Cutoff wavelengths of metallic waveguides with elliptical cross section

The cutoff wavelengths ¿
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of metallic waveguides with elliptical cross section are determined analytically. Two alternative methods, namely, a field and a shape perturbation method are used in the proposed analysis. Exact, closed form expressions, free of Mathieu as well as of Bessel functions, are obtained for the cutoff wavelengths, when the solution is specialized to small values of the eccentricity of the elliptical cross section. Numerical results for all types of modes are also included.