Abstract: A new approach to the computation of the lowest cutoff frequencies of TE and TM models in uniform waveguides is presented, which uses the method of moment(MoM) combined with a conformal mapping. A conformal mapping is applied to transform the waveguides section onto the circle, and the lowest cutoff frequencies is calculated by the MoM. Comparisons with numerical results found in the literature validate the presented method.

Key words: cutoff frequencies, conformal mapping, method of moment