
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Ba, Seydou Nourou. "Efficient digital baseband predistortion for modern wireless handsets." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31760.
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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010.Committee Chair: Altunbasak, Yucel; Committee Co-Chair: Zhou, G. Tong; Committee Member: Al-Regib, Ghassan; Committee Member: Kenney, James Stevenson; Committee Member: Ma, Xiaoli; Committee Member: Pan, Ronghua. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Johnson, Daniel Eric. "Adaptive Digital Predistortion with Applications for LMDS Systems." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/34964.
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A limiting factor in the widespread deployment of LMDS systems is the limited distance of current systems. Rain attenuation and limited transmitter power are the primary causes of the limited distance. Adaptive digital predistortion is presented as a method of increasing effective transmitter power.
A background on LMDS link design, non-linear amplification, and predistortion is presented to assist the reader. A developed simulation uses AM-AM and AM-PM characteristics obtained from laboratory measurements of a 28 GHz amplifier to determine the effect of several predistortion implementation options and to confirm the feasibility of the proposed architecture.
The potential impact of this predistortion architecture on LMDS system design is considered. The presented multi-stage predistortion architecture is found to be capable of implementation at Msymbol/second rates utilizing a FPGA or custom IC and a moderate speed digital signal processor.
Master of Science
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Ding, Lei. "Digital predistortion of power amplifiers for wireless applications." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-04022004-020955/unrestricted/ding%5Flei%5F200405%5Fphd.pdf.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2004.J. Stevenson Kenney, Committee Member ; G. Tong Zhou, Committee Chair ; W. Marshall Leach, Committee Member ; Ye (Geoffrey) Li, Committee Member ; Jianmin Qu, Committee Member. Includes bibliographical references (leaves 100-103).
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Giesbers, David Mathew. "Adaptive digital polynomial predistortion linearisation for RF power amplifiers." Thesis, University of Canterbury. Electrical and Computer Engineering, 2008. http://hdl.handle.net/10092/2044.
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Development of linear modulation schemes has opened the way for spectrally efficient, high speed digital communication systems for voice and data applications. A trend has been to develop ultra wide and wide bandwidth modulation formats, which has meant feedback linearisation schemes (both analogue and digital) are no longer effective. This has in turn led to a number of approaches that involve predistorting the signal prior to amplification, with a characteristic that is the inverse to that of the power
amplifier (PA). This thesis presents a polynomial based predistortion for linearisation of an RF PA. The predistortion characteristic is adaptive, using the LMS algorithm
to minimise the mean squared error between output of the PA, and a scaled version of the baseband signal. This system can reduce third-order intermodulation by 40 dB when running in real time.
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Barradas, Filipe Miguel Esturrenho. "Modeling and digital predistortion of wireless radio frequency transmitters." Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/18661.
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Doutoramento em Engenharia ElectrotécnicaNos atuais sistemas de telecomunicações, os transmissores de rádio-frequência são desenvolvidos tendo maioritariamente em conta a eficiência da conversão da potência fornecida da fonte em potência de rádio-frequência. Este tipo de desenho resulta em amplificadores de potência com características de transmissão não-lineares, que distorcem severamente o envelope de informação no processo de amplificação, gerando distorção fora da banda. Para corrigir este problema utiliza-se um processo de compensação não linear, sendo que a pré-distorção digital se tem favorecido pela sua flexibilidade e precisão. Este método é tipicamente aplicado de uma forma cega, por força bruta até se obter a compensação desejada. No entanto, quando o método se mostra ineficaz, como se verificou em amplificadores de potência baseados em transístores de nitreto de gálio, é difícil saber o que modificar nos sistemas para os tornar de novo úteis. De forma a compreender e desenhar sistemas de pré-distorção digital robustos é necessário, por um lado, perceber o comportamento dos amplificadores de rádio-frequência, por outro, perceber as limitações e relações entre os modelos digitais e o comportamento real do amplificador. Nesse sentido, esta tese explora e descreve estas relações de forma a suportar a escolha de modelos de pré-distorção, desenvolve novos modelos baseados no comportamento dos transístores, e propõe métodos de caracterização para os amplificadores de RF.
In current telecommunication systems, the main concern when developing the radio frequency transmitter is power efficiency. This type of design generally leads to a highly nonlinear transmission characteristic, mainly due to the radio frequency power amplifier. This nonlinear transmission severely distorts the information envelope, leading to spectral regrowth, out-of-band distortion. To correct this problem a nonlinear compensation process is employed. For this application, digital predistortion is generally favored for its flexibility and accuracy. Digital predistortion is mostly applied in a blind manner, using brute force until the desired compensation is achieved. Because of this, when the method fails, as it has in gallium nitride based power amplifiers, it is difficult to modify the system to achieve the desired results. To understand and design robust predistortion systems, it is both necessary to have knowledge of the power amplifiers’ behavior, on one hand, and understand the limitations and relations between the digital models and these behaviors, on the other. To do this, this thesis explores and describes these relationships, granting support to the digital predistortion model choice, it further develops new predistortion models based on the physics of the transistors’ behaviors, and it proposes methods for the characterization of radio frequency power amplifiers.
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Huang, Jeffrey B. "Exploring predistortion training algorithms in a Cartesian feedback-trained digital predistortion system for RF power amplifier linearization." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36799.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 117-118).
A Cartesian feedback-trained digital predistortion system for RF power amplifier linearization offers many advantages with its combination of two different linearization techniques. This thesis describes such a system, focusing on the important issue of predistorter training. It examines and analyzes in great detail the promising loop filter pre-charging optimization and the tradeoffs associated with such training, developing a model that provides many valuable system design insights. In order establish a means to experimentally verify the theory and explore predistortion training algorithms, this thesis presents the design, development, and characterization of a mock-up prototype that models the essential features of the actual Cartesian feedback-trained digital predistortion system. The mock-up serves as a standalone proof-of-concept system that demonstrates the benefits and tradeoffs of loop filter pre-charging in predistorter training. It confirms the theory while also revealing practical issues pertaining to the limits on performance.
by Jeffrey B. Huang.
M.Eng.
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Mengozzi, Mattia. "Direct Learning Power Amplifier Digital Predistortion using Multi-Objective Optimization." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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All’interno di una stazione radio base l’amplificatore di potenza a radiofrequenza (RF PA) è di gran lunga l’elemento più importante dal punto di vista energetico, dato che il suo compito è quello di fornire al segnale la potenza necessaria per essere trasmesso. Di conseguenza sono state sviluppate numerose tecniche per aumentare l’efficienza e la linearità dei PA. Ad esempio, le architetture di Envelope Tracking (ET) migliorano l’efficienza complessiva del sistema modulando la tensione di alimentazione in banda base (LF), mentre la digital predistortion (DPD) ne incrementa la linearità distorcendo il segnale RF in ingresso.
In generale, possiamo dire che il comportamento di un transistor dipende dalle terminazioni che ad esso vengono mostrate alla frequenza della portante e alle sue armoniche, inclusa la dc. L’obiettivo della tesi è quello di fornire un approccio generale al problema dell’ottimizzazione di un RF PA: in cui lo scopo sia manipolare le terminazioni del dispositivo per massimizzare una o più figure di merito (FoM), come la potenza media traferita al carico, l'efficienza e linearità complessiva. Quindi viene proposto un metodo di ottimizzazione numerica multiobiettivo che ottimizzi una o più FoM di un PA manipolando il segnale si sorgente RF e quello di alimentazione LF. Il problema viene trattato come un metodo generalizzato di DPD, dove i coefficienti complessi del predistorsore rappresentano le variabili manipolate dall'algoritmo di ottimizzazione numerica.
Vengono quindi mostrati dei risultati di simulazione, comparando le prestazioni ottenute con questo metodo con quelle di un ET PA linearizzato con DPD basata su un'architettura di learning indiretto (ILA DPD). Infine, vengono mostrati dei risultati preliminari di misura su un PA al nitruro di gallio (GaN), in cui viene ottimizzato solo segnale di sorgente RF. I risultati raggiunti mostrano come questa tecnica possa superare le prestazioni ottenibili con una classica ILA DPD.
