The Research Of Application Of Differential Antenna In Wireless Communication System

Antenna asthe transmitting and receiving equipment of signal,to a large extent determines the performance of the system.But with the development trend of wireless communication system,a single antenna doesn't work independently,but more and more integrated with other devices together to deal with the signal,to realize miniaturization and integration.Due to the balance circuit can greatly reduce the crosstalk,RF front-end circuit often use differential technology.Currently,most of the antennas used in the system are designed to operate as a single port and can not be directly connected to other communication units.Instead,it is necessary to introduce a balun(balanced-unbalanced converter)to convert the differential signal into a single-ended signal.The introduction of balun,on the one hand will reduce the system integration,on the other hand will bring unnecessary loss to the system and reduce the efficiency of system.Differential antenna is a good candidate to solve these problems,which use of two feed ports,input differential signal can be directly connected with the digital differential circuit.Avoid use of balun,which not only reduce the loss of front signal of the system,but also RF front end has a higher degree of integration.In addition,differential antenna also has a series of advantages,including the suppression of common mode signal,high isolation and very low cross-polarization pattern,etc.,so the differential antenna is attracting more and more scholars to study.In this paper,several antennas which used of advantages of differential antenna technology are designed for different wireless communication systems.The main work is as follows:1.A differential dual-band slot MIMO antenna with high common mode rejection ratio is proposed for WLAN system.The MIMO antenna comprises four orthogonal planar antenna elements,each unit is being feeding by a differential microstrip line.Four cells are separated by four orthogonal slots.The antenna has good common mode suppression ratio and high different isolation in the entire frequency band,and the two operating frequency band can be adjusted independently.2.Two differential UWB slot antennas are proposed for UWB systems.One is a single antenna unit and the other is a four-unit MIMO antenna.Both of them used the dual-portdifferential feed,which have good radiation pattern,stable gain and high common mode rejection ratioin the whole band.Besides,the MIMO antenna has a rectangular notch characteristic,and the notch frequency and bandwidth can be controlled.3.A differential dual-polarized broadband base station antenna with high isolation and low cross polarization is proposed for 2G/3G/LTE communication systems.The antenna adopts differential-fed directly with four coaxial cables,which achievesa bandwidth of 67.5%(1.65 to3.33 GHz)for SWR<1.5,and can completely cover the 2G/3G/LTE requirements of the operating frequency band: 1.71–2.69 GHz.In the entire frequency the proposed antenna has high isolation,high cross polarization ratio,stable radiation pattern,stable gain,stable half power beam width,and can suppress common mode noise signal.