Study On Decoupling Of The Conformal Array Based On Bandwidth Enhanced Single-negative Materials

With the development of wireless communication technology,conformal array antennas play an important role in wireless systems due to their unique characteristics,such as conformal structure,multi-beam and omnidirectional coverage.However,the mutual coupling between conformal array elements may hinder the applications of conformal arrays because it deteriorates the antenna performances,such as gain,efficiency,radiation pattern,side lobes,and axial ratio.Therefore,research on effective suppression mutual coupling methods has played a crucial role in the design of conformal array antennas.At the same time,the electromagnetic wave suppression characteristics of single-negative metamaterials(SNG)have important applications in reducing antenna mutual coupling.However,most of the current researches are directed at planar arrays,and research on conformal array mutual coupling suppression techniques based on single-negative materials is very scarce.In this paper,a wideband single-negative material is designed and studied by using various techniques such as electric/magnetic hybrid resonance,and the single-negative material is applied to a circularly polarized,wide-band conformal antenna array to reduce the mutual coupling effect.The main research results and contents of this paper are as follows:1.A broadband SNG isolator,“?”-shaped isolator,was designed and applied to the mutual coupling suppression of a circularly polarized antenna array.First,a wideband SNG “ ? ”-shaped isolator with meander line and multiple resonant units techniques is designed.The isolator is applied to a binary ultra-wideband circular polarized array antenna to achieve mutual coupling suppression.The simulation results show that the loading of the SNG “?”-shaped isolator has no effect on the impedance matching and radiation pattern of the antenna compared to the unloaded one.In addition,the isolation of the array antenna loaded with the broadband SNG isolator is improved in the 4.3GHz to 5.9GHz band.Moreover,the isolation is even increased by 42.5dB at f=5.5GHz.2.A wide-band SNG-wheel-shaped(SNG-wheels)isolator was designed by using various techniques,such as electric/magnetic hybrid resonance,and the isolator was applied to a arched binary common array to reduce the mutual coupling.For the problem of suppressing the coupling between the conformal array antenna elements,a broadband SNG-wheels isolator is designed according to the electric/magnetic hybrid resonance technique and the multi-resonance frequency method.First,we analyzed the working principles and performances of the SNG-wheels isolator,and then it is loaded into the conformal array antenna to study its electromagnetic properties.Both simulation and measurements show that the isolation of the conformal array antennas loaded with SNG-wheels isolators is greatly improved from 4.6 GHz to 5.4 GHz compared with the conformal array antennas without SNG-wheels isolators.At 4.5 GHz,25 dB isolation enhancement is observed for the conformal array antenna.While the introduction of SNG-wheels isolators have little impact on some performances of the corresponding conformal array antenna,such as impedance matching and axial ratio.Finally,placement parameters of the antenna/isolator and the parameters of conformal structure were studied and optimized.3.Pattern synthesis of two-and nine-elements conformal array antennas are studied under the conditions of loaded and unloaded SNG-wheels isolators.Simulation studies show that,compared to the unloaded condition,the loading of the SNG-wheels isolator improves the isolation and pattern gain of the antenna.Moreover,the side lobes of the antenna are also significantly improved.Mean while,the loading of the SNGwheels isolator has no effect on the operating frequency.In addition,SNG isolators have the advantages of simple structure,easy loading and affordable,which makes them practical in the application of MIMO communication systems.