Pier Andrea Traverso

An Empirical Bipolar Device Nonlinear Noise Modeling Approach for Large-Signal Microwave Circuit Analysis

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

A Double-Pulse Technique for the Dynamic I/V Characterization of GaN FETs

Standard dynamic characterization methods based on periodic narrow-pulse low duty-cycle excitation waveforms provide suboptimal I/V curves when used along with GaN field effect transistors (FETs), due to complex nonlinear charge trapping effects. Thus, a double-pulse technique for the dynamic characterization of GaN FETs is here presented. The double-pulsed I/V characteristics are shown to be not only isothermal but also corresponding to a fixed charge trapping state.

New pulsed measurement setup for GaN and GaAs FETs characterization

A new setup is proposed for the measurement of current–voltage pulsed characteristics of electron devices. The main advantages of the system consist in: shorter pulse widths through generation in a 50-Ω environment, simple average current monitoring through separation of the direct and alternate current paths, setting of average voltage values independently of pulse amplitudes and duty cycle, and stability of the setup guaranteed by wide-band dissipative terminations. The system is used for the characterization of dispersive effects due to carrier energy traps and thermal phenomena in GaAs and GaN on SiC field effect transistors. The basic differences between the two technologies are highlighted in the paper.

Accurate prediction of PHEMT intermodulation distortion using the nonlinear discrete convolution model

A general-purpose, technology-independent behavioral model is adopted for the intermodulation performance prediction of PHEMT devices. The model can be easily identified since its nonlinear functions are directly related to conventional DC and small-signal differential parameter measurements. Experimental results which confirm the model accuracy at high operating frequencies are provided in the paper.

A Nonquasi-Static Empirical Model of Electron Devices

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

GaN FET Nonlinear Modeling Based on Double Pulse

A state-space empirical nonlinear model for GaN-based field-effect transistors (FETs) is defined, along with the associated identification procedures based on a recently published double pulse measurement technique. Charge trapping phenomena are dealt with in terms of a nonlinear state equation, which describes the rate of change of the trap state as a function of its actual distance from the corresponding steady state. Model experimental validation is carried out, after on-wafer characterization of a 1-mm AlGaN-GaN on SiC FET, both under strong and mild nonlinear operation.

{ I}/{ V}

Abstract The empirical “black-box” characterization of non-linear systems with memory is a complex problem which cannot be dealt with by means of a unique, general-purpose mathematical approach such as the Volterra series. In fact, from a metrological point of view, the feasibility and reliability of the measurement procedure must be the criterion on the basis of which any mathematical approach for modelling purposes must be evaluated. This paper describes different solutions for the behavioural identification of non-linear dynamic systems, all based on a modified Volterra series, which are characterized by a reduced number of operators with respect to the classical Volterra approach. The operator reduction, which does not affect the accuracy of the obtained models if a mild assumption on the system memory time duration is satisfied, allows a reliable extraction of the model parameters by means of conventional instrumentation, without the need for the generation of complicated input probing signals or additional approximations. A detailed discussion is provided in order to estimate when each of the proposed approaches can be practically used, by pointing out the hypotheses that must be taken into account in order to minimise the modified series truncation errors. Experimental examples, showing the validity of the proposed approaches, are given in the last section of the paper, as well as a comparison between the performances of the different solutions when applied to the important field of electron device characterization.

Characteristics

A non-linear dynamic empirical model, based on a Volterra-like approach, was previously proposed by authors for the time-oriented characterization of S/H-ADC devices. In this paper, the experimental procedure for model parameter measurement is presented, as well as techniques devoted to the implementation of the model in the framework of main commercial CAD tools for circuit analysis and design. The results of simulations, performed on the obtained model both in time and frequency domain, are proposed which show model capability to point out the dynamic non-linear effects in the device response.

Non-linear dynamic system modelling based on modified Volterra series approaches

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.

A non-linear dynamic S/H-ADC device model based on a modified Volterra series: identification procedure and commercial CAD tool implementation

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.