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A technology-independent, inherently nonlinear approach is proposed for the compact modelling of high-frequency noise in microwave transistors under large-signal operating conditions. For the compact nonlinear noise model formulation we assume that noise generation can be described by a suitable set of distributed stochastic processes perturbing a very general, non-quasi-static deterministic description of the electron device, in accordance with the strategies adopted in physics-based methods for the choice and exploitation of microscopic diffusion noise sources. The propagation of the internal distributed noise sources up to the intrinsic device terminals leads to a set of non-stationary, correlated equivalent noise generators, nonlinearly controlled by the instantaneous large-signal working point of the device. Starting from a first formulation for the generators, formally derived from a physics-based description of the noise generation mechanisms widely adopted in distributed numerical modeling, mild approximations provide a fully behavioral representation that can be empirically extracted on the basis of measurement data only, and can be easily implemented into commercial computer-aided design tools by means of conventional, uncorrelated noise sources. As far as small-signal (i.e., linear) bias-dependent operation is concerned, it is shown how well-known, widely applied compact models for high-frequency noise can be considered as linearized special cases of the proposed approach. For a full validation, experimental examples are provided, both in small-and large-signal operation, for a GaAs-pHEMT, by considering the case study of a broad-band low-noise amplifier progressively driven into nonlinear regime by an increasing power interferer. © 2014 IEEE.

A 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.

In this paper, a new cyclostationary nonlinear low-frequency (LF) noise model for field-effect microwave transistors is presented based on the general theory of the technology-independent Charge-Controlled Nonlinear Noise modeling approach. The model definition, experimental extraction, and validation are described. For model parameter identification, the characterization of the device in terms of both LF noise in quiescent operation and its up-conversion into phase noise under large-signal RF oscillating conditions was performed using in-house developed measurement setups. The model is exploited in the design of a C-band monolithic microwave integrated circuit (MMIC) voltage-controlled oscillator (VCO) developed for space applications. The selected technology is a space-qualified GaAs 0.25-μm pseudomorphic HEMT (pHEMT) process. The large-signal technique adopted for the VCO design is also highlighted. Comparisons between measurements and simulations are provided, which show the validity of the design methodology and demonstrate the accuracy of the proposed cyclostationary noise modeling approach for phase-noise large-signal analyses of pHEMT-based circuits. The MMIC exhibits 350-MHz bandwidth at 7.3 GHz, with 14-dBm output power and -86-dBc/Hz single-sideband phase noise at 100 kHz from the carrier.

In 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.

This paper addresses both experimentally and through simulations the effects of a microwave tone on the lowfrequency noise properties of GaInP/GaAs heterojunction bipolar transistors. The aim is to contribute to the still unsolved controversy on which modulation strategy should be adopted for the low-frequency noise sources when they should face large signal conditions, as in the cases of oscillators and mixers. An approach similar but not equal to the modulated stationary noise model has been adopted for three different kinds of noise source modulation strategy in the frame of a bias-dependent compact low-frequency noise model.

Low-frequency dispersive phenomena due to self-heating and/or “traps” (that is, surface-state densities and deep-level traps) cause important dynamic deviations in the I/V characteristics of III-V devices and they must be taken into account when an accurate large-signal dynamic model is needed. To this end, different low-frequency dispersive I/V models have been proposed by the research community and, quite often, a characterization based on pulsed I/V measurement systems has been suggested as the most appropriate for the identification of model parameters. Unfortunately, besides requiring special-purpose setups, pulsed characterization may suffer from some drawbacks, as discussed in this article. As an alternative, a simple large-signal measurement setup is presented here, which is based on low-frequency sinusoidal excitations and can be easily implemented by means of conventional general-purpose laboratory instrumentation. The proposed setup is successfully adopted in this article to identify the dispersive I/V characteristics of a GaAs PHEMT large-signal model providing excellent prediction of intermodulation distortion at Ka-band frequencies. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.

In this paper the Discrete-Time Convolution Model behavioural approach is proposed for the characterization/empirical modelling of high-performance broad-band A/D channels or stand-alone A/D converters, designed for the acquisition of signals up to the field of microwaves. Thanks to its inherent capability of separately describing all the non-idealities of different nature within the channel, and in particular the non-linear dynamic effects, the method is particularly suitable for the A/D channels implemented in modern high-frequency instrumentation and RF receiver architectures. In this framework, the experimental procedures devoted to the extraction of model parameters have been re-designed in order to allow for the application of the approach without the need for higher-performance reference A/D devices. Experimental results are provided, which validate the analytical/functional formulation of the method and the related measurement procedures/set-ups, for a state-of-the-art, 1-GHz analogue bandwidth 1-GSa/s A/D acquisition channel space-qualified for satellite radar applications.

