Study On Ultra-wideband Multi-polarization Reconfigurable Plasma Antenna

Today,in order to respond to the complicated electromagnetic environment,the anti-multipath capability,stealth target detection capability,wide-angle scanning capability of VHF radar should be improved.In order to achieve improvements in these areas of ability,different frequency,different polarization and antenna elements in different radiation being efficiently integrated is the key technology that should be studied.To break through the technical difficulties,ultra-wideband multi-polarization reconfigurable plasma antenna is studied in this paper.Based on dual-sleeve ultra-wideband antenna theory proposed by the project team,through simulation studies,we designed an ultra-wideband antenna who's operating frequency band is 28.7MHz¹02MHz on condition that S₁₁<-10dB.Its impedance bandwidth is 3.55:1 and the relative bandwidth reaches 112%.It's an extremely rare ultra-wideband antenna in the form of whip antenna and dipole antenna.In the30MHz¹00MHz operating frequency band that project required,S₁₁ are less than-11.75dB.Coaxial slot horizontally polarized antenna is a less popular field of study,but if it is integrated with existing vertically polarized antenna efficiently and produce more polarizations,that will significantly enhance the performance of a single vertically polarized antenna.In this paper,from the beginning of the cylindrical slot antenna,then the coaxial slot antenna,and then to a slot antenna based on dual-sleeve coaxial structure,step by step,we achieved the integration of horizontally polarized antenna and vertically polarized antenna.We made vertical slot on the outer sleeve of the vertically polarized antenna and through non-traditional and new way of slot antenna feed,we completed the design of coaxial slot antenna based on the dual-sleeve structure of the vertically polarized antenna.The experiment proved that the design is feasible.Dual-sleeve structure is the clever combination key of the vertically polarized antenna and the horizontally polarized antenna.For the purpose of horizontally polarized slot antenna operating in the30MHz¹00MHz frequency range,we especially proposed electrically small implementations of the slot antenna based on media filling.Through the media filling and rotation of the feeding Port,we realized the design of the coaxial slot electrically small antenna.Here,we broke d/?=0.117limit of coaxial slot antennas and it provides new solutions to narrow vertical and horizontal size,and that will improve the applicability of low-frequency coaxial slot antenna.The bandwidth of coaxial slot antenna is narrow,to make it work at30MHz¹00MHz frequency range and be continuously adjustable,we studied implementations of sweeping based on plasma sheltering.The implementation makes use of the characteristic of plasma similar to metal,using plasma to shield the ends of the slot,adjusting the length of the plasma,namely changing the effective length of the radiating slot,to achieve the change of its operating frequency.To enhance the usefulness of the antenna,we designed broadband matching program of feeding based on a filter.Adding filter between the feed and the antenna made that the match is still good while the feed point is at a fixed position.30MHz¹00MHz frequency band belongs to the HF,VHF band,the frequency is low and the antenna size is huge,so that the earth seriously affects the performance of the antenna.Its specific impact manner is reflecting electromagnetic wave,elevating the radiation main lobe of antenna.To solve this problem,we studied and designed scheme of reconfigurable pattern based on the plasma reflection array.For different frequency,achieving the radiation lobe of the antenna in the horizontal plane can be realized by controlling the length of plasma column in the plasma reflection array.