Representation of Electromagnetic Responses in Time Domain Using State-Space System Identification Method

This paper presents a control system methodology based on system identification (SI) to derive state matrices and system dynamics for the extrapolation of simulated time-domain electromagnetic (EM) responses using both input and output data. The method is applied to model transient responses for a dielectric resonator and a wideband slot antenna computed by the finite-integration method using non-Gaussian excitation pulses typically employed in digital signals. Using state-space SI formulation, a compact representation of the output time-domain signal is derived, including the early-time transient responses, and its numerical implementation depicts no instability in late-time responses plotted well beyond the steady state. Furthermore, all the system poles are found to lie within the unit circle in the complex plane. Excellent model corroboration is achieved with independently computed frequency domain data or measured results using modest computer resources.