Of Fdm In The Calculation Of The Waveguide Cutoff Frequency And Attenuation Constant

The Finite-Difference Method (FDM) is one of the pioneer methods of numerical computation in the calculation of electromagnetic fields. As early as century 50' s, with the characteristics of simplicity and direct, it got the extensive application in the field of numerical analysis of electromagnetic fields. This paper has dealt with the application of FDM in computing cutoff frequency and attenuation coefficient of waveguide.1. The seven-grid difference format and nine-grid difference format of Helmholtz equation in right coordinate in the way of Taylor series method have been derived.2. The five-grid difference format of Helmholtz equation in slanting coordinate have been derived.3. Based on the relations among Et, Ht and Hz,or Ht, Et,and Ez in rightangular coordinate, and cylindrical coordinate, the procedure of calculating cutoff frequency and attenuation coefficient with FDM has been presented for determining the parameters of waveguides, the rectangular waveguide, circular waveguide, fan-shaped waveguide, and isosceles-right triangular waveguide have been analyzed.4. The programs to compute cutoff frequency and attenuation coefficient of waveguides are finished with the FORTRAN language, some results have been obtained.5. A novel family of waveguides for HPM transmission is introduced. Lastly the numerical results that agree very well with ones obtained by other methods are given.