DBS 수신용 이동체 탑재형 도파관 어레이 안테나 급전부의 특성에 관한 연구

Abstract

Recently, the technical development of advanced radio communication equipment for PCS(Personal Communication System) and mobile Car/Ship/Aircraft communication is rapidly increased. In contrast with this situation, it is also desired more smaller radio communication equipment in size with high performance and lightweight for convenience.

In the fields of antenna system development, the antenna has to have high efficiency and high gain in high frequency band as well as the stable structure and the compact size. This research will be developed a single-layer feed waveguide π-junction with inductive wall for a planar waveguide slot antenna system. This feed antenna system which will be used for mobile DBS reception should be considered stabilization of antenna structure including the simple fabrication and so on. In case of conventional single-layer feed waveguide antenna, the phase and the amplitude of signal division were controlled by the position and the height of the inductive post. However, since the inductive post was directly controlled by person in fabrication, the antenna efficiency remarkably decreased and the manufacturing cost was expensive. To solve these problems, a single-layer feed waveguide π-junction with the inductive wall instead of the inductive post is proposed in this thesis. A feed waveguide is placed on the same layer in radiating waveguide. It is a two-dimensional structure and is easily analyzed and designed. In order to divide the incident power to densely arrayed waveguides in phase, one coupling window on the narrow wall of the feed waveguide needs to feed into two radiating waveguides. A cascade of π-junctions composes the multiple-way power divider. By increasing the number of junctions, the reflection from each coupling window is also increased. To reduce the reflection of a junction and to widen the overall bandwidth, an inductive wall is located in front of the coupling window of each π-junction. High efficiency of power division and low cost by the simple fabrication can be realized by the fixed inductive wall on feed waveguide.

This thesis is divided by six chapters except introduction.

Chapter 2 presents the electromagnetic wave analysis and the optimum design for short circuit and 4-port π-junction unit with the inductive wall are conducted by using the Galerkin's method of moment to suppress the reflection loss.

Chapter 3 presents the power dividing characteristics of a π-junction obtained by FDTD method are compared with one of Galerkin's method of moments.

Chapter 4 describes the measured values of fabricated junction. From the above obtained optimum parameters, the π-junction structure is fabricated and measured.

Chapter 5 and 6 are proposed a 8-port feeder waveguide for planar slot waveguide array antennas. From the optimum simulation results based on the feeder waveguide using π-junction in standard waveguide at 3.95 GHz and 11.85 GHz, we are obtained the scattering matrices of the non-standard feeder waveguide at 11.85 GHz. Their characteristics are compared with the standard waveguide ones with 8-port feeder array. The bandwidth of -20 dB below is about 700 MHz. The fabrication of planar slot waveguide antenna using the 16-port feeder waveguide is carried out by BG Tech Co., Ltd. Frequency characteristics and phase variation of the fabricated feeder array structure is evaluated by measurement.

Chapter 7 summarizes this study and presents the future work.