This paper describes the design and implementation of a C-band MMIC VCO developed in the framework of activities oriented to the improvement of products for space applications. The circuit exploits a single device with a microstrip integrated resonator coupled with varactors. The exploited technology is a space-qualified GaAs 0.25-um pHEMT process. The MMIC exhibits 350-MHz bandwidth at 7.3 GHz, with 14 dBm output power and −86 dBc/Hz single side-band phase noise at 100 kHz from the carrier. Measured performances are in good agreement with simulations. The active device adopted for the design was characterized in terms of both low-frequency noise in quiescent bias-dependent operation and its up-conversion into phase noise under large-signal RF oscillating conditions, using in-house developed measurement setups. A new compact nonlinear noise model was identified, implemented and exploited for phase noise simulations. The model features cyclostationary equivalent noise generators. Comparisons between measurements and simulations show that the nonlinear cyclostationary modeling approach is more accurate than conventional noise models in oscillator phase noise analyses of pHEMT based circuits.

Phase noise (PN) performance of microwave oscillators can be strongly affected by the device non-linear RF working regime; indeed PN performance are related to the frequency stability of the circuit, which depends not only on the circuit Q factor, but also on the large-signal (LS) device operating condition. Besides the device operating bias point, also its dynamic LS load line and amplifying class of operation have a significant role for the oscillator PN. In this paper a very flexible measurement set-up is described with load and source pull capabilities, designed for the characterization of the PN and frequency stability of electron devices in controlled oscillating conditions. This innovative set-up is a very useful tool for both the design of low phase noise (LPN) oscillators and the parameter extraction and validation of non-linear noise models of electron devices.

A fully automated measurement setup is described, which is aimed at investigating the time dispersion (or ldquowalkoutrdquo) of microwave electron-device characteristics. The proposed setup has the original capability of characterizing device degradation under a nonlinear dynamic operation. Such information is invaluable when the success of a project is inherently related to the end-of-life performance of each system component (e.g., military and space applications). Some previous works underline the importance of such information, but they are not oriented to device characterization and, moreover, are focused on a particular application (e.g., power amplifier design). The commonly adopted measurement techniques, which are essentially focused on high-field static operations, are extremely useful to perform accelerated stress, but they cannot be adopted to obtain exhaustive information about the time dispersion of device characteristics under realistic operative conditions. Through the proposed system, the stress procedure can be carried out under static (DC) and nonlinear dynamic (RF) operations to give the maximum flexibility in gathering useful information on the device degradation in different operating regimes. In particular, the device under test (DUT) is fed in rf-stressing conditions by applying a large-amplitude excitation signal at moderately high frequency at either the input (forward mode) or output (reverse mode) port of the device. The system features, in fact, a symmetrical dual-channel architecture. The DUT can be either a bipolar- or a field-effect transistor, and the walkout of its characteristics can be observed both at the end of the stress test and in real-time during the test execution. A special-purpose control software automates the measured data acquisition. Several experiments that were performed using the proposed setup are discussed in the paper.

In this paper, we present a flexible measurement setup for the characterization of the phase noise (PN) and frequency stability of microwave electron devices operating under nonlinear oscillating conditions. The setup embeds the device-under-test (DUT) within a feedback loop, and forces it into a large signal (LS) oscillating regime, by controlling the loop amplitude and phase. The DUT input and output terminations are also controlled, by exploiting load- and source-pull capabilities. By exploiting this setup, we demonstrate that the PN performance of microwave oscillators can be strongly affected by the device nonlinear RF working regime. As well known, the oscillator PN is mainly related to the frequency stability of the circuit and the active device low-frequency noise up-conversion to RF mechanisms. By using measurements performed with the proposed setup, it is shown that these aspects depend also on the device LS operating conditions; hence, the dynamic LS load line and the amplifying class of operation have a significant role for the oscillator PN. The experimental results described in the paper, along with the analyses proposed by using simulations, are in accordance with recently published nonlinear noise modeling approaches based on cyclostationary noise sources. The investigation performed by means of the setup can provide information for both the design of low-phase-noise (LPN) oscillators and the parameter extraction and validation of nonlinear noise models of electron devices. Furthermore, this setup is also proposed as a tool for the evaluation of power amplifier PN when a dedicated residual phase noise measurement system is not available.

A nonlinear empirical model is here adopted to model the cold-FET behaviour of a GaAs PHEMT, in the framework of a resistive mixer application. The model, purely mathematical and technology independent, is suitably identified in the device operative region of interest and is validated in large-signal conditions by exploiting a measurements setup based on LS-VNA.

