General model for delayed feedback and its application to transimpedance amplifier's bandwidth optimization

Delays in real systems can be of two types: i) intrinsic delays - due to the physical principles of operation of each electronic device; ii) designed delays - due to extra circuits used to add the desired delay. Previous work established the possibility of achieving bandwidth improvements using small delays inside the feedback loop of feedback amplifiers. The modeling approach followed on these contributions used only one designed delay element. The bandwidth reduction effect due to intrinsic delays was not considered on these contributions. This paper extends the concept to the general case of feedback amplifiers that incorporates delays of both types. An experimental demonstration using a simple 0.35μm BiCMOS transimpedance amplifier further confirms the proposed model. © 2006 IEEE

Photonic Delay Systems as Machine Learning Implementations

Nonlinear photonic delay systems present interesting implementation platforms for machine learning models. They can be extremely fast, offer great degrees of parallelism and potentially consume far less power than digital processors. So far they have been successfully employed for signal processing using the Reservoir Computing paradigm. In this paper we show that their range of applicability can be greatly extended if we use gradient descent with backpropagation through time on a model of the system to optimize the input encoding of such systems. We perform physical experiments that demonstrate that the obtained input encodings work well in reality, and we show that optimized systems perform significantly better than the common Reservoir Computing approach. The results presented here demonstrate that common gradient descent techniques from machine learning may well be applicable on physical neuro-inspired analog computers

Dynamic Voltage Rail Audio Amplifier

The goal of this project is to create a high-quality, power-efficient audio amplifier. Most modern audio amplifiers use a constant amount of power regardless of the signal that is being amplified. This means that both loud and quiet portions of the audio signal require the same amount of power to amplify. The idea for this high-quality, power-efficient audio amplifier is that the quieter portions of the audio signal can be amplified using less power. This will be achieved by first analyzing the audio signal and controlling the power source based on the signal’s needs. Therefore, louder parts of the audio signal will use the typical amount of power, while quieter parts of the signal will not use as much power. When comparing a standard audio amplifier and the high-quality power-efficient audio amplifier, the average power usage for the power-efficient amplifier should be less than the standard amplifier

Data acquisition electronics and reconstruction software for directional detection of Dark Matter with MIMAC

Directional detection of galactic Dark Matter requires 3D reconstruction of low energy nuclear recoils tracks. A dedicated acquisition electronics with auto triggering feature and a real time track reconstruction software have been developed within the framework of the MIMAC project of detector. This auto-triggered acquisition electronic uses embedded processing to reduce data transfer to its useful part only, i.e. decoded coordinates of hit tracks and corresponding energy measurements. An acquisition software with on-line monitoring and 3D track reconstruction is also presented.Comment: 17 pages, 12 figure

A laboratory breadboard system for dual-arm teleoperation

The computing architecture of a novel dual-arm teleoperation system is described. The novelty of this system is that: (1) the master arm is not a replica of the slave arm; it is unspecific to any manipulator and can be used for the control of various robot arms with software modifications; and (2) the force feedback to the general purpose master arm is derived from force-torque sensor data originating from the slave hand. The computing architecture of this breadboard system is a fully synchronized pipeline with unique methods for data handling, communication and mathematical transformations. The computing system is modular, thus inherently extendable. The local control loops at both sites operate at 100 Hz rate, and the end-to-end bilateral (force-reflecting) control loop operates at 200 Hz rate, each loop without interpolation. This provides high-fidelity control. This end-to-end system elevates teleoperation to a new level of capabilities via the use of sensors, microprocessors, novel electronics, and real-time graphics displays. A description is given of a graphic simulation system connected to the dual-arm teleoperation breadboard system. High-fidelity graphic simulation of a telerobot (called Phantom Robot) is used for preview and predictive displays for planning and for real-time control under several seconds communication time delay conditions. High fidelity graphic simulation is obtained by using appropriate calibration techniques

An event-related potential study on changes of violation and error responses during morphosyntactic learning

Based on recent findings showing electrophysiological changes in adult language learners after relatively short periods of training, we hypothesized that adult Dutch learners of German would show responses to German gender and adjective declension violations after brief instruction. Adjective declension in German differs from previously studied morphosyntactic regularities in that the required suffixes depend not only on the syntactic case, gender, and number features to be expressed, but also on whether or not these features are already expressed on linearly preceding elements in the noun phrase. Violation phrases and matched controls were presented over three test phases (pretest and training on the first day, and a posttest one week later). During the pretest, no electrophysiological differences were observed between violation and control conditions, and participants’ classification performance was near chance. During the training and posttest phases, classification improved, and there was a P600-like violation response to declension but not gender violations. An error-related response during training was associated with improvement in grammatical discrimination from pretest to posttest. The results show that rapid changes in neuronal responses can be observed in adult learners of a complex morphosyntactic rule, and also that error-related electrophysiological responses may relate to grammar acquisition

An auxiliary capacitor based ultra-fast drive circuit for shear piezoelectric motors

Shear piezoelectric motors frequently require large voltage changes on very short time scales. Since piezos behave electrically as capacitors, this requires a drive circuit capable of quickly sourcing or sinking a large amount of current at high voltages. Here we describe a novel circuit design using a high voltage amplifier, transistor switching stage, and auxiliary capacitor. This circuit can drive piezoelectric motors at higher speeds and lower costs than conventional methods and with greater flexibility for computer automation. We illustrate its application in a controller for a scanning tunneling microscope coarse approach mechanism and discuss other possible applications and modifications of this circuit.National Science Foundation CAREER programNational Science Foundation MRSEC ProgramResearch Corporation Cottrell Scholarshi

