| Mobile phone design is facing the most intense competition in communication industry, and mobile phone antennas design is the most important procedure in product design, which requires capabilities of fast antennas design and phone performance assessment. And with the development of public health recognition, the human effect of microwave energy should be concerned in antennas design and measured by SAR; on the other hand, human body should also influence the antennas performance less. Besides, more and more functions are merged into mobile phone and faster data communication is sought, which need to design wider bandwidth of antennas. Meanwhile, the antenna size become smaller due to fashion and style factors adopted in industry design of phone, leading to much more difficult in antennas design.Based on various requirements mentioned above, the thesis has done following research:1. The equivalent circuits of antennas and mobile phone are established, and several factors influencing radiation efficiency and bandwidth are discussed. Practical mobile phone model is simulated by using SEMCAD, and the efficiency difference between simulation and measurement is discussed.2. The SAR distribution and impedance characteristic of various antennas are researched, and the fundamental discipline is analyzed. A type of PIFA whose ground plane can select frequency is proposed to solve the SAR problem of monopole antenna. The relationship between antenna bandwidth and human effect reduction is verified, and important effects to improve the radiation efficiency under human model are found.3. Based various methods for miniaturizing de-resonant broadband antennas, multi-resonance method for widen bandwidth and coupling and short structure for reducing antennas size are integrated to design an UWB mobile antenna by simulation, covering 740~2740MHz.4. The UWB mobile antenna proposal is manufactured and optimized to obtain better performance, covering 700~2900MHz. The superior and robustness of this antenna is confirmed by comparing with a common monopole antenna, a long-ground UWB antenna and the circumstance under head and hand model. The passive and active performances of the antenna achieve the design goal, after planted in practical mobile phone. |