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Vieira, Luis Carlos. "Digital baseband modelling and predistortion of radio over fibre links." Thesis, University of Kent, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.594103.
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Radio-over-Fibre (RoF) is an alternative solution for the distribution of RF communication signals between a central base station and remote antenna units (RAUs) and can be seen as an enabling · technique to increase the coverage area of broadband wireless access networks. However, the nonlinear distortion introduced by the ReF link may impose serious limitations on the system performance, especial ly considering the high peak-Ie-average power ratio PAPR of complex signal formats, such as orthogonal frequency-division multiplexing (OFDM) and Widehand Code Division Multiple Access (WCD:MA). The objectives of this research are to study and model the nonlinearities of ReF links and to investigate a predistortion approach for this type of link, considering an environment of broadband wireless services. A baseband-behavioural-based modelling approach has been adopted for the nonlinear modelling studies of RoF links and the performance of an off- line training digital predistortion approach to RoF links has been experimentally investigated. The application of memory polynomials (MPs) to the baseband behavioural modelling of both nonlinear and memory effects of directly modulated RoF links has been reported. The robustness of this model as a baseband representation of nonlinear RoF links was demonstrated considering different operating conditions and model parameters. with excellent modelling accuracy reported for most of the experimental cases. The performance of a memory-po lynomial-based digital predistortion technique fo r OFDM-RF RoF links has been investigated within the RF frequency range from 1.85 to 3.7 GHz, up to 20 link lengths. For example, the spectral regrowth was reduced by around 17.5 dB and the = error vector magnitude (EVM) from 8.4 % to 1.4 % for a 2A7·GHz link case. This work represents the first experimental demonstration of the memory-polynomial·based digital predistortion approach to OFDM-RF RoF links using an off-line least-squares-based identification method.
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Andersson, Erik, and Christian Olsson. "Linearization of Power Amplifier using Digital Predistortion, Implementation on FPGA." Thesis, Linköpings universitet, Elektroniksystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-112258.
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The purpose of this thesis is to linearize a power amplifier using digital predistortion. A power amplifier is a nonlinear system, meaning that when fed with a pure input signal the output will be distorted. The idea behind digital predistortion is to distort the signal before feeding it to the power amplifier. The combined distortions from the predistorter and the power amplifier will then ideally cancel each other. In this thesis, two different approaches are investigated and implemented on an FPGA. The first approach uses a nonlinear model that tries to cancel out the nonlinearities of the power amplifier. The second approach is model-free and instead makes use of a look-up table that maps the input to a distorted output. Both approaches are made adaptive so that the parameters are continuously updated using adaptive algorithms. First the two approaches are simulated and tested thoroughly with different parameters and with a power amplifier model extracted from the real amplifier. The results are shown satisfactory in the simulations, giving good linearization for both the model and the model-free technique. The two techniques are then implemented on an FPGA and tested on the power amplifier. Even though the results are not as well as in the simulations, the system gets more linear for both the approaches. The results vary widely due to different circumstances such as input frequency and power. Typically, the distortions can be attenuated with around 10 dB. When comparing the two techniques with each other, the model-free method shows slightly better results.
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Eriksson, Marcus. "Analysis of Digital Predistortion in a Wideband Arbitrary Waveform Generator." Thesis, Linköpings universitet, Kommunikationssystem, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-123410.
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Digital predistortion is a signal processing technique used to remove undesired distortions caused by nonlinear system effects. This method is predominately used to linearize power amplifiers in communication systems in order to achieve efficient transmitter circuits. However, the technique can readily be applied to cancel undesired nonlinear behavior in other types of systems. This thesis investigates the effectiveness of digital predistortion in the context of a wideband arbitrary waveform generator. A theoretical foundation discussing nonlinear system models, predistortion architectures and system identification methods is complemented with a simulation study and followed by verification on a real system. The best predistorter is able to fully suppress the undesired distortions for any fixed two-tone sinusoidal signal. Furthermore, the results indicate the existence of a wideband predistorter which yield acceptable suppression over a frequency range of several hundred MHz.Digital predistorsion är en signalbehandlingsteknik som används för att undertrycka oönskade distorsioner orsakade av icke-linjära effekter i elektriska system. Denna metod används i huvudsak för att linjärisera effektförstärkare i kommunikationssystem för att erhålla effektiva sändarkedjor men tekniken kan utan större problem även tillämpas på andra typer av icke-linjära system. Denna uppsats undersöker i vilken utsräckning digital predistorsion kan användas för att undertrycka oönskade signaldistorsioner i en bredbandig signalgenerator. Uppsatsen presenterar en bakgrund som utgår ifrån teorin om icke-linjära systemmodeller, arkiteturer för predistorsion och systemidentifieringsmetoder. En kvantitativ studie i en simuleringsmiljö åtföjs av en utvärdering på ett verkligt system. Det bästa predistorsionssystemet åstadkommer en fullständig linjärisering i testfallet med en fix tvåtonssignal. Resultaten indikerar även att det existerar ett system som linjäriserar signaler i ett frekvensområde som uppgår till hundratals MHz.
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Haskins, Christopher Burke. "Diode Predistortion Linearization for Power Amplifier RFICs in Digital Radios." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/31888.
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The recent trend in modern information technology has been towards the increased use of
portable and handheld devices such as cellular telephones, personal digital assistants (PDAs),
and wireless networks. This trend presents the need for compact and power efficient radio
systems. Typically, the most power inefficient device in a radio system is the power amplifier
(PA). PA inefficiency requires increased battery reserves to supply the necessary DC bias
current, resulting in larger devices. Alternatively, the length of time between battery charges is
reduced for a given battery size, reducing mobility.
In addition, communications channels are becoming increasingly crowded, which presents the need for improved bandwidth efficiency. In order to make more efficient use of the frequency spectrum allocated for a particular system, there is a push towards complex higher order digital modulation schemes in modern radio systems, resulting in stricter linearity requirements on the system. Since power efficient amplifiers are typically nonlinear, this poses a major problem in realizing a bandwidth and power efficient radio system. However, by employing various linearization techniques, the linearity of a high efficiency PA may be improved.
The work presented in this thesis focuses on diode predistortion linearization, particularly for PA
RFICs in digital radios. Background discussion on common linearization techniques available to
the PA designer is presented. In addition, a discussion of traditional and modern methods of
nonlinearity characterization is presented, illustrating the nonlinear PA effects on a modulated
signal. This includes the use of two-tone analysis and the more modern envelope analysis. The operation of diode predistortion linearizers is discussed in detail, along with diode optimization
procedures for PA linearization with minimum impact on return loss and gain. This diode
optimization is effective in improving the ability to integrate the predistorter into a single,
linearized PA RFIC chip. MESFET and HBT based diode linearizers are studied for use with
corresponding MESFET and HBT based PAs in the 2.68 GHz and 1.95 GHz frequency bands,
respectively. Results show an improvement in adjacent channel power ratio (ACPR) due to the
linearizer in both MESFET and HBT cases. A fully integrated 1.95 GHz linearizer and PA RFIC
in HBT technology is also presented. Design considerations, simulations, and layouts for this
design are presented. Finally, several recommendations are made for continued research in this
area.
Master of Science
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Naraharisetti, Naveen. "Linearization of Concurrent Dual-Band Power Amplifier Using Digital Predistortion." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406151856.
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Hadi, Muhammad Usman. "Digital predistortion for compensation of nonlinearities in Radio over Fiber Links." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
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In order to cope up with the ever increasing demand for larger transmission bandwidth, Radio over Fiber technology is a very beneficial solution. These systems are expected to play a major role within future fifth generation wireless networks due to their inherent capillary distribution properties.
Nonlinear compensation techniques are becoming increasingly important to improve the performance of telecommunication channels by compensating for channel nonlinearities. Indeed, significant bounds on the technology usability and performance degradation occur due to nonlinear characteristics of optical transmitter, nonlinear generation of spurious frequencies, which, in the case of RoF links exploiting Directly Modulated Lasers , has the combined effect of laser chirp and optical fiber dispersion among its prevailing causes.
The purpose of the research is to analyze some of the main causes of harmonic and intermodulation distortion present in Radio over Fiber (RoF) links, and to suggest a solution to reduce their effects, through a digital predistortion technique.
