Design Of Next Generation Mobile Terminal Antennas

In recent years,with the rapid development of mobile communication systems,mobile terminals have been updated rapidly,and the update of mobile phones is particularly fast.The antenna is the front end of the mobile terminal and is a device that transmits and receives electromagnetic signals,so it is crucial for the mobile terminal.The rapid development of mobile terminals has also placed higher demands on the design of antennas.The pursuit of faster data transmission rates requires that the antenna must be able to provide a wider frequency band and support multiple input and multiple output(MIMO);to pursue global communication,the antenna must be able to cover the global communication bands;the pursuit of aesthetics in industrial design makes metal-rimmed phones are becoming more popular.In particular,the recent trend of full-screen and high screen ratio on mobile terminals require that the antenna only occupy a small clearance on the system circuit board.At the same time,the fifth-generation communication system is coming soon.The mobile terminal needs to sustain the frequency bands of the fourth-generation and fifth-generation communication systems(4G and 5G)at the same time,which requires that the mobile phone antenna can support both the 4G and 5G frequency bands,and support MIMO in the 5G frequency band.Therefore,the small clearance,multi-band antenna and MIMO antenna of mobile phone terminals are the hotspots and difficulties of research.According to the development trend of mobile terminal antennas,four antennas applied to metal frame mobile phone terminals are proposed in this master's thesis.The theoretical basis and development status of the theory of characteristic modes(TCM)are first introduced in the third chapter of this thesis.Then,based on TCM,a hepta-band metal-rimmed mobile phone antenna is proposed.The detailed process of using the TCM to guide the antenna design is presented.And the simulated and measured results are given.Subsequently,on the basis of the first antenna,using the advantages of TCM,a small clearance hepta-band metal frame mobile phone antenna was designed,and the measured impedance bandwidths with reflection coefficients less than-6d B are 800-1000 MHz and 1.7-2.78 GHz.It can cover seven communication bands of WWAN(GSM850/900/DCS/PCS/UMTS2100)and LTE(LTE2300/2500).The measured results of the antenna are excellent,which prove that the antenna has potential for practical application.Based on the previous chapter,a hepta-band metal-rimmed mobile phone antenna with a clearance of only 4mm is further realized in the fourth chapter of this thesis,and the simulated results of the antenna are analyzed.Subsequently,in order to realize multiple antennas,the 2×2 MIMO antenna is realized by using the same antenna unit as the diversity antenna on the clearance of the other end of the ground on the basis of retaining the main antenna.The simulated results for multiple antennas show that the main antenna and the diversity antenna can cover seven communication bands of WWAN(GSM850/900/DCS/PCS/UMTS2100)and LTE(LTE2300/2500).At the same time,the isolation,total efficiency and envelope correlation coefficients are all acceptable,which proves the potential of the antenna to be practically used.In the fifth chapter of this thesis,a 4G/5G reconfigurable metal frame 4×4 MIMO mobile phone antenna is designed by using a width of 2 mm between the ground and the metal frame.With reconfigurable technology,the antenna can operate in two states.When the antenna is working in state 1,the impedance bandwidth of the four antenna elements with a reflection coefficient less than-6d B is 1700-2730 MHz,which can cover five communication bands of DCS/PCS/UMTS2100 and LTE2300/2500.When the antenna is in operation 2,the impedance bandwidth of the four antenna elements with a reflection coefficient less than-6d B is 3.38-3.82 GHz,which can cover the 5G band of the sub-6G(LTE band 42/43).The simulated performance(S parameter,total efficiency and envelope correlation coefficient)of the antenna in working state 1 and state 2 are all meeting the requirements,and since the antenna is mainly realized by the gap between the ground and the metal frame,the clearance is only 2 mm.Therefore,this antenna has the potential to be applied in high-screen ratio mobile phones.