Tunable lumped element notch filter for UHF communications systems

Benson, Peter-Luke (2018-03)

Thesis (MEng)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: The focus of this work is to solve for the electromagnetic problem of large linear antenna arrays efficiently and accurately within the context of two-dimensional (2D), transverse magnetic (TM) Method of Moments (MoM). Provided that the meshing size is small enough, the MoM can provide accurate results for electromagnetic simulations. However, the memory storage and computational time scale as O(N2) and O(N3) respectively, where N is the number of basis functions. The electrical size solvable with given computational resources is therefore limited. To analyze large antenna arrays, the Characteristic Basis Function Method (CBFM) is employed. This technique decomposes the entire geometry into subdomains, over which, physics-based macro basis functions called CBFs are defined. By using macro basis functions, the aim is to define the same electromagnetic problem using fewer degrees of freedom as compared to the standard MoM. Firstly, a CBFM code where a subdomain is defined to be an antenna element is implemented. The results of CBFM using up to quaternary CBFs (higher-order CBFs) are compared to that of the MoM. Secondly, CBFM with larger overlapping subdomains which span multiple antenna elements in an array is defined, so as the mutual coupling in dense antenna arrays is better represented. To generate higher-order CBFs, the distance-based criterion is proposed which is found to be a more efficient procedure than the conventional tree-based approach, for larger subdomain CBFM. The results for larger subdomain CBFM including the distancebased criterion are compared to the conventional single antenna subdomain CBFM over a range of frequencies.

AFRIKAANSE OPSOMMING: Die fokus van hierdie werk is om die elektromagnetiese probleem van groot, liniêre antenna samestellings effektief en akkuraat op te los, binne die konteks van die tweedimensionele (2D), transversaal-magnetiese (TM) Moment Metode (MoM). Indien die maas-grootte klein genoeg is, dan lewer die MoM akkurate elektromagnetiese simulasie resultate, maar die rekenaargeheue en berekeningstyd skaleer as O(N2) en O(N3), onderskeidelik, waar N die aantal basisfunksies verteenwoordig. Die oplosbare elektriese grootte met gegewe rekenaarkrag, is dus beperk. Die Karakteristieke Basisfunksie Metode (KBFM) word gebruik om groot antenna samestellings te analiseer. Hierdie tegniek breek die geometrie op in sub-strukture, waaroor fisies-gefundeerde makro basisfunksies genaamd KBFs, gedefinieer word. Die doel van makro basisfunksies is om die gegewe elektromagnetiese probleem se oplossing met minder vryheidsgrade voor te stel, in vergelyking met die standaard MoM. ’n KBFM kode waar die sub-strukture ooreenstem met die antenna elemente, is eerstens geïmplementeer. KBFM resultate met tot vierde-orde KBFs word vergelyk met die MoM. Tweedens word die KBFM met groter, oorvleuelende sub-strukture wat oor verskeie antenna elemente strek, gedefinieer, sodat wedersydse koppeling in digte antenna samestellings beter in ag geneem word. Om hoër-orde KBFs te skep, word ’n afstand-gebaseerde kriterium voorgestel, en daar word bepaal dat dit ’n meer effektiewe prosedure is as die konvensionele boomstruktuur gebaseerde benadering, vir groter sub-struktuur KBFM. Resultate vir groter sub-struktuur KBFM met afstand-gebaseerde kriterium, word vergelyk met die konvensionele enkel-antenna sub-struktuur KBFM, oor ’n wye frekwensiebereik.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/103660
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