Study On The Propagation Properties Of Fin - Line Waveguide Family

The finite difference time domain (FDTD) method is a numerical computationmethod in electromagnetic field which has been developed rapidly in recent years andwidely used in many areas, including electromagnetic radiation, scattering, antenna,microwave, millimeter technology, photoelectronics， and bioelectromagnetics. Inthis thesis, FDTD method is introduced in detail and the procedure how to calculatethe cutoff frequency of the fin-line waveguide has been described. By the designedgeneral program, the change law of the fin-line cutoff frequency, with differentgeometry parameters and filling medium parameters, has been obtained.Firstly， the basic concept of the FDTD method is briefly introduced. Thedifference formula of calculating the electromagnetic field problem by FDTD methodis given. The requirement of the time interval and numerical stability condition,various boundary conditions, and optimization design of the excitation sources arealso discussed.Secondly, by the designed general program, the cutoff frequency of the higherorder modes of the single fin-line, bilateral fin-line and antipodal fin-line have beenanalyzed, and the influence of substrate, fine-size, and dielectric parameter have alsobeen studied.Finally, based on the designed general program, by changing the fin length, finheight and dielectric size, the changing law of the cutoff frequencies of TE modes inthe symmetrical fin line and asymmetric fin line have been obyained and discussed.