Sparsity-Aware Low-Power ADC Architecture with Advanced Reconstruction Algorithms

Compressive sensing (CS) technique enables a universal sub-Nyquist sampling of sparse and compressible signals, while still guaranteeing the reliable signal recovery. Its potential lies in the reduced analog-to-digital conversion rate in sampling broadband and/or multi-channel sparse signals, where conventional Nyquist-rate sampling are either technology impossible or extremely hardware costly. Nevertheless, there are many challenges in the CS hardware design. In coherent sampling, state-of-the-art mixed-signal CS front-ends, such as random demodulator and modulated wideband converter, suffer from high power and nonlinear hardware. In signal recovery, state-of-the-art CS reconstruction methods have tractable computational complexity and probabilistically guaranteed performance. However, they are still high cost (basis pursuit) or noise sensitive (matching pursuit). In this dissertation, we propose an asynchronous compressive sensing (ACS) front-end and advanced signal reconstruction algorithms to address these challenges. The ACS front-end consists of a continuous-time ternary encoding (CT-TE) scheme which converts signal amplitude variations into high-rate ternary timing signal, and a digital random sampler (DRS) which captures the ternary timing signal at sub-Nyquist rate. The CT-TE employs asynchronous sampling mechanism for pulsed-like input and has signal-dependent conversion rate. The DRS has low power, ease of massive integration, and excellent linearity in comparison to state-of-the-art mixed-signal CS front-ends. We propose two reconstruction algorithms. One is group-based total variation, which exploits piecewise-constant characteristics and achieves better mean squared error and faster convergence rate than the conventional TV scheme with moderate noise. The second algorithm is split-projection least squares (SPLS), which relies on a series of low-complexity and independent l2-norm problems with the prior on ternary-valued signal. The SPLS scheme has good noise robustness, low-cost signal reconstruction and facilitates a parallel hardware for real-time signal recovery. In application study, we propose multi-channel filter banks ACS front-end for the interference-robust radar. The proposed receiver performs reliable target detection with nearly 8-fold data compression than Nyquist-rate sampling in the presence of -50dBm wireless interference. We also propose an asynchronous compressed beamformer (ACB) for low-power portable diagnostic ultrasound. The proposed ACB achieves 9-fold data volume compression and only 4.4% contrast-to-noise ratio loss on the imaging results when compared with the Nyquist-rate ADCs

