V.A. Monaco

A nonlinear integral model of electron devices for HB circuit analysis

A 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 presented. >

Computer-Aided Analysis of Microwave Circuits

The most relevant techniques that have either found or should find useful application in analyzing microwave circuit performances in the frequency domain are surveyed. The particular needs of the microwave engineer are briefly discussed. Circuit equation formulations in terms of voltages and currents and wave variables are presented and the solution of the set of circuit equations by sparse-matrix techniques is illustrated. Methods based on multiport connection are also reviewed. The techniques for computing the first- and second-order sensitivity are illustrated and a comparison is made between the direct method and the transpose-matrix method, which is in certain cases similar to the method based on the adjoint circuit.

Mathematical approaches to electron device modelling for non-linear microwave circuit design: State of the art and present trends†

The accuracy of CAD techniques for the design of non-linear microwave circuits is strongly dependent on the features of the models used for the characterization of electron devices (i.e. MESFET, bipolar transistors, diodes etc.,.). At present, empirical equivalent circuits are widely used. These models, which are in many cases sufficiently accurate, require, however, quite refined numerical and measurement techniques to extract from measured data the parameters of a model which is strongly dependent on the particular physical structure of each device. Moreover, when using equivalent circuit models, the design of non-linear microwave circuits must be carried out by using numerical optimization techniques. In this respect a simple mathematical model described in the frequency domain in terms of explicit equations between the electrical variables, would be preferable for the designer. Mathematical models, in fact, allow quite easy, direct procedures for circuit design. This paper deals with the problem of mathematical modelling of electron devices operating under large-signal conditions at microwave frequencies. In particular, mathematical models based on the describing-function and Volterra-series approach are considered also taking into account their application to circuit design. The advantages of a recently proposed mathematical modelling approach based on mild assumptions valid for most types of electron devices, are also discussed in the paper.

A harmonic-balance-oriented modeling approach for microwave electron devices

A technology-independent model of microwave electron devices, the Nonlinear Integral Model, is proposed. This model is rigorously derived from the Volterra series under mild assumptions valid for most types of electron devices and is particularly suitable for circuit analysis based on harmonic-balance techniques. Moreover, it makes it possible to compute the large-signal response of an electron device directly in terms of data obtained by physics-based numerical simulations. The validity of the model is confirmed both by simulation and by experimental results.<<ETX>>

Large-Signal Narrow Band Quasi-Black-Box Modelling of Microwave Transistors

A method is proposed for the large-signal narrow-band characterization of microwave active devices. It does not require a detailed knowledge of the device internal structure, but only some measurements of small signal S parameters effected under different bias conditions and some other simple large-signal measurements to be effected by a standard network analyzer.

Computationally Efficient Multitone Analysis of Non-Linear Microwave Circuits

A new approach to the Harmonic-Balance analysis of non-linear microwave circuits driven by multitone excitations is proposed. It is based on the observation that in many practical cases of multitone analyses, signal spectra are characterized by a highly non uniform distribution. In such conditions, a convenient representation of the signal spectra in conjunction with a suitable approximation introduced on the frequency response of the reactive components, allow a relevant decoupling of the Harmonic-Balance circuit equations; consequently, a relevant reduction of computing effort can be easily obtained. By using the approach proposed, the intermodulation analysis of quite complex circuits operating under multitone excitations can be carried out even on small-size computers (e.g., workstations). The validity of the method has been verified in intermodulation analyses of mixers and distributed amplifiers.

Accurate prediction of intermodulation distortion in GaAs MESFETs

A previously proposed look-up-table based mathematical approach for the modeling of microwave active devices, the Nonlinear Integral Model, is applied for the prediction of intermodulation distortion (IMD) in GaAs MESFETs. Theoretical considerations and experimental results show that the intermodulationcharacteristics of GaAs MESFETs can be predicted with excellent accuracy by using the proposed model together with suitable electron-device-oriented interpolation techniques, directly on the bases of conventional measuremerts (DC characteristics and bias/frequency dependent small-signal S-parameters).

A Design Method for Parallel Feedback Dielectric Resonator Oscillators

A method is proposed for the design of parallel feedback DR oscillators where output power, frequency stability and other basic performance parameters are simultaneously taken as design objectives. After introducing suitable performance indexes which define the stability and self-starting capability of the oscillator, an efficient procedure aimed at searching for the optimal compromise between opposing design requirements is described. The method has been validated by considering, as a design example, a microstrip DR oscillator using a medium power GaAs MESFET.

VLSI reliability: Contributions from a three year national research program

The continuous trend to further I.C. miniaturization implies increased local electric field strength and power dissipation density, and a perverse scaling, behaviour of metal interconnections and contacts. This will result in new failure mechanisms while old ones, non under control, may become a threat again. This work reports on the most relevant results, related to VLSI reliability, obtained by the seven University Research Teams involved in a three years Research Program sponsored by the Italian Ministero Pubblica Istruzione. In particular new methods to investigate electromigration and to localize latch-up phenomena have been successfully developed. Also test and diagnosis techniques to analyze faults in digital I.C. with emphasis on ECL and custom VLSI have been studied, and electromagnetic interference effects, in operational amplifiers have been modelled and simulated.

Large-signal modelling of Dual-Gate GaAs MESFETs

A mathematical approach, which has been recently proposed for the nonlinear modelling of microwave transistors, is adopted for the large-signal performance prediction of Dual-Gate GaAs MESFETs in the framework of Harmonic-Balance circuit analysis. Unlike classical equivalent circuits, the nonlinear model adopted here can be directly identifled on the bases of DC characteristics and small-signal biasdependent AC parameters without need for optimisation-based procedures for parameter extraction. The validity of the large-signal modelling approach is confirmed by accurate physics-based numerical simulations of a Dual-Gate GaAs MESFET mixer.