Circuits and Systems: Theory and Applications

Research focus

The Peer review has evaluated this group as Average

The Circuits and Systems Theory and Applications group is mainly active in methodological and fundamental research aspects of circuits and systems theory that are relevant in circuit analysis and design. Among the main activities of the research group, we mention: reliable and accurate modeling of devices and circuits, extraction of model parameters, development of robust frames and tools for their numerical analysis and design, study of novel numerical methods and algorithms. These research activities are strongly inspired and finalized by state of the art electronic applications. During the four-year period 2003-2006 attention has been mainly devoted to the following topics: Circuit model of parasitic phenomena The technological evolution of integrated circuits and the employment of some manufacturing processes (i.e. SOI, GaAs) have made parasitic phenomena of crucial importance. The interest of scientific community is oriented to the achievement of a general methodology able to incorporate relevant parasitic effects into the design process (parasitic-aware design). Being these phenomena inherently spatially distributed, their reliable inclusion into circuit models poses several problems both of theoretical and applicative nature. Among parasitic effects, heating phenomena in analog circuits are getting extremely relevant and becoming an important cause of degradation of nominal performances and an effective limit of the system reliability. The feasibility of electro-thermal simulation for thermal-aware analog design involves the following problems. 1) Realization of circuital thermal models of the heat diffusion phenomena in integrated circuits. These models should be accurate and of limited complexity (compact models). 2) Realization of CAD frame for the automatic extraction of compact thermal networks directly from the integrated circuit layout and for the electro-thermal simulation. Another relevant parasitic phenomenon is signal degradation due to long wiring on-chip interconnects. It is widely recognized that interconnects play a key role in determining signal propagation and time delays in sub-micron layouts; in addition the interaction between adjacent interconnects can cause cross talk noise and signal integrity corruption. The first step of interconnect modelling consists in determining parasitic capacitance values both through direct measurements on layout structures and/or through predictive simulations with software extraction tools. Numerical methods for circuit analysis The evolution of IC manufacturing technology leads to circuit models which are evermore complex both in terms of number of elements and in terms of nonlinear behavior. At the same time, various applications introduce the needs of novel kinds of analysis such as noise and conjugate electrothermal analysis. All these facts have renewed the interest in methods and algorithms for the analysis and design of analog circuits. Particular attention has been devoted in literature to radio frequency circuits being widespread and very demanding in term of accurate simulations. Many problems to be solved are related to the effects of technology scale down: very large circuits manufactured with deep submicron technologies display extreme parasitic effects and severe non linear component characteristics; simulation of these circuits still poses many unsolved problems. Convergence of traditional analysis methods can in fact be hindered by components with a very large range of values, this is often the case when simulating netlists obtained from post layout parasitic extraction of submicron layouts. 287 Other problems are due to the strict "low noise" requirements posed by most Radiofrequency applications. The algorithms for phase noise simulations that are now available in state of the art circuit simulators can fail in many significant cases. For instance, frequency warping due to integration algorithm can occur and can lead to erroneous design of oscillators and filters.

Departments

Dipartimento di Elettronica e Informazione (DEI)

Professors

Vito Amoia (full professor)
Angelo Brambilla (full professor)
Dario D’Amore (full professor)
Amedeo Premoli (full professor)
Mauro Santomauro (full professor)
Paolo Maffezzoni (associate professor)
Giancarlo Storti Gajani (associate professor)
Lorenzo Codecasa (assistant professor)
Giambattista Gruosso (assistant professor)