Abstract:

Radar Non-Line-of-Sight(N-LOS) target detection is a significant issue in an urban environment,where obstacles such as buildings obstruct the line of sight between the radar and the target,thereby limiting the detection performance.Traditional methods utilize the reflection of electromagnetic waves from surfaces like walls to detect targets in blind zones.However,the attenuation of electromagnetic waves at reflective surfaces and during propagation restricts the detection range.The Reconfigurable Intelligent Surface(RIS) is a planar array controlled by low-power electronic circuits,it can manipulate electromagnetic wave reflections in the spatial domain and focus energy on desired locations by adjusting the reflection coefficients of elements.The RIS,with its low cost,ease of deployment,and low energy consumption,can be widely applied in urban environments.Inspired by the signal controlling capability of the RIS,this paper proposes the use of the RIS to aid the radar NLOS detection method,forwarding signals to bypass obstacles and reach the target.Reflection coefficients are optimized employing an alternating optimization algorithm,with the aim of improving the radar's target detection performance in N-LOS scenarios and broadening radar applications in urban environments.Simulation results demonstrate that compared with traditional methods,the RIS aided radar achieves an improved N-LOS target detection range.Additionally,increasing the number of RIS elements and positioning the RIS closer to either the radar or the target further enhances the detection performance.

Key words: non-line-of-sight, target detection, reconfigurable intelligent surface, alternating optimization