Predistortion is an effective and interesting solution to linearize and this allows to demonstrate that the laser’s chirp and the optical fiber’s dispersion are the main causes which generate harmonic distortion. The improvements illustrated are only theoretical, based on a feasibility point of view. The simulations performed lead to significant improvements for short and long distances of radio over fiber link lengths.
The algorithm utilized for simulation has been implemented on MATLAB. The effects of chirp and fiber nonlinearity in a directly modulated fiber transmission system are investigated by simulation, and a cost effective and rather simple technique for compensating these effects is discussed. A detailed description of its functional model is given, and its attractive features both in terms of quality improvement of the received signal, and cost effectiveness of the system are illustrated.
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Gilabert, Pinal Pere Lluís. "Multi Look-Up Table Digital Predistortion for RF Power Amplifier Linearization." Doctoral thesis, Universitat Politècnica de Catalunya, 2008. http://hdl.handle.net/10803/6915.
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Aquesta Tesi Doctoral se centra en el disseny d'un nou linealitzador de Predistorsió Digital (Digital Predistortion - DPD) capaç de compensar la dinàmica i els efectes no lineals introduïts pels Amplificadors de Potència (Power Amplifiers - PAs). Un dels trets més rellevants d'aquest nou predistorsionador digital i adaptatiu consisteix en ser deduïble a partir d'un model de PA anomenat Nonlinear Auto-Regressive Moving Average (NARMA). A més, la seva arquitectura multi-LUT (multi-Taula) permet la implementació en un dispositiu Field Programmable Gate Array (FPGA).La funció de predistorsió es realitza en banda base, per tant, és independent de la banda freqüencial on es durà a terme l'amplificació del senyal de RF, el que pot resultar útil si tenim en compte escenaris multibanda o reconfigurables. D'altra banda, el fet que aquest DPD tingui en compte els efectes de memòria introduïts pel PA, representa una clara millora de les prestacions aconseguides per un simple DPD sense memòria. En comparació amb d'altres DPDs basats en models més computacionalment complexos, com és el cas de les xarxes neuronals amb memòria (Time-Delayed Neural Networks - TDNN), la estructura recursiva del DPD proposat permet reduir el nombre de LUTs necessàries per compensar els efectes de memòria del PA. A més, la seva estructura multi-LUT permet l'escalabilitat, és a dir, activar or desactivar les LUTs que formen el DPD en funció de la dinàmica que presenti el PA.
En una primera aproximació al disseny del DPD, és necessari identificar el model NARMA del PA. Un dels majors avantatges que presenta el model NARMA és la seva capacitat per trobar un compromís entre la fidelitat en l'estimació del PA i la complexitat computacional introduïda. Per reforçar aquest compromís, l' ús d'algoritmes heurístics de cerca, com són el Simulated Annealing o els Genetic Algorithms, s'utilitzen per trobar els retards que millor caracteritzen la memòria del PA i per tant, permeten la reducció del nombre de coeficients necessaris per caracteritzar-la. Tot i així, la naturalesa recursiva del model NARMA comporta que, de cara a garantir l'estabilitat final del DPD, cal dur a terme un estudi previ sobre l'estabilitat del model.
Una vegada s'ha obtingut el model NARMA del PA i s'ha verificat l'estabilitat d'aquest, es procedeix a l'obtenció de la funció de predistorsió a través del mètode d'identificació predictiu. Aquest mètode es basa en la continua identificació del model NARMA del PA i posteriorment, a partir del model obtingut, es força al PA perquè es comporti de manera lineal. Per poder implementar la funció de predistorsió en la FPGA, cal primer expressar-la en forma de combinacions en paral·lel i cascada de les anomenades Cel·les Bàsiques de Predistorsió (BPCs), que són les unitats fonamentals que composen el DPD. Una BPC està formada per un multiplicador complex, un port RAM dual que actua com a LUT (taula de registres) i un calculador d'adreces. Les LUTs s'omplen tenint en compte una distribució uniforme dels continguts i l'indexat d'aquestes es duu a terme mitjançant el mòdul de l'envoltant del senyal.
Finalment, l'adaptació del DPD consisteix en monitoritzar els senyals d'entrada i sortida del PA i anar duent a terme actualitzacions periòdiques del contingut de les LUTs que formen les BPCs. El procés d'adaptació del contingut de les LUTs es pot dur a terme en la mateixa FPGA encarregada de fer la funció de predistorsió, o de manera alternativa, pot ser duta a terme per un dispositiu extern (com per exemple un DSP - Digital Signal Processor) en una escala de temps més relaxada. Per validar l'exposició teòrica i provar el bon funcionalment del DPD proposat en aquesta Tesi, es proporcionen resultats tant de simulació com experimentals que reflecteixen els objectius assolits en la linealització del PA. A més, certes qüestions derivades de la implementació pràctica, tals com el consum de potència o la eficiència del PA, són també tractades amb detall.
This Ph.D. thesis addresses the design of a new Digital Predistortion (DPD) linearizer capable to compensate the unwanted nonlinear and dynamic behavior of power amplifiers (PAs). The distinctive characteristic of this new adaptive DPD is its deduction from a Nonlinear Auto Regressive Moving Average (NARMA) PA behavioral model and its particular multi look-up table (LUT) architecture that allows its implementation in a Field Programmable Gate Array (FPGA) device.
The DPD linearizer presented in this thesis operates at baseband, thus becoming independent on the final RF frequency band and making it suitable for multiband or reconfigurable scenarios. Moreover, the proposed DPD takes into account PA memory effects compensation which represents
an step forward in overcoming classical limitations of memoryless predistorters. Compared to more computational complex DPDs with dynamic compensation, such Time-Delayed Neural Networks (TDNN), this new DPD takes advantage of the recursive nature of the NARMA structure to relax the number of LUTs required to compensate memory effects in PAs. Furthermore, its parallel multi-LUT architecture is scalable, that is, permits enabling or disabling the contribution of specific LUTs depending on the dynamics presented by a particular PA.
In a first approach, it is necessary to identify a NARMA PA behavioral model. The extraction of PA behavioral models for DPD linearization purposes is carried out by means of input and output complex envelope signal observations. One of the major advantages of the NARMA structure regards its capacity to deal with the existing trade-off between computational complexity and accuracy in PA behavioral modeling. To reinforce this compromise, heuristic search algorithms such the Simulated Annealing or Genetic Algorithms are utilized to find the best sparse delays that permit accurately reproducing the PA nonlinear dynamic behavior. However, due to the recursive nature of the NARMA model, an stability test becomes a previous requisite before advancing towards DPD linearization.
Once the PA model is identified and its stability verified, the DPD function is extracted applying a predictive predistortion method. This identification method relies just on the PA NARMA model and consists in adaptively forcing the PA to behave as a linear device. Focusing in the DPD implementation, it is possible to map the predistortion function in a FPGA, but to fulfill this objective it is first necessary to express the predistortion function as a combined set of LUTs.
In order to store the DPD function into a FPGA, it has to be stated in terms of parallel and cascade Basic Predistortion Cells (BPCs), which are the fundamental building blocks of the NARMA based DPD. A BPC is formed by a complex multiplier, a dual port RAM memory block acting as LUT and an address calculator. The LUT contents are filled following an uniform spacing procedure and its indexing is performed with the amplitude (modulus) of the signal's envelope.
Finally, the DPD adaptation consists in monitoring the input-output data and performing frequent updates of the LUT contents that conform the BPCs. This adaptation process can be carried out in the same FPGA in charge of performing the DPD function, or alternatively can be performed by an external device (i.e. a DSP device) in a different time-scale than real-time operation.
To support all the theoretical design and to prove the linearization performance achieved by this new DPD, simulation and experimental results are provided. Moreover, some issues derived from practical experimentation, such as power consumption and efficiency, are also reported and discussed within this thesis.
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Isaksson, Magnus. "Radio Frequency Power Amplifiers : Behavioral Modeling, Parameter Reduction, and Digital Predistortion." Doctoral thesis, KTH, Signalbehandling, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-24198.
