Broadband Radar Invisibility with Time-Dependent Metasurfaces

TL;DR

This paper introduces a broadband radar invisibility method using a time-dependent metasurface that dynamically adjusts reflected signals, effectively concealing moving objects across a wide frequency range by exploiting radar signal processing vulnerabilities.

Contribution

It presents a novel signal-processing approach with a temporally modulated metasurface to achieve broadband invisibility of moving objects from radar detection.

Findings

Successfully concealed a moving metal plate in a 20% bandwidth around 1.5GHz.

Demonstrated dynamic phase control to induce Doppler shifts that mask target motion.

Achieved invisibility by making the radar perceive the target as static.

Abstract

Concealing objects from interrogation has been a primary objective since the integration of radars into surveillance systems. Metamaterial-based invisibility cloaking, which was considered a promising solution, did not yet succeed in delivering reliable performance against real radar systems, mainly due to its narrow operational bandwidth. Here we propose an approach, which addresses the issue from a signal-processing standpoint and, as a result, is capable of coping with the vast majority of unclassified radar systems by exploiting vulnerabilities in their design. In particular, we demonstrate complete concealment of a 0.25 square meter moving metal plate from an investigating radar system, operating in a broad frequency range approaching 20% bandwidth around the carrier of 1.5GHz. The key element of the radar countermeasure is a temporally modulated coating. This auxiliary structure is designed to dynamically and controllably adjust the reflected phase of the impinging radar signal, which acquires a user-defined Doppler shift. A special case of interest is imposing a frequency shift that compensates for the real Doppler signatures originating from the motion of the target. In this case the radar will consider the target static, even though it is moving. As a result, the reflected echo will be discarded by the clutter removal filter, which is an inherent part of any modern radar system that is designed to operate in real conditions. This signal-processing loophole allows rendering the target invisible to the radar even though it scatters electromagnetic radiation. This application claims the benefit of patent number 273995, filed on April 16 2020.