TIME DOMAIN SOLUTION OF ELECTROMAGNETIC PROBLEMS

After a brief review of the contemporary time-domain methods for solving electromagnetic problems, the FDTD (Finite Difference Time Domain) technique is discussed in detail. The visualization of electromagnetic field distribution, a unique feature of FDTD, is emphasized by applying the technique to simulate electromagnetic wave propagation in unbounded medium. Results obtained with various absorbing boundary conditions are compared. The field distributions in the vicinity of microwave integrated circuit components such as branch-line coupler, bandpass and lowpass filters as well as patch antennas are displayed. In addition, the mapping of the RF (Radio Frequency) magnetic field in a human head is also illustrated to show the applicability of FDTD to aid in the analyses of RF coils developed for magnetic resonance imaging. The extraction of frequency-domain information by Fourier transforming the transient time response generated by pulse excitation is another salient feature of the time-domain methods. The scattering parameters over a wide frequency band are obtained in this manner for microwave integrated circuit components. An efficient extrapolation technique based on Prony's method to generate accurate scattering parameters is also discussed.