Microwave response of tessellated metal surfaces and their constituent elements
Biginton, Matthew Paul
Thesis or dissertation
University of Exeter
Reason for embargo
some items not published and currently writing papers
Over the last century the electromagnetic (EM) spectrum has become ever more accessible with advances in technology. As a result, EM filters (or Frequency Selective Surfaces (FSSs)) have been developed for many applications. Such filters have been used on satellites and radomes. In this thesis, novel single layer and dual layer FSS have been studied and characterised, experimentally and using Finite Element Method (FEM) modelling, showing very good agreement between the data and models. The interesting transmission properties of these structurally complicated FSS are explained and the physics of the resonant modes that mediate transmission is explored. Enhanced transmission through an array of sub-wavelength apertures close to the diffraction limit has been a popular area of physics for many years. In addition enhanced reflection from metal patch arrays has been of great interest. This thesis studies original extensions of conventional FSS. The work is split into two main sections: single layer FSS and dual layer FSS. In the first experimental chapter (chapter 5) two new single layered FSS comprising complementary elements tessellated into composite arrays are explored (a connected array and a disconnected array). The behaviour of these arrays is compared with that of arrays of the constituent elements that either exhibit enhanced transmission or enhanced reflection phenomena. The behaviour of the connected composite array can be inferred from the behaviour of arrays of the constituent elements. Interestingly for the disconnected composite array, the behaviour can not be inferred from the constituent elements as without one or the other of the elements in situ, the modes supported on the composite array are not supported for the arrays of constituent elements. The second and third experimental chapters (Chapters 6 and 7) explore the transmission through dual layer arrays composed of either capped holes or capped annuli. Despite the holes being capped with a metal disc, the array exhibits a remarkably high transmission, mediated by the annular cavity formed between the caps and apertured metal sheet. In Chapter 7 concentrically nested annular patches above annular slots are used to achieve multiple transmission pass bands. For many applications it is often desirable to miniaturise resonant elements. Developing this concept further, chapter 8 explores the resonant frequency of a structured capped aperture. The internal structure of metal inclusions, give control over the resonant frequency of the cavity, reducing it's resonant frequency significantly and miniaturising the size of the cavity compared to the incident wavelength.
PhD in Physics