Wideband Impedance Matching in Transient Regime of Active Circuit Using Lossy Nonuniform Multiconductor Transmission Lines

This paper focuses on the electromagnetic compatibility domain, coupling in microwave circuits and wideband (WB) impedance matching in time domain using a purely temporal method, such as the centered-points Finite Difference Time Domain (FDTD). The paper here presents a new approach of WB impedance matching in transient regime and coupling context, of active circuits such as multiple complex nonlinear components (represented here by metal semiconductor field-effect transistors (MESFETs)), using Nonuniform Multiconductor Transmission Lines (NMTL) with frequency dependent losses and FDTD as modeling method. The FDTD method has several positive aspects such as the ease to introduce nonlinear components in the algorithm, the ease to use NMTL and the gain in simulation time and memory space. Also the FDTD method allows the study of WB impedance matching in time domain without recourse to the frequency domain. Systematic comparisons of the results of this method with those obtained by PSpice are done to validate this study. These comparisons show a good agreement between the method presented here and PSpice. The technique presented in this paper shows higher efficiency and ease to implement when compared to PSpice in regard to the treatment of frequency dependent losses, or shapes of transmission lines.