Nonlinear circuit stability; oscillator noise


Available commercial CAD/EDA software tools implement small-signal tests to assess microwave circuit stability in any regime of operation. In particular, nonlinear circuits such as power amplifiers, mixers and frequency doublers operate in nonlinear conditions, often being driven into a periodic or quasi-periodic steady steady state. Therefore techniques for the nonlinear stability analysis, conceived as a study of the perturbation of the periodic or quasi-periodic working point, are an added value for the circuit designer. A viable alternative for such nonlinear stability analysis is offered by the application of Floquet theory to the large-signal steady state by means of the explicit calculation of the Floquet exponents, directly implemented in the frequency domain. Specialized algorithms are available, that make such determination rather efficient and implementable into circuit simulators with a comparatively reduced effort.
Floquet theory can also be applied to the determination of the noisy state of autonomous oscillators, providing a solid foundation to the computation of phase and amplitude noise. This research deals with the exploitation of the Floquet base for the decomposition of the noisy signal leading to the uncovering of strictly nonlinear phenomena, such as the amplitude noise impact on the oscillation frequency.

ERC sectors 

  • PE7_4 (Micro- and nano-) systems engineering
  • PE7_6 Communication systems, wireless technology, high-frequency technology


  • Circuit stability
  • Circuit simulation
  • Bifurcation
  • Floquet theory