Дисертації з теми "Compensation of nonlinearity"
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1
Kulig, Gabriel, and Gustav Wallin. "R/2R DAC Nonlinearity Compensation." Thesis, Linköpings universitet, Elektroniksystem, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-84481.
Повний текст джерелаАнотація:
The resistor ladder (R/2R) digital-to-analogue converter (DAC) architecture is often used in high performance audio solutions due to its low-noise performance. Even high-end R/2R DACs suffer from static nonlinearity distortions. It was suspected that compensating for these nonlinearities would be possible. It was also suspected that this could improve audio quality in audio systems using R/2R DACs for digital-to-analogue (A/D) conversion. Through the use of models of the resistor ladder architecture a way of characterizing and measuring the faults in the R/2R DAC was created. A compensation algorithm was developed in order to compensate for the nonlinearities. The performance of the algorithm was simulated and an implementation of it was evaluated using an audio evaluation instrument. The results presented show that it is possible to increase linearity in R/2R DACs by compensating for static nonlinearity distortions. The increase in linearity can be quite significant and audible for the trained ear.
2
Zhu, Likai. "Computationally efficient digital backward propagation for fiber nonlinearity compensation." Doctoral diss., University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4728.
Повний текст джерелаАнотація:
The next generation fiber transmission system is limited by fiber nonlinearity. A distributed nonlinearity compensation method, known as Digital Backward Propagation (DBP), is necessary for effective compensation of the joint effect of dispersion and nonlinearity. However, in order for DBP to be accurate, a large number of steps are usually required for long-haul transmission, resulting in a heavy computational load. In real time DBP implementation, the FIR filters can be used for dispersion compensation and account for most of the computation per step. A method of designing a complementary filter pair is proposed. The individual errors in the frequency response of the two filters in a complementary filter pair cancel each other. As a result, larger individual filter error can be tolerated and the required filter length is significantly reduced. Unequal step size can be used in DBP to minimize the number of steps. For unrepeatered transmission with distributed Raman amplification, the Raman gain as a function of the distance and the effective fiber length of each DBP step need to be calculated by solving the differential equations of Raman amplification. The split-step DBP is performed only for transmission where the signal power is high. In comparison with solving the nonlinear Schrodinger equation (NLSE) for the total field of the WDM signal, solving the coupled NLSE requires a smaller step number and a lower sampling rate. In addition, the phase-locking between the local oscillators is not necessary for solving the coupled NLSE. The XPM compensation of WDM long-haul transmission by solving the coupled NLSE is experimentally demonstrated. At the optimum power level of fiber transmission, the total nonlinear phase shift is on the order of 1 radian. Therefore, for transoceanic fiber transmission systems which consist of many (>100) amplified fiber spans, the nonlinear effects in each span are weak. As a result, the optical waveform evolution is dominated by the dispersion. Taking advantage of the periodic waveform evolution in periodically dispersion managed fiber link, the DBP of K fiber spans can be folded into one span with K times the nonlinearity. This method can be called "distance-folded DBP". Under the weakly nonlinear assumption, the optical waveform repeats at locations where accumulated dispersions are identical. Consequently, the nonlinear behavior of the optical signal also repeats at locations of identical accumulative dispersion. Hence for a fiber link with arbitrary dispersion map, the DBP steps can be folded according to the accumulated dispersion. Experimental results show considerable savings in computation using this "dispersion-folded DBP" method. Simulation results show that the dramatically reduced computational load makes the nonlinearity-compensated dispersion-managed fiber link a competitive candidate for the next-generation transmission systems.ID: 031001391; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Title from PDF title page (viewed May 28, 2013).; Thesis (Ph.D.)--University of Central Florida, 2011.; Includes bibliographical references.
Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics
3
Tayebi, Niloufar. "Laser nonlinearity compensation for subcarrier multiplexed optical transmission systems." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7665.
Повний текст джерелаАнотація:
Subcarrier multiplexing efficiently uses the available fiber bandwidth in video transmission. Semiconductor lasers are usually used as optical transmitters in such systems. A semiconductor laser exhibits nonlinear characteristics. Nonlinearity degrades system performance. For nonlinearity compensation, a nonlinear predistortion block is assumed to be incorporated prior to the laser. Characteristics of this nonlinear block invert those of the laser. Performance of the subcarrier multiplexed system with and without predistortion is evaluated by harmonic distortion and intermodulation distortion analyses. Nonlinear distortion level decreases significantly when predistortion is employed prior to the laser. This enhancement results in system requirements for carrier-to-noise ratio being met.
