Use of the finite difference time domain method to study broadband antennas for millimeter wave point-to-point and point-to-multipoint communications

Abstract

<p>This thesis presents an in-depth investigation of new broadband millimeter wave antennas, which can be used in millimeter wave point-to-point and point-to-multipoint communications. A very powerful design tool--the Finite Difference Time Domain (FDTD) method is presented in its regular uniform grid form, which is referred to as Yee's method, its non-uniform grid form, and its General Curvilinear Coordinate (GCC) form. Accompanying formulas are presented in each case. The advantages of these different formulas are discussed, their use for solving different complex electromagnetic problems is demonstrated, as well. Different absorbing boundary conditions (ABC) are used to design antennas, their beam forming networks and transitions, for example Mur's first order ABC, Litva's dispersive ABC and Modified Perfect Matched Layers (M-PML). Here Litva's ABC is presented in detail, and some case studies are given to prove that it is a very good ABC for printed circuit applications. A research based FDTD 3-Dimensional Structure Simulator (FDTD 3D SS) is used to design these new wide-band antennas and transitions. More than 500 simulations have been calculated for this study within less than a year. The Tapered Slot Antennas (TSA) and different type feed structures for TSA are reviewed in Chapter 2. As a member of the class of traveling wave antennas, the TSA's are wide-band elements with very good directivities. Based on the Suspended Microstrip Line (SML) and the Inverted Microstrip Line (IML), three new feed structures have been developed, by using FDTD 3D SS, for millimeter wave wide-band applications. The Vivaldi antenna, which belongs to the traveling wave antenna category and shares the same features as TSA, is used as a very short element (antenna length L < λo /2) to design an 120-degree-vertical-polarization sector antenna. The experimental study shows that the design gives very good results and meets the specifications in real applications. It has a potential to be used as a sector antenna with different horizontal beam-widths. This design shows antenna engineers a novel approach to design sector antennas without worrying about the antenna input impedance bandwidth. (Abstract shortened by UMI.)</p>