A METHOD OF CALCULATING THE STEP-SHAPE CHARACTERISTIC IN A RECTANGULAR WAVE-GUIDE USING A TRANSMISSION EQUATION

It is demonstrated that the step shapes in a rectangular waveguide can be treated rigorously by a transmission equation. An efficient method for computing the characteristics of the step shapes is proposed base d on the transmission equation. It is recognized that the step shape i s the one in which the derivatives of the shape change in the axial di rection diverges. Then the transmission equation is simplified. It is shown that the frequency dependence can be eliminated from the transmi ssion equation if there is no thermal loss in the step shape and that the scale dependence can also be eliminated if the cross-sectional sha pe is similar. By the foregoing procedure, the computation time and th e number of computation of the F matrix which consumes the most time i n the transmission equation method can now be reduced substantially. I t is found that the computation speed can be accelerated effectively b y more than one order of magnitude in comparison Co the method in whic h the F matrix is computed by numerical integration. The results are v erified experimentally.