| Left-handed materials(LHM)have many novel properties that natural materials do not possess,such as negative refractive index,negative phase velocity and so on.The design of left-handed materials faces many problems such as large size and narrow frequency band.Aiming at these problems,this paper proposes a method for realizing multi-frequency and broadband left-handed materials at the same time.Nowadays,the problem of shortage of radio spectrum resources in the world is becoming more and more serious.Ultra Wide Band(UWB)-Multiple Input Multiple Output(MIMO)antennas have been widely concerned by antenna scholars all the world because of their advantages of large bandwidth,high rate and large channel capacity.However,UWB-MIMO antennas have the disadvantage of wide-band radiated energy,which is easy to interfere with other frequency bands.The traditional notch technology also has disadvantages of narrow and single notch frequency band.In antenna design,the LHM can play the role of notch,miniaturization,improved isolation and so on.Aiming at these problems,first of all,this paper innovatively proposes an ultra-wideband regular hexagon self-compensating UWB antenna,while achieving miniaturization,increasing antenna gain and expanding working bandwidth.Then,by loading a multi-frequency LHM structure,we can accurately suppress UWB-antenna's electromagnetic radiation in specific frequency bands,reduce the interference to other devices,and improve anti-interference ability in specific frequency bands simultaneously.The detailed work of this paper is as follows:First of all,a method for realizing single-sided multi-frequency LHM is proposed:on the basis of maintaining the original electromagnetic field and current distribution,new branches are introduced to achieve Multi-band left-handed performance.Based on the method,this paper proposes three LHM structures and their equivalent circuit models.Then the structure 3 is proposed.On the basis of structure 2,new branches are introduced to realize four left-hand frequency bands,which cover 3.01-5.19GHz,7.5-7.65GHz,8.09-8.66GHz and 9.82-10.67GHz,and the maximum left-hand bandwidth is 2.18GHz.Secondly,innovatively combining regular hexagons with self-compensation technology,a series of miniaturized,high-gain,large-bandwidth UWB antennas are proposed.At the same time,the effect of regular hexagonal side length changes on the ratio of effective radiation area of the antenna is carefully studied.In this chapter,it is found that the radiation pattern of the antenna can be adjusted by the position of the complementary metal surface.The size of the third-order quasi-self-complementing antenna proposed in this chapter is only 20mm × 15mm × 1.2mm,and the working frequency band of the antenna is 4.39-25.39GHz and the bandwidth is up to 21 GHz.Finally,a series of two-unit MIMO antennas are designed,which are composed of the antenna proposed in chapter 4.By loading the multi-band LHM structure,the multi-band notch of the UWB antenna is realized.At the same time,we can improve the isolation of the antenna unit through orthogonal distribution of the port.At last,a three-band notch UWB-MIMO antenna with a working frequency band of 2.511Ghz is obtained.The notch frequency bands are 3.08-3.6GHz,4.71-5.58GHz and 7.15-7.75GHz,covering the commonly used 5G frequency bands(3.3-3.6GHz,4.85.0GHz)and WLAN 802.11a frequency band.The S21 of the antenna in 2.5-11GHz is below-17dB. |
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