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This work considers behavioral modeling, parameter-reduction, and digital predistortion of radio frequency power amplifiers. Due to the use of modern digital modulation methods, contemporary power amplifiers are frequently subjected to signals characterized by considerable bandwidths and fast changing envelopes. As a result, traditional quasi-memoryless amplitudeto-amplitude (AM/AM) and amplitude-to-phase (AM/PM) characteristics are no longer sufficient to describe and model the behavior of power amplifiers; neither can they be successfully used for linearization. In this thesis, sampled input and output data are used for identification and validation of several block structure models with memory. The time-discrete Volterra model, the Wiener model, the Hammerstein model, and the radial-basis function neural network are all identified and compared with respect to in-band and out-of-band errors. Two different signal types (multitones and noise), with different powers, peak-to-average ratios, and bandwidths have been used as inputs to the amplifier. Furthermore, two different power amplifiers were investigated, one designed for third generation mobile telecommunication systems and one for second generation systems. A stepped three-tone measurement technique based on digitally modulated baseband signals is also presented. The third-order Volterra kernel parameters were determined from identified intermodulation products. The symmetry properties of the Volterra kernel along various portions of the three dimensional frequency space were analyzed and compared with the symmetry of the Wiener and Hammerstein systems.QC 20100824
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Deleu, Thibault. "Digital predistortion and equalization of the non-linear satellite communication channel." Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209212.
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In satellite communications, non-linear interference is created by the non-linear power amplifier aboard the satellite. Even in the case of a memoryless power amplifier, the channel is a non-linear system with memory due to the presence of linear filters on ground and aboard the satellite. The non-linear interference degrades the system performance, especially when considering high-order modulations or in case of several signals being amplified by the same power amplifier. In this thesis, we have proposed algorithms at the transmitter and at the receiver to digitally compensate this interference. In particular, a new predistortion algorithm has been proposed, which significantly improves state-of-the-art algorithms. Since the complexity of this algorithm is an issue, low-complexity algorithms have also been proposed and achieve almost the same performance as the initial algorithm. We have also proposed joint predistortion and turbo-equalization algorithms to further improve the system performance. / En communications par satellite, de l’interférence non-linéaire est créée par l’amplificateur de puissance non-linéaire à bord du satellite. Même si l’amplificateur peut être considéré comme sans mémoire, le canal est malgré tout un système non-linéaire avec mémoire de par la présence de filtres linéaires au sol ou à bord du satellite. L'interférence non-linéaire dégrade les performances du système, en particulier lorsqu’on considère des modulations d’ordre élevé ou plusieurs signaux amplifiés par le même amplificateur de puissance. Dans cette thèse, nous avons proposé des algorithmes à l’émetteur et au récepteur pour compenser numériquement cette interférence. En particulier, nous avons proposé un nouvel algorithme de prédistorsion qui améliore de façon significative les algorithmes de l’état-de-l’art. La complexité de l’algorithme étant très élevée, nous avons proposé des algorithmes de plus faible complexité atteignant pratiquement les mêmes performances par rapport à l’algorithme initial. Nous avons aussi proposé des algorithmes de prédistorsion et d’égalisation conjointes, permettant d'atteindre des performances plus élevées qu'avec la prédistorsion seule.Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Lee, Kok Chew. "Analysis and implementation of adaptive digital predistortion techniques for transmitter linearisation." Thesis, University of Birmingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409072.
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Kim, Ji Woo. "A GENERALIZED ARCHITECTURE FOR THE FREQUENCY-SELECTIVE DIGITAL PREDISTORTION LINEARIZATION TECHNIQUE." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1339690468.
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Patel, Jayanti. "Adaptive digital predistortion linearizer for power amplifiers in military UHF satellite." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000230.
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Franco, Marcelo Jorge Herczfeld Peter R. "Wideband digital predistortion linearization of radio frequency power amplifiers with memory /." Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/485.
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Wang, Siqi. "Study on complexity reduction of digital predistortion for power amplifier linearization." Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC1011/document.
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Ce travail concerne la linéarisation des amplificateurs de haute puissance en utilisant la pré-distorsion numérique. L’amplificateur de haute puissance est un composant non-linéaire. La pré-distorsion numérique adaptative en bande de base est un technique efficace pour linéariser ses non-linéarités et ses effets de mémoire. Les modèles de la pré-distorsion numérique de basse complexité sont étudiés dans cette thèse. Un algorithme est proposé pour déterminer une structure optimale de modèle uni-étage ou multi-étage en prenant compte du compromis entre la précision de modélisation et la complexité. La structure cascadée, qui est avantageuse en complexité comparé avec celle d'uni-étage, est étudiée avec des méthodes d'identifications différentes. En termes d'implémentations expérimentales, l'étude d'impact des choix de gain différents est approfondie dans cette thèse. Toutes les études ont été évaluées par un amplificateur de puissance DohertyThis dissertation contributes to the linearization techniques of high power amplifier using digital predistortion method. High power amplifier is one of the most nonlinear components in radio transmitters. Unfortunately, for most current types of power amplifiers, a good efficiency is obtained at the price of a poor linearity especially with modern communication waveforms. Baseband adaptive digital predistortion is a powerful technique to linearize the power amplifiers and allows to push the power amplifier operation point towards its high efficiency region. Linearization of power amplifiers using digital predistortion with low complexities is the focus of this dissertation. An algorithm is proposed to determine an optimal model structure of single-stage or multi-stage predistorter according to a trade-off between modeling accuracy and model complexity. Multi-stage cascaded digital predistortions are studied with different identification methods, which have advantages on complexity of model identification compared with single-stage structure. The linearization performances are validated by experimental implementations on test bench. In terms of experimental implementations, this dissertation studies the impact of different gain choices on linearized power amplifier. All studies are evaluated with a Doherty power amplifier
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Bondar, Dmytro. "Advanced digital predistortion of power amplifiers for mobile and wireless communications." Thesis, University of Westminster, 2009. https://westminsterresearch.westminster.ac.uk/item/90vz6/advanced-digital-predistortion-of-power-amplifiers-for-mobile-and-wireless-communications.
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This research work focuses on improving the performances of digital predistorters while maintaining low computational complexity for mobile and wireless communication systems. Initially, the thesis presents the fundamental theory of power amplifiers, overview of existing linearisation and memory-effects compensation techniques and reveals the current issues in the field. Further, the thesis depicts the proposed solutions to the problems, including the developed in-band distortion modelling technique, model extraction methods, memoryless digital predistortion technique based on distortion components iterative injection, baseband equalisation technique for minimising memory effects, Matlab-ADS co-simulation system and adaptation circuit with an offline training scheme. The thesis presents the following contributions of the research work. A generalized in-band distortion modelling technique for predicting the nonlinear behaviour of power amplifiers is developed and verified experimentally. Analytical formulae are derived for calculating predistorter parameters. Two model extraction techniques based on the least-squares regression method and frequency-response analysis are developed and verified experimentally. The area of implementation and the trade-off between the methods are discussed. Adjustable memoryless digital predistortion technique based on the distortion components iterative injection method is proposed in order to overcome the distortion compensation limit peculiar to the conventional injection techniques. A baseband equalisation method is developed in order to provide compensation of memory effects for increasing the linearising performance of the proposed predistorter. A combined Matlab-ADS co-simulation system is designed for providing powerful simulation tools. An adaptation circuit is developed for the proposed predistorter for enabling its adaptation to environmental conditions. The feasibility, performances and computational complexity of the proposed digital predistortion are examined by simulations and experimentally. The proposed method is tuneable for achieving the best ratio of linearisation degree to computational complexity for any particular application.
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Eklund, Henrik. "Linearization of Resistive Digital-to-Analog Converter for RF-Applications Using Compensator and Digital Predistortion." Thesis, Linköpings universitet, Elektroniska Kretsar och System, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-177574.
