Design And Application Of Compact UWB MIMO Antennas

UWB technology has attracted a lot of scholars' attention due to its high data rate and wide bandwidth.Multiple Input Multiple Output(MIMO)technology transmits data on multiple channels by using multiple antennas at both ends of the transceiver simultaneously,which can increase channel capacity and achieve diversity performance to reduce the impact of multipath effects.In recent years,scholars have combined UWB technology with MIMO technology and developed it into UWB-MIMO technology.UWB-MIMO systems are widely used in broadband communications with short-distance and high-data-rate.Miniaturization,high isolation and multiple band-notched characteristic are three important indicators of UWB-MIMO antennas.Because of the compact size and ultra-wide bandwidth of the antenna,it will cause strong electromagnetic coupling between the antenna units,and will also be subject to interference caused by other narrow-band signals.In this thesis,the miniaturization,high isolation and multiple band-notched characteristic of UWB-MIMO antennas are studied in depth.The research contents are as follows:Firstly,Studying high isolation.In order to slove the problem that most decoupling structures work in narrow bands,the work of decoupling in wideband is studied.A UWBMIMO antenna with decoupling in wideband is designed by using the electromagnetic band gap(EBG)structure based on a T-shaped ground branch.The decoupling structure reduces the coupling in the low and middle frequency bands by adding a T-shaped branch on the ground,and achieve high isolation in high frequency bands by using the mushroom-type EBG structures.The size of the proposed antenna is 34mm×23mm×1.6mm,and the isolation is more than 20 dB in the entire UWB band.Secondly,studying multiple band-notched characteristic.In order to solve the problem that the method of achieving band-notched characteristic by slotting raditating patch or ground will affect the antenna performance,the work of using a ground parasitic structure to achieve band-notched characteristic is studied.A UWB-MIMO antenna with dual band-notched characteristic is designed.By adding two parasitic strips on both sides of the T-shaped ground branch,the dual band-notched characteristic is realized.The size of the proposed antenna is 34mm×23mm×1.6mm,and the isolation is more than 17 dB in the entire UWB band.At the same time,the dual band-notched characteristic was achieved at 3.3-4.2GHz and 5-6.2GHz.Thirdly,studying miniaturization of UWB-MIMO antennas.In order to solve the problem that the performance of most antennas will be affected while achieving miniaturization,the work of the slot antenna to achieve miniaturization by sharing a slot is studied.A four-port UWB-MIMO antenna is designed.The antenna consists of four microstrip lines and a rhombus slot.This design can greatly reduce the overall size of the antenna.The antenna has a very compact size,with a size of only 34mm×34mm×1.6mm.By sliting two slots on the microstrip line and adding an EBG structure next to the microstrip line,the proposed antenna obtains three notched bands of 3.4-4.1GHz,5-5.8GHz,and 7.6-8.6GHz.At the same time,by adding parasitic strips on the ground,isolation between antenna units is improved,and the isolation is more than 15 dB in the entire UWB band.