| The transmitting and receiving signal of any communication system must be realized by antenna.With the continuous development of various communication systems and the band becomes a very crowded resource.And the emergence of ultra wideband antenna improves the phenomenon of the shortage of wireless communication frequency band.Ultra wideband(Ultra-Wideband,UWB)antenna,as the name indicates,is that the antenna has a very wide impedance bandwidth.The relative bandwidth is greater than 20 percent,or the absolute bandwidth is greater than 500 MHz.The relative bandwidth means that the values of VSWR of the band less than 2 or its return loss values less than-10 dB.The transmission rate ultra wideband antenna is higher than 100 Mps.Ultra wideband antenna has many advantages over common antennas,such as low cost,low transmission power,low loss and high resolving power.In 2002 the Unite State Federal Communications Commission(FCC)announced that the public could also use the band of 3.1GHz ~ 10.6GHz.Therefore the ultra wide band technology the limitation is breakthroughs that the technology just applies in the field of military,and it has become a hot research topic in commercial and civil wireless communication systems.Ultra wide band antenna is a very important part of ultra wideband communication system,so the study of ultra wide bang antenna is very important for the development of ultra wideband communication system.With the development of ultra wideband technology,the bandwidth of antenna is becoming wider and wider.However,the size of the antenna is becoming larger and larger,which is not easy to the integration and digitalization of ultra wideband communication systems,so that the miniaturization of antenna ultra wideband antenna is a very important research direction.In this paper,we focus on studying the broadband and miniaturization of UWB antenna,which is suitable for the modern ultra wideband impulse radio system.Firstly,the development history and current situation of the development of ultra wideband antenna were introduced in this paper.The performance parameters of the antenna and the feed mode of the micro-strip antenna are discussed in this paper.Secondly,the basic theory of the antenna,the performance parameters of the antenna and several kinds of feeding modes of the micro strip antenna are introduced in this paper.It is found that the coplanar waveguide can broaden the frequency band of the antenna.Thirdly,based on the previous theory,two ultra wideband monopoleantennas are designed and simulated by HFSS,and the performance parameters of the antenna were calculated.The results show that both of the antennas meet the design requirements of ultra wideband antenna.Because of the bands of two antennas are very wide,including 3.1GHz ~ 10.6GHz.Make samples,test and verify the performance of the antenna.In this paper,the following two main contents were finished:1.An ultra wideband circular monopole antenna fed by coplanar waveguide is presented.At first,a micro strip fed monopole antenna is designed,and the back side of the dielectric substrate is a partial floor.The result of HFSS simulation of the antenna frequency band does not meet the design requirements of ultra wideband antenna.Then the method of coplanar waveguide feed is adopted,and the gap between feeder and floor is optimized.The return loss values band includes 3.1GHz ~ 10.6GHz after the optimization.So the antenna meets the design requirements of ultra wideband antenna.The width of the floor is also optimized,and the band width is 15.7GHz after the optimization.But the size of the antenna is large,which is not conducive to system integration.2.Although the above design of the antenna impedance bandwidth is large,but the size is relatively large,which is not conducive to the integration of ultra wideband communication systems.First,a small size rectangular monopole antenna is designed.The bandwidth of the antenna decreases with the decrease of the antenna size,therefore,the antenna bandwidth does not meet the design requirements of ultra wideband antenna.Then the antenna's performance is improved by changing the shape of the radiating patch.The change is that cutting two triangles from the rectangular patch and adding a half ellipse.The simulation result shows that the impedance bandwidth of the antenna to reach 21 GHz,and has omni directional radiation characteristics in certain frequency band.3.In this paper,two samples are processed and tested,and the accuracy of the simulation results is verified.At the end of the paper,the shortcomings of antenna design and the future improvement are discussed. |
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