Browsing by Author "Malan, D. H. (Daniel Hugo) "
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- ItemHybrid finite element and moment method modelling of microstrip patches(Stellenbosch : Stellenbosch University, 1995) Malan, D. H. (Daniel Hugo) ; Davidson, D. B.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.ENGLISH ABSTRACT: Numerical modelling can be used to find an approximate solution to Maxwell's equations within a region of interest. From the solution a number of characteristic parameters of the region can be derived. In this thesis, a mathematical formulation of the hybrid finite element method and method of moments (FEM/MoM) technique is presented that is suitable for application to the analysis of radiating microstrip structures. Specific emphasis is placed on the creation of an algorithm that can readily be implemented on computer. Edge-based brick elements are presented as a suitable discretisation scheme for the class of problems that will be attempted. A FEM/MoM computer program was written, and is discussed in detail. Problems invariably encountered in programs of this nature are excessive computational and memory requirements. Data structuring techniques to optimize matrix storage and so reduce memory demands are presented. Various ways to improve the execution speed of the program are also considered. Different approaches to solving a system of linear equations exist. Three of the most popular are Gaussian elimination and the conjugate and biconjugate gradient methods. All three techniques are implemented, and their merits in the context of this FEM/MoM formulation are compared. It is shown that the radar cross section (RCS), input impedance and radiation pattern of a cavity backed microstrip structure can be found once the electric field in the cavity is known. These parameters are computed using the hybrid FEM/MoM technique for a number of different configurations, and compared with published results. Excellent agreement is found between the computed and published RCS results, and good agreement is found between the published radiation pattern and input impedance results. A microstrip patch antenna was built, and the input impedance and radiation patterns were measured and compared with those computed with the program. In general a close correspondence is found.