| Nowadays,the worldwide satellite navigation systems mainly include Global Navigation System,European Galileo system,Russian GLONASS and Chinese Compass system.If the navigation system can work in two or more modes at the same time,it will effectively improve the performance and compatibility of the navigation system.Therefore,the multi frequency antenna technology is needed.According to the wide-band and multi-band technology of the microstrip antennas analyzed in the thesis,we propose a designing scheme of two-layer antenna which can work in the frequencies of GPS L1 band and GALLONASS L2 band.The upper layer patch is fed by the coaxial pin,and the lower radiation patch is fed through electromagnetic coupling.Firstly,we introduce the basic theory of microstrip antenna,and analyze its radiation mechanism and feed methods,the applications of multi frequency technology and wide-band technology,the design of round-polarization of antenna.According to the related technology of antenna design,we propose an antenna model,then analyze the main antenna characteristics with the electromagnetic simulation software HFSS.We mainly focus on the influence of antenna parameters on antenna characteristics and the optimization of the parameters.Among them,we analyze two factors affecting the SWR of antenna,feed position and substrate thickness,and through the optimization of two parameters,the antenna bandwidth and SWR meet the design requirements.At the same time,according to the circular polarization performance of the antenna,we analyze the influence of the corner-cut size on axial ratio performance and the optimization of the parameter,by which the antenna can work well on the required frequencies.Through the optimization,the circular polarization antenna radiates right-handed circular polarization wave,and the peak gain and axial ratio reach the design requirements.Intended to extend higher frequency bandwidth,we analyze the two parameters,area of substrate and area of ground,which could effect on the antenna characteristics performance.Through the optimization of the two parameters,we optimize the structure of the antenna dielectric substrate and improve the characteristics of the antenna.Considering that it may exits reflection wave in real install environment,we also analyze the simulation of the antenna with a mental reflection-board,and draw conclusion that the reflector installed under the antenna has influence on electromagnetic radiation of antenna.Moreover,based on sensitivity analysis,we analyze the sensitivity of antenna performance to design parameters.Based on statistical analysis,we analyze the effect of antenna fabrication tolerance on antenna performance in practical application.Referring to the parameter sizes of the antenna modal,we fabricate an antenna.In two cases with and without the metal reflector,we measure its S parameters(return loss)and radiation directivity pattern in anechoic chamber.We analyze the difference between the actual measurement results and the simulation results of the antenna,and the measurement results are similar with the simulation results,which could verify the effectiveness of the design. |
