1,721,077 research outputs found
Mathematical approach to large-signal modelling of electron devices
Full text linkA general purpose mathematical approach is proposed for the large-signal modelling of microwave electron devices (e.g. MESFETs, bipolar transistors, diodes, etc.). The mathematical model, which is based on mild assumptions valid both for field effect and bipolar devices in typical large-signal operating conditions, can easily be identified through conventional measurements and is particularly suitable for nonlinear microwave circuit analysis based on harmonic balance technique
The vector-gradient Hough transform for identifying straight-translation generated shapes
No full textThe paper introduces the vector-gradient Hough transform (VGHT), a modified version of the gradient weighted Hough transform (GWHT), defined in vector space and able to exploit all the vector information of the gradient of luminosity. The new formulation, directly derived from the Radon transform, is analyzed and compared with the GWHT, in order to point out the improvement in selectivity provided by the VGHT in a strictly polar parametric space, without any relevant increase in computational complexity. This approach can be very suitable for identifying a specifically defined model of shapes in gray level images, ideally generated by a translation in the 2D space of a 1D luminosity profile. Finally, the suitability of the VGHT in real applications is shown with examples in the area of defect identification for automated visual inspection. © 1996 IEEE
A highly selective HT based algorithm for detecting extended, almost rectilinear shapes
No full textThe paper presents an highly selective algorithm for detecting extended and almost rectilinear shapes in digital images, in presence of structured and unstructured noise; it exploits the Gradient-based Hough Transform, followed by a special purpose correlation process in the parameter space. The paper discusses the algorithm and its application in a quality inspection task for detecting fabrication defects in mechanical pieces
Charge-conservative GaN HEMT nonlinear modeling from non-isodynamic multi-bias S-parameter measurements
No full textGuaranteeing charge conservation of empirically extracted Gallium Nitride (GaN) High-Electron-Mobility Transistor (HEMT) models is necessary to avoid simulation issues and artifacts in the prediction. However, dispersive effects, such as thermal and charge-trapping phenomena, may compromise the model extraction flow resulting in poor model accuracy. Although GaN HEMT models should be extracted, in principle, from an isodynamic dataset, this work deals with the systematic identification of an approximate, yet most suitable, charge-conservative empirical model from standard multi-bias S-parameters, i.e., from non-isodynamic data. Results show that the obtained model maintains a reasonable accuracy in predicting both small- and large-signal behavior, while providing the benefits of charge conservation
A nonlinear integral model of electron devices for HB circuit analysis
Full text linkA technology-independent large-signal model of electron devices, the nonlinear integral model (NIM), is proposed. It is rigorously derived from the Volterra series under basic assumptions valid for most types of electron devices and is suitable for harmonic-balance circuit analysis. Unlike other Volterra-based approaches, the validity of the NIM is not limited to weakly nonlinear operation. In particular, the proposed model allows the large-signal dynamic response of an electron device to be directly computed on the basis of data obtained either by conventional measurements or by physics-based numerical simulations. In this perspective, it provides a valuable tool for linking accurate device simulations based on carrier transport physics and harmonic-balance circuit analysis algorithms. Simulations and experimental results, which confirm the validity of the NIM, are also presente
Tool for efficient intermodulation analysis using conventional HB packages
No full textA simple and efficient approach is proposed for the intermodulation analysis of nonlinear microwave circuits. The algorithm, which is based on a very mild assumption about the frequency response of the linear part of the circuit, allows for a reduction in computing time and memory requirement. Moreover. It can be easily implemented using any conventional tool for harmonic-balance circuit analysi
A finite-memory nonlinear model for microwave electron devices
No full textA teclinology-independent, mathematical approach is proposed for the look-up-table based nonlinear modeling of electron devices. The model allows for accurate large-signal performance prediction at high operating frequencies, even in the presence of important parasitic and low-frequency dispersive effects. All the nonlinear functions which characterise this black-box model are directly related to conventional measurements which can be carried out with automatic instrumentation. Preliminary experimental results are presented which confirm the validity of the approach. © 1997 IEEE
Stability Characterizing Function for Electronic Circuit Design Based on Frequency-Domain Analysis With Parametric Damping
Full text linkA stability characterizing function (SCF) to be used for small and large-signal stability analysis and design of single and multitransistor electronic circuits is proposed. Stability constraints based on this function can be integrated with the framework of standard computer-aided design (CAD) procedures. The method is based on the bounded-input–bounded-output (BIBO) stability criterion, where a suitable set of input and output variables is chosen at the ports of all the nonlinear intrinsic electron device (IED) models. These variables are linked by a nonlinear state perturbation (NSP) matrix, whose elements are directly computed by analyzing an associated parametrically damped (PD) (i.e., stabilized) circuit. The proposed SCF is defined in terms of the NSP matrix elements and is a scalar function of frequency and the damping parameter. Circuit stability margins are easily evaluated by visual inspection of the plot of this function. Preliminary experiment validation is carried out by applying this approach for checking the self-starting capabilities of an oscillator as well as for the small and large-signal stability analysis of a two-transistor balanced amplifier and a single-transistor PA
Frequency stability in resonator-stabilized oscillators
Full text linkA simplified stability analysis of resonator-stabilized oscillators is carried out by using the describing function approach. On this basis a criterion for the evaluation and optimization of the frequency stabilization introduction in an oscillator by a resonating element with a large quality factor is proposed. In particular, a frequency-stabilization index which can be conveniently used in the design of highly stable oscillators is defined. The validity of this performance index has been verified in the design of microwave oscillators using dielectric resonators as frequency-stabilizing element
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