Off-campus UMass Amherst users: To download dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.
Non-UMass Amherst users, please click the view more button below to purchase a copy of this dissertation from Proquest.
(Some titles may also be available free of charge in our Open Access Dissertation Collection, so please check there first.)
Hybrid 3-D finite element and moment method analysis for designing antennas with dielectric covers
This work investigates the use of hybrid 3-D Finite Element Method (FEM) and Moment Method (MoM) analysis techniques in designing antennas with dielectric covers. These dielectric covers can be seen as the radome of an antenna system. To ensure a proper design, the effects of the dielectric covers must be included in the analysis. A novel hybrid 3-D FE/MoM technique is developed initially with the Tapered Slot Antenna (TSA) array in mind. The antenna structure and feed are modeled in the FEM domain while the dielectric cover, which may have single or multiple layers, is modeled in the MoM domain. In this way, the method handles arbitrary antenna structural and material complexity while avoiding the need to discretize the dielectric cover, which may be very thin. The method is applied to various antennas successfully. However, there are practical difficulties of using the hybrid technique for modeling the TSA. Nevertheless, a number of examples showed that the hybrid method is versatile and useful for modeling new prototype antennas. Due to difficulties with the hybrid FE/MoM technique, a stand-alone MoM technique is the preferred analysis method for the dual-polarized TSA array. An improved MoM code is developed and used in a parameter study to produce a guide for designing a wideband, widescan TSA array. With this guide and the use of plated-through vias, an infinite dual-polarized TSA array with 5.8:1 bandwidth, scanning to &thetas; = 50° in all scan planes is designed. By assuming that only the dominant Floquet mode contributes to the interaction of the array and radome, a simple two-port network, together with a Genetic Algorithm (GA) is developed to design a suitable multi-layered radome for the TSA array. Two 8 element by 9 element arrays and an A-sandwich radome are built based on the design procedure. Measured results substantiate some of the analytical predictions and show that finite array effects are quite severe at lower frequencies. Although complete validations of the predicted performance cannot be proven due to the finite array effects, the experiments have yielded useful information about TSA array design, fabrication and performance.
Chio, Tan-Huat, "Hybrid 3-D finite element and moment method analysis for designing antennas with dielectric covers" (1999). Doctoral Dissertations Available from Proquest. AAI9950142.