The Theoretical Research And Design Of Novel Water Antenna

Compared with the traditional antenna,the antenna with liquid as radiation material has many advantages.Especially,the structure of the liquid antenna is easy to change compared with the solid antenna,so the reconfigurable ability of the antenna is greatly improved.Most liquid antennas use liquid metal materials,but some of which are expensive and harmful to human body.To solve these problems,in the early 20 th century,researchers put forward the concept of water antenna,which uses water and its salt solution as the main material for liquid antenna.Water antenna not only solves the shortcomings of liquid metal antenna,but also has the advantages of transparency and high dielectric constant,so it has great engineering value.In this paper,some broadband reconfigurable monopole antennas are designed by using seawater.Then three kinds of broadband hybrid DRA(Dielectric Resonator Antenna)are designed using distilled water.In this paper,the broadband principle of cylindrical metal monopole antenna is analyzed.Based on this principle,a cylindrical seawater monopole antenna is designed.The effects of parameters such as water column height and radius on antenna impedance bandwidth and efficiency are analyzed.After optimizing the parameters,a broadband cylindrical seawater monopole antenna is obtained.The efficiency of the antenna in its frequency band is basically more than 50%,and the relative bandwidth is 95.5%.In order to reduce the weight of this antenna,a circular seawater monopole antenna is proposed.Based on the principle of equivalent radius of uniform section monopole antenna,a rectangular seawater monopole antenna is designed,and the main parameters affecting the performance of the antenna are analyzed.The antenna has a larger bandwidth after optimization.In order to make the antenna have the ability to reconfigure frequency bands and patterns,a rectangular seawater monopole antenna loaded with T-shaped water column is designed.The reconfigurable principle of the antenna is analyzed.After optimizing the parameters,the antenna has better frequency band and pattern reconfigurable ability.Then,in order to reduce the size of floor of rectangular seawater monopole antenna,a low profile rectangular seawater monopole antenna with transition structure is proposed,and the improvement of antenna impedance matching by using transition structure is analyzed.After parameter optimization,the antenna has a large bandwidth and its profile height is very low.The relative bandwidth of antenna can reach 64.6%,and the profile height is only 4% of thecorresponding wavelength of the working upper limit.Based on the broadband characteristics of conical monopole antenna,a conical seawater monopole antenna with seawater cylinder loaded at the top is proposed,and the influence of the height of loaded seawater cylinder on the bandwidth of the antenna is analyzed.After optimizing the parameters,the antenna has a large bandwidth.In order to increase the horizontal gain of the antenna at high frequency,a concentric annular seawater column is loaded around it.The results show that loading annular seawater column not only realizes the reconfigurable pattern at high frequency,but also reduces the reflection coefficient of the antenna.Before and after loading the annular water column,the absolute bandwidth of the working frequency band of the antenna is more than212 MHz,and the octave is more than 4.2.Based on the working principle of hybrid DRA,a kind of annular distilled water hybrid DRA,loaded with metal cylinder is proposed to realize a wide working frequency band by adjusting the coupling between feed probe and circular distilled water DR(Dielectric Resonator)through metal tube.In order to further increase the bandwidth,a new type of distilled water hybrid DRA,is designed.By combining conical and hemispherical distilled water DR,the antenna realizes better impedance matching and improves the working bandwidth to a certain extent.Finally,in order to reduce the dielectric loss of water,a new annular distilled water hybrid DRA with improved feed structure is proposed..By adding a conical transition structure between the coaxial inner conductor and the antenna probe,a better impedance matching is realized.The bandwidth of the antenna is much higher than that of the two kinds of hybrid DRA proposed before.Its relative bandwidth can reach 83.8%,and the dielectric loss of water is greatly reduced because of the low working frequency of the antenna.