| UWB-MIMO antenna not only has UWB technology with high data transmission rate,great system capacity,low cost,low power,but also with good performances in huge channel capacity,high efficiency of MIMO technology.Thus it is playing an increasingly important role in the modern wireless communication system and has aroused extensive attention and research.Left-handed materials(LHM)and other emerging artificial electromagnetic materials have so better properties than natural electromagnetic materials,that different structres of LHM cell have been applied to increase the antenna multi-frequency characteristics,enhance the gain,expand broadband,improve the radiation direction and so on.This paper aims to study the design in the UWB-MIMO antenna unit,notch structure,decoupling structure,especially how to use the LHM cell in the antenna design.A series of butterfly-like structures of LHM cells and small UWB-MIMO antennas which combine the LHM cell with notched band,high isolation,are proposed in this paper.The main achievements are summarized as follows:Firstly,a simple LHM cell structure is proposed,which can realize dual negative frequency bands at 5.64?6.65GHz.Then,based on the basic structure,four types of deformation are extended for different applications.The first is the butterfly-like LHM cell with SRR,which can relaize two LHM bands of 3.75?4.02GHz and 5.50?6.25GHz;the second is the wideband butterfly-like LHM cell with arc tails,working at:5.91?7.54GHz;the third is the couple butterfly-like LHM cell,to explore the couple butterfly-like structure by the vertical placement,without changing the size,which can expand the LHM band from 5.64?6.65GHz to 4.85?7.08GHz.The fourth,the meandering butterfly-like LHM cell,can achieve the LHM band of 3.75?4.28GHz,in the case of reducing 20%size of the basic structure.Then,a series of CPW-fed UWB-MIMO antennas based on the benzene ring structure are proposed,which have a compact size of 22mm×38mm×1.6mm.The influence of the benzene ring structure's growth and the influence of the different ground structures on the UWB impedance matching are analyzed.The effect of three kinds of UWB-MIMO units' placement directions,side-by-side,reverse side-by-side and quadrature distribution on the return loss and isolation of antenna is discussed.The isolation of the side-by-side UWB-MIMO antenna with a metal strip between the two UWB antennas is better than-22dB,and the isolation of the reverse side-by-side UWB-MIMO antenna with a couple LHM cell between them is better than-23dB.In addition,through the loading of two classic circular SRRs in the benzene rings as notch structure,the UWB-MIMO antenna gets a nocthed band of 5.42?5.74GHz.Finally,a microstrip-fed UWB-MIMO antenna with a butterfly-shaped LHM cell patch is proposed wth the size of 27mm×30mm×0.8mm.Through loading the quarter-wavelength parasitic branches on the ground,the antenna can achieve X-band stopband.The isolation in the most operating band of 3.10?10.92GHz is lower than-25dB due to the DGS between the two ports,and the peak gain keeps in the range of 2?4dB.This UWB-MIMO antenna is small,thin,and good omnidirectional performance,which can be well used in handheld devices and other high-speed short-range communication occasions. |
PDF Full Text Request