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Finite-Difference Time-Domain Simulations to Characterize Dielectric Horn Antennas Neelakantam Venkatarayalu. Co-advisor : Prof. Robert Lee Co-advisor : Prof. Fernando L. Teixeira Abstract Finite difference time domain (FDTD) method is used to characterize the input impedance of a class of dielectric horn antennas. A method to feed the antenna structure with a two wire transmission line is presented. A calibration procedure to compute the reflection coefficient and hence the input impedance of the structure fed by the modeled transmission line is presented. A study on the performance of exponential time differencing(ETD) to model lossy dielectric is carried out for a one-dimensional problem. The performance of this scheme is compared with the traditional time averaged scheme. Numerical modeling of resistive cards which are typically used in antennas to control ringing and to improve bandwidth, is presented and the performance of the card with various sheet resistance profiles (linear, quadratic and exponential) is studied. The input impedance of a dielectric horn antenna with two conical perfect electrical conductor (PEC) plates as launcher is computed numerically. Impedance of the launcher plates without the dielectric horn is computed and results are compared with analytical solution. Efficient modeling of thin PEC plates which avoids stair-casing errors is carried out for both the two-dimensional and the three-dimensional cases. The results are compared with the stair-casing case. Various impedance curves for the original antenna geometry, varying the parameters like the horn angle, launcher plate angle and the dielectric constant of the material of the horn are generated. Back |