Wideband magneto-electric dipole antennas for beyond 4G wireless communication systems
應用於後 4G 無線通信系統中的寬帶磁電偶極子天線
Student thesis: Doctoral Thesis
Related Research Unit(s)
This thesis discusses research on wideband antennas that are suitable for beyond 4G (fourth generation) wireless communication systems. The major driving force for the beyond 4G wireless communication system is the large demand for mobile data communication, which helps people enjoy internet connections at any time and in any place. Many challenges appear in multiple disciplines, such as in communication theory, RF/microwave and millimeter wave circuit design, and antenna theory and design. It is also a golden opportunity that provides many interesting topics for academic research. Several novel antenna designs will be demonstrated in this thesis to provide helpful solutions for this technology trend. One of the most critical techniques used is the complementary radiating source, which is a general theoretical concept and is primarily realized in the form of magneto-electric dipole antenna. First, a complementary waveguide slot antenna element modified from the traditional design was illustrated. And a 16×16 high gain antenna array was constructed with this modified slot element. By loading two L-shaped metallic strips on the conventional waveguide slot radiator, a wideband band directional complementary antenna with more than 8 dBi gain was realized. Based on such a superior radiator, an antenna array with 16×16 elements was developed and showed 32 dBi gain. The feeding network was realized by using several cascaded waveguide T-junction splitters with equal amplitude distributions. This array design could be used as a backhaul antenna in base station and is also suitable for satellite communication systems because of its planar features. Second, a dual-band dual-polarized antenna using magneto-electric dipole was developed, which corresponds to the practical demand from the industry. As the space requirement for base station becomes stringent and the frequency spectrum for the current wireless communication standards is crowded, a single antenna structure hat can accommodate several existing standards at the same time is highly desirable. The most ambitious proposal is to devise an antenna that can cover 690 MHz ~ 960 MHz for the low band and 1710 MHz ~ 2690 MHz for the higher band. A research effort was conducted on such an antenna with a low band fractional bandwidth of 21.2% and a high band fractional bandwidth of 28.4%. Further refinements for this design are needed, especially on the high band radiator. Third, a wideband dual-mode MIMO cube antenna was proposed to provide both pattern diversity and polarization diversity. Five dual-polarized elements were integrated together to radiate two orthogonal broadside patterns and two omnidirectional patterns. For the broadside radiation patterns, the performances were radiated from a wideband dual-polarized radiator mounted on the top of the whole structure. For the omnidirectional radiation patterns, the characteristics were realized by four rotationally placed dual-polarized elements. And one omnidirectional pattern resembled the performance of an electric dipole and the other behaved like the radiation from a magnetic dipole. With such flexibility, this antenna could be used in both LOS (Line-of-Sight) and NLOS (Non-Line-of-Sight) propagation environments. Fourth, a wideband massive MIMO antenna was thoroughly investigated. Research on beyond 4G and even 5G wireless communication has become highly attractive. Several large companies have announced research plans regarding this challenging Several large companies have announced research plans regarding this challenging provide tremendous improvements of approximately 100 times the current 4G LTE communication speeds. One of the most promising solutions for future communication systems is the massive MIMO scheme, which incorporates very large number of antennas together. Therefore, a massive MIMO antenna with thirty-two coaxial input ports was developed using the magneto-electric dipole concept, which demonstrated wide impedance matching performance and low mutual coupling characteristics. The MIMO antenna-related figures of merits were also investigated in the thesis, including the ECC (Envelop Correlation Coefficient) and the MEG (Mean Effective Gain). The demonstrated results of the proposed antenna showed good potentials for the future wireless systems. Finally, a conclusion was drawn at the end of this thesis. With the approaching era of data-hungry communication, many new applications will be motivated and many new requirements will be forced onto the communication systems. As part of the entire system, antenna research and development is indispensable and contributes greatly to wireless communications.
- Electromagnetic theory, Wireless communication systems, Antennas, Dipole, Design and construction, Broadband communication systems