1,720,996 research outputs found
VCO Behavioral Modeling
No full textThis workshop provides a comprehensive overview of different aspects of oscillator theory, design and practical implementation. Topics include the principles of oscillator design, including start-up and steady-state operation conditions, simplified circuit analysis and basic equations using bipolar and field-effect transistors and the theories required to design low phase noise oscillators with predictions of the optimum conditions for minimum phase noise. The effect of flicker noise and four techniques currently available for flicker noise reduction will then be described. Wideband voltage controlled oscillators (VCOs) are used in a variety of RF and microwave systems. The basic concepts of their circuit design and specific circuit solutions using lumped elements and transmission lines to improve the frequency tuning characteristics are described. A special topic will focus on accurate VCO behavioural modelling based on the Volterra-series approach with possible implementation in the system-level simulation tools. Finally, numerous practical examples of RF and microwave oscillators including VCOs based on MOSFET, MESFET, BJT and HBT technologies are given
VCO Behavioral Model Based on the Nonlinear-Discrete Convolution Approach
Full text linkA purely mathematical,behavioral model for Voltage Controlled Oscillators (VCO)is derived.It is based on a Non-Linear Discrete Convolution approach [1 ] whichllows a time-domain formulation compatible with commercial system-level simulators.The approach enables the VCO nonlinear dynamics to be described with great accuracy and computational efficiency,and its influence on the performance of an entire subsystem to be investigated. Model validation,implementation in commercial system- level simulation tools as well as application examples are provided in the paper
Global modeling of GaN HEMT resistive current including charge trapping and self-heating for multi-bias multi-class PA performance prediction
No full textAn empirical Gallium Nitride (GaN) HEMT model, suitable for multi-bias and multi-class power amplifier (PA) performance prediction, is formulated. In addition to the fast dynamically-nonlinear capture mechanisms normally considered for local modeling, dynamically-linear charge trapping is taken into account here. A straightforward empirical identification procedure based on tailored double-pulsed IV measurements is described. Validation experiments carried out on a 8×125 pm (gate length: 0.25 pm) GaN-on-SiC HEMT show good model prediction capabilities under different drain bias conditions and class AB, B, and C large-signal PA operation at both low-frequency (f = 4 MHz) and RF (f = 2.5 GHz)
Implementation of non-conventional nonlinear models for electron devices in commercial CAD tools
Full text linkIn nowadays CAD environments for integrated microwave circuit design, dedicated tools for the implementation of user defined component models are becoming more and more important. These tools are mainly oriented to the definition of equivalent circuit models.However, the need for more accurate prediction of nonlinear electron device performance pushes the modelling community towards the research of new, often non-conventional, modelling approaches (e.g., frequency-domain, behavioural, integral models, look-up-table based,state-space based, etc.). In such a context, the model implementation tools usually available may result not sufficiently flexible. The paper provides useful hints andpoints out the main limitations which can be encountered in the implementation of non-conventional electron device models. As an example, the implementation of a Nonlinear Discrete Convolution model will be considered by usingthree different advanced tools: the Model Wizard of AWR Microwave Office, the Model Development Kit and Verilog-A Language of Agilent ADS
Charge-controlled GaN FET modeling by displacement current integration from frequency-domain NVNA measurements
No full textWe propose an efficient procedure for the extraction of a charge-controlled nonlinear model of a 1-mm gallium nitride on silicon carbide field-effect transistor (L = 0.25μm) from nonlinear vector network analyzer acquisitions. A fast, single-shot measurement technique is described, in which the two device-under-test (DUT) ports are excited by single-tone sources at carefully selected tone frequencies, acquiring calibrated waveforms at the on-wafer DUT ports with an almost complete coverage of the voltages domain. The gate and drain charge functions identification is executed by the integration of the displacement currents in the frequency domain. A suitable approach for separating the conductive and displacement drain current components is provided. The presence of thermal self-heating and charge trapping phenomena is empirically evaluated, and accounted through an equivalent voltage approach. Experimental validation is provided at 2.5 and 5 GHz for a continuous-wave excitation, and at 2.5 GHz for a two-tone excitation
A ku band monolithic power amplifier for TT&C applications
Full text linkThe paper describes the design of a 38 dBm monolithic power amplifier at Ku band. The amplifier has to be used as the final stage of the downlink transmitter of a TT&C system. A commercial power p-HEMT process capable of handling a power density higher than 1 W/mm of active area has been selected for the amplifier design. The power capability of this process makes it possible to integrate in a monolithic chip the functionality up today supplied by hybrid modules. Since the circuit is a space product, the attention is focused on reliability issues; therefore performances have to be matched imposing the devices to work at de-rated conditions respect to the process maximum ratings. In this perspective, the device channel temperature becomes a very tight design objective and has to be carefully controlled by means of a thermal simulator. The paper describes the three dimensional thermal model built to predict the devices thermal behavior in the environment of a finite difference thermal simulator. The design of the circuit is also described from the specifications to the final layout
Iso-thermal and iso-dynamic direct charge function characterization of GaN FET with single large-signal measurement
No full textA fast and simple method for the direct characterization of nonlinear charge functions of electron devices is presented. The input and output transistor ports are simultaneously excited through single-tone sources at different frequencies and calibrated large signal waveforms are measured by means of an advanced NVNA-based setup. Proper choice of the two frequencies guarantees an almost complete coverage of the voltages domain in a single and very fast measurement set and allows the extraction of the charge functions by direct integration of currents in the frequency domain, since, contrary to other methods, the measured waveforms are both iso-thermal and iso-dynamic (i.e. at fixed charge trapping status). The method is validated by characterizing the gate charge function of a 5W 8×125μm GaN FET and implementing a simple table-based model of the transistor input port. Very good results are achieved by comparison with large-signal measurements under conditions different than the ones used for the characterization
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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