Internally Positive Representation of a Class of Continuous Time Systems

The problem of realizing arbitrary transfer functions as combinations of positive filters, or, more in general, of representing arbitrary systems by means of Internally Positive Representations (IPRs), has been widely investigated in the discrete-time framework. An IPR is a positive state-space representation, endowed with input, state and output transformations, that realizes arbitrary input-state-output dynamics. This technical note investigates the problem of the IPR construction for continuous-time systems, and proposes a technique that provides stable IPRs for a particular class of systems.