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High-speed digital-to-analog converters are critical components in many radiofrequency (RF) applications. The resistive DAC (RDAC) architecture is suitable for high-speed implementation in extremely scaled digital circuit nodes. An RDAC core can be implemented as a resistance network and a digital block, consisting of inverters as drivers to the resistive network. One disadvantage of the architecture is the input code-dependent supply current. Combined with a non-zero supply network impedance, the code-dependent current will introduce non-linearity in the output voltage. One way to circumvent the problem is to use a high-performance voltage regulator, which counteracts the voltage variation in the impedance in the RDAC supply network. In this thesis work, two alternative solutions are investigated; Compensation with another signal-dependent impedance in parallel with the RDAC core to reduce the impedance variations and a digital predistorter (DPD) which corrects the non-linearities of RDAC output voltage. The investigated techniques can be used for improving the linearity of an RDAC in certain cases. The current compensation technique works best at low frequencies, while the DPD can be used for all frequencies to relax requirements on routing resistance or voltage regulation design.
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Trinh, Jessica. "ADS och Matlab för optimering av pre-distortion av effektförstärkare." Thesis, Linköpings universitet, Institutionen för systemteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-119222.
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This master’s thesis deals with integrating simulations using Agilents Electronic Design Automation tool ADS with customized Matlab scripts, for solving complex analog and digital radio architectures. In particular, it addresses predistortion, realized in the digital domain, of power amplifiers, modeled in the analog domain. The former is implemented in Matlab while the latter is implemented in ADS. Two versions of integrating the two systems have been tested: 1) Iterative approach on sample basis and 2) Scheduled batch solution by matrix inversion. The concept has been tested on two different PA configurations: 1) a standard class-AB PA and 2) a Doherty PA architecture. Evaluation has also been done on ADS ability to correctly simulate memory effects in PAs and on the actual DPD-algorithms ability to compensate for these memory effects. An integrated simulation environment for ADS and Matlab was successfully established within the work of this thesis. Matlab scripts, used in predistortion algorithms in the digital domain, could interact directly with component-based PA models, in an enclosed simulation system. The simulation results show that sample basis method is the most accurate, fast and reliable method to linearize a PA. The PA1 proved to be easier than the DPA to linearize, except for when being close to saturation where better IMD-suppression was achieved with the DPA. ADS is clearly able to simulate memory effects in the analog domain. At low gain-levels the applied compensating memory-algorithms showed a great improvement to the linearization of the output signal of the PA. At higher gain-levels though, the compensation for memory effects lost their efficiency because the non-linearity of the PA became too significant.
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Erdogdu, Gozde. "Linearization Of Rf Power Amplifiers By Using Memory Polynomial Digital Predistortion Technique." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614420/index.pdf.
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In modern wireless communication systems, new modulation types are introduced in order to support more users by considering spectral efficiency. These new signals are ensitive to nonlinearity when they have high peak to average ratio. The main part in the system that causes nonlinearity is the power amplifier. For power amplifiers, between linearity and efficiency, there is a trade-off. However, by using predistortion techniques, both linearity and efficiency
can be obtained. In this thesis, various predistortion methods are explained and memory polynomial digital predistortion is studied because of its great advantages. The results are obtained by simulations through MATLAB and experiments. An open loop test bench is built up with real amplifier. During experimental procedure, as input two tone signal, 8psk modulated signal and pi/2 bpsk modulated signal are used. Predistortion with memory and memoryless predistortion performances are compared and superiority of the predistortion with memory is shown. Predistortion performance with respect to memory depth and polynomial order is also studied. Moreover, predistortion model range is investigated through evaluation of performance by applying predistorter function estimated at a specific bandwidth and power to
other signals having different bandwidth and power. Besides these works, the details of predistortion algorithm and the problems that can be countered in practice are explained.
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Buckley, Richard James. "A digital signal processing-based predistortion technique for reduction of intermodulation distortion /." Online version of print, 1993. http://hdl.handle.net/1850/11455.
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Cabarkapa, Milan. "Digital predistortion of RF amplifiers using baseband injection for mobile broadband communications." Thesis, University of Westminster, 2014. https://westminsterresearch.westminster.ac.uk/item/8yq22/digital-predistortion-of-rf-amplifiers-using-baseband-injection-for-mobile-broadband-communications.
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Radio frequency (RF) power amplifiers (PAs) represent the most challenging design parts of wireless transmitters. In order to be more energy efficient, PAs should operate in nonlinear region where they produce distortion that significantly degrades the quality of signal at transmitter’s output. With the aim of reducing this distortion and improve signal quality, digital predistortion (DPD) techniques are widely used. This work focuses on improving the performances of DPDs in modern, next-generation wireless transmitters. A new adaptive DPD based on an iterative injection approach is developed and experimentally verified using a 4G signal. The signal performances at transmitter output are notably improved, while the proposed DPD does not require large digital signal processing memory resources and computational complexity. Moreover, the injection-based DPD theory is extended to be applicable in concurrent dual-band wireless transmitters. A cross-modulation problem specific to concurrent dual-band transmitters is investigated in detail and novel DPD based on simultaneous injection of intermodulation and cross-modulation distortion products is proposed. In order to mitigate distortion compensation limit phenomena and memory effects in highly nonlinear RF PAs, this DPD is further extended and complete generalised DPD system for concurrent dual-band transmitters is developed. It is clearly proved in experiments that the proposed predistorter remarkably improves the in-band and out-of-band performances of both signals. Furthermore, it does not depend on frequency separation between frequency bands and has significantly lower complexity in comparison with previously reported concurrent dual-band DPDs.
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Guérin, Alexandre, Guy Lesthievent, Jean-Pierre Millerioux, Jacques Sombrin, Xavier Giraud, Philippe Bellocq, Emmanuel Midan, and Jacques Oster. "Digital Predistortion of Power Amplifier Non-Linearity Applied to CCSDS/DVB-S2 Satellite Telemetry." International Foundation for Telemetering, 2013. http://hdl.handle.net/10150/579579.
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ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NVThe CNES (French Space Agency) has studied memoryless predistortion techniques for power amplifier nonlinearity of satellite payload telemetry. These techniques are applied to high order modulations taken from the DVB-S2 standard and the associated CCSDS blue book. An easy-to-implement calibration method was also developed. The predistortion was implemented at two times the symbol rate after Square Root Raised Cosine shaping on a breadboard model of a 16APSK modulator associated to a Solid State Power Amplifier. It allows to reduce the amplifier back-off and thus to increase the power added efficiency for an equivalent signal quality.
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Woo, Wangmyong. "Hybrid Digital/RF Envelope Predistortion Linearization for High Power Amplifiers in Wireless Communication Systems." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6924.
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Hybrid Digital/RF Envelope Predistortion Linearization for High Power Amplifiers in Wireless Communication Systems
Wangmyong Woo
151 Pages
Directed by Dr. J. Stevenson Kenney
The objective of this research is to implement a hybrid digital/RF envelope predistortion linearization system for high-power amplifiers used in wireless communication systems. It is well known that RF PAs have AM/AM (amplitude modulation) and AM/PM (phase modulation) nonlinear characteristics. Moreover, the distortion components generated by a PA are not constant, but vary as a function of many input conditions such as amplitude, signal bandwidth, self-heating, aging, etc. Memory effects in response to past inputs cause a hysteresis in the nonlinear transfer characteristics of a PA. This hysteresis, in turn, creates uncertainty in predictive linearization techniques. To cope with these nonlinear characteristics, distortion variability, and uncertainty in linearization, an adaptive digital predistortion technique, a hybrid digital/RF envelope predistortion technique, an analog-based RF envelope predistortion technique, and a combinational digital/analog predistortion technique have been developed.
A digital adaptation technique based on the error vector minimization of received PA output waveforms was developed. Also, an adaptive baseband-to-baseband test system for the characterization of RF PAs and for the validation of linearization algorithms was implemented in conjunction with the adaptation technique. To overcome disadvantages such as limited correction bandwidth and the need for a baseband input signal in digital predistortion, an adaptive, wideband RF envelope predistortion system was developed that incorporates a memoryless predistortion algorithm. This system is digitally controlled by a look-up table (LUT). Compared with conventional baseband digital approaches, this predistortion architecture has a correction bandwidth that is from 20 percent to 33 percent wider at the same clock speeds for third to fifth order IMDs and does not need a digital baseband input signal.
For more accurate predistortion linearization for PAs with memory effects, an RF envelope predistortion system has been developed that uses a combination of analog-based envelope predistortion (APD) working in conjunction with digital LUT-based adaptive envelope predistortion (DPD). The resulting combination considerably decreases the computational complexity of the digital system and significantly improves linearity and efficiency at high power levels.
