Double Step Analysis of Dielectric Rectangular Waveguides Using Modal Expansions Technique

In this paper the junction parameters of a double step discontinuity of dielectric rectangular wave guide have been obtained. The complex power in the direction of propagation due to both propagating and non-propagating modes has been find out using the modal expansion technique. The expressions for admittance and susceptance have been obtained and evaluated numerically. The results have been obtained for the dielectric constant of 9 using only the bound mode analysis and neglecting the continuous spectrum. The susceptance values have been depicted for different step ratios at the frequency of 89 Ghz and also for a frequency range of 80-100 Ghz for a fixed step height. Graphical representations of calculated results using modal expansions technique and the simulated results using FDTD have been provided which depict a good agreement between the two.