| With the advent of the 5G era and smart phones move towards full screen and ultra-thin body,the design of mobile phone antennas is become more and more difficult.How to design a mobile antenna in a limited space and the application of MIMO technology in mobile phone antennas are the focus of this thesis.This thesis first introduced the development process of the communication system and mobile phone antennas.Then it introduced the current application of the MIMO antenna in 5G communication.In the second chapter,the passive paramerter index and the active test index are introduced first.Then the method of adjusting the matching of the matching of the mobile phone antenna by using the matching circuit and the Smith Chart is introduced.Then the method of mobile phone antenna's miniaturization and the multi-band/wideband is summarized.Fially,it introduces the main processing methods of the the mobile phone antenna.Based on these theory,two LTE/WWAN handset antennas and a dual-band eight-port MIMO antenna for 5G application are designed.The results are as follows: First,I use a monopole as the radiating element because the resonant length of a monopole antenna is a quarter of a wavelength,shorter than that of a loop antenna.By using bending radiation branch and electromagnetic coupling technique and combine the primary mode with the high-order modes of the radiation branch and the short-circuit parasitic branch,this handset antenna eventually covers the eight frequency band of specified by current LTE/WWAN.Then the current distribution of each resonant mode is analyzed.After the simulation and optimization of the antenna,the designed antenna is processed and measured.The comparison between simulation and measurement shows that the antenna has good working characteristics and can be applied to the current LTE/WWAN system.Secondly,due to the popularity of full-screen mobile phones,the non-ground region height of the antenna becomes lower and lower.We designed a seven band mobile antenna with a low height of nonground region.The antenna uses a variety of radiation modes of the monopole antenna,the coupling of grounding parasitic branches,L-shaped monopole,and the vertical direction of copper plate to cover the remaining seven frequency bands except LTE700,which meets the needs of 4G communication band in China.The measured results show that the reflection coefficient,namely S11,of each frequency band of the antenna is less than-6dB.The antenna pattern has good omnidirectional characteristics and the radiation efficiency of the antenna is good.It shows that the low height of nonground region and multi frequency antenna is suitable for the current smart phone.Finally,the specific parameters and decoupling methods of the MIMO antenna are studied.Then a MIMO antenna element with dual frequency characteristics is designed.Then the dual frequency eight-port MIMO antenna is obtained by using the centrally symmetric arrangement around the medium plate.In order to improve isolation,we load gaps between MIMO antenna elements on the floor,and analyze the influence of antenna arrangement on isolation and bandwidth of the MIMO antenna.According to the simulation and experimental data,it is shown that the dual frequency eight-port MIMO antenna can cover the WLAN band of the 5.8GHz and the 3.3-3.6GHz of 5G middle band,and the isolation degree is above the 15 dB,which shows that the antenna has practical value in 5G communication. |
PDF Full Text Request