1,721,082 research outputs found
Experimental technique for the performance evaluation and optimization of 1/f noise spectrum investigation in electron devices
No full textIn this paper, a fast and systematic experimental technique is proposed, which is devoted to the performance evaluation of power spectral density non-parametric estimators, in the framework of 1/f-noise bias-varying investigation at the ports of semiconductor electron devices. The methodology, which allows to overcome the need both for cumbersome analytical computation of a-priori moments, and non-reliable and time-consuming conventional statistical inference, provides the performance of the estimator and related parameters under investigation from a single realization, by exploiting the frequency stationarity of non-parametric algorithms in the relative and asymptotical sense. The technique has been applied to the case-study of a power MOSFET, by considering Bartlett, Welch and circular Welch estimators and different time windows and data record segmentation strategies, in order to verify its capabilities and, in particular, to identify the optimal non-parametric estimation of 1/f noise spectrum. In addition, results obtained by means of conventional statistical inference are compared to the estimates provided by the technique proposed, to the aim of further experimental assessment
Digital Radio Frequency Transport over Optical Fiber for 5G Fronthaul Links
No full textRadio over fiber (RoF) is an empowering technology for the next-generation wireless networks including fifth generation cloud radio access networks. In this paper, we propose a new fronthaul interface which has been demonstrated for a 20-MHz LTE signal having 64-Quadrature amplitude modulation (QAM) modulation over 50 km of standard single-mode fiber. The proposed methodology potentially reduces the overall bandwidth requirement of the link. The performance analysis has been demonstrated for conventional analog RoF (A-RoF) and proposed digital RoF (D-RoF). As a figure of merit, the performance evaluation of the two architectures is reported by analyzing error vector magnitude (EVM), signal-to-noise ratio and eye-opening penalty. It is shown that digital optical links can mitigate the impairments present in A-RoF links and can support the transmission up to 50 km. Moreover, it is shown that efficient D-RoF links can be obtained with a relatively low amount of analog-to–digital-converter resolution bits. For the D-RoF link, the EVM was measured to be less than 2 % at 50 km. This is within the LTE specifications, proving it as a cost and power effective solution for next-generation wireless networks
An Integrated Co-Simulation Framework for the Design, Analysis, and Performance Assessment of EIS-Based Measurement Systems for the Online Monitoring of Battery Cells
Full text linkElectrochemical impedance spectroscopy (EIS) is widely used at the laboratory level for monitoring/diagnostics of battery cells, but the design and validation of in situ, online measurement systems based on EIS face challenges due to complex hardware–software interactions and non-idealities. This study aims to develop an integrated co-simulation framework to support the design, debugging, and validation of EIS measurement systems devoted to the online monitoring of battery cells, helping to predict experimental results and identify/correct the non-ideality effects and sources of uncertainty. The proposed framework models both the hardware and software components of an EIS-based system to simulate and analyze the impedance measurement process as a whole. It takes into consideration the effects of physical non-idealities on the hardware–software interactions and how those affect the final impedance estimate, offering a tool to refine designs and interpret test results. For validation purposes, the proposed general framework is applied to a specific EIS-based laboratory prototype, previously designed by the research group. The framework is first used to debug the prototype by uncovering hidden non-idealities, thus refining the measurement system, and then employed as a digital model of the latter for fast development of software algorithms. Finally, the results of the co-simulation framework are compared against a theoretical model, the real prototype, and a benchtop instrument to assess the global accuracy of the framework
Reduction of harmonic distortion in radio over fiber links through digital preprocessing
No full textExperimental characterization of low-frequency noise in power MOSFETs for defectiveness modelling and technology assessment
Full text linkIn this work we analyse the applicability of low-frequency (LF) noise measurement in order to study the defectiveness in the gate oxide of power MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors). To this purpose, we implement a low-noise experimental set-up, which is able to measure, in particular, the flicker ("1/f'') contribution to the drain noise current of the device under test, with high accuracy in terms of noise floor and the adequate bias system flexibility required by the application. First, we show how these measurements can be used to empirically detect the physical model and related compact expressions, which best describe the source of 1/f-like fluctuations in this type of devices. Then, according to the selected physical model, the defect density in the gate oxide is extracted. In order to validate the proposed methodology, experimental data are reported and discussed in the case of power U-MOSFETs
A compact low-noise broadband digital picoammeter architecture
