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Performance enhancement of the ground radiation antenna

Performance enhancement of the ground radiation antenna
Moon, Sung Jin
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This dissertation is a study on a ground radiation antenna that utilizes ground as a radiator for a small antenna. Generally, as the size of the antenna increases, the radiation performance improves, so it is advantageous to utilize ground plane. The ground is a large platform for high radiation performance and has wide bandwidth and high radiation resistance because it has very low quality factor. The antenna that excites the ground is a small platform, which has a narrow bandwidth and low radiation resistance because it has a higher quality factor than the ground. The coupling between the antenna and the ground is critical for high radiation performance. To study the technique of using ground as a radiator, the impedance at the input terminal determined by the combination of antenna and ground is discussed based on the Theory of Characteristic Mode (TCM) as well as the two-port network analysis. The TCM is a theory that the arbitrary shape of the ground is analyzed through numerical analysis. The ground characteristic mode changes only by the shape and size of the ground, and is independent of the source and feeding (antenna). The resonance frequency of the ground is a frequency at which the characteristic value (eigenvalue) becomes zero, and the rectangular shape ground has a λ / 2 dipole current distribution at the first resonance frequency. Then, the radiation performance is determined by changing the excited mode through the feed configuration. In other words, depending on the shape, position, and size of the antenna, the coupling with the characteristic mode changes, which affects the radiation performance. This dissertation introduced a ground radiation antenna, which is a novel antenna type that excites the ground characteristic mode. In general, the characteristic mode of a rectangular conductor ground is that of the strength of the electric field is strong at the end of the terminal, and the magnetic field strength is strong at the center. In the past, monopole antennas with good radiation performance at the end of the ground were mainly studied. However, the ground radiation antenna, has the loop structure, and the radiation performance is optimized in the center of the ground with strong magnetic field strength. Chapter 1 discusses changes in antenna technology with the development of communication technology. Chapter 2 discusses the basic theory of antennas, the theory of characteristic mode, the coupling between ground and antenna, and the ground radiation antenna. Chapter 3 analyzes and discusses the combination of the ground radiation antenna and the ground according to the presence or absence of clearance. Chapter 4 discusses the technology to increase the bandwidth by utilizing the ground resonance mode. Chapter 5 discusses the technique of obtaining the broadband characteristics by adjusting the impedance of the feeding structure of the ground radiation antenna. Finally, Chapter 6 discusses techniques to improve isolation and reduce correlation in MIMO with two or more antennas.
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