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Farabegoli, Alessio [Verfasser]. "Digital Predistortion and Crest Factor Reduction Architectures for Mobile Radio Handset Transmitters / Alessio Farabegoli." München : Verlag Dr. Hut, 2016. http://d-nb.info/1084386585/34.
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Mitrevski, Dragan. "Design and Characterization of a 6 W GaN HEMT Microwave Power Amplifier with Digital Predistortion Linearization." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-12612.
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In this thesis, characterization of a 6W GaN HEMT power amplifier for optimal operating conditions through load pull simulations and measurements is investigated.The purpose is to find source and load impedances to achieve for instance maximum efficiency and maximum output power, and investigate whether thesimulated results can be replicated in a measurement setup. Simulations show that when matching for maximum output power, a peak output power of 13W is achieved, while in 1 dB compression, an output powerof 11.40W together with a power added efficiency of nearly 67% is obtained, a remarkable for a 6W device. Matching for maximum efficiency yields a peak power added efficiency of 78% and a peak drain efficiency of 90 %, however, in 1 dB compressionthese levels are 71% and 74 %, respectively. Load pull measurements are performed with a prototype design, however, due to problems with the softwarecontrolling the measurement equipment, the tuning process had to be done manually, which effectively limited the possibility of replicating the simulated results.With manual tuning in coarse steps, two sets for semioptimal operating conditions are found. For the first set of impedances, a peak output power greaterthan 11 W, with a peak power added efficiency of 68% is obtained, while for the second set of impedances, an output power of 7.40W with a peak power addedefficiency of 70% is achieved. The measured performance indicate that the simulated results can be replicated once the measurement setup is working optimally.In addition, the topics of blackbox characterization and digital predistortion linearization of microwave power amplifiers are investigated. Microwave power amplifiersobtain maximum operational performance when operated close to the saturation point. However, due to the nonlinear behavior of the device when operated inthis region, the output signal will be distorted and cause interference with neighboring channels. Thus, in order to maintain the high operational performanceand avoid adjacent channel interference, it is of great importance to characterize the nonlinear behavior of the device, and compensate for the introduced distortionterms. Digital predistortion linearization is considered to be among the most costeffective linearization schemes as of today, providing flexibility and good performance.The design of a digital predistortion unit amounts to three main steps: deriving a behavioral model of the microwave power amplifier, estimating themodel parameters for the inverse characteristic, and the implementation of the preinverse filter. For behavioral modeling, wellknown nonlinear models, such asthe Volterra series are investigated, and used with an indirect learning architecture to estimate the parameters of the inverse system.Simulations of the different linearization algorithms show that in an ideal environment, the adjacent channel power ratio can be reduced with up to 25 dB, almostindependent of the model used for the predistorter design. However, when used in a real measurement setup, a maximum reduction in adjacent channel power ratioof only 15 dB is obtained. The relatively large difference in performance is most likely caused by a combination of long term memory effects due to semiconductortrapping phenomena, noise, and modeling errors.
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Feng, Xiaowen. "Efficient baseband digital predistortion techniques for linearizing power amplifier by taking into account nonlinear memory effect." Nantes, 2015. https://archive.bu.univ-nantes.fr/pollux/show/show?id=3619006c-f9da-4c0b-8b67-4445eda2c7b1.
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Les techniques de pré-distorsion numérique (DPD) en bande de base permettant de linéariser un amplificateur de puissance (PA) avec effets mémoires non linéaires sont étudiées. Des éléments de base liés à la linéarisation du PA sont introduits, tels que le comportement non-linéaire du PA, son influence sur les systèmes de communication, sa modélisation et caractérisation. . . Puis certaines techniques de linéarisation existantes sont décrites, telles que le recul de puissance, le feedforward, la boucle de retour, l’amplification linéaire avec des composants non linéaires et la DPD. La DPD est la technique de linéarisation la plus prometteuse. L’architecture d’implémentation et les algorithmes d’identification de la DPD sont décrits. Dans cette thèse, quatre méthodes originales de DPD sont proposées. La première méthode (MP/LUT DPD) combine un modèle polynomial à mémoire (MP) avec une simple LUT. L’amplitude et la phase du signal prédistordu sont calculées par cette LUT. La deuxième méthode consiste à ajouter une interpolation linéaire à cette méthode. La troisième méthode consiste à améliorer la technique d’interpolation par une interpolation quadratique. La quatrième méthode exploite conjointement la MP DPD et un réseau de neurones. L’innovation principale dans cette dernière, réside dans l’apprentissage du réseau de neurones avec les échantillons du signal pré-distordu par la MP DPD. Enfin, les résultats de simulation et expérimentaux en termes de linéarisation, d’amélioration spectrale, de rotation de constellation et de temps de calculs sont fournis. Les méthodes proposées permettent différents compromis entre les performances de linéarisation et la complexitéBaseband digital predistortion (DPD) techniques for linearizing power amplifiers (PA) with memory effects are investigated in this thesis. Firstly, the relevant elements concerning PA linearization are introduced, such as PA nonlinearity behavior, its influence on the communication systems, its modeling and characterization. . . Then some existing linearization techniques are presented, such as power backoff, feedforward, feedback, linear amplification with nonlinear components and DPD. DPD is the most promising linearization technique. After that, the implementation architecture and identification algorithms of DPD are described. In this thesis, four DPD methods are proposed. The first method (MP/LUT DPD) is to combine a memory polynomial (MP) model and a simple non-interpolated LUT. Both the amplitude and phase of the predistorted signal are calculated by LUT. The second method is to add linear interpolation technique to MP/LUT DPD. The third method improves the second one by using a quadratic interpolation technique to MP/LUT DPD. The fourth method is to combine MP DPD and feed forward neural network. The principal innovation is that the training samples of the neural networks are the predistorded signal obtained by MP DPD. Finally, simulation results and experimental results are given and analyzed. The proposed methods provide different trade-off between the linearization performance, time efficiency and complexity
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Yu, Xin [Verfasser], and Georg [Akademischer Betreuer] Fischer. "Contributions to Digital Predistortion of Radio-Frequency Power Amplifiers for Wireless Applications / Xin Yu. Betreuer: Georg Fischer." Erlangen : Universitätsbibliothek der Universität Erlangen-Nürnberg, 2012. http://d-nb.info/1026365481/34.
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Ku, Hyunchul. "Behavioral modeling of nonlinear RF power amplifiers for digital wireless communication systems with implications for predistortion linearization systems." Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04052004-180035/unrestricted/ku%5Fhyunchul%5F200312%5Fphd.pdf.
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Baschieri, Lorenzo. "Feasible predistortion loop for the linearization of Radio-over-Fiber system based on 850 nm Vertical Cavity Surface Emitting Laser and standard G.652 fiber." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22266/.
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The main purpose of the work is to investigate a low-cost solution for systems designed for the distribution of the RF signal employing the Radio Over Fiber (RoF) technology, including the additional feature of a possible digital predistortion of the modulating signal to compensate the detrimental effects of the system nonlinearities.
A Vertical Cavity Surface Emitting Laser (VCSEL) operating at 850 nm and the standard single mode fiber G-652 have been used with this purpose, since their combination is one of the cheapest possible solutions that can be implemented.
The main problem present in this configuration is due to the fact that, using this kind of lasers in a fiber like G-652, that has been realized to work at wavelengths higher than 1260 nm, an undesired bimodal behavior is present in the fiber connection.
We have then tested a solution based on commercial 1310nm/1550nm couplers, which are theoretically able to separate in different branches the two modes arising at 850 nm. This allows to realize an almost-Single Mode RoF link based on G-652 fiber and 850 nm VCSEL with the additional feature of making available a possible feedback signal to realize an appropriate signal pre-distortion.
Aim of this thesis work is then to insert the coupler at the laser section, using the direct path to feed link based on G-652 fiber, while using the feedback path in order to digitally pre-distort the signal which modulates the laser itself.
The improvements in the sysetm performance will be presented in terms of NMSE (nominal mean square error), ACPR (adjacent channel power ratio), EVM (error vector magnitude) and spectral regrowth reduction, and will allow to appreciate the beneficial effect of signal digital predistortion feature introduced.