No full textA low-noise (?4 fA/?Hz), broadband (?100 kHz) compact architecture and related operation solutions are proposed for portable and low-cost time-domain acquisition of currents with effective resolution in the order of 1 pA and below. The front-end architecture is based on an integrating-differentiating scheme to achieve the optimal performance in terms of input-referred equivalent noise, but it overcomes the typical noise/bandwidth trade-off by making the sampling frequency of the A/D conversion independent from the rate at which the analog front-end is reset. In order to strongly mitigate the main drawback, i.e., the introduction in the system of an inherent time-variance, a Track-and-Hold circuit synchronized with the reset is exploited.For validation purposes, a dual-channel prototype was implemented in a low-cost CMOS technology. The prototype is characterized by standard figures of merit and is experimentally validated by two simple case studies, which are typical of practical applications
Experimental characterization of bandwidth limits in hall sensors
No full textModern power applications are demanding for broadband current sensors. Hall sensors are a good solution from a general standpoint, but practical implementations are limited to a few hundred kHz. In fact, many parasitic dynamic effects perturb the time response of the Hall sensor, making difficult to experimentally assess the fundamental frequency limit and achieve it in the applications. This paper presents an equivalent electrical model that helps to design a test aimed at experimentally estimating the intrinsic time response of the sensor. According this test, the paper demonstrates that Hall sensors have an upper bandwidth limit defined by the overall capacitive load. Moreover, some of the parasitic dynamic effects, which degrade the time response in real operation, are identified and investigated
The DTCM characterization approach for the qualification of dynamic non-linearities within A/D channels
No full textThe behaviour of both stand-alone ADCs and entire A/D acquisition channels under time-varying input excitations exhibits non-idealities which are peculiar to the dynamic operation and can not be described by the characteristics of the static response. In addition, even the common dynamic parameters suggested by the current standards usually fail to separately qualify the purely-dynamic non-linearities from all other perturbation effects on the system response. In this paper, the features of the Discrete-Time Convolution Model are discussed by pointing out the properties of the general approach from which it derives, with particular emphasis to the capability of separately describing all the system non-idealities on the basis of their nature. It will be shown how the DTCM characterization methodology and the set of related model parameters represent a suitable resource towards the separate qualification of dynamic non-linearities in A/D channels
Multi-bias nonlinear characterization of GaN FET trapping effects through a multiple pulse time domain network analyzer
No full textA recently proposed setup for the pulsed characterization of electron devices is adopted for a more detailed and accurate evaluation of charge trapping effects in UMS 0.25 μm GaN FETs. Experimental results obtained by this instrumentation, which acts as a Multiple Pulse Time Domain Network Analyzer, show that two different kinds of charge trapping phenomena, involving both linear and nonlinear dynamics, play a relevant role in determining the device behavior. Dynamically linear and nonlinear trap effects are characterized and quantified by defining two different lag functions, which may lead to future improvements of multibias empirical nonlinear models and technology evaluation criteria
Methodologies and integrated architecture for advance sensing on next-generation smart battery cells
No full textBatteries are the catalyst for the shift towards sustainable and smart mobility, as well as supplying clean, affordable, and renewable energy sources. To improve the battery performance at level of management and control of the system, new methodologies need to be found to monitor in operando and in situ the batteries' state parameters, thus strengthening safety, reliability, and cycle life of batteries. The vision of this PhD project is to integrate smart functionalities at the cell level and study possible data fusion algorithms to create predictive models of the battery state parameters. In particular, the thesis is focused on the investigation of the Elecrochemical Impedance Spectoscopy (EIS) as diagnosis tool for the online monitoring of the battery. The first step towards this goal is to define the sensing technologies to be integrated in a single battery cell to enable the in operando and in situ measurement of battery physical quantities. EIS can respond to the challenges of shortening the measurement time and reducing the dimensions of the system to be integrated into the battery cell. A novel approach to perform broadband EIS based on a multi-band multisine excitation signal is proposed to optimize the measurement time and signal-to-noise ratio (SNR). The related EIS-based sensing system based on a sigma-delta architecture is developed and tested as impedance demonstrator for a future integration at the cell level. Finally, experimental EIS data of lithium battery cells are collected and evaluated, to demonstrate that the proposed methodologies are suitable for the online battery monitoring
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