Time and Frequency Macromodeling Techniques for Electromagnetic Systems with Propagation Delays

This paper presents a comprehensive analysis of the strengths and limitations of macromodeling techniques in both the frequency and time-domains, explicitly focusing on methods such as Vector Fitting (VF) and Delayed Vector Fitting (DVF) for the frequency-domain, and Piecewise Linear Fitting (PWLFIT) for the time-domain. We will demonstrate how the VF and DVF models can analyze systems through state-space representations, enabling efficient and accurate system analysis. Additionally, we will show how the PWLFIT method can be applied to convolution schemes to accelerate the convolution process. In particular, we illustrate how adopting Segment Fast Convolution (SFC) schemes further enhances computational efficiency. The work provides a detailed comparison of these techniques, highlighting their advantages and challenges.