Antenna Analysis And Design In Mobile Communication System

Antenna is one of the key components of mobile communication systems. With the fast development of mobile communication system, the system is more and more complex, which demands the characters of antennas with higher quality. So the research on antennas in mobile communication system is an important issue with great theory and engineering meaning. The antennas in mobile communication system have three key types: base station antennas, terminal antennas and microwave transmission antennas. This dissertation makes deeply insight into the antennas in mobile communication system. Firstly, the base station antenna element is analyzed and designed, and is used in the practical mobile communication systems. A novel fast analysis method based on MoM and synthetic functions is presented to analyze the base station antennas or another complex antenna arrays. The hybrid method of PSO and the fast analysis method is used to design the beams of base station antennas and the broadcast beam of the TD-SCDAM smart antenna array. The hybrid method of GA and MoM is used to design the terminal antennas for dual frequency band, including GSM and WLAN. And finally the Bodies of Revolution MoM equations are presented. The small aperture reflector antennas for microwave transmission system are designed based on BoR MOM. The author's major contributions are as follows:1. Firstly the base station antenna elements are designed. The tree types of antenna elements are analyzed using MoM, including the L-Probe fed thick-substrate patch antenna, the V-shaped dipole antenna with reflector and the umbrella-shaped antenna with reflector. The antennas above have the characters of broad band and compact structure, and are already used widely in base station antennas.2. Then an innovative approach to analyze electrical large and complex array antennas is presented. The method is based on the separation of the overall geometry into smaller blocks. On each block, basis functions called synthetic functions are generated with support on the entire block, that are subsequently used as basis functions for the analysis of the complete structure. Only a small number of these functions is required to obtain an accurate solution. Therefore, the overall number of unknowns is drastically reduced with consequent impact on storage and solution time. The synthetic functions are obtained from the responses to all sources via a procedure based on the singular-value decomposition. This method is very adaptive to analyze base station antennas.3. An optimization method based on PSO and the above fast analysis method for shaping the vertical beam of base station antennas is given, which can shape the beam in 360o coverage. The optimization method is applied in designing 8, 11 and 16 elements array. The broadcast beam of TD-SCDMA smart antenna array is designed using this method, too.4. A hybrid method of MoM and genetic algorithm is used to design the dual-band or multi-band terminal antennas. Integral to efficient GA/MoM integration is the use of direct Z-matrix manipulation (DMM). In DMM a"mother"structure is selected and its corresponding impedance or Z-matrix is filled only once prior to beginning the GA optimization process. The GA optimizer then optimizes the design by creating substructures of the mother structure as represented by the corresponding subsets of the original mother Z-matrix. Application of DMM with GA/MoM significantly reduces the total optimization time by eliminating multiple Z-matrix fill operations.5. In order to solve the object with axisymmetry property, the moment method equations based on the bodies of revolution are presented. This approach is used to analyze small aperture reflector antennas with complex feeds. In the designing of microwave transmission antennas, the key problems are the feed type and the main reflector's shape. The self-supported rear-radiation feed is designed in this paper, and the near parabolic main reflector is obtained based on the phase pattern of feed. The phase center of the feed is determined and the methods to increase the back to front ratio are discussed at last.