Empirical electron device models based on lumped equivalent circuits are usually identified through nonlinear optimization procedures, which are based on the best fitting between the extrinsic model behavior and measurements carried out under multibias static and small-signal excitations. In this paper, a new error function is proposed for equivalent circuit model parameter optimization. Although still being defined through standard static and small-signal measurement data, the new error function can be configured so as to obtain models tailored to specific large-signal applications. Experimental results, which confirm the validity of the proposed identification approach, are provided for a GaAs microwave pseudomorphic HEMT model aimed at the design of highly linear power amplifiers.

An empirical bipolar transistor nonlinear noise model for the large-signal (LS) noise analysis of microwave circuits is described. The model is derived according to the charge-controlled nonlinear noise behavioral modeling approach, and includes nonlinearly controlled equivalent noise (EN) generators describing the low-frequency (LF) noise up-conversion encountered in LS RF operation. LS-modulated shot-noise sources and parametric LF noise in parasitic resistors are also taken into account for improved model accuracy. Details for the implementation of the proposed cyclostationary EN generators in the framework of a computer-aided design tool are presented. As an application example, a simplified version of the proposed nonlinear noise model for two GaInP–GaAs HBTs has been formulated and empirically characterized on the basis of both bias-dependent LF noise and phase-noise measurements. Measured and simulated noise performance of a monolithic voltage-controlled oscillator over a set of different operating conditions is shown for the validation of the proposed approach.

In this paper, an automated laboratory setup for the characterization of microwave and millimeter-wave electron devices under dc small- and large-signal operations is described, which is based on a generalized technology-independent bias system. The biasing parameters adopted, which are a linear combination between currents and voltages at the device ports, allow for a complete characterization of the desired empirical data (e.g., multifrequency S-matrix) throughout all the regions, in which the quiescent operation of the device can be conventionally divided without any need for switching between the different biasing strategies. The lookup tables of the experimental data obtained, which are carried out homogeneously versus the same couple of bias parameters of the quiescent regions investigated independently, are particularly suitable for the characterization of the empirical nonlinear dynamic models for the electron device.

Many different nonlinear modeling approaches for electron devices have been proposed in the last few years, and quite often circuit designers suffer from the lack of reliable comparison criteria, on the basis of which the most suitable model for a specific application can be identified. Moreover, similar strategies are needed even by research groups, whose activity is devoted to the model identification and extraction, in order to quantify the degree of accuracy that will be achievable by the modelling approach adopted. In this paper, a new metric for the estimation of large-signal model accuracy is discussed, which is simply based on the comparison between deembedded measurements and model predictions of small-signal Y-parameters versus the bias voltages at the intrinsic device ports.

Theoretical and practical issues concerning the nonlinear dynamic modelling of electron devices are discussed in this article. All the different dynamic phenomena, which are important for the description of the device behaviour, are comprehensively dealt with by means of a unified mathematical derivation. In particular, both the fast dynamics associated with charge-storage phenomena at high operating frequencies and the slow dynamics of low-frequency dispersion, due to device self-heating and charge-trapping effects in deep-bulk and surface regions, are simultaneously taken into account. The result is an empirical, technology-independent and nonquasi-static model of electron devices, suitable for a simple and reliable identification procedure and based on conventional measurements of static characteristics and bias- and frequency- dependent small-signal parameters. The model implementation in the framework of commercially available CAD tools is also outlined in this article. Experimental validation, based on a GaAs p-HEMT, is also presented.

A new nonquasi-static nonlinear model of electron devices is proposed by adopting a perturbed charge-controlled approach. The model is based on the definition of a virtual quasi-static device, associated with the actual one, which is controlled by means of equivalent voltage sources. The advantage of this approach is that conventional purely quasi-static models can be still adopted even at very high frequencies, if suitable equivalent voltages are applied. Identification from small-signal measurements and implementation into commercially available computer-aided design tools of the new nonquasi-static model are described in this paper. Finally, by considering a GaAs p-high electron mobility transistor, accurate prediction capabilities at microwaves and millimeter frequencies are experimental verified and compared with a more conventional equivalent-circuit-based model.

Large-signal modeling of electron devices for nonlinear MMIC design is a fundamental topic for the microwave community. Many different nonlinear modeling approaches have been proposed in the last years, and quite often circuit designers suffer from the lack of reliable comparison criteria, on the basis of which identify what model, between those available, could be the most suitable for the desired application. Moreover, similar strategies are needed even from the research groups, whose activity is devoted to the model identification and extraction, in order to quantify the degree of accuracy achievable by the modeling approach adopted. In this paper an approach to verify large-signal model accuracy will be discussed, which is simply based on the comparison between de-embedded measurements and model predictions of Y-parameters versus the bias voltages at the intrinsic device ports.