Model Based Optimal Longitudinal Vehicle Control

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2016Thesis (Ph.D.) -- İstanbul Technical University, Institute of Science and Technology, 2016Otomotiv sektöründeki zorlu rekabet ortamı göz önüne alındığında, otomotiv üreticileri müşterilerine daha çekici ve fonksiyonel araçlar sunabilmak için birbirleri ile sürekli bir yarış halindelerdir. Maliyet, emisyon, yakıt ekonomisi, gürültü ve titreşim, dayanıklılık, performans ve araç sürüş özellikleri gibi kriterlerde yapılan iyileştirmeler sayesinde üreticiler rakip firmaların araçlarına göre daha avantajlı bir yere gelmeyi hedeflerler. Bu özelliklerin her biri müşterilerin kullandığı / kullacağı araç için olumlu bir algı oluşturulmasında önemli katkısı vardır. Bilişim ve elektronik sektöründeki araştırma ve gelişmeler faaliyetleri sonucunda elde edilen yeni teknolojiler ışığında otomobil mimarisindeki elektro-mekanik istemlerin kullanımı oldukça artmıştır. Buna ek olarak malzeme bilimi ve üretim teknolojisinde gelişmeler ışığında dizel yakıtlı içten yanmalı motorlarun tork ve güç eğrileri 20 yıl önce üretilen motorlardaki tork ve güç seviyelerine göre neredeyse 2 katına çıkmıştır. Ayrıca araçların ivmelenme manevralarındaki hızlanma tepki seviyeleri de özellikle hava yolu kontrolündeki yenilik ve gelişmeler doğrultusunda oldukça artmıştır ve araçları çok daha çevik ve sürücülerin gaz pedalı hareketine bağlı isteklerine çok daha fazla duyarlı hale getirmiştir. Motor tork ve güç kapasitelerindeki gelişmeler doğrultusunda araçların gaz pedalı tepkileri ciddi oranda değişmiş ve iyi bir araç sürüş özellikleri kalibrasyonuna ihtiyaç doğmuştur. Tüm gelişmelerin neticesinde araç sürüş özellikleri, müşteri memnuiyeti kriterleri arasında önemli bir paya sahip olmuştur. Bu tez çalışması araç sürüş üzellikleri simulasyon programları ve model bazlı kontrol algoritmaları kullanarak iyileştirmeyi amaçlamaktadır. Aracın güç ünitesi olan motorlardan tekerlekler vasıtasıyla yola olan tork ve kuvvet iletimi son derece karmaşık bir yapıya sahiptir ve araç sürüş özellikleri düşünüldüğünde dikkatli bir şekilde ele alınmalıdır. Aracın gaz pedalı hareketine olan tepkisi gecikme içermemeli, yeteri kadar hızlı ve seri olmalı aynı zamanda vurma, sarsıntı, salınım ve yığılma gibi hata modları içermemelidir. Bununla birlikte araç aktarma organları bileşenlerindeki doğrusal olmayan sistemler düşünüldüğünde, yukarıda bahsedilen araç sürüş özellikleri beklentilerini karşılamak son derece zorlu bir hal almaktadır. Eski araçlardaki gaz pedalı ve kelebeği arasındaki bağlantı teli vasıtasıyla sağlanan mekanik araç doğrusal ekseni kontrolünden farklı olarak, günümüzün modern araçları elektromekanik sistemler ile donatılmıştır. Motor kontrol üniteleri araç dorusal ekseni hareketini regülatif ve müşteri beklentileri ile uyumlu şekilde sağlamak için onlarca sensör sinyalini algıladıkdan sonra milisaniyeler içersinde işleyerek, motor ve araç aktüatörlerinin kontrolü için uygun sinyalleri üretirler. Araç sürüş özellikleri algoritmları düşünüldüğünde otomobil üreticileri gaz pedalı deplasmanına bağlı sürücü tork isteğini yumuşatan veya filtreleyen algorithmalar kullanırlar. Bu algoritmalar genellikle harita bazlıdırlar ve ana misyonları özellikle araç aktarma organlarındaki dişli mekanizmalarındaki boşluklardan geçerken geçerken tork artış ve azalma hızlarını limitleyerek araç sürüş özelliklerini iyileştirmektir. Sistem herhangi bir kapalı döngü içermediği için, bu algoritmalar subjectif kalibrasyon yöntemleri olarak tanımlanabilirler ve sistemin doğru çalışması, bu haritaları kalibre edem kalibrasyon mühendisinin hislerine ve yeteneğine bağlıdır. Ayrıca bu haritalardaki araç hızı, pedal pozisyonu ve vitese bağlı kombinasyonlar içerirler ve tüm olası koşulları içeren bir kalibrasyon yapılması oldukça zaman almaktadır. Mevcut kalibrasyon yapısının yukarıda bahsedilen kusurları göz önüne alındığında; araç sürüş özelliklerinin iyileştirilmesi için performans ve konfor gibi birbirleriye çelişen isteklerin optimizasyonunu barındıran gelişmiş tork kontrolü, otomobil üreticileri ve akademik dünyada son derece ilgi çeken bir konu haline gelmiştir. Araç doğrusal ekseni hareket kontrolü algoritmalarının başarılı bir şekilde kullanılabilmesi için motorun anlık olarak ürettiği torkun bilinmesi oldukça önemlidir. Günümüz araçlarının yanma kontrolü incelendiğinde, mevcut yapının harita bazlı olduğu görülür ve bu yapıda üretilen torkun doğrulaması yapılmamaktadır. Bu haritalar motor test dinamometrelerinde normal hava koşulları için (25 derece sıcaklık ve deniz seviyesi irtifa) doldurulurlar. Genellikle bu haritaların eksenleri motor hızı ve istenilen indike tork şeklinde olup, haritanın içeriğini ise istenilen yanma parametresinin belirtilen motor hızı ve indike torktaki değeri oluşturur. Bu yapı araçlarda kullanılırken bazı sıkıntılar yaratabilir. Motorlarda yanmayı oluşturan yakıt yolu parametreleri kontrolü çok daha hassas bir şekilde yapılırken (istenilen yakıt özellikleri: basınç, zamanlama ve miktar), gecici rejim manevraları düşünüldüğünde hava yolu parametreleri özellikle turbo şarj içeren dizel motor motorlarda istenilen değerden sapma gösterebilir. Bu durum “turbo gecikmesi” olarak adlandırılır ve üretilen torku ciddi şekilde etkiler. Aşırı sıcak yada soğuk ve yüksek irtifa koşulları düşünüldüğünde üretilen torktaki sapmalar çok daha fazla olur. Literature incelendiğinde araç eksenel doğrultusu için geliştirilen motor tork kontrol algoritmaları bakımından istenilen anlık torkun motor tarafından verildiği düşünülür. Fakat yukarıda belirtilen nedenlerden dolayı bu durum gerçekleşemez. Bu yüzden literaturde belirtilen araç doğrulsal ekseni için geliştirilen motor tork kontrolü algoritmalarında motor tork karakteristiği ya hiç düşünülmemiştir