4
Cavaco, Telmo Filipe Pedrosa. "Compensation of MZ-IQ-modulator nonlinearity based on FPGA algorithms." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/12677.
Повний текст джерелаАнотація:
Mestrado em Engenharia Electrónica e TelecomunicaçõesNos últimos anos, a crescente necessidade de largura de banda e a evolução das técnicas de processamento digital de sinal renovaram o interesse pelos sistemas de comunicação ópticos coerentes. O modulador IQ assume-se como um componente chave nestes transmissores, sendo responsável pela conversão de informação do domínio eléctrico para o domínio óptico. Os moduladores Mach-Zehnder que constituem este dispositivo recebem sinais de drive com uma excursão controlada, garantindo a utilização de uma região aproximadamente linear das suas funções transferência e a geração de constelações sem distorções de fase. No entanto, existem vantagens em explorar a extensão completa da característica dos moduladores. Neste contexto, torna-se relevante efectuar um estudo acerca das técnicas de pré-distorção electrónica que permitem corrigir os efeitos das não-linearidades associadas a este método de transmissão. Esta dissertação foca-se no estudo da compensação dos impactos que a característica não-linear do modulador Mach-Zehnder tem nos sistemas de transmissão ópticos coerentes. Após a identificação e desenvolvimento de soluções matemáticas para o problema, realizaram-se vários testes utilizando um simulador integrado em ambiente MATLAB. Um sistema de transmissão coerente utilizando formatos de modulação QAM e os respectivos algoritmos de compensação foram posteriormente implementados em FPGA. Desenvolveram-se também co-simulações que permitiram garantir que o hardware concebido produzia os resultados desejados. Para além disso, realizaram-se vários testes utilizando um modulador IQ disponível no “Laboratório de Óptica” do Instituto de Telecomunicações de Aveiro. O objectivo consistiu em operar o sistema em condições laboratoriais e analisar o desempenho dos algoritmos de compensação em ambiente real.
In recent years, the ever-increasing bandwidth demand and the evolution of digital signal processing techniques renewed the interest for the optical coherent systems. The IQ-Modulator is a key component in optical coherent transmitters, being responsible for the conversion of information from electrical to optical domain. The Mach-Zehnder modulators that compose this device receive driving signals with a controlled excursion, in order to use an approximately linear region of their transfer function and produce constellations without phase distortions. However, there are advantages in exploit the full range of the modulators’ characteristic. In this context, a study about the electronic predistortion techniques required to overcome the nonlinear effects associated to this transmission method becomes relevant. The subject of this dissertation is the compensation of impairments related to the nonlinear characteristic of the Mach-Zehnder Modulator in coherent optical transmission systems. After the identification and development of mathematical solutions for the problem, several tests were made using a simulator that runs in a MATLAB environment. A QAM coherent transmitter system and the compensation algorithm were then implemented in a FPGA platform. Co-simulations were performed in order to prove that the designed hardware was generating correct results. Furthermore, some tests were conducted using an IQ-Modulator available in the “Optics Laboratory” at Telecommunications Institute of Aveiro. The goal was to operate the system under laboratorial conditions and analyze the performance of the compensation algorithm in a real case scenario.
5
Lyman, Raphael J., and Qingsong Wang. "A DECOUPLED APPROACH TO COMPENSATION FOR NONLINEARITY AND INTERSYMBOL INTERFERENCE." International Foundation for Telemetering, 2002. http://hdl.handle.net/10150/605571.
Повний текст джерелаАнотація:
International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, CaliforniaTo achieve good efficiency in a space-based radio transmitter, its final amplifier must be operated near the saturation point, in its nonlinear region. Because of strict band limitations, this nonlinear operation is combined with the problem of intersymbol interference. Normally, these problems are addressed using a combination of equalization and power back-off, resulting in reduced power efficiency. Many proposed receiver-based methods, such as Volterra equalization, attempt to compensate for the nonlinearity and ISI in a single block before the detector, allowing higher efficiency operation, but introducing a great deal of complexity. We propose a receiver-based method in which the two effects are dealt with in separate blocks, an equalizer and a linearizer, resulting in considerable simplification. We go further and place the detector before the linearizer, achieving improved performance by eliminating the errors introduced by the linearizer. Simulation results compare favorably with the performance of a linear AWGN channel.
