Research On Scattering Reduction Technology Of Vivaldi Phased Arrays

With the development of modern military technology,the low-scattering military carrier platform represented by stealth aircraft has gradually become the focus of the military competition of great countries.It imposes urgent demands on the low scattering performance of their installed devices and the platforms themselves.Stealth and low scattering here mean reducing the target’s radar cross section（RCS）to mitigate the detected probability effectively.Vivaldi antenna array is extremely suitable for airborne installed phased array developments because of its ultra-wide bandwidth and wide scanning angle.But it often destroys the platforms’ stealth property.In some situations,the antenna array becomes an important scattering source on stealthy platforms.However,the low scattering design of antenna arrays still faces many difficulties and challenges.Based on the requirements of practical engineering,this thesis focuses on the scattering reduction technology of the Vivaldi phased array.The main work of this thesis can be summarized as follows:At first,an ultra-wideband low scattering Vivaldi phased array operating at 6-18GHz（3:1 bandwidth）is proposed.In this work,two techniques are developed to reduce the in-band scattering of Vivaldi antenna arrays.Firstly,a novel Vivaldi antenna element with inherent low scattering level is proposed based on the extraction of the scattering and radiating currents.Secondly,a chessboard artificial magnetic conductor（AMC）surface with 180° reflection phase difference is developed to cancel out the scattering caused by the antenna array.Owing to the two techniques,an average of 5-10 d B in-band monostatic RCS reduction is realized while the radiation performance of the 6-18 GHz Vivaldi phased array with ±60° scanning range in the E-/H-planes is preserved.Finally,the prototypes of the proposed 8×8 Vivaldi phased array and a reference array are fabricated and measured to demonstrate the effectiveness of the in-band scattering reduction techniques for both normal and oblique incident waves with HH/VV polarized scattering.In addition,a low scattering Vivaldi phased array operating at X-band is proposed.Compared with the previous work,the RCS reduction method when plane waves incident along the antenna polarization direction is studied in this work.Based on the scattering separation method of the port open circuit and short circuit model,the scattering current of the 1×8 reference Vivaldi line array is analyzed.Then,the low scattering Vivaldi phased array and element is obtained by introducing the slots over the antenna patch.Obtained by the Vivaldi linear array further extending,the 8×8 low-scattering Vivaldi phased array can achieve an operating bandwidth from 8 GHz to 12 GHz in the scanning range of ±60° in E-/H-planes and effective in-band RCS reduction in the wide angular region.Finally,the prototypes of the low-scattering Vivaldi phased array and a reference array are fabricated,assembled,and measured.The measured and simulated results are in good agreement,which fully proves the feasibility of the scattering reduction technique.