Research On Shipboard Reconfigurable Helical Antenna Based On Liquid Metal

With the wide application of the antenna in the fast developing communication system,the traditional shipborne antenna faces an unprecedented challenge:In limited space,the increasing number of antennas leads to multipath signal interference."Reconfigurable antenna" uses a high performance antenna instead of the traditional antenna system.By changing the physical structure or size of the antenna,an antenna can have the function of multiple antennas.In this way,not only the cost is reduced,but also the electromagnetic interference is avoided.Therefore,the reconfigurable antenna has important research significance and application value.Traditional reconfigurable antenna design mainly uses electrical signal switch,micro-electromechanical switch and et al,but there are some problems,such as high insertion loss,complication of the DC offset design and low reliability caused by material fatigue.To solve this question,the reconfigurable technology based on liquid metal is researched in this dissertation.The conical helical antenna based on the liquid metal,the frequency reconfigurable conical helical antenna based on liquid metal,the polarization reconfigurable conical helical antenna based on liquid metal,the function reconfigurable antenna based on liquid metal and an application for array antenna pattern synthesis based on IABC-Keans algorithm are studied.The main innovation achievements are as follows:(1)A novel conical helical antenna based on the liquid metal is presented.The purpose is to study the feasibility of liquid metal application in helical antenna.The proposed antenna is designed,simulated and optimized with HFSS software,and good circular polarization radiation and impedance characteristics are obtained.The simulated results show that:under the criterion of |S11|<-10dB,the measured frequency range is from 1.35GHz to 2.02GHz.The simulated 3dB axial ratio frequency range is from 1.36GHz to 1.88GHz and the gain of the antenna achieves 8.5dBic.The results show that it is feasible to use liquid metal to realize conical helical antenna.(2)A novel frequency-reconfigurable conical helical antenna based on the liquid metal was presented.The antenna is realized by two conical helical tubes sharing a matching conductor sheet.The antenna is designed,simulated and optimizated.When the centrer frequency of the antenna is 1.6GHz and 2.49GHz respectively,the relative impedance bandwidth is 35.9%and 35.3%(|S11|<-10dB)respectively,and the 3dB axial ratio bandwidth is 38%and 42.1%respectively.The gain of the antenna is greater than 5.8dBic in both operating frequency bands.The proposed liquid metal frequency reconfigurable antenna can be a good candidate for shipborne multi-mode satellite navigation antenna.(3)A novel polarization-reconfigurable conical helical antenna based on the liquid metal is presented.The antenna is implemented using truncated structure,variable pitch angle,a matching sheet and a mechanical autorotation device.The measured results show that the measured frequency range is from 1.32GHz to 1.92GHz(|S11|<-10dB)for both left-handed circular polarization and right-handed circular polarization.In the entire working band,the gain of the antenna achieves higher than 8 dBic and the 3 dB axial ratio bandwidth are both 26.5%.It can be used in maritime satellite communication and the Beidou Navigation System for sending short messages.(4)A function reconfigurable antenna based on liquid metal was presented.The antenna is composed of 3D printed hollow cavities and liquid metal.By filling the liquid metal into different hollow cavities,reconfigurable functions are generated,including right-handed circular polarization(beam directions are 0°,18°and 345°),omnidirectional linear polarization and omnidirectional left-handed circular polarization.The measurement results agree well with the simulated ones in terms of return loss,radiation pattern,gain,and axial ratio.For the five reconfigurable states,the measured relative bandwidths for |S11|<-10dB are 44.7%,28.1%,30.4%,41.7%and 10.8%,respectively,which cover the bands of global navigation satellite system,wireless local area network system,and radio frequency identification communication system.Attributing to the advantages of compact structure and flexible conversion,the proposed antenna meets the demands of maritime transportation on ships,including satellite navigation,wireless local area network,and radio frequency identification on ships.The number of ship antennas can be reduced,thus the multipath signal interference is reduced.(5)The IABC-Keans algorithm,which combines K-means clustering algorithm and the improved artificial bee colony,is applied in the field of linear array antenna pattern synthesis.The simulation results show that the sidelobe level is decreased by 5.42dB comparing IABC-Keans algorithm with ABC algorithm.The maximum sidelobe level is suppressed and broad null,single null and deep null are achieved.The algorithm improves the convergence speed and has good solution precision.The algorithm balances the global and local search capabilities in terms of suppressing the antenna sidelobe level and null control.