yada bazı temel gecikme ve filtrele fonksiyonları ile modellenmiştir. Tüm bu anlatılanlar düşünüldüğünde bu tez çalışmasının temelini oluşturan motor tork modeli içeren araç doğrusal ekseni kontrol algoritması literatürdeki diğer çalışmaşlarda ayrışır. Önerilen “Silindir için basınç öngörümlü motor tork kontrol modeli algoritması” araç sürüş özellikleri kontrol yapısı ile uyumlu bir şekilde çalışarak araç tepki karakterini iyileştirir. Bu çalışma kapsamında MATLAB/Similink modelle ortamında, 4 atalet kütlesi, 2 set yay ve sönüm elemanı ve lastik karakteristiği içeren, 4 serbbestlik dereceli bir aktarma organları modeli oluşturulmuştur. Sadece araç doğrusal ekseni araç dinamiğini içeren model validasyonu, gaz basma ve gazdan çekme gibi yük değişimi manevralarını içeren araç seviyesi tesler ile yürütülmüştür. Test ölçüm sonuçları ve model çıktıları karşılaştırıldığında geliştirilen aktarma organları modelinin araç doğrusal ekseni hızlanma profili için karşılaşılan hata modlarını da içerecek şekilde yansıttığı görülmüştür. Son olarak araç aktarma organları uygulaması düşünüldüğünde, araç sürüş özelliklerini iyileştirme için sürücü talebi doğrultusunda oluşan tork isteğini araç doğrulsal ekseni hareketinde oluşabilecek salınımları engelleyen model bazlı öngörümlü tork kontrol algoritması geliştirilmiştir. Bu algoritmada 4 serbestlik dereceli model, içerdiği doğrusal olmama durumu yüzünden kullanılamamıştır. Bu yüzden basitleştirilmiş 2 ve 3 serbestlik dereceli araç aktarma organları modelleri oluşturulmuştur. Yapılan çalışmalar doğrultusunda hem 2 hem de 3 serbestlik dereceli modellerin, model bazlı öngörümlü tork kontrol algoritmasını düzgün şekilde çalıştırabilmek için yeterli doğruluk ve çözünürlükde olduğu görülmüştür. Bu çalışmanın amacı kapalı devre bir araç sürüş özellikleri algoritması ortaya çıkarmak olduğu için ve geliştirilen algoritma teknik nedenler dolayısıyla araçta denenemediği için, 4 serbestlik dereceli motor aktarma organları modeli, 2 ve 3 serbestlik dereceli motor aktarma organları modelli içeren model bazlı öngörümlü tork kontrol algoritmalarını çalıştırmak üzere kullanılmıştır. Geliştirilen 2 ve 3 serbestlik dereceli modellerin araç sürüş özellikleri önemli derecede iyileştirdiği görülmüştür. Özellkile ivmelenme profilinin düzgünlüğü ve neden olusan sistem gecikmesi düşünüldüğünde 2 serbestlik dereceli aktarma organları modeli bazlı kontrol algoritmasnın daha iyi sonuç verdiği görülmüştür. Geliştirilen tork kontrol modelli aktarma organları bazlı araç salınımları ciddi oranda azaltsada, tamamen ortadan kaldırmadığı görülmüştür. Bu doğrultuda araç ivmelenme karakteristiğinden minimum seviyede ödün vererek, oluşan salınımları daha da azaltmak ve ivmelenme profilini daha düzgün hale getirmek için temel olarak motor ve araç hızı farkını elimine etme prensibine dayanan bir doğrulsal (P) kontrolcü, model bazlı öngürümlü tork kontrol algoritmasına eklenmiştir. Literatürde bu konuda yapılan çalışmalar incelendiğinde tüm araçtırmacıların model bazlı öngürümlü algoritmayı tek başına kullandıkları görükmektedir ve bu çalışmada önerilen doğrusal kontrolcü eklenmiş model bazlı öngörümlü tork kontrol algoritması bir yenilik olarak mevcut literatür içeriğine eklenmiştir.Considering the competitive environment in automotive industry, original equipment manufacturers (OEMs) in this industry are in a challenging competition with each other to offer their customers more attractive vehicles. Cost, emissions, fuel economy, noise vibration & harshness (NVH), durability, performance and driveability properties make a product able to distinguish from its competitors’ products. Each of these attributes has a major contribution of forming a perception of the customers’ choosiness. New technologies as a result of the research and developments activities in electronics resulted with complex electro-mechanical systems in automobiles. With the addition of recent developments in materials and manufacturing processes on top of it, especially in diesel fuelled internal combustion engines (ICE), torque and power delivery had almost doubled with respect to the conventional engines developed not more than two decades ago. Additionally as a result of latest developments at air path and gas exchange systems control, torque build up rate had significantly increased enabling the vehicles to be more agile and reactive to load change request manoeuvres. As a result of all these capability improvements, vehicle response characteristics to high torque and power capacity engines changed extremely altering the necessity of proper and robust driveability calibration requirements. Driveability properties of the vehicles had gained significant importance in terms of customer satisfaction. This dissertation focuses on improving vehicle driveability properties taking advantage of simulation tools and model based control. The overall profit of this thesis is providing improved driveability via using engine torque production and vehicle models and controllers at the same time. Torque transmission from the vehicle’s power unit to the road surface via tires is a complex structure which should be handled with extreme care considering the overall driveability performance of the vehicle. An agile throttle response of the vehicle is aimed without error modes like acceleration initial kick, bump, response delay, stumble or shuffle. However considering the nonlinearities resulting from the complex structures at the drivetrain of the vehicle, this requirement becomes significantly challenging. Despite mechanical control at longitudinal motion in conventional vehicles, modern vehicles are equipped with electromechanical systems. Thanks to technological developments in the automotive industry that current capability of the vehicles