Electronics > Circuits and systems: theory and applications


The research group “Circuit and System Theory and Applications” is mainly focused on fundamental and methodological research topics that are relevant for the modelling, design and simulation of circuits. Among the activities of the group, the most relevant are:
1. Advanced circuit simulation methods
2. RF circuit macro-modelling for communication applications.
3. advanced electro-magnetic field simulation and device modelling
4. multi-physics modelling and simulation of renewable energy production systems
All these research activities, eventhough pursued at the fundamental level are directly inspired and tested on real world, state of the art applications.

Most relevant research achievements

Advanced methods for Circuit Analysis
- Advanced simulation techniques for the time-domain analysis of non-linear circuits for communication electronics have been developed. These techniques include highly accurate implicit Runge-Kutta integrations as well as very efficient envelope-following method.
- Development of efficient numerical algorithms in the time domain running on multi-core computers and GPUs for the simulations of non-linear circuits. These algorithms have been used to determine the steady state behaviour of hybrid systems, i.e. of circuits that are modelled by DAEs with a discontinuous vector field and variables that undergo a “reset” action.
- Simulation of systems modelled with different levels of abstraction such as mixed analog-digital circuits.

Macro-modelling of RF circuits for communication electronics
- A general methodology for the phase-domain macro-modelling of oscillators has been assessed. Macro-modelling has been exploited to study the synchronization phenomena of injection-locking e injection-pulling in oscillators and in the design of injection-locked frequency dividers (ILFDs). This last activity has been developed in collaboration with the University College Cork (UCC), Cork, Ireland and with the team of Prof. Michael Peter Kennedy. In 2010, the cooperation was supported in part by Science Foundation Ireland under Grant 06/RFP/ENE009 and Grant 08/IN.1/I854.
- In the field of the stochastic analysis of non-linear circuits in the presence of noise, it has been investigated how the intrinsic phase-noise in oscillators can be reduced by the injection of small-amplitude signals.

Advanced simulation of electromagnetic field and modeling for electrical device implementation
- Various questions arising for the Cell Method for the Electromagnetic Simulation have been considered: discretization of constitutive relations, discretization of energetic and boundary quantities. As a major result an extension to the Cell Method has been obtained for discretization of electromagnetic problems over generic polyhedral grids. From these results a novel extension of the FDTD from Cartesian to tetrahedral grids has been proposed which preserves all the main properties of the basic method, being explicit, consistent, conditionally stable. This method is currently under implementation within the commercial software CST Microwave Studio.
- Within this area, the research activities have been devoted also to the modelling of electrical devices. The study was addressed to the extraction of the parameters in order to obtain circuit models and at the same time to study the physical phenomena of second approximation as eddy currents, the structure of the materials and thermal phenomena, or dispersive.

Multi-physics modelling and simulation of systems for renewable energy production
- A novel multi-physics modelling and simulation of an hybrid photovoltaic system for the production of electrical and thermal energy.
These circuits include self-sustained high-Q oscillators, “stiff” and strongly nonlinear circuits. A robust method to formulate the nodal analysis equations has been proposed which exploits a “fall-back” technique. An accurate transient analysis based on the “Runge-Kutta” numerical integration has been introduced. Novel algorithms for the “steady-state” and “envelope” simulation of RF circuits have been devised and implemented in electrical simulators.

A novel approach to the macro-modeling of electronic oscillators has been proposed.
The method relies on the Floquet Theory of linear-periodically-varying systems and has been implemented in the simulator 'pan', freely downloadable from the Web. This activity has been supported by the PRIN 2006 project.