Thesis - Open Access
Master of Science (MS)
In antenna theory and practice, an increased directivity of the antenna improves the total system performance. Narrow beamwidth allows discriminating (on reception) against interfering signals from directions other than that of the desired signals, and on transmission it minimizes interference with receiving stations other than the desired direction. Sharp directivity, however, is undesirable in some applications. For example, in entertainment broadcasting and in certain forms of communication an omnidirectional horizontal pattern is required. Furthermore, three-dimensional omnidirectionality may be desired in unstabilized spacecraft applications. Omnidirectionality in a horizontal plane is fairly simple to obtain. In this paper, two crossed small loops with a quadrature combiner are examined. The definition and principle of true omnireception networks are given in Chapter 2. For many years, LC lattice and hybrid combiners have been adopted to achieve omnidirectional wide-band reception. The conceptual diagram of a conventional commercial combiner is given, and an analysis of its power transfer characteristics is conducted in Chapter 3. Some modified versions of omni-reception system are then suggested and discussed in detail. The proposed combiner proves to be more. 2 efficient than the conventional one. A comparison of the two systems is also given in Chapter 4. The proposed system consists of two main parts, bandpass filters and lattice networks. The general background of filter design is presented in Chapter 5, followed by a description of lattice network design technique. Then the processes applied to design desired circuits are explained in Chapter 5. PCAP programs are introduced to test the designed circuit and are included in the Appendices. Other possible applications of omni-systems are suggested and discussed briefly at the end of the Chapter 5.
Library of Congress Subject Headings
Radio -- Receivers and reception
Television -- Receivers and reception
Number of Pages
South Dakota State University
Kwak, Han-Tak, "HF Wide-Band Omnidirectional Antenna System" (1987). Electronic Theses and Dissertations. 4452.