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Donati, Giovanni [Verfasser], Georg [Gutachter] Fischer, and Jan-Erik [Gutachter] Müller. "Advanced Digital Predistortion Algorithms for modern Base-Station Front-Ends. A physically motivated approach / Giovanni Donati ; Gutachter: Georg Fischer, Jan-Erik Müller." Erlangen : FAU University Press, 2017. http://d-nb.info/1152079050/34.
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Tua-Martinez, Carlos Gustavo. "Behavioral Model and Predistortion Algorithm to Mitigate Interpulse Instabilities Induced by Gallium Nitride Power Amplifiers in Multifunction Radars." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/74445.
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The incorporation of Gallium Nitride (GaN) Power Amplifiers (PAs) into future high power aperture radar systems is certain; however, the introduction of this technology into multifunction radar systems will present new challenges to radar engineers. This dissertation describes a broad investigation into amplitude and phase transients produced by GaN PAs when they are excited with multifunction radar waveforms. These transients are the result of self-heating electrothermal memory effects and are manifested as interpulse instabilities that can negatively impact the coherent processing of multiple pulses. A behavioral model based on a Foster network topology has been developed to replicate the measured amplitude and phase transients accurately. This model has been used to develop a digital predistortion technique that successfully mitigates the impact of the transients. The Moving Target Indicator (MTI) Improvement Factor and the Root Mean Square (RMS) Pulse-to-Pulse Stability are used as metrics to assess the impact of the transients on radar system performance and to test the effectiveness of a novel digital predistortion concept.Ph. D.
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Jagla, Lukáš. "Adaptace digitálního předzkreslovače pro linearizaci zesilovačů s použitím komparátoru." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2020. http://www.nusl.cz/ntk/nusl-413157.
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Diplomová práce pojednává o návrhu nového hardwaru využívající komparátor ve zpětné vazbě systému pro digitální předzkreslování signálu. Vybrané vlastnosti navrhované architektury jsou ověřeny pomocí simulací a následně jsou zvoleny komponenty vhodné pro vysokofrekvenční použití za účelem implementace. Na bázi předložené architektury je navržen akviziční modul včetně obvodové realizace a vytvoření plošného spoje. Zhotovený plošný spoj je osazen a připraven pro další testování. Dále je navržen příslušný firmware pro příjem a vysílání signálu a získávání naměřených dat. Obdržené výsledky jsou určeny pro zhodnocení vlastností hardwaru a budoucího využití architektury v systémech digitálních předzkreslovačů.
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Yang, Xi. "Filter-less Architecture for Multi-Carrier Software Defined Radio Transmitters." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1321403816.
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Sperlich, Roland. "Adaptive power amplifier linearization by digital pre-distortion with narrowband feedback using genetic algorithms." Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-06232005-152633/.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006.Leach, William M., Committee Member ; Sills, James A., Committee Member ; Kenney, J. Stevenson, Committee Chair ; Zhou, G. Tong, Committee Co-Chair ; Fenney, Robert K., Committee Member.
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Fu, Zhu. "Digital Pre-distortion for Interference Reduction in Dynamic Spectrum Access Networks." Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-dissertations/152.
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Given the ever increasing reliance of today’s society on ubiquitous wireless access, the paradigm of dynamic spectrum access (DSA) as been proposed and implemented for utilizing the limited wireless spectrum more efficiently. Orthogonal frequency division multiplexing (OFDM) is growing in popularity for adoption into wireless services employing DSA frame- work, due to its high bandwidth efficiency and resiliency to multipath fading. While these advantages have been proven for many wireless applications, including LTE-Advanced and numerous IEEE wireless standards, one potential drawback of OFDM or its non-contiguous variant, NC-OFDM, is that it exhibits high peak-to-average power ratios (PAPR), which can induce in-band and out-of-band (OOB) distortions when the peaks of the waveform enter the compression region of the transmitter power amplifier (PA). Such OOB emissions can interfere with existing neighboring transmissions, and thereby severely deteriorate the reliability of the DSA network. A performance-enhancing digital pre-distortion (DPD) technique compensating for PA and in-phase/quadrature (I/Q) modulator distortions is proposed in this dissertation. Al- though substantial research efforts into designing DPD schemes have already been presented in the open literature, there still exists numerous opportunities to further improve upon the performance of OOB suppression for NC-OFDM transmission in the presence of RF front-end impairments. A set of orthogonal polynomial basis functions is proposed in this dissertation together with a simplified joint DPD structure. A performance analysis is presented to show that the OOB emissions is reduced to approximately 50 dBc with proposed algorithms employed during NC-OFDM transmission. Furthermore, a novel and intuitive DPD solution that can minimize the power regrowth at any pre-specified frequency in the spurious domain is proposed in this dissertation. Conventional DPD methods have been proven to be able to effectively reduce the OOB emissions that fall on top of adjacent channels. However more spectral emissions in more distant frequency ranges are generated by employing such DPD solutions, which are potentially in violation of the spurious emission limit. At the same time, the emissions in adjacent channel must be kept under the OOB limit. To the best of the author’s knowledge, there has not been extensive research conducted on this topic. Mathematical derivation procedures of the proposed algorithm are provided for both memoryless nonlinear model and memory-based nonlinear model. Simulation results show that the proposed method is able to provide a good balance of OOB emissions and emissions in the far out spurious domain, by reducing the spurious emissions by 4-5 dB while maintaining the adjacent channel leakage ratio (ACLR) improvement by at least 10 dB, comparing to the PA output spectrum without any DPD.
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Brandon, Mathilde. "Optimisation conjointe de méthodes de linéarisation de l'émetteur pour des modulations multi-porteuses." Phd thesis, Université de Cergy Pontoise, 2012. http://tel.archives-ouvertes.fr/tel-00762747.
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Les modulations multiporteuses apparaissent aujourd'hui comme une technologie éprouvée pour la transmission de données à haut-débits sur des canaux pouvant être très perturbés. L'OFDM (Orthogonal Frequency Division Multiplexing) a d'ailleurs été choisie dans plusieurs normes de télécommunications (ADSL, Wi-Max, IEEE 802.11a/g/n, LTE, DVB,...). Cependant un des inconvénients de ce type de modulation est la forte variation de la puissance instantanée à transmettre. Cette propriété rend ces modulations très sensibles aux non-linéarités des composants analogiques, en particulier celles de l'amplificateur de puissance à l'émission. Or l'amplificateur de puissance est un élément déterminant dans une chaîne de communication dans la mesure où il a une influence prépondérante sur le bilan global de la transmission en termes de puissance, de rendement et de distorsion. Plus l'on souhaite que l'impact de ses non linéarités soit faible et plus son rendement est faible, et inversement. Il est donc nécessaire d'effectuer un compromis linéarité/rendement.L'objectif de la thèse est d'éviter cette détérioration du rendement tout en conservant de bonnes performances de linéarité, de surcroit pour des signaux OFDM. Pour ce faire nous proposons d'utiliser conjointement des méthodes de linéarisation (prédistorsion numérique en bande de base) et d'amélioration du rendement (envelope tracking) de l'amplificateur de puissance ainsi qu'une méthode de réduction de la dynamique du signal (active constellation extension). La prédistorsion numérique classique échouant aux fortes puissances, nous proposons une méthode d'amélioration de cette technique à ces puissances. Nos résultats sont validés par des mesures sur un amplificateur de puissance 50W. Nous proposons également une association des méthodes permettant d'améliorer simultanément les performances en terme de linéarité hors bande et de rendement en minimisant les dégradations des performances de taux d'erreur binaire.
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Warm, Stefan. "Electronic predistortion strategies for directly modulated laser systems." Aachen Shaker, 2009. http://d-nb.info/997825057/04.
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Pojani, Giacomo. "Implementazione su fpga di un pre-distorsore digitale a banda larga per sistemi a microonde di backhaul." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7637/.
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The development of next generation microwave technology for backhauling
systems is driven by an increasing capacity demand. In order to provide higher data
rates and throughputs over a point-to-point link, a cost-effective performance
improvement is enabled by an enhanced energy-efficiency of the transmit power
amplification stage, whereas a combination of spectrally efficient modulation
formats and wider bandwidths is supported by amplifiers that fulfil strict
constraints in terms of linearity.