enables us to develop better platforms for improving driveability characteristics. Modern engine control units (ECUs) have the capability of processing thousands of signals in a less than tens of milliseconds and as a result regulate numerous actuators which results with displacement of the vehicle complying all regulative requirements and customer expectations. Acceleration throttle pedal input signal is recorded by electronic control unit, processed and finally used to control the parameters for the combustion systems. In terms of driveability control, automotive manufacturers’ engine control algorithms employ input shaping or simple filtering algorithms. These algorithms use look-up tables and main control strategy is to slew the pedal oriented torque request for the tip-in and tip-out manoeuvres in an open loop control methodology especially in backlash transition region of the driveline. Considering the fact that there is no close loop control and these features become subjective calibration methodologies and outcome becomes strongly dependant on calibrator’s capability and performance. Moreover filling look-up tables for all gear, engine speed and pedal position combinations requires significant amount of calibration development time. Taking into consideration all of these obstacles of the current driveability features, the subject of automated torque control for improved driveability is a state of the art research topic both within automotive manufacturers and academic researchers as it can be described as an optimization problem dealing with performance and comfort counter measures. Knowledge of the instantaneous produced torque by the engine is a key item with respect to satisfying above stated attributes in vehicle longitudinal motion control. Currently common approach for combustion management is the usage of look-up table based structures with the drawback of poor conformity of the produced torque. Look-up tables define air and fuel quantity setpoints in order to produce requested indicated torque without feedback of the produced torque. These look-up tables are filled at engine dynamometer test benches at normal ambient conditions. In general fuel and air quantity setpoint maps have the axes of engine speed and indicated torque and requested amount of desired variable is filled to the corresponding point of the look-up table. In real world driving conditions fuel quantity control is robust however especially with turbocharged systems; requested air quantities may deviate from the setpoint values especially when considering transient manoeuvres. This phenomenon is called “turbo/boost lag” and significantly affects the produced torque. The situation is much worse for non-standard conditions, extreme hot and cold and altitude. In the literature most of the proposed vehicle longitudinal motion control related engine torque control algorithms base on the fact that requested torque will be generated immediately from the diesel engine. However as explained above this is not the case in real life applications. Therefore engine characteristic is either not included or covered with a simple filtering algorithm in conventional vehicle longitudinal motion related engine torque control methodologies. Engine brake torque model combined driveability control algorithm proposed in this thesis is differentiated from the previous studies in the literature within this perspective. Proposed “In cylinder pressured based engine brake torque model algorithm” works in harmony with the driveability control structure and improves overall vehicle response characteristics. Within the scope of this study a 4 degree of freedom powertrain model consisting of 4 inertias, 2 set of spring and damper elements with tyre characteristics, is built in MATLAB/Simulink environment. Model validation considering longitudinal vehicle dynamics is performed with employing vehicle level tests using a tip-in followed by a tip-out acceleration pedal signal input load change manoeuvres. Comparison of simulation results and measured vehicle test data shows that proposed model is capable of capturing vehicle acceleration profile revealing unintended error states for the specified input signals. Considering the driveability control perspective, a Model Predictive Control (MPC) algorithm employed to manipulate the pedal map oriented torque demand signal in an automotive powertrain application in order attenuate the powertrain oscillations in longitudinal vehicle motion control. 4 mass model could not be employed at with the MPC algorithm due to very high level of nonlinearity. Therefore two simplified versions of 2 and 3 mass models have been developed. It has been verified that both 2 and 3 mass vehicle models are accurate enough to employ the MPC torque control algorithm. As the aim of this study is to develop a close loop driveability algorithm for real world applications, the 4 mass vehicle model is used as replacement environment for the subjected vehicle in order to employ 2 and 3 mass vehicle model based control algorithm. MPC algorithms via using both models showed good capability, however smoothness of the driving profile with the 2 mass vehicle model is slightly better than the 3 mass model. Moreover to further improve the powertrain oscillations without compromising from overall system response speed, an additional anti-shuffle control element, basically a P controller based on the speed difference of engine and vehicle speeds, has been implemented to the MPC control algorithm. Literature review about the engine torque control for improved driveability show that all the researcher use MPC alone. Proposed MPC with additional P controller is a new contribution to the literature in the subjected area of research.DoktoraPh.D

