Study On Scattering Characteristics Of Typical Targets Based On Vortex Electromagnetic Wave

Vortex electromagnetic wave carrying orbital angular momentum has been paid attention to,because of its characteristics different from the traditional electromagnetic wave.The generation,reception and application research in communication and radar of vortex electromagnetic wave are widely carried out.In order to make better use of vortex electromagnetic wave,researches on scattering characteristics of targets illuminated by vortex electromagnetic wave have been carried out.However,compared with researches on the scattering characteristics of targets under traditional planar electromagnetic wave,relevant researches include simple target types,and is limited to the situation where the target is aligned with the beam axis.The phase distribution of vortex electromagnetic wave is related to space,and the shape and posture of the target will affect the spatial distribution,so as to modulate the phase of the scattered echo and further affect the modal spectrum distribution of the echo.In response to the above problems,based on spectral decomposition method,definition of radar cross-section and reflection coefficient and other relevant research theories,this thesis carries out modeling,data simulation and characteristic analysis for the scattering research of targets with different shapes and postures.The object shape involves typical objects such as plate,ball and cone,asymmetric object composed of a ball and a cube,and coated object.The characteristics involve echo modal spectrum,radar cross-sections,and reflection coefficient.The final research results show that the lower the symmetry of the target shape,the greater the spatial posture change of the target,the higher the mode order and the lower the proportion of the main mode of the target scattering echo.The radar cross-section of the target under vortex electromagnetic waves is different from that under traditional electromagnetic waves.Specifically,the forward scattering peak disappears but there are two peaks symmetrical about a 0° pitch angle.Under the same incidence angle,the reflection coefficient under vortex electromagnetic waves is also different from that under plane waves and it will changes with azimuth angle.In addition,a vortex electromagnetic wave generator is designed based on a quasioptical mode exciter in this thesis.Based on microwave propagation theory,geometric optics theory,and coupled wave theory,a vortex electromagnetic wave generator composed of a Gaussian horn,a quasi-optical parabolic reflector,and a coaxial resonant cavity is designed.The operating frequency of this generator is 34 GHz and it can output vortex electromagnetic waves with a mode number of-6.Research on the scattering characteristics of targets under vortex electromagnetic waves shows that the scattered echoes are affected by the spatial distribution of the target.For example,the modal spectrum of the scattered echoes will undergo different degrees of expansion after being modulated by the target.This research is expected to the scenarios and content of research on scattering characteristics under vortex electromagnetic waves and can provide a reference for target detection.