Effect of finite substrate width on higher-order mode generation of electrically shielded symmetric microstrip

The effect of finite substrate width on the higher-order mode generation of an electrically shielded microstrip is investigated. By employing the full-wave mixed potential mode-matching method the microstrip on a finite-width substrate can be accurately analysed. The dispersion characteristics of microstrip on two different substrate widths were compared in the frequency range of interest. The results indicated that the use of conventional three-dimensional simulators assuming homogeneous layered (stratified) multi-dielectric substrates may not work well above the first cutoff frequency of microstrip on a finite-width substrate.