Metasurfaces Enable Active-Like Passive Radar

TL;DR

This paper introduces a metasurface-enabled passive radar system that can actively enhance and localize targets without source control, demonstrating real-time UAV tracking in interference-rich environments.

Contribution

The paper presents a novel metasurface-based passive radar that transforms passive sensing into an active-like system, enabling interference suppression and accurate target tracking without source control.

Findings

Successful real-time UAV imaging and tracking

Performance comparable to active radar systems

Effective operation in interference-rich environments

Abstract

Passive radars (PRs) provide a low-cost and energy-efficient approach to object detection by reusing existing wireless transmissions instead of emitting dedicated probing signals. Yet, conventional passive systems require prior knowledge of non-cooperative