| With the development of information technology and the demand for high performance antenna, the previous linearly polarized antennas are very difficult to meet the people's needs. Circularly polarized microstrip antenna combines the advantages of microstrip antenna such as compact structure, small size, light weight, low profile, easy fabrication, easy integration, easy to be attached to any surface and the advantages of circularly polarized wave such as suppress the interference of rain and fog, anti-multipath reflection, better mobility. So circularly polarized microstrip antenna has been widely used in satellite communications, radar, mobile communications and a variety of wireless communication devices.BGAN is an abbreviation of Broadband Global Area Network, which is a fourth-generation global satellite mobile communications system built by INMARSAT costing over 1.5 billion dollars. It is compatible with the 3G communication and combined with mobile, broadband, network communication needs in satellite communications. It is a revolutionary communications system which can provide users around the world with secure and reliable transmission of audio and video streaming, e-mail, internet access services. With the launch of the most sophisticated commercial communications satellites, BGAN can provide users with speeds up to 492kbps for mobile broadband services using a very small user terminal at a reasonable price. Antennas, as part of its terminal equipment components, play a vital role in communication quality.This paper is set in BGAN system portable mobile terminal antennas for engineering applications. Research and analysis about microstrip antenna for wideband and circular polarization technology have been conducted based on the previous studies. Several broadband circularly polarized microstrip antenna structures were designed for BGAN portable mobile terminal with the method of combing theoretical calculations, numerical simulations and experimental verifications. The author's main work is as follows:(1) It describes the performance parameters of microstrip antenna and the key technologies of microstrip antenna of realization broad bandwidth, circular polarization and link matching. It gives a systematic introduction to the principles of circularly polarized microstrip antennas and the ways to improve the performance of circular polarization.(2) It focuses on the electromagnetic numerical simulation algorithm-Finite Element Method and engineering optimization algorithm-Taguchi's method. The optimal design of GPS microstrip antenna was achieved by combination of both the Ansoft HFSS software based on the finite element method and the Taguchi's Method based on orthogonal experimental design.(3) An antenna structure for BGAN land-mobile Class-2 terminal was proposed based on the analysis and research of the single-fed circularly polarized microstrip antenna technology. The antenna was carried out by simulation and experimental validation. The measured results show that the antenna has good CP radiation characteristics with its VSWR less than 1.2 and Gain higher than 13dB over the INMARSAT working band. The measured results are in good agreement with the simulated ones. The antenna has many characteristics such as small size, light weight, compact structure, simple production and suitable for portability and mobility. It has a good prospect of application and extension.(4) An antenna structure for BGAN land-mobile Class-1 terminal was proposed based on the analysis and research of the dual-fed circularly polarized microstrip antenna technology. The antenna was carried out by simulation and experimental validation. The measured results show that the antenna has good characteristics with its VSWR less than 1.35, Gain higher than 14dB and 3dB wide angle axial ratio more than 40°over the INMARSAT working band. A good agreement between experiments and simulations is found The proposed antenna with wide bandwidth, high gain and wide-angle circular polarization characteristics can be high-quality, high efficiency to achieve signal transmission and reception during the working band. The designed antenna has been successfully applied to HNS9201 outdoor mobile terminal to verify the feasibility of the design. The proposed antenna has a low-cost, easy-fabrication, suitable for high-volume production, and etc. It provides a practical transceiver antenna for BGAN land mobile satellite communications terminals.(5) A wideband circularly polarized microstrip slot antenna for L-band satellite communications was proposed based on the technique for an array to generate circular polarization with several linearly polarized elements. The antenna was carried out by simulation and experimental validation. According to the simulations and measurements, the antenna has its gain to 8dB with bandwidth VSWR<1.5 and AR<3dB of 52% and 49%, respectively. The antenna has good circular polarization radiation characteristics. The designed antenna has a high practical value in addition to simple and compact structure, low price and wide bandwidth. It also applies to small low speed inmarsat terminals.
|
PDF Full Text Request