Analysis of pentagonal waveguides for high-power transmission by use of eigenmode expansion

In this paper, the eigenmode expansion technique is proposed to analyze the pentagonal waveguide for high-power microwave transmission. The analysis is implemented by expanding the electromagnetic fields inside a pentagonal waveguide with the infinite summation of the cylindrical waveguide modes. To obtain the numerical cutoff wavelength, the infinite summation has to be truncated, and then the point-matching technique is used on the boundary. Once the linear equation is obtained, which is the function of the cutoff wavenumber, the determinant about the eigenvalue is solved. The numerical results are in good agreement with those published. The propagation characteristics of the pentagonal waveguides, such as attenuation constant, power-handling capability, and characteristic impedance, are also analyzed.