Analysis and design of simple antenna geometries for broadband high frequency communications.

A thesis submitted to the Faculty of Engineering. University of the Witwatersrand. Johannesburg in fulfilment of the requirements for the degree of Doctor of Philosophy.The general argument of the thesis is that the design of broadband antennas demands a thorough understanding of the factors influencing the current distribution on antenna wires. Specifically. current distribution concepts are used to improve the evaluation and design of small broadband antennas for the high frequency (HF) 2 to 30 MHz range. The current distribution on an antenna governs its input impedance, radiation efficiency and radiation patterns. (Abbreviation abstract)Andrew Chakane 201

Applications of the conjugate gradient FFT method in scattering and radiation including simulations with impedance boundary conditions

The theoretical and computational aspects related to the application of the Conjugate Gradient FFT (CGFFT) method in computational electromagnetics are examined. The advantages of applying the CGFFT method to a class of large scale scattering and radiation problems are outlined. The main advantages of the method stem from its iterative nature which eliminates a need to form the system matrix (thus reducing the computer memory allocation requirements) and guarantees convergence to the true solution in a finite number of steps. Results are presented for various radiators and scatterers including thin cylindrical dipole antennas, thin conductive and resistive strips and plates, as well as dielectric cylinders. Solutions of integral equations derived on the basis of generalized impedance boundary conditions (GIBC) are also examined. The boundary conditions can be used to replace the profile of a material coating by an impedance sheet or insert, thus, eliminating the need to introduce unknown polarization currents within the volume of the layer. A general full wave analysis of 2-D and 3-D rectangular grooves and cavities is presented which will also serve as a reference for future work

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion

Generation and measurement of microwaves

Part I reviews methods of generating microwaves in the shorter cm and mm region examining their possibilities, technical problems and limitations. It concludes that the spark microwave generator has its part to play in this field. A historical survey of past work on microwave spark generators which has been published by the author in Brit.I.R.E. Journal 13, 1953. p.490 is attached as Appendix I, Part II analyses the theory and evidence in support of the characteristic radiation from a dipole type spark generator. It also examines in detail methods of frequency analysis and spectrum filtering by a large variety of semi-optical and waveguide devices. The Boltzmann interferometer is dealt with exhaustively. Some discussion of available power is also included. Part III describes some technical problems of spark generation and methods of solving them. Experiments are described to test waveguide devices which permit the control of radiated frequency band and result in a source tunable over a 2 to 1 range of frequencies. The established principles can be used to test waveguide components for matching characteristics and filters - in particular wide band filters - for their response and any spurious effects. The range covered extends from 8 mm to 5 cm. Appendix II contains a paper on the theory of a quarter wave transformer filter which is due to appear in "Wireless Engineer", Appendix III dealing with the diffraction of non-monochromatic e.m. waves by a slit and a grating is a reprint from Proc, Phys. Soc, 68B, 1955. p.171

Electromagnetic wave propagation on helical conductors

Based on the author's (Sc. D.) thesis, Dept. of Electrical Engineering, Massachusetts Institute of Technology, 1951.Samuel Sensiper