6
Lee, Chin Hee. "Characterisation and compensation of direct laser modulation nonlinearity in radio-over-fibre systems." Thesis, University of Leeds, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405746.
Повний текст джерела
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Bozic, M. "Joint compensation of I/Q impairments and PA nonlinearity in mobile broadband wireless transmitters." Thesis, University of Westminster, 2016. https://westminsterresearch.westminster.ac.uk/item/9yxv7/joint-compensation-of-i-q-impairments-and-pa-nonlinearity-in-mobile-broadband-wireless-transmitters.
Повний текст джерелаАнотація:
The main focus of this thesis is to develop and investigate a new possible solution for compensation of in-phase/quadrature-phase (I/Q) impairments and power amplifier (PA) nonlinearity in wireless transmitters using accurate, low complexity digital predistortion (DPD) technique. After analysing the distortion created by I/Q modulators and PAs together with nonlinear crosstalk effects in multi-branch multiple input multiple output (MIMO) wireless transmitters, a novel two-box model is proposed for eliminating those effects. The model is realised by implementing two phases which provide an optimisation of the identification of any system. Another improvement is the capability of higher performance of the system without increasing the computational complexity. Compared with conventional and recently proposed models, the approach developed in this thesis shows promising results in the linearisation of wireless transmitters. Furthermore, the two-box model is extended for concurrent dual-band wireless transmitters and it takes into account cross-modulation (CM) products. Besides, it uses independent processing blocks for both frequency bands and reduces the sampling rate requirements of converters (digital-to-analogue and analogue-to-digital). By using two phases for the implementation, the model enables a scaling down of the nonlinear order and the memory depth of the applied mathematical functions. This leads to a reduced computational complexity in comparison with recently developed models. The thesis provides experimental verification of the two-box model for multi-branch MIMO and concurrent dual-band wireless transmitters. Accordingly, the results ensure both the compensation of distortion and the performance evaluation of modern broadband wireless transmitters in terms of accuracy and complexity.
8
Jarajreh, Mutsam Abdel-karim. "Coherent optical OFDM modem employing artificial neural networks for dispersion and nonlinearity compensation in a long-haul transmission system." Thesis, Northumbria University, 2012. http://nrl.northumbria.ac.uk/9596/.
Повний текст джерелаАнотація:
In order to satisfy the ever increasing demand for the bandwidth requirement in broadband services the optical orthogonal frequency division multiplexing (OOFDM) scheme is being considered as a promising technique for future high-capacity optical networks. The aim of this thesis is to investigate, theoretically, the feasibility of implementing the coherent optical OFDM (CO-OOFDM) technique in long haul transmission networks. For CO-OOFDM and Fast-OFDM systems a set of modulation formats dependent analogue to digital converter (ADC) clipping ratio and the quantization bit have been identified, moreover, CO-OOFDM is more resilient to the chromatic dispersion (CD) when compared to the bandwidth efficient Fast-OFDM scheme. For CO-OOFDM systems numerical simulations are undertaken to investigate the effect of the number of sub-carriers, the cyclic prefix (CP), and ADC associated parameters such as the sampling speed, the clipping ratio, and the quantisation bit on the system performance over single mode fibre (SMF) links for data rates up to 80 Gb/s. The use of a large number of sub-carriers is more effective in combating the fibre CD compared to employing a long CP. Moreover, in the presence of fibre non-linearities identifying the optimum number of sub-carriers is a crucial factor in determining the modem performance. For a range of signal data rates up to 40 Gb/s, a set of data rate and transmission distance-dependent optimum ADC parameters are identified in this work. These parameters give rise to a negligible clipping and quantisation noise, moreover, ADC sampling speed can increase the dispersion tolerance while transmitting over SMF links. In addition, simulation results show that the use of adaptive modulation schemes improves the spectrum usage efficiency, thus resulting in higher tolerance to the CD when compared to the case where identical modulation formats are adopted across all sub-carriers. For a given transmission distance utilizing an artificial neural networks (ANN) equalizer improves the system bit error rate (BER) performance by a factor of 50% and 70%, respectively when considering SMF firstly CD and secondly nonlinear effects with CD. Moreover, for a fixed BER of 10-3 utilizing ANN increases the transmission distance by 1.87 times and 2 times, respectively while considering SMF CD and nonlinear effects. The proposed ANN equalizer performs more efficiently in combating SMF non-linearities than the previously published Kerr nonlinearity electrical compensation technique by a factor of 7.
