Research And Development Of Multi-band Mobile Phone Antennas

At present,the mobile communication has been rapidly evolving.The mobile phone,as a personal information terminal,has developed substantially over the past two decades.Thus the antennas for mobile phones are upgrading gradually as well.In order to serve all mobile communication bands,the antenna of the mobile phone should be able to be multiband.In addition,since there is usually a large screen and a narrow frame for the modern mobile phones,the space is quite limited for implementing the mobile phone antennas.Therefore,how to design a multiband mobile phone antenna with a small size,is not only a major technical challenge,but also a basic requirement.In this thesis,three kinds of muti-band mobile phone antennas are studied and designed.The main contents of this thesis include the following parts.1)The first part mainly introduces the development history and the research of the mobile phone antennas domestically(in China)and abroad,as well as the significance of the research about the multiband mobile phone antennas.2)The second part of the study introduces some basic theories of mobile phone antenna design.Firstly,the bandwidth,efficiency,gain,pattern and other parameters of mobile phone antenna are briefly described.Then the basic antenna forms such as PIFA,monopole and loop antenna are analyzed and compared.Finally,the multi-frequency technology of mobile phone antenna is introduced in detail.3)In the third part of the thesis,two tunable mobile phone antennas with a metal frame for LTE/WWAN applications are proposed with a reconfigurable low band and fixed high band.These two antennas are featured with varied arms of different electric length to achieve multi-band resonance.The matching circuits are added to the mobile phone antenna to adjust the antenna matching for good performance.The low-frequency band coverage of the antenna is realized through the change of the value of the variable capacitance.The first antenna is mainly composed of loop antenna,monopole antenna and a varactor based control circuit.Through the metal frame and lumped element matching circuit,the overall radiation performance of the antenna can be optimized and enhanced,and the bandwidth of 700MHz-960 MHz and 1.7GHz-2.7GHz can be covered.The second mobile phone antenna is mainly composed of multi-mode theory,frequency reconfigurable technique,and coupling parasitic technology.A matching circuit and lumped elements are also applied for tuning.The final antenna could cover all the bandwidth covering 700MHz-960 MHz and 1.7GHz-2.7GHz of the mobile phone.The test results show that the two antennas have good performance.The low-frequency radiation efficiency is more than 30% and the maximum high-frequency radiation efficiency can reach more than 70%.4)In the fourth part of this paper,a new reconfigurable LTE / WWAN / 5G band mobile phone antenna with the metal frame is implemented,which is characterized by multi-band,tunable low frequency band,and fixed high frequency radiation.The tunable antenna is composed of a single capacitance loop and a control circuit.Through the metal frame and lumped element matching circuit,the overall radiation performance of the antenna is optimized and enhanced.The final antenna could well cover all the bandwidth of 700MHz-960 MHz and 1.7GHz-6GHz for the 5G mobile phones.