Physics-based electron device modelling and computer-aided MMICdesign

On overview on the state of the art and future trends in physics-based electron device modelling for the computer-aided design of monolithic microwave ICs is provided. After a review of the main physics-based approaches to microwave modeling, special emphasis is placed on innovative developments relevant to circuit-oriented device performance assessment, such as efficient physics-based noise and parametric sensitivity analysis. The use of state-of-the-art physics-based analytical or numerical models for circuit analysis is discussed, with particular attention to the role of intermediate behavioral models in linking multidimensional device simulators with circuit analysis tools. Finally, the model requirements for yield-driven MMIC design are discussed, with the aim of pointing out the advantages of physics-based statistical device modeling; the possible use of computationally efficient approaches based on device sensitivity analysis for yield optimization is also considered     

Finite memory non-linear model of a S/H-ADC device

A new model has been proposed for the characterisation of the non-linear dynamic effects of a S/H-ADC device and a new mathematical approach has been introduced to describe its non-ideal dynamic behaviour. The measurement procedure to deduce the parameters of the proposed model is given together with the experimental results on a commercial device.     

A non-linear dynamic modelling approach for the characterization and error compensation in sampling oscilloscopes

A mathematical modelling approach is proposed for measurement-based characterization of non-linear dynamic sources of error in the vertical channel of a sampling oscilloscope. The proposed approach has been derived from a recently proposed modified Volterra series expansion which, under particular conditions, provides fast convergence and can be truncated to the first integral term. A possible characterization procedure, based on instrument testing under sinusoidal AC input signals with different frequencies and variable DC bias components, is described and used to evaluate the performances of a commercial oscilloscope. The waveforms obtained by using the identified model are compared with the experimental ones for model validation; successively the model is used for the error compensation of the memory effects.     

The effect of time-jitter in equispaced sampling wattmeters

This paper evaluates the effect of time-jitters in the equally spaced sampling wattmeters on the hypothesis of jitters uncorrelated with the input signals. The general case of two distinct time-jitters is considered, one common to the two channels and the other different for each one of them. The performance of the wattmeter has been evaluated by considering the asymptotic statistic parameters of the output. It has been shown that the different time-jitters introduce a bias and that both time-jitters contribute to the variance of the output. In any case, time-jitters introduce further bandwidth limitations which must be taken into account in the wattmeter accuracy evaluation. The theoretical results have been compared with simulated and experimental findings. Experimental results were obtained with a prototype in which both common and different time-jitters were separately added to the equally spaced sampling instants of the two input channels. In both cases, all the results were in good agreement with theoretical expectations     

Recursive random-sampling strategy for a digital wattmeter

A recursive random-sampling strategy is proposed for the implementation of a digital broadband wattmeter. In this strategy each sampling instant is obtained by adding to the preceding one a predetermined constant lag plus a random increment. In order to correlate the measurement uncertainty to the bandwidth, the asymptotic mean-square error arising from the sampling strategy and the filtering algorithm is evaluated and analyzed; it has been shown that the proposed sampling strategy does not limit the bandwidth of the instrument if an appropriate statistical distribution of the random increments is selected. The theoretical results are compared with those obtained by simulating the measurement process     

Tolerance assignment in nonconvex acceptability regions

In circuit design the optimal assignment of component nominal values and tolerances is usually carried out supposing that the acceptability region is monodimensionally convex. A method is proposed, based on minimisation techniques, for verifying the validity of a solution obtained under this hypothesis. The same method can also be used for tolerance reassignment when the verification result is negative.     

Performance function for time-jittered equispaced samplingwattmeters

This paper evaluates the effect of time-jitter in the equally spaced sampling wattmeters on the hypothesis of equal effects in the two channels and a jitter uncorrelated with the input signals. It is shown that time-jitter, which is a random fluctuation with respect to the nominal sampling time, introduces a frequency limitation which is evaluated together with that due to the sampling strategy and filtering algorithm. The theoretical results are compared with the simulated ones     

Non-linear dynamic modelling of broad-band GHz-field analogue-to-digital acquisition channels

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.     

Tool for efficient intermodulation analysis using conventional HBpackages

A 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 analysis     

Physical modeling of GaAs MESFETs in an integrated CAD environment:from device technology to microwave circuit performance

The linkage between a physical device simulator for small- and large-signal characterization and CAD (computer-aided design) tools for both linear and nonlinear circuit analysis and design is considered. Efficient techniques for the physical DC and small-signal analysis of MESFETs are presented. The problem of physical simulation in a circuit environment is discussed, and it is shown how such a simulation makes possible small-signal models accounting for propagation and external parasitics. Efficient solutions for physical large-signal simulation, based on deriving large-signal equivalent circuits from small-signal analyses under different bias conditions, are proposed. The small- and large-signal characterizations allow physical simulation to be performed efficiently in a circuit environment. Examples and results are presented