Low-frequency (LF) dispersive phenomena due to device self-heating and/or the presence of "traps" (i.e., surface state densities and bulk spurious energy levels) must be taken into account in the large-signal dynamic modeling of III-V field-effect transistors when accurate performance predictions are pursued, since these effects cause important deviations between direct current (dc) and dynamic drain current characteristics. In this paper, a new model for the accurate characterization of these phenomena above their cutoff frequencies is presented, which is able to fully exploit, in the identification phase, large-signal current-voltage (I-V) measurements carried out under quasi-sinusoidal regime using a recently proposed setup. Detailed experimental results for model validation under LF small- and large-signal operating conditions are provided. Furthermore, the I-V model proposed has been embedded into a microwave large-signal pseudomorphic high electron-mobility transistor (pHEMT) model in order to point out the strong influence of LF modeling on the degree of accuracy achievable under millimeter-wave nonlinear operation. Large-signal experimental validation at microwave frequencies is provided for the model proposed, by showing the excellent intermodulation distortion (IMD) predictions obtained with different loads despite the very low power level of IMD products involved. Details on the millimeter-wave IMD measurement setup are also provided. Finally, IMD measurements and simulations on a Ka-band highly linear power amplifier, designed by Ericsson using the Triquint GaAs 0.25-/spl mu/m pHEMT process, are shown for further model validation.

Large-signal dynamic modelling of III-V FETs cannot be simply based on dc i/v characteristics, when accurate performance prediction is needed. In fact, dispersive phenomena due to self-heating and/or traps (surface state densities and deep level traps) must be taken into account since they cause important deviations in the dynamic drain current. In this paper, a recently proposed large-signal i/v measurement setup is exploited to extract an empirical model for low-frequency dispersive phenomena in microwave electron devices. This i/v model is then embedded into a microwave large-signal PHEMT model. Eventually, a Ka-band highly linear power amplifier, designed by Ericsson using the Triquint GaAs 0.25µm PHEMT process, is used for model validation. Excellent intermodulation distortion predictions are obtained with different loads despite the extremely low power level of IMD products involved. This entitles the proposed model to be also used in the PA design process instead of conventional loadpull techniques whenever the high-linearity specifications play a major role.

The adoption of complex digital modulation techniques in wireless communication systems has posed a great demand on RF and microwave power amplifier performance. When high linearity is required, the amplifier characterization is based on intermodulation or, more commonly, on Adjacent Channel Power Ratio (ACPR) and other parameters more directly related to the actual circuit operation. In this paper a previously proposed Harmonic Balance (HB) algorithm is adopted for the ACPR simulation of power amplifiers excited by digitally modulated signals. With respect to other approaches the proposed technique provides fast and accurate results using a conventional HB engine without requiring special purpose algorithms.

Measurement-based, circuit-oriented non-linear noise modeling of microwave electron devices is still an open field of research, since existing approaches are not always suitable for the accurate prediction of low-frequency noise up-conversion to RF, which represents an essential information for the non-linear circuit analyses performed in the CAD of low phase-noise oscillators. In this paper a technology-independent, empirical approach to the modeling of noise contributions at the ports of electron devices, operating under strongly non-linear conditions, is proposed. Details concerning the analytical formulation of the model, which is derived by considering randomly time-varying perturbations in the basic equations of an otherwise conventional charge-controlled non-linear model, are presented, along with a discussion about the measurement techniques devoted to its experimental characterization. An example of application of the proposed Charge-Controlled Non-linear Noise (CCNN) model is considered in the case of a HBT transistor. Techniques devoted to the implementation of the obtained model in the framework of commercial CAD tools for circuit analysis and design are provided as well.

In this paper, a measurement set-up is described for the investigation on microwave electron device characteristic time dispersion (or “walkout”), occurring in nonlinear dynamic operation. The stress procedure is carried out by applying a large amplitude excitation signal at moderately high frequency at either the input or the output port of the device. The corresponding forward or reverse mode of operation can be easily configured by means of a switch manipulation, exploiting the symmetrical, dual-channel architecture of the system. The walkout of the device characteristics, which can be either a bipolar- or a field effect-transistor, can be observed both at the end of the stress test and in real-time during the test execution.

Large-signal dynamic modelling of 111-V FETs cannot he simply based on DC i/v characteristics, when accurate performance prediction is needed. In fact, dispersive phenomena due to self-heating and/or traps (surface state densities and deep level traps) must be taken into account since they cause important deviations in the low-frequency dynamic drain current. Thus, static drain current characteristics should he replaced with a suitable model which also accounts for low-frequency dispersive effects. The research community has proposed different modelling approaches and quite often a characterisation by means of pulsed i/v measurement systems has been suggested as the more appropriate for the identification of lowfrequency drain current models. In the paper, a new largesignal measurement setup is presented which is based on simple low-frequency sinusoidal excitations and it is easily reproducible with conventional general-purpose lab instrumentation. Moreover, the proposed setup is adopted in the paper to extract a hackgating-like model for dispersive phenomena