Design of stepped microstrip components

The analysis of the impedance step by the mode matching procedure using a waveguide model for the microstrip line yields an explicit design formula for the frequency-dependent equivalent series inductance. The single-section quarter-wavelength transformer is calculated under the assumption of interacting steps. It turns out that in regard to practical design the neighbouring steps can be considered to be decoupled so that the calculation can be done simply with the results given before. Finally the derived results for the impedance step are used to calculate the scattering matrix of an n-section tapered transmission line. Experimental data show good agreement with theory.