Abstract:

The process and expressions for calculating the cut off wavelength of camrectangular waveguide are discussed by using boundary element method (BEM). An approximate general field expression for the dominant mode, where the real exponent of the power function is found with the variational method, is built according to field components fitting the boundary condition of completely conducting metal waveguide. Then the approximate expressions can be found. The cut off wavelengths and the exponent constant for the different dimensions of the guide in X band are computed .

Key words: waveguide　cutoff-wavelength, boundary element method, variational method