High gain and bandwidth current-mode amplifiers : study and implementation

Doutoramento em Engenharia ElectrotécnicaEsta tese aborda o problema do projecto de amplificadores com grandes produtos de ganho por largura de banda. A aplicação final considerada consistiu no projecto de amplificadores adequados à recepção de sinais ópticos em sistemas de transmissão ópticos usando o espaço livre. Neste tipo de sistemas as maiores limitações de ganho e largura de banda surgem nos circuitos de entrada. O uso de detectores ópticos com grande área fotosensível é uma necessidade comum neste tipo de sistemas. Estes detectores apresentam grandes capacidades intrínsecas, o que em conjunto com a impedância de entrada apresentada pelo amplificador estabelece sérias restrições no produto do ganho pela largura de banda. As técnicas mais tradicionais para combater este problema recorrem ao uso de amplificadores com retroacção baseados em configurações de transimpedância. Estes amplificadores apresentam baixas impedâncias de entrada devido à acção da retroacção. Contudo, os amplificadores de transimpedância também apresentam uma relação directa entre o ganho e a impedância de entrada. Logo, diminuir a impedância de entrada implica diminuir o ganho. Esta tese propõe duas técnicas novas para combater os problemas referidos. A primeira técnica tem por base uma propriedade fundamental dos amplificadores com retroacção. Em geral, todos os circuitos electrónicos têm tempos de atraso associados, os amplificadores com retroacção não são uma excepção a esta regra. Os tempos de atraso são em geral reconhecidos como elementos instabilizadores neste tipos da amplificadores. Contudo, se usados judiciosamente, este tempos de atraso podem ser explorados como uma forma da aumentar a largura de banda em amplificadores com retroacção. Com base nestas ideias, esta tese apresenta o conceito geral de reatroacção com atraso, como um método de optimização de largura de banda em amplificadores com retroacção. O segundo método baseia-se na destruição da dualidade entre ganho e impedância de entrada existente nos amplificadores de transimpedância. O conceito de adaptação activa em modo de corrente é neste sentido uma forma adequada para separar o detector óptico da entrada do amplificador. De acordo com este conceito, emprega-se um elemento de adaptação em modo de corrente para isolar o detector óptico da entrada do amplificador. Desta forma as tradicionais limitações de ganho e largura de banda podem ser tratadas em separado. Esta tese defende o uso destas técnicas no desenho de amplificadores de transimpedância para sistemas de recepção de sinais ópticos em espaço livre.This thesis addresses the problem of achieving high gain-bandwidth products in amplifiers. The adopted framework consisted on the design of a free-space optical (FSO) front end amplifier able to amplify very small optical signals over large frequency bandwidths. The major gain-bandwidth limitations in FSO front end amplifiers arise due to the input circuitry. Usually, it is necessary to have large area optical detectors in order to maximize signal reception. These detectors have large intrinsic capacitances, which together with the amplifier input impedance poses a severe restriction on the gain-bandwidth product. Traditional techniques to combat this gain-bandwidth limitation resort to feedback amplifiers consisting on transimpedance configurations. These amplifiers have small input impedances due to the feedback action. Nevertheless, transimpedance amplifiers have a direct relation between gain and input impedance. Thus reducing the input impedance usually implies reducing the gain. This thesis advances two new methods suitable to combat the above mentioned problems. The first method is based on a fundamental property of feedback amplifiers. In general, all electronic circuits have associated time delays, and feedback amplifiers are not an exception to this rule. Time delays in feedback amplifiers have been recognized as destabilizing elements. Nevertheless, when used with appropriate care, these delays can be exploited as bandwidth enhancement elements. Based on these ideas, this thesis presents the general concept of delayed feedback, as a bandwidth optimization method suitable for feedback amplifiers. The second method is based on the idea of destroying the impedance-gain duality in transimpedance amplifiers. The concept of active current matching is in this sense a suitable method to detach the optical detector from the transimpedance amplifier input. According to this concept, a current matching device (CMD) is used to convey the signal current sensed by the optical detector, to the amplifier’s input. Using this concept the traditional gainbandwidth limitations can be treated in a separate fashion. This thesis advocates the usage of these techniques for the design of transimpedance amplifiers suited for FSO receiving systems

Energy efficient DBA algorithms for TWDM-PONs

Energy efficiency is of a vital significance in the design of next generation time and wavelength division multiplexed passive optical networks (TWDM-PONs). In this paper, we first review strategies to save energy in TWDM-PONs using the state-of-the-art dynamic bandwidth allocation (DBA) algorithms. The DBA algorithms should not only minimize energy consumption but should impose a minimal penalty on delay performance. In this context, mainly two DBA design paradigms can be exploited: offline and online. After reviewing the performance of various design paradigms, we propose an optimal algorithm, which minimizes the energy consumption at both the OLT and the ONUs, by combining the energy efficiency due to sleep modes and the load dependent use of transceivers at the OLT. Due to this, the average energy consumption is reduced to 31%

Real-time Digital Simulation of Guitar Amplifiers as Audio Effects

Práce se zabývá číslicovou simulací kytarových zesilovačů, jakož to nelineárních analogových hudebních efektů, v reálném čase. Hlavním cílem práce je návrh algoritmů, které by umožnily simulaci složitých systémů v reálném čase. Tyto algoritmy jsou prevážně založeny na automatizované DK-metodě a aproximaci nelineárních funkcí. Kvalita navržených algoritmů je stanovana pomocí poslechových testů.The work deals with the real-time digital simulation of guitar amplifiers considered as nonlinear analog audio effects. The main aim is to design algorithms which are able to simulate complex systems in real-time. These algorithms are mainly based on the automated DK-method and the approximation of nonlinear functions. Quality of the designed algorithms is evaluated using listening tests.