Antenna Design For 5G Terminal Applications

With the rapid development of wireless communication technology,we are now in a world with the latest 4G system under commercial use.However,the standard of 4G system has failed to meet people's demand for higher data transmission rate.Then,5G has become the focus in the construction of the mobile communication system.The research of 5G system for 2020 and beyond is now in a hot atmosphere.The future 5G system will focus on the whole frequency band,that is not only limit to the low frequency band(6GHz and below)but also the high frequency band(millimeter wave frequency band).Antenna plays a vital role in the mobile communication system,so its design is really important.As 5G terminal is one of the basic modules in 5G deployment,the antenna design for 5G terminal comes to be very necessary.In view of this,the antenna that can be applied to 5G terminal has been designed in this thesis.Firstly,the basic knowledge of MIMO antenna and the working principle of phased array antenna have been studied in this thesis.The antenna types which are often used in mobile phones are analyzed.Several common decoupling methods used in mobile phones are given.The working principle of phased array antenna is analyzed.Secondly,for the low frequency band of 5G,4 models of 5G mobile phone antennas operating at 3.5GHz are proposed.All these four antennas can cover the 3.4-3.6GHz band.The first antenna is composed of eight L-shaped monopole slot elements.By optimizing the parameters of the L-shaped slot and the feedline,the ground clearance can be reduced to 1.5mm.This antenna has a simple structure and a small ground clearance which makes it suitable for a widescreen mobile phone.The second antenna is a hybrid antenna which composed of four L-shaped monopole slot elements and four IFA elements.Due to the different excitation mechanisms of these two kinds of antenna elements,the mutual coupling of this antenna is effectively reduced.The third antenna is composed of eight IFA elements.By utilizing the method of orthogonal polarization and central symmetrical structure,the isolations between the antenna elements are improved.The fourth antenna is similar to the third antenna,but it utilizes two kinds of antenna elements.The isolation can reach up to 12.5d B.Finally,for the high frequency band of 5G,two phased array mobile phone antennas working at 28 GHz are designed.Both the antennas can cover the 27-29 GHz band.The first antenna is an 8-element linear phased array antenna which consists of eight printed dipole elements.By arranging the antenna elements in a reasonable distance,the antenna array can achieve the capability of wide-angle scanning.The second antenna array which consists of four sub arrays can achieve the capability of three-dimensional beam scanning.Three of the sub arrays are positioned at the top edge of the ground plane,and each of them are composed of eight coupled-fed rectangular-shaped patch antenna elements.The three sub arrays are placed perpendicular to each other to perform the ability of radiating forward,upward,and downward,and meanwhile scanning in the three directions.The fourth sub array which composed of eight dipole elements is placed at the bottom edge of the ground plane to cover the rear space.The mobile phone antennas designed in this thesis for both 5G low frequency band and high frequency band can well meet the requirements for bandwidth,isolation,efficiency,and gain.