Study On Vehicle Antennas, Airborne Antennas And Wireless Mobile Communication Antennas

With the rapid development of science and technology, wireless communication systems have been penetrated into every aspect of our daily life. As one of the most important part of a wireless communication system, antenna has a significant effect on the performance of the whole system. The demand for the performance and appearance of an antenna strongly depends on the scenario for which the antenna is applied. In this dissertation, thorough research is presented on antennas for vehicle, airplane and wireless mobile communication applications, which are closely related to our life. Several antennas are designed and a software platform is developed in accordance with the problems existed in each scenario.Specifically, the major contributions of this dissertation are summarized as follows:1. Three types of vehicle antennas are designed. The first type of antenna is a self-matched slim monopole. The matching structure is designed embedded in the antenna structure to remain the slim appearance of the monopole. The dimensions of the matching structure are optimized by the DE and CMA-ES algorithms to broaden the impedance bandwidth of the antenna. The second type of antenna is a wideband, wide beam circularly polarized antenna for satellite communications. The impedance bandwidth of the antenna is broadened by two pairs of rectangular patches which are terminated with open circuits. A broadband 90° power divider is used to feed the proposed antenna and to realize circular polarization. The third type of antenna is a high gain, loaded monopole antenna. A car body is included in the simulation model as well as the antenna structure. The effect of the car body on the performance of the antenna is studied and alleviated by optimizing the locations and values of the two loaded reactive elements of the antenna.2. Two types of airborne antennas are designed. The first type of antenna is miniaturized annular ring slot antenna. By using a folded matching structure, the size of antenna is reduced while remaining its impedance matching. By adjusting the dimensions of the matching structure, single-band or dual-band characteristic can be realized. The most novel advantage of this type of antenna is that it is insensitive to the surrounding environment due to the metal vias on the edge of the antenna. The antenna is suitable for embedding in a small metallic UAV. The second type of antenna is omnidirectional, multi-horn antenna based on SIW technology. It has the advantage of low profile, low cost and ease to be integrated with other lumped elements. The effects of the number of horns, different matching methods on the performance of the antenna are studied. This type of antenna is suitable for small nonmetallic UAVs.3. Two types of wireless mobile communication antennas are designed. The first type antenna is diversity antenna. We designed two such antennas. One is a pattern diversity antenna and the other is a pattern and polarization diversity antenna. Both are integrated antennas which consist of two single antennas. The structure of the single antennas are integrated and reused. The difficulties of placing coaxial cables are simply solved by reusing part of the antenna structure. The antennas are suitable for 2G/3G/4G indoor applications. The second type of antenna is high gain, switched parasitic array antenna. High gain is realized by a series fed dipole array and beam scanning is realized by controlling the state of the parasitic elements. The antenna achieves high gain while remaining a wide beam radiation pattern on horizontal plane. The electrical downtilt angle can be easily realized by adjusting the dimensions of the antenna. This type of antenna is expected to solve the backhaul problems for 5G wireless mobile communications.4. A software platform based on C++ is developed for 5G wireless mobile communications. Firstly, it enables users to create the array model fast. Secondly, a novel method for fast analysis of massive MIMO antenna array is presented. The large scaled antenna array can be simulated efficiently on a computer of relatively low performance. Thirdly, the platform provides a beamforming algorithm which optimizes the radiation pattern of the array antenna according to the input template file. Lastly, the platform can calculate some commonly used electrical properties of the antenna array. Thus users can evaluate the performance of the antenna by comparing the calculated values with the professional standard.