9
Sackey, Isaac [Verfasser], Klaus [Gutachter] Petermann, Nick [Gutachter] Doran, and Ronald [Gutachter] Freund. "Kerr nonlinearity compensation using polarization-independent fiber-based optical parametric amplifier in high-speed optical transmission systems / Isaac Sackey ; Gutachter: Klaus Petermann, Nick Doran, Ronald Freund." Berlin : Technische Universität Berlin, 2016. http://d-nb.info/1153013150/34.
Повний текст джерела
10
Bakri, Nizar. "Asservissement par camera d'un pendule inverse." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13222.
Повний текст джерела
11
Bui, Dang Thanh. "Étude et réalisation d'un système instrumental de stabilisation d'un modulateur électrooptique : application à l'amélioration du comportement d'un oscillateur optoélectronique." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2011. http://tel.archives-ouvertes.fr/tel-00618230.
Повний текст джерелаАнотація:
Les modulateurs electro-optiques (EOM) sont des composants importants dans les systemes de telecommunication. Malheureusement, ils ne sont pas parfaitement stables dans Ie temps et leur fonction de transfert (TF) a tendance a se decaler durant Ie temps d'operation. La derive de la TF d'un EOM peut etre expliquee par des effets differents tels que les changements de la temperature ambiante, de la polarisation ou de l'efficacite de couplage optique. La these presente une methode de me sure de la derive de la TF de I'EOM (a grace d'estimation du comportement non-linearite du modulateur, NLl), et propose deux systemes instrumentaux pour ameliorer son fonctionnement: Ie premier pour contraler la temperature de l'EOM, il est possible de forcement reduire cette derive, Ie deuxieme pour compenser la derive (la stabilisation du point de fonctionnement autour du point quadrature est obtenue jusqu'au 0,22% ou la fluctuation de phase est de 0,44°). Ces techniques ont ete aussi appliquees pour ameliorer Ie comportement d'un oscillateur optoelectronique haute frequence. Nous avons realise les experiences par asservissement de temperature, par compensation de la derive. Pour une stabilite de I'OEO a court terme, la stabilisation de la frequence est amelioree jusqu'a 28% en utilisant un contrale de temperature seule etjusqu'a 71 % avec les deux processus. Pour une stabilite de l'OEO a long terme, en deux cas sans contra Ie, I'OEO fonctionne pendant 3 heures et pendant 1,6 heure (puis I'OEO ne marche plus). En utilisant une compensation de la derive de la TF de I'EOM, l'OEO fonctionne bien meme apres 7 heures et 8 heures.
12
Cerqueira, Auciomar Carlos Teixeira de. "Estima??o e compensa??o de n?o linearidades inerentes aos atuadores dos processos industriais." Universidade Federal do Rio Grande do Norte, 2009. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12916.
Повний текст джерелаАнотація:
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Previous issue date: 2009-12-16The oscillations presents in control loops can cause damages in petrochemical industry. Canceling, or even preventing such oscillations, would save up to large amount of dollars. Studies have identified that one of the causes of these oscillations are the nonlinearities present on industrial process actuators. This study has the objective to develop a methodology for removal of the harmful effects of nonlinearities. Will be proposed an parameter estimation method to Hammerstein model, whose nonlinearity is represented by dead-zone or backlash. The estimated parameters will be used to construct inverse models of compensation. A simulated level system was used as a test platform. The valve that controls inflow has a nonlinearity. Results and describing function analysis show an improvement on system response
As oscila??es presentes nas malhas de controle podem causar preju?zos ? ind?stria petroqu?mica. Anular, ou at? mesmo amenizar tais oscila??es, acarretaria em uma grande economia. Estudos identificaram que um dos causadores destas oscila??es s?o as n?o linearidades presentes nos atuadores dos processos industriais. O presente trabalho tem como objetivo desenvolver uma metodologia para cancelamento dos efeitos nocivos destas n?o linearidades. Ser? proposto um m?todo de estima??o de par?metros para o modelo de Hammerstein, cuja n?o linearidade ? representada pela zona-morta ou pela folga. Os par?metros estimados ser?o usados na constru??o de modelos inversos de compensa??o. Utilizou-se um sistema de n?vel simulado como plataforma de testes, o qual possui uma v?lvula de controle de fluxo da vaz?o de entrada com uma n?o linearidade associada. Resultados e a an?lise por fun??o descritiva mostram a melhoria do comportamento da sa?da do processo
13
Liu, Chia-Hsin, and 劉家馨. "Predistortion Compensation for Transmitter Nonlinearity in MC-CDMA systems." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/45507857463622012039.
