RCS Diversity of Electromagnetic Wave Carrying Orbital Angular Momentum

Chao Zhang,Dong Chen,Xuefeng Jiang

doi:10.1038/s41598-017-15250-7

Abstract

An electromagnetic (EM) wave with orbital angular momentum (OAM) has a helical wave front, which is different from that of the plane wave. The phase gradient can be found perpendicular to the direction of propagation and proportional to the number of OAM modes. Herein, we study the backscattering property of the EM wave with different OAM modes, i.e., the radar cross section (RCS) of the target is measured and evaluated with different OAM waves. As indicated by the experimental results, different OAM waves have the same RCS fluctuation for the simple target, e.g., a small metal ball as the target. However, for complicated targets, e.g., two transverse-deployed small metal balls, different RCSs can be identified from the same incident angle. This valuable fact helps to obtain RCS diversity, e.g., equal gain or selective combining of different OAM wave scattering. The majority of the targets are complicated targets or expanded targets; the RCS diversity can be utilized to detect a weak target traditionally measured by the plane wave, which is very helpful for anti-stealth radar to detect the traditional stealth target by increasing the RCS with OAM waves.

Highlights

orbital angular momentum (OAM) was employed in optical fibre transmission
The OAM wave irradiates on a target, which is composed of a single metal ball as a simple target (Fig. 1c) and two metal balls as a complicated target (Fig. 1d)
Different from the co-axial receiving in OAM wave communications, due to the signal reflection and scattering from only a small part of the phase plane incident to the target, the whole spiral phase plane cannot be received at the receiving end for radar detection

Summary

Introduction

OAM was employed in optical fibre transmission. Due to the orthogonality of OAM lights with co-axial reception, different OAM waves can be transmitted and received in the same frequency[5]. In the case that the OAM wave is scattered by a complicated target, due to the spatial phase difference of the incident wave, the backscattered wave is definitely not the same as that of the plane wave. The radar cross section (RCS) of the target is expected to be different among OAM waves carrying different mode numbers.

Results

Conclusion