A simple estimate for cut-off wave number of lowest-order TM mode of a hollow metallic waveguide of arbitrary cross-section

Based on two inequalities, it is presented that the cut-off wave number of the lowest order transverse magnetic (TM) mode of a hollow metallic wavegui de of arbitrary cross-section is a function of the area, the perimeter and the inscribed circle radius, The results obtained by the derived formulas a re compared with exact data reported in the literature. It shows that the p roposed method is the reliable general purpose tool for computing the cut-o ff wave number of the lowest order TM mode of a hollow metallic waveguide o f arbitrary cross-section, (C) 2000 John Wiley & Sons, Inc.