Повний текст джерелаАнотація:
碩士元智大學
電機工程研究所
89
Multi-Carrier Code-Division-Multiple-Access technique is the combination of conventional DS-CDMA with OFDM. The advantages of MC-CDMA are high data rate transmission, robustness against multipath delay spread and high spectral efficiency. MC-CDMA is a promising candidate for future wireless communication systems. However, MC-CDMA is significantly more sensitive to nonlinear distortions caused by power amplifier(PA) due to its high peak to average power ratio(PAR) due to OFDM. In this thesis, we use baseband digital adaptive signal predistorter to compensate for distortions introduced by nonlinear PA. The predistorters we tested include Parallel Adaptive Predistortion Linearizer previously used for OFDM signals, Real-valued Fixed Point Iteration Predistorter used for MC-CDMA signals and Look Up Table based Predistorter(FLUT) previously used for OFDM signals. To improve the performance, we propose to use interpolation in FLUT. Simulations are conducted to compare the convergence rate, training time, performance in terms of total degradation and the spectral distribution of signal powers. We propose to use the sum of the in-band signal power and the difference of the in-band and out-band signal power as a performance measure to be maximized. Compare to total degradation, this measure can more directly reflect the suppression of outband intermodulation.
14
Запорожець, О. В., and Н. О. Запорожець. "Using artificial neural network for compensation of thermistor conversion function nonlinearity." Thesis, 2019. http://openarchive.nure.ua/handle/document/12351.
Повний текст джерела
15
Chen, Hsi-Ming, and 陳喜明. "Design and analysis of ADC with A Differential Nonlinearity Compensation Circuit." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/2y53ge.
Повний текст джерела
16
Awadalla, Ahmed. "Electronic Pre-Compensation of Intra-Channel Nonlinearity in a 10Gb/s Optical Transmission System." Thesis, 2007. http://hdl.handle.net/10012/3140.
Повний текст джерелаАнотація:
We introduce several new algorithms for compensating intra channel
nonlinearities in lightwave systems through electronic
predistortion. These were optimized and modeled assuming realistic
conditions at Nortel and were found to be insensitive to normal
environmental and design fluctuations in commercial systems. We
also present an upper bound on system performance that agrees well
with measured results.
17
Ahmed, Nisar. "Electronic post-compensation of optical fiber nonlinearity in high-speed long-haul wavelength division multiplexed transmission systems /." Diss., 2010. http://purl.umn.edu/59730.
Повний текст джерела
18
Kai-ShengChen and 陳楷升. "Practical Phase Conjugation for Compensating Fiber Nonlinearity over Optical Communication Systems." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/43584492187984950124.
Повний текст джерелаАнотація:
碩士國立成功大學
電腦與通信工程研究所
100
Self-phase modulation (SPM) and cross-phase modulation (SPM) are leading nonlinear transmission penalty in optical communication systems. In nonlinear optical media, an interesting phenomenon of the intensity dependence of the refractive index occurs through SPM or XPM, which leads to spectral broadening of optical pulses and therefor degrade system performance. A novel scheme for fiber nonlinearity compensation based on the principles of optical phase conjugation (OPC) is proposed to reduce the phase distortion in optical communications. A phase modulator is used to modulate the phase of the data pulses in the middle of fiber spans. The magnitude of the phase modulation is proportional to the detected pulse intensity, and the sign is opposite to that of the nonlinear phase shift caused by self-phase modulation. Thus, the nonlinear phase noise induced by amplitude fluctuation and SPM in the first-half fiber is partially compensated for in the second-half fiber. Using an optimum value of the phase deviation of the optical phase modulator, we show by numerical simulations that a non-return-to-zero (NRZ) format transmission for 720 km in dispersion-managed system at 40 Gb/s with such nonlinearities compensation can provide greater than 2 dB increase in launch power .