Abstract: Perturbation method of boundary geometry (PMOBG) is used in rectangular waveguides with one-dimension perturbed walls and mode analyses are made.The boundary conditions are transformed into perturbation form firstly.Then the governing equation is separated into ε０ and ε１　order problem by using the method of strained parameters.Finally the solution is obtained via the solvability conditions of differential equation.Moreover,the effect of boundary perturbation on mode degeneration,transmitting parameters and field structure is discussed by comparing with regular rectangular waveguides.The results show that the effect is able to come down to analyzing two perturbation factors,i.e.perturbation factor of boundary geometry (PFBG) and perturbation factor of relative cut-off wavelength (PFRCW).

Key words: quasi-rectangular waveguide, mode analysis, Perturbation method of boundary geometry (PMOBG)