Engineering Education and Research Using MATLAB

MATLAB is a software package used primarily in the field of engineering for signal processing, numerical data analysis, modeling, programming, simulation, and computer graphic visualization. In the last few years, it has become widely accepted as an efficient tool, and, therefore, its use has significantly increased in scientific communities and academic institutions. This book consists of 20 chapters presenting research works using MATLAB tools. Chapters include techniques for programming and developing Graphical User Interfaces (GUIs), dynamic systems, electric machines, signal and image processing, power electronics, mixed signal circuits, genetic programming, digital watermarking, control systems, time-series regression modeling, and artificial neural networks

A fast engineering approach to high efficiency power amplifier linearization for avionics applications

This PhD thesis provides a fast engineering approach to the design of digital predistortion (DPD) linearizers from several perspectives: i) enhancing the off-line training performance of open-loop DPD, ii) providing robustness and reducing the computational complexity of the parameters identification subsystem and, iii) importing machine learning techniques to favor the automatic tuning of power amplifiers (PAs) and DPD linearizers with several free-parameters to maximize power efficiency while meeting the linearity specifications. One of the essential parts of unmanned aerial vehicles (UAV) is the avionics, being the radio control one of the earliest avionics present in the UAV. Unlike the control signal, for transferring user data (such as images, video, etc.) real-time from the drone to the ground station, large transmission rates are required. The PA is a key element in the transmitter chain to guarantee the data transmission (video, photo, etc.) over a long range from the ground station. The more linear output power, the better the coverage or alternatively, with the same coverage, better SNR allows the use of high-order modulation schemes and thus higher transmission rates are achieved. In the context of UAV wireless communications, the power consumption, size and weight of the payload is of significant importance. Therefore, the PA design has to take into account the compromise among bandwidth, output power, linearity and power efficiency (very critical in battery-supplied devices). The PA can be designed to maximize its power efficiency or its linearity, but not both. Therefore, a way to deal with this inherent trade-off is to design high efficient amplification topologies and let the PA linearizers take care of the linearity requirements. Among the linearizers, DPD linearization is the preferred solution to both academia and industry, for its high flexibility and linearization performance. In order to save as many computational and power resources as possible, the implementation of an open-loop DPD results a very attractive solution for UAV applications. This thesis contributes to the PA linearization, especially on off-line training for open-loop DPD, by presenting two different methods for reducing the design and operating costs of an open-loop DPD, based on the analysis of the DPD function. The first method focuses on the input domain analysis, proposing mesh-selecting (MeS) methods to accurately select the proper samples for a computationally efficient DPD parameter estimation. Focusing in the MeS method with better performance, the memory I-Q MeS method is combined with feature extraction dimensionality reduction technique to allow a computational complexity reduction in the identification subsystem by a factor of 65, in comparison to using the classical QR-LS solver and consecutive samples selection. In addition, the memory I-Q MeS method has been proved to be of crucial interest when training artificial neural networks (ANN) for DPD purposes, by significantly reducing the ANN training time. The second method involves the use of machine learning techniques in the DPD design procedure to enlarge the capacity of the DPD algorithm when considering a high number of free parameters to tune. On the one hand, the adaLIPO global optimization algorithm is used to find the best parameter configuration of a generalized memory polynomial behavioral model for DPD. On the other hand, a methodology to conduct a global optimization search is proposed to find the optimum values of a set of key circuit and system level parameters, that properly combined with DPD linearization and crest factor reduction techniques, can exploit at best dual-input PAs in terms of maximizing power efficiency along wide bandwidths while being compliant with the linearity specifications. The advantages of these proposed techniques have been validated