Research And Design Of The High Isolation UWB MIMO Antennas

With the continuous development of social economy,people's demands for wireless communication systems are constantly increasing.New requirements have been put forward on the capacity and transmission rate of the communication system.The multiple-input-multiple-output(MIMO)antenna system can effectively increase the channel capacity within a limited bandwidth,speed up the information transmission rate,and improve the reliability of an effective way.However,placing multiple antenna elements in a small space will cause terrible coupling of the antenna elements with each other,exciting the coupling surface current,and thus affecting the overall performance of the antenna.For this reason,how to improve isolation has become a core issue in the development of MIMO antenna technology.At the same time,how to maintain good isolation between the antenna elements of the MIMO antenna in the broadband range is also an important research direction.The main research content of this article is as follows:1.This paper proposes an ultra-wideband antenna with a defective ground structure.The antenna uses a coplanar waveguide feed structure.The antenna's radiating patch and grounded floor are on the same side of the dielectric substrate.The characteristic impedance of the feed of the antenna is the 50 ohms.The size of the antenna is only 20.8mm*26.1mm,and the thickness is 1.6mm.The dielectric substrate uses FR4(relative permittivity is ?r=4.4);the working frequency range of this antenna is from 3GHz to 14.5GHz;the shape radiation of this antenna uses a fan-shaped structure.By using the defective ground structure and controlling the size of the aperture between the connection point of the feed line and the radiation patch,the current distribution is changed,then the coupling between the antenna and the floor is well controlled,finally,The antenna has a achived good impedance match.2.Basis on the first UWB antenna,we designed two UWB notch antennas: The first ultra-wideband notch antenna achieves a good impedance matching of the antenna through the use of a defective ground structure by the simulation.The notch frequency band of the antenna is 4.3-6.7 GHz,while the working bandwidth is 3-14.5 GHz,and the antenna shows good omnidirectionality throughout the entire working bandwidth.The second ultra-wideband notch antenna is also based on the first ultra-wideband antenna by etching an elliptical split-ring resonant ring on its radiating patch,finally achieve the operating bandwidth of the antenna from 3.1-15 GHz with the 5-6GHz notch frequency band.3.A only 23.73mm*50.53mm*0.8mm sized MIMO antenna was designed.The antenna uses an FR4 dielectric substrate with a relative permittivity of 4.4.The operating frequency band of this antenna is 3.1-16.8 GHz.By etching the T-slot on the floor and adding parasitic metal strips between the antenna floors,The isolation of the designed ultra-wideband MIMO antenna in this paper exceeds 17 dB in the whole bandwidth of the work and exceeds 20 dB in most of the bandwidth,and the size of the designed UWB MIMO antenna in this paper is much smaller than similar antenna.