Electromagnetic Analysis Of 3-D Oscillating Cavity And Cavity-backed Microstrip Patch Antennas With Time Domain Finite Element Method

First of all, the basic principle and procedure of time-domain finite-element method (TDFEM) are introduced in this thesis. And then, the operating frequency of each mode in 3-D oscillator driven by a point magnetic current is computed with TDFEM. By fast Fourier transform (FFT) method from the transient response obtained with TDFEM, the oscillating modes of rectangle cavity, cylinder cavity and complex cavity are investigated respectively. Simulated frequencies are compared with analytical results, and good agreements are found with about 1% numerical errors. The accuracy of 3-D TDFEM is validated consequently. Furthermore, the first order Mur absorbing boundary condition is applied to TDFEM for 3-D electromagnetic analysis. Numerical results presented in the thesis show that the Mur absorbing boundary condition can be applied to truncate the computational area accurately with a little affect on the condition number of generated TDFEM coefficient matrix.And then, TDFEM combined with Mur absorbing boundary condition is applied to compute the input impedance of microstrip patch antenna residing in a cavity. The frequency-domain finite-element method is presented firstly to calculate the input impedance of the antenna loaded with a 50Ωresistor. Through comparing the modeling input impedance with reference results, the algorithm and associated part of codes are validated. Furthermore, TDFEM is implemented to calculate the input impedances of the cavity-backed antenna loaded with 50Ωresistor or shorted pin or open pin respectively. High accuracy is acquired by comparing the TDFEM results with reference results. Finally, the key parameters of TDFEM such asτandΔt are investigated in detail. Although the unconditionally stable scheme- Newmark-beta iteration method is employed in the presented TDFEM, numerical error and CPU time are increased with largeΔt for the bad condition of generated coefficient matrix which dramatically affects the convergence rate of conjugated gradient (CG) solver.In this thesis, commercial software Patran is applied for geometry modeling and grid generation. In the computation procedure of the above problems, compact storage method and CG solver are used, so that the memory consumption and CPU time are saved consequently.