through experimental tests and the obtained results are analyzed and discussed along this thesis.Aquesta tesi doctoral proporciona unes pautes per al disseny de linealitzadors basats en predistorsió digital (DPD) des de diverses perspectives: i) millorar el rendiment del DPD en llaç obert, ii) proporcionar robustesa i reduir la complexitat computacional del subsistema d'identificació de paràmetres i, iii) incorporació de tècniques d'aprenentatge automàtic per afavorir l'auto-ajustament d'amplificadors de potència (PAs) i linealitzadors DPD amb diversos graus de llibertat per poder maximitzar l’eficiència energètica i al mateix temps acomplir amb les especificacions de linealitat. Una de les parts essencials dels vehicles aeris no tripulats (UAV) _es l’aviònica, sent el radiocontrol un dels primers sistemes presents als UAV. Per transferir dades d'usuari (com ara imatges, vídeo, etc.) en temps real des del dron a l’estació terrestre, es requereixen taxes de transmissió grans. El PA _es un element clau de la cadena del transmissor per poder garantir la transmissió de dades a grans distàncies de l’estació terrestre. A major potència de sortida, més cobertura o, alternativament, amb la mateixa cobertura, millor relació senyal-soroll (SNR) la qual cosa permet l’ús d'esquemes de modulació d'ordres superiors i, per tant, aconseguir velocitats de transmissió més altes. En el context de les comunicacions sense fils en UAVs, el consum de potència, la mida i el pes de la càrrega útil són de vital importància. Per tant, el disseny del PA ha de tenir en compte el compromís entre ample de banda, potència de sortida, linealitat i eficiència energètica (molt crític en dispositius alimentats amb bateries). El PA es pot dissenyar per maximitzar la seva eficiència energètica o la seva linealitat, però no totes dues. Per tant, per afrontar aquest compromís s'utilitzen topologies amplificadores d'alta eficiència i es deixa que el linealitzador s'encarregui de garantir els nivells necessaris de linealitat. Entre els linealitzadors, la linealització DPD és la solució preferida tant per al món acadèmic com per a la indústria, per la seva alta flexibilitat i rendiment. Per tal d'estalviar tant recursos computacionals com consum de potència, la implementació d'un DPD en lla_c obert resulta una solució molt atractiva per a les aplicacions UAV. Aquesta tesi contribueix a la linealització del PA, especialment a l'entrenament fora de línia de linealitzadors DPD en llaç obert, presentant dos mètodes diferents per reduir el cost computacional i augmentar la fiabilitat dels DPDs en llaç obert. El primer mètode se centra en l’anàlisi de l’estadística del senyal d'entrada, proposant mètodes de selecció de malla (MeS) per seleccionar les mostres més significatives per a una estimació computacionalment eficient dels paràmetres del DPD. El mètode proposat IQ MeS amb memòria es pot combinar amb tècniques de reducció del model del DPD i d'aquesta manera poder aconseguir una reducció de la complexitat computacional en el subsistema d’identificació per un factor de 65, en comparació amb l’ús de l'algoritme clàssic QR-LS i selecció de mostres d'entrenament consecutives. El segon mètode consisteix en l’ús de tècniques d'aprenentatge automàtic pel disseny del DPD quan es considera un gran nombre de graus de llibertat (paràmetres) per sintonitzar. D'una banda, l'algorisme d’optimització global adaLIPO s'utilitza per trobar la millor configuració de paràmetres d'un model polinomial amb memòria generalitzat per a DPD. D'altra banda, es proposa una estratègia per l’optimització global d'un conjunt de paràmetres clau per al disseny a nivell de circuit i sistema, que combinats amb linealització DPD i les tècniques de reducció del factor de cresta, poden maximitzar l’eficiència de PAs d'entrada dual de gran ample de banda, alhora que compleixen les especificacions de linealitat. Els avantatges d'aquestes tècniques proposades s'han validat mitjançant proves experimentals i els resultats obtinguts s'analitzen i es discuteixen al llarg d'aquesta tesi

Air Force Institute of Technology Research Report 2003

This report summarizes the research activities of the Air Force Institute of Technology’s Graduate School of Engineering and Management. It describes research interests and faculty expertise; lists student theses/dissertations; identifies research sponsors and contributions; and outlines the procedures for contacting the school. Included in the report are: faculty publications, conference presentations, consultations, and funded research projects. Research was conducted in the areas of Aeronautical and Astronautical Engineering, Electrical Engineering and Electro-Optics, Computer Engineering and Computer Science, Systems and Engineering Management, Operational Sciences, and Engineering Physics