An optimal trade-off between these conflicting requirements can be achieved by
resorting to flexible digital signal processing techniques at baseband.
In such a scenario, the adaptive digital pre-distortion is a well-known linearization
method, that comes up to be a potentially widely-used solution since it can be
easily integrated into base stations. Its operation can effectively compensate for the
inter-modulation distortion introduced by the power amplifier, keeping up with the
frequency-dependent time-varying behaviour of the relative nonlinear
characteristic.
In particular, the impact of the memory effects become more relevant and their
equalisation become more challenging as the input discrete signal feature a wider
bandwidth and a faster envelope to pre-distort.
This thesis project involves the research, design and simulation a pre-distorter
implementation at RTL based on a novel polyphase architecture, which makes it
capable of operating over very wideband signals at a sampling rate that complies
with the actual available clock speed of current digital devices. The motivation
behind this structure is to carry out a feasible pre-distortion for the multi-band
spectrally efficient complex signals carrying multiple channels that are going to be
transmitted in near future high capacity and reliability microwave backhaul links.
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Qian, Hua. "Power Efficiency Improvements for Wireless Transmissions." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/11649.
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Many communications signal formats are not power efficient because of their large peak-to-average power ratios (PARs). Moreover, in the presence of nonlinear devices such as power amplifiers (PAs) or mixers, the non-constant-modulus signals may generate both in-band distortion and out-of-band interference. Backing off the signal to the linear region of the device further reduces the system power efficiency. To improve the power efficiency of the communication system, one can pursue two approaches: i) linearize the PA; ii) reduce the high PAR of the input signal.
In this dissertation, we first explore the optimal nonlinearity under the peak power constraint. We show that the optimal nonlinearity is a soft limiter with a specific gain calculated based on the peak power limit, noise variance, and the probability density function of the input amplitude. The result is also extended to the fading channel case.
Next, we focus on digital baseband predistortion linearization for power amplifiers with memory effects. We build a high-speed wireless test-bed and carry out digital baseband predistortion linearization experiments. To implement adaptive PA linearization in wireless handsets, we propose an adaptive digital predistortion linearization architecture that utilizes existing components of the wireless transceiver to fulfill the adaptive predistorter training functionality.
We then investigate the topic of PAR reduction for OFDM signals and forward link CDMA signals. To reduce the PAR of the OFDM signal, we propose a dynamic selected mapping (DSLM) algorithm with a two-buffer structure to reduce the computational requirement of the SLM method without sacrificing the PAR reduction capability. To reduce the PAR of the forward link CDMA signal, we propose a new PAR reduction algorithm by introducing a relative offset between the in-phase branch and the quadrature branch of the transmission system.
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Hamoud, Houssam Eddine. "Linéarisation par pré-distorsion numérique d'amplificateurs de puissance pour les nouvelles générations des systèmes de télécommunications." Thesis, Limoges, 2019. http://www.theses.fr/2019LIMO0110.
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Les systèmes de communication modernes convergent vers un fonctionnement multi-standard associé à des formats de modulation à fort PAPR où l’amplificateur de puissance doit être d’abord optimisé en rendement et où la linéarité sera corrigée ensuite par l’ajout d’un prédistorteur. Si cette solution semble fonctionnelle, elle parait inadaptée et peu efficace sur les systèmes 5G où les largeurs de bandes visées posent à la fois des problèmes d’architecture (complexité de la voie d’observation) etde précision des modèles comportementaux usuels basés sur une simplification de la série de Volterra dans sa forme discrète (GMP, DDR) face à des effets de mémoire exacerbés mais également d’efficacité énergétique du système linéarisé (DPD+PA). Il devient nécessaire dans ce contexte d’aller vers un modèle de prédistorteur moins dépendant des caractéristiques du signal à linéariser, notamment par le modèle TPM (Two path Memory) développé à XLIM, basé sur une simplification de la série de Volterra dans sa forme continue, s’avère indépendant des caractéristiques du signal à linéariser.Notre travail s’est attaché à évaluer les performances en linéarité des modèles classiques (GMP, DDR) et du modèle TPM sur différents amplificateurs de puissance, soit à partir de simulations ou à partir de mesures physiques du PA. Pour ce faire nous avons mis en place un environnement de simulation ainsi qu’un banc d’évaluation des modèles de prédistorsion avec le PA physique afin de quantifier les performances en ACPR suivant la variation de caractéristique du signal (puissance, fréquence, statistique). L’ensemble de ces expérimentations ont permis de vérifier d’une part la faible robustesse des approches classiques (GMP/DDR), d’autre part la stabilité des performances de l’approche TPM quel que soit le scenario envisagé. Cette étude ouvre donc la voie d’une nouvelle génération de prédistorteur qui, extrait une fois pour toute, ne nécessiterait qu’une mise à jour sur des phénomènes à dynamique lente (vieillissement) et permettrait d’envisager une architecture simplifiée de la voie d’observation du DPD ; donc une amélioration de l’efficacité énergétique globale du système linéariséModern communications systems converge towards multi-standard operation combined with high PAPR modulation formats where the power amplifier must first be optimized in efficiency and where linearity will then be corrected by adding a predistorter. If this solution seems functional, it seems inadequate and ineffective on 5G systems where the targeted bandwidths pose both architectural problems (complexity of the observation path) and problems of accuracy of the usual behavioural models based on a simplification of the Volterra series in its discrete form (GMP, DDR) in the face of exacerbated memory effects but also of energy efficiency of the linearized system (DPD+PA). In this context, it becomes necessary to move towards a predistorter model less dependent on the characteristics of the signal to be linearized, in particular by the TPM (Two path Memory) model developed at XLIM, based on a simplification of the Volterra series in its continuous form, is independent of the characteristics of the signal to be linearized.Our work focused on evaluating the linearity performance of the classical models (GMP, DDR) and the TPM model on different power amplifiers either from simulations or from physical measurements of the PA. To do this, we have set up a simulation environmentand an evaluation bench for predistortion models with physical PA in order to quantify ACPR performance according to the variation in signal characteristics (power, frequency, statistics). All these experiments made it possible to verify, on the one hand,the poor robustness of traditional approaches (GMP/DDR) and, on the other hand, the stability of the performance of the TPM approach, whatever the scenario envisaged. This study therefore paves the way for a new generation of pre-distributor which, if extracted once and for all, would only require an update on slow dynamic phenomena (ageing) and would make it possible to consider a simplified architecture of the DPD observation path; thus improving the overall energy efficiency of the linearizedsystem
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CHEN, HAO-ZHE, and 陳浩哲. "Doherty Power Amplifier Design with Digital Predistortion." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/76e833.
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碩士國立中正大學
電機工程研究所
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In this study, a power amplifier is designed for efficiency and linearity by using gallium nitride high electron mobility transistors. The gain of this power amplifier is about 13 dB and the output power is 38 dBm. The architecture of this power amplifier is based on Doherty topology of which having the advantages of high linearity and efficiency. Doherty architecture uses active load modulation technology at output port and combines the characteristics with class AB and class C operations to implement high linearity and efficiency. The final result is that the third-order intermodulation distortion being reduced to be lower than -30 dBc when the output power of the two-tone measurement is 36 dBm and the one-tone input power is 25 dBm. The output power is 38.2 dBm as the efficiency being 41.9 % at 3.2 GHz. The second part of this study is focused on the power amplifier combined with baseband digital pre-distortion methods to improve linearity. This study improves the linearity of power amplifier by taking the memory effects into considerations during employing baseband digital pre-distortion methods. In wireless communication systems, the power amplifier is a crucial component in transmitter. Because of its inherent nonlinear and memory properties, causing signal distorted not only in-band , but also regrowing out-of-band. It affects the power efficiency at the same time. The baseband digital pre-distortion is one of the most effective ways to compensate for distortion. In this study, via Ethernet, Keysight’s SystemVue software was used to control the signal generator and capture the output signals of the power amplifier with the signal analyzer by the software of VSA89600. The resulted power amplifier performance behaves with a EVM value of 1.06% (-39.5 dB) through the assistance of digital pre-distortion.