Research on electromagnetic scattering and plasma stealth design of S-shaped inlet

Abstract

Inlet duct is a strong scattering source of radar waves due to its cavity structure which can make multiple reflections of electromagnetic wave through the cavity walls. Moreover, the complicated cavity structure always makes it difficult to obtain its scattering characteristic. S-shaped inlet is a frequently-used design to reduce return radar wave, but the hiding effect is limited. Relying on its great advantages over traditional stealth technologies, plasma stealth is an emerging technology which attracts the attention of many researchers. Considering the particular structure of S-shaped inlet, a kind of closed plasma was designed to be conformal to the inlet to improve the stealth performance of S-shaped inlet. Firstly, the electromagnetic scattering characteristic of S-shaped airplane inlet was analyzed by using shooting and bouncing ray (SBR) method. Mathematical principle of SBR method was described through three procedures: geometric optical ray tracing, field intensity tracking and physical optics aperture integral. To improve SBR method, a Keller cone model was presented to obtain the contribution of edge diffraction. Then the radar cross section (RCS)of a cylindrical inlet model was calculated using SBR method and the result tallies well with that in reference, which proves the effectiveness of SBR method and the correction model for calculating scattering characteristic of inlet. Then on this basis, the RCS of a S-shaped inlet was calculated by SBR method. At last, to verify the stealth effect of plasma stealth, the RCS of the inlet with plasma was assessed.