Research On VHF Broadband Antenna And Scattering Characteristics

With the development of communication technology,the VHF communication system has always played an important role due to its stable transmission method and high communication rate,especially in the fields of directional,omnidirectional communication and array direction finding.As an indispensable part of the system,VHF antenna has increasingly higher requirements on its size and performance.This article studies the broadband,miniaturization and scattering characteristics of VHF antennas for different applications.The research content is divided into three parts:1.This thesis studies the frequency band broadening,optimized design and miniaturized feeding technology of VHF broadband Yagi antennas.The method of equivalently thickening the diameter of the active dipole is used to broaden the working bandwidth;in the case of limited size,the adaptive differential evolution algorithm is used to optimize the design of the Yagi antenna;a miniaturized feed structure design is proposed based on the principle of the plate line balun.The design shows that the longitudinal length of the feed structure is reduced by about 80%,the antenna operating bandwidth reaches 22%,and the gain reaches 8d Bi.An engineering prototype of the antenna is finally produced,and the test results were in good agreement with the simulation results.2.This thesis studies the method of broadening the VHF monopole and reducing the scattering characteristics.Based on the analysis of the antenna installation environment,the design of the drop-shaped monopole antenna is used to broaden the working bandwidth of the antenna combined with the loading technology;the scattering characteristics of the antenna are analyzed,and by changing the shape of the area where the current distribution of the antenna is weak,the omnidirectional radar cross section of the antenna in the horizontal plane is reduced.The design results show that the antenna achieves a working bandwidth of 3.7:1 and the omnidirectional radar cross section of the horizontal plane is less than-10 d Bsm.3.This thesis studies the technology of the angle-of-arrival direction-finding antenna based on dual antenna.The design of the planar inverted-F antenna is optimized and the medium loading technology is used to achieve the broadband miniaturization of the antenna unit;in the dual-antenna direction-finding antenna array,a method of adding a “head-loss-like scatterer” structure is proposed to improve the receiving phase difference of the dual antenna under a short baseline.The results show that the size of the antenna unit is reduced by about 30%,the antenna bandwidth has reached 35.9%,and the receiving phase difference of the dual antennas has increased by more than 2.3 times,which provides an effective solution to the accuracy of dual-antenna angle-of-arrival direction finding under a short baseline.