Study Of Mobile Terminal Multi-Antenna

With the development of the wireless and mobile communication, the requiredamount of data is increasing and the demands of users for high-speed data transmissionbecomes higher and higher. The high capacity and high data rate and high stability inmobile multimedia transmission become not only the goal but also urgent problems tosolve. According to this, traditional communications systems using single antennatransmit and receive signals are confronted with a stiff challenge. Fortunately, a novelcreative technology, namely multi-antenna mobile communication technology, hasprovided an innovative solution to this problem. Through theoretical and experimentaldemonstration, multi-antenna mobile communication technology can multiply thecapacity and quality within the same frequency band at no additional power expenditure.Multi-antenna mobile communication technology is considered to be a new generationof wireless communications technology revolution and causes a high degree of attentionin academia and industry.Multi-antenna mobile communication system generally uses more than twoantennas, so multi-antenna design, especially for the compact handheld terminals,becomes an important yet knotty issue. Based on this, this thesis focuses on the mobileterminal multi-antenna design. With the overview of multi-antenna mobilecommunication technology and the principle of the multi-antenna used in mobileterminals, the thesis introduces the design method of multiply antennas and designsthree forms of handset antenna. Moreover, the proposed antennas are used as materialfor analysis and discussion about multi-antenna configuration isolation andantenna efficiency. Finally, a new method of antenna efficiency analysis inmulti-antenna systems is proposed and a novel isolation device is designed.First, the research background is reviewed. According to reviewing thedevelopment process of mobile communication, the multi-antenna mobilecommunication technology is discussed. Then the current status of this technology isintroduced.Second, the design requirement of mobile terminal multiple antennas is introduced.Then the thesis describes various diversity schemes and the criteria for the diversity.Based on the previous description, the principle of mobile terminal antenna design ispresented. Then the several commonly used methods in computational electromagnetic are presented, which can establish the theoretic basis for the antenna design.Third, taking handset as representative of mobile terminal equipment, three formsof handset antenna are analyzed and described according to the research focus andtrends, including the inverted-F antenna, planar inverted-F antenna and loop antenna.Furthermore, three different antennas (one for each form) are designed in order to pavethe way for the investigation of low frequency multiple antennas.Finally, dual-antenna diversity configurations which are composed of the proposedthree different antennas are designed. In order to essentially realize the problem aboutisolation and antenna efficiency that exists in low-frequency handset diversity system,the proposed dual-antenna diversity models are simulated and analyzed from the viewsof the length of the ground, space-coupling, the forms of antennas, etc. Then the impactof impedance matching on antenna performance in a dual-antenna handset isinvestigated. The main antenna efficiency depends largely on the matching state of thevice antenna. The proposed dual-antenna configuration is regarded as atwo-port-network equivalent circuit and the load-pull method is employed to analyzethe main antenna efficiency. Novel conception of equal-efficiency area in the Smithchart is conceptualized based on the analysis method. The analysis method and theconception of equal-efficiency area can provide significant potential contribution on thedesign of multi-antenna handsets. At last, a novel isolator is presented. Themetamaterial based isolator serves as an electromagnetic shield, thus enabling it to bebuilt in a sub-wavelength size of0.0002λ02×0.003λ0, which can effectively solve theisolation problem.