Time domain identification of passive multiport RC networks with convex optimization: An application to thermal impedance macromodeling

In this paper a novel time-domain identification procedure for passive RC multiport networks is introduced, based on convex optimization and allowing the straightforward enforcement of basic physical constraints, specifically tailored to thermal impedances. The identification is performed in two steps. First, the time constants are identified for each element of the thermal impedance matrix by means of standard nonlinear optimization techniques, which allows ensuring that all corresponding network poles are real. Subsequently, a matrix form for the response is assembled with the evaluated common set of time constants, and residue matrices are computed through a convex optimization algorithm, minimizing the approximation error while enforcing the passivity constraints.