On the Analysis of Horns, Reflectors, and Periodic Structures

Doktorsavhandling, 1997

The design and manufacturing of a dual-frequency horn is presented. The dual-depth corrugated horn is fed by a circular and a coaxial waveguide, in the upper and lower frequency band, respectively. The reason for choosing a waveguide-only feeding network is discussed. Predicted and measured data are compared and the numerical design procedure, including optimization, is presented. Based on measured horn radiation patterns, reflector antenna patterns are calculated and system performance is estimated. The Arecibo Gregorian dual-reflector feed performance is analyzed. A cluster feed geometry is studied with respect to field of view performance. It is shown that, using a sub-optimal (high spillover) element geometry, a seven-element cluster feed with good performance for all seven beams can be realized. Physical optics calculations are used to verify the performance of the dual-reflector feed which was designed using geometrical optics. Numerical waveguide simulators are easy to implement and can model non-physical boundary conditions. A number of different periodic structures are analyzed with a numerical waveguide simulator. The calculated data are compared to results computed using other numerical methods, with good agreement. Effective electromagnetic material parameters of infinite periodic structures consisting of two separate homogeneous materials are studied. The analysis provide effective dielectric constants of various geometries. It shown that transmission line solutions agree well with rigorous three-dimensional solutions, for periods less than half a wavelength. A numerically efficient method for analyzing finite periodic arrays is introduced. Based on a combination of a global uniform array approximation and element-by-element analysis, the method separates an array into an interior region and edge regions. Advantages and restrictions of the method are discussed and numerical comparisons with rigorous solutions are given.