The application of impact factors to scheduling VLBI Intensive sessions with twin telescopes

This thesis deals with the scheduling of special purpose, 1h-long VLBI sessions, so-called Intensives, and its further extension by twin radio telescopes. The daily VLBI Intensive measurements make an important contribution to the regular monitoring of Earth rotation variations. Since these variations are quite rapid their knowledge is important for navigation with GNSS and for investigations in Earth sciences. Unfortunately, the precision of VLBI Intensive observations is 2-3 times worse than the precision of regular 24h-VLBI measurements with networks of 5-10 radio telescopes. For economical and logistical reasons, these are performed only twice a week and have the disadvantage of a latency of the results of about ten days. However, for reliable predictions of the Earth’s rotation, the results have to be available as rapidly as possible. For these reasons, the International VLBI Service for Geodesy and Astrometry (IVS) carries short duration (1h) sessions on a daily basis. The major task of research in this thesis is the improvement of VLBI Intensive results by using twin radio telescopes instead of single radio telescopes. Therefore, a new scheduling method for creating Intensive observing plans has been developed. With the aim of finding an appropriate method to schedule VLBI observations, preparatory investigations of Intensive sessions have been done using a regression diagnostics tool which is based on singular value decomposition of the design matrix and cluster analysis methods. These investigations suggest that the impact factors of the observations are well suited for the identification of the most influential observations which are needed for the determination of certain parameters within the entire design of a VLBI session. Thus, by using the impact factors of the observations as selection criteria, the developed scheduling method is designed for optimizing the observations’ geometry for a given network of radio telescopes and a predefined set of parameters to be estimated. The configuration of at least two twin telescopes, or one twin and two single telescopes, offers the possibility of building pairwise sub-nets that observe two different radio sources simultaneously. As a consequence, the number of viable observations within a session duration increased. In addition to an optimized observing plan, a special parametrization for twin telescopes leads to an improved determination of the Earth rotation variations, as it is shown by simulated observations in this thesis. In general, an improvement of about 50 percent in the formal errors can be realized by using twin radio telescopes.Die Verwendung von Einflussfaktoren bei der VLBI Intensive-Beobachtungsplanung mit Zwillings-Teleskopen Die vorliegende Arbeit beschäftigt sich mit der Erstellung von Beobachtungsplänen für VLBI Intensives und deren Erweiterung durch Zwillings-Radioteleskope. Täglich durchgeführte VLBI Intensive Messungen leisten einen wichtigen Beitrag zur regelmäßigen Überwachung von Erdrotationsvariationen. Da diese Variationen von relativ schneller Natur sind, ist deren Kenntnis wichtig für die Navigation mit GNSS und für Forschungen auf dem Gebiet der Erdwissenschaften. Leider ist die Genauigkeit von VLBI Intensives 2-3 mal schlechter als die der regulären 24-Stunden VLBI Messungen mit einem Netzwerk bestehend aus 5-10 Radioteleskopen. Diese werden allerdings aus wirtschaftlichen und logistischen Gründen nur zweimal in der Woche durchgeführt und haben den Nachteil, dass die Ergebnisse erst etwa zehn Tage später zu Verfügung stehen. Für zuverlässige Prädiktionen der Erdrotationsgeschwindigkeit sind allerdings schnell verfügbare Daten erforderlich. Aus diesem Grund betreibt der International VLBI Service for Geodesy and Astrometry (IVS) tägliche Kurzzeitbeobachtungen (1h). Das Hauptforschungsthema dieser Arbeit stellt die Verbesserung von VLBI Intensive Ergebnissen durch den Einsatz von Zwillings-Radioteleskopen anstelle von Einzel-Radioteleskopen dar. Zu diesem Zwecke wurde eine neue Planungsstrategie entwickelt um Intensive-Beobachtungspläne zu erstellen. Um eine geeignete Methode zur Erstellung von Beobachtungsplänen zu entwickeln, wurden vorbereitende Untersuchungen von Intensive-Beobachtungsplänen mittles Regressionsanalyse durchgeführt. Die angewandte Regressionsanalyse basiert auf der Singulärwertzerlegung der Designmatrix eines Ausgleichungsproblems und Clusteranalyse-Verfahren. Diese Untersuchungen weisen darauf hin, dass die Einflussfaktoren der Beobachtungen gut geeignet sind, um einflussreiche Beobachtungen zur Bestimmung gewisser Parameter unter Berücksichtigung des gesamten Designs eines VLBI-Experiments zu detektieren. Durch die Nutzung von Einflussfaktoren der Beobachtungen als Auswahlkriterium ist die entwickelte Methode zur Beobachtungsplanerstellung darauf ausgelegt die Beobachtungsgeometrie für ein bestehendes Stationsnetzwerk von Radioteleskopen und einen vordefinierten Satz an zu schätzenden Parametern zu optimieren. Die Konfiguration von mindestens zwei Zwillings-Radioteleskopen, oder einem Zwillings-Radioteleskop und zwei Einzel-Radioteleskopen bietet die Möglichkeit der Paarbildung zwischen den Teleskopen und somit das zeitgleiche Beobachten von zwei unterschiedlichen Radioquellen. Eine Konsequenz daraus ist eine erhöhte Beobachtungsanzahl innerhalb der Dauer eines Experiments. Neben einem optimierten Beobachtungsplan führt auch die spezielle Parametrisierung aufgrund der räumlichen Nähe der Zwillings-Radioteleskope zueinander zu einer verbesserten Bestimmung der Erdrotationsvariationen, wie es in dieser Arbeit mit Hilfe simulierter Beobachtungen gezeigt wird. Im Allgemeinen kann eine Verbesserung des formalen Fehlers um 50 Prozent und mehr durch die Verwendung von Zwillings-Radioteleskopen für tägliche Intensive Messungen realisiert werden

Economical sampling of parametric signals

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 107-115).This thesis proposes architectures and algorithms for digital acquisition of parametric signals. It furthermore provides bounds for the performance of these systems in the presence of noise. Our simple acquisition circuitry and low sampling rate enable accurate parameter estimation to be achieved economically. In present practice, sampling and estimation are not integrated: the sampling device does not take advantage of the parametric model, and the estimation assumes that noise in the data is signal-independent additive white Gaussian noise. We focus on estimating the timing information in signals that are linear combinations of scales and shifts of a known pulse. This signal model is well-known in a variety of disciplines such as ultra-wideband signaling, neurobiology, etc. The signal is completely determined by the amplitudes and shifts of the summands. The delays determine a subspace that contains the signals, so estimating the shifts is equivalent to subspace estimation. By contrast, conventional sampling theory yields a least-squares approximation to a signal from a fixed shift-invariant subspace of possible reconstructions. Conventional acquisition takes samples at a rate higher than twice the signal bandwidth.(cont.) Although this may be feasible, there is a trade-off between power, accuracy, and speed. Under the signal model of interest, when the pulses are very narrow, the number of parameters per unit time-the rate of innovation-is much lower than the Fourier bandwidth. There is thus potential for much lower sampling rate so long as nonlinear reconstruction algorithms are used. We present a new sampling scheme that takes simultaneous samples at the outputs of multiple channels. This new scheme can be implemented with simple circuitry and has a successive approximation property that can be used to detect undermodeling. In many regimes our algorithms provide better timing accuracy and resolution than conventional systems. Our new analytical and algorithmic techniques are applied to previously proposed systems, and it is shown that all the systems considered have super-resolution properties. Finally, we consider the same parameter estimation problem when the sampling instances are perturbed by signal-independent timing noise. We give an iterative algorithm that achieves accurate timing estimation by exploiting knowledge of the pulse shape.by Julius Kusuma.Ph.D

MOCAST 2021

The 10th International Conference on Modern Circuit and System Technologies on Electronics and Communications (MOCAST 2021) will take place in Thessaloniki, Greece, from July 5th to July 7th, 2021. The MOCAST technical program includes all aspects of circuit and system technologies, from modeling to design, verification, implementation, and application. This Special Issue presents extended versions of top-ranking papers in the conference. The topics of MOCAST include:Analog/RF and mixed signal circuits;Digital circuits and systems design;Nonlinear circuits and systems;Device and circuit modeling;High-performance embedded systems;Systems and applications;Sensors and systems;Machine learning and AI applications;Communication; Network systems;Power management;Imagers, MEMS, medical, and displays;Radiation front ends (nuclear and space application);Education in circuits, systems, and communications

Application of advanced technology to space automation

Automated operations in space provide the key to optimized mission design and data acquisition at minimum cost for the future. The results of this study strongly accentuate this statement and should provide further incentive for immediate development of specific automtion technology as defined herein. Essential automation technology requirements were identified for future programs. The study was undertaken to address the future role of automation in the space program, the potential benefits to be derived, and the technology efforts that should be directed toward obtaining these benefits