Decoupling Of Compact Antenna Array Based On Eigenmodes

With the rapid development of communication technology,array antennas,especially smart antennas,have received more and more attention and research.Research in the current stage shows that studies on smart antenna represented by adaptive array antenna have become a hot topic and been widely used.There are many factors that affect the performance of smart antenna array.For the compact antenna array,the coupling of the array elements will lead to the mismatch of array ports,the difference between the input impedances of the array element and the isolated element,the distortion of the radiation pattern,the decrease of the radiation efficiency,the decrease of the radiation gain,etc.There are many ways to reduce the coupling effects,such as compensation and suppression.The thesis intends to study the decoupling performance of the antenna array based on the eigenmode decoupling network,and analyse the influence of mutual coupling on the performance of antenna array.This thesis introduces the research background of the decoupling for compact antenna array based on the eigenmodes and analyses the common methods and research status of reducing or eliminating the effects of coupling on the performance of compact antenna array.Based on the theoretical basis of array and array decoupling,the thesis studiesthe decoupling network based on eigenmodes.Based on the scattering matrix and impedance matrix ofthe antenna array,the decoupling theory based on eigenmodes is expounded.Then,the mode decoupling networks of the four-monopole array are designed,and the L-type impedance matching network is used to match the decoupled ports,and the decoulping of the four-monopole array based on eigenmodes are realized.Four orthogonal radiationpatterns of antenna array based on eigenmodes are given.These four patterns are the basic modes used in this thesis to study the performance of the antenna array on beamforming.Using theopen circuit voltage method,the coupling factor of antenna array is introduced.Based on the radiation patterns of thecompact antenna array,the decoupling performance of thecompact antenna array based on eigenmodes is studied.By the sampling matrix inversion algorithm and the recursive least square algorithm,the feed weights for the antenna array beamforming are calculated based on thefour orthogonal patterns of two mode decoupling antenna arrays,and then the four orthogonal modes are fed on the ports,thus the beamforming is realized.From the three aspects,the maximum direction angle of beam radiation,the radiation gain and the normalized radiation electric field,the influence of coupling on the performance of the antenna array is analyzed,and the improvement effect on the antenna array performance when loading mode decoupling network is studied.By the research and analysis,the decoupling network is used to decouple the compact antenna array,which can effectively improve the performance of the antenna array.It makesthe maximum direction angle of the radiation pattern of antenna array beamforming more accurate,the radiation gain improved,the electric field level in the undesired direction of the normalization radiation suppressed,and the radiation efficiency improved.