The Performance Ananlysis Of The Adjustable Beamwidth Of The ELEVEN Feed Antenna

Research and developmemnt of ultra-wideband(UWB)antenna systems become a hotspot at present.Many international radio astronomy research projects including VLBI2010(very long baseline interferometry),SKA(Square Kilometre Array)and the National 863 Project:Radio Probe to Dark Energy—"Tianlai Plan" have made very high technical requirements for the next generation radio telescopes.The new circular ELEVEN antenna has high aperture efficiency,stable pattern,fixed phase center,refrigeratable features within 10:1 bandwidth,making it one of the main candidates of the international next generation radio telescopes.Currently,ELEVEN feeds have been applied in some American and German astronomical stations.In order to further its application and produce feed for rotating parabolic antenna reflectors that have been built.This paper will focus on the problem that the circular log periodic folded dipole array antenna has a fixed lobe pattern and we have an idea to change the beamwidth by increasing the feed point gap and the distance between two circular dipoles based on the unit of the ELEVEN antenna structure.In this method,by calculating the BOR1 efficiency of two units of ELEVEN feed antenna(linear dipole array and symmetrical circular dipole array)and comparing the advantages and disadvantage of both of them,so we choose the cicular dipole array as the research subject of this paper.By observing the surface current of the tilted circular dipole array,we can know the setup conditions of the ideal discrete port in CST,and then we use MATLAB software to analyze the impact of feeding gap on beamwidth.By analyzing and constructing 3D mathematical model of the inclined circular dipole array,and reasonable assumptions of the circular dipole surface current distribution,we derived the far field functions,and programming in MATLAB software.Through simulation and caculation,we found that this method can effectively change the antenna beamwidth and radiation performance.This method provides a reference for the production of a ELEVEN feed for different aperture reflector antenna.At the same time,we take the tilted circular dipole array as a feed antenna,then we calculate the far field function of the parabolic reflector surface in MATLAB software.In this calculation process,we use two methods:Geometrical Optics(GO)and Physical Optics(PO)and verify the correctness by comparing the two methods.Meanwhile,combined with the circular ELEVEN feed antenna structure and the analysis of the dipole surface currents in the process of regulation of feeding gap,we designed a Directional dual-band slotted semi-circular inverted-F antenna for WLAN applications for the smart home system.The measurement results of the prototype agree quite well with the simulation results.According to the measurement results,the antenna has a strong directionality in low frequency band(2.4-2.48 GHz)and high frequency band(5.2-5.8 GHz).Besides,the proposed antenna is compact,low cost and easy to fabricate,making it ready to be applied in a WLAN-based smart home system.