Study of TE/sub 0/ and TM/sub 0/ modes in dielectric resonators by a finite difference time-domain method coupled with the discrete Fourier transform

An application of a numerical method of finite differences in the time domain (FDTD) coupled with the discrete Fourier transform is presented to determine the resonant frequencies of the TE/sub 0/ and TM/sub 0/ modes of axially symmetric dielectric resonators closed in a cavity. The technique is conceptually and computationally simple, and it allows access at once to information on the entire modal spectrum by means of the fast Fourier transform (FFT) applied to the time series. The cylindrical cavity dielectrically loaded at the base and the resonant frequency of the TE/sub 01 delta / mode are analyzed in two systems: a cylindrical cavity with a cylindrical dielectric resonator of variable radius, and the shielded dielectric resonator on a microstrip substrate. The results obtained are compared with the rigorous (exact) theoretical solutions and with experimental results.