| With the rapid development of wireless communication technology,the information communication between people has become more and more "arbitrary",which should be attributed to the continuous innovation of modern wireless communication equipment.Looking back on the 1G to 4G era,almost every new communication system has completely changed the way people communicate with each other,and accompanied by the rise of a large number of emerging industries.At present,5G has begun to be commercialized,and the Internet of all things has become the main theme of this era.In the wireless communication equipment,the device that can radiate and receive electromagnetic wave is called antenna,and it is located at the end of the whole wireless communication system.Therefore,the quality of the antenna is directly related to the performance of the whole system.With the fast-paced life and convenient travel conditions in modern society,people are more inclined to miniaturized and intelligent wireless communication equipment,but the number of antennas is limited by the narrow space inside the portable wireless communication equipment.For this reason,a multi-band multi-antenna system has been proposed.Therefore,how to reduce the mutual interference between the multi-band and multi-antenna as much as possible becomes a problem that needs to be solved urgently.In this thesis,the decoupling between antennas and the design of filtering antenna are studied in depth.The specific contents are divided into the following three aspects:First,the decoupled research of the dual-frequency MIMO monopole antenna which operates at 0.9GHz,2.1GHz and is placed in a short distance is carried out.By loading the dual-frequency decoupling and branch matching network at the feeders of the dualfrequency MIMO coupled monopole antenna,the isolation of the MIMO antenna at its operating frequency is enhanced to more than 29 d B,and the reflection coefficients are-18.45 d B and-20.58 d B respectively.In addition,the envelope correlation coefficient of the MIMO antenna is also reduced.Secondly,for the decoupling between distinct frequency antennas,two methods are proposed in this thesis: one is to integrate the distinct frequency monopole antennas with filters,using the filters' passband insertion loss and out-of-band suppression characteristics,only signals within the working frequency bands of the antennas are allowed to pass through,and signals outside the band are shield,so that the isolation between the distinct frequency monopole antennas at the operating frequency of 2.4GHz and 3.6GHz is increased to more than 30 d B.Another method is to improve the edge selectivity and out-of-band rejection level of microstrip patch antenna by generating new radiation zeros on the antenna,so that the isolation of 1.88-2.14 GHz and 2.34-2.68 GHz in the working frequency band is more than 30.5d B.Thirdly,by integrating the feeding line of monopole antenna with wide stopband filter,a filtering monopole antenna with broadband harmonic suppression at 2.86-15 GHz is realized.Compared with ordinary monopole antenna,the radiated gain of the filtering monopole antenna in the stopband has decreased by 10 d B on average.In addition,this thesis also combines the filtering antenna technology with the first decoupling technology between distinct frequency antennas introduced in the previous chapter,and obtains a distinct frequency monopole antennas with broadband harmonic suppression and high isolation.In other words,it not only suppresses the high-order harmonic generated by monopole antenna within 18 GHz,but also realizes the decoupling between different monopole antennas.Among them,the isolation of the antennas with different frequencies at 2.45 GHz and 3.5GHz are 48.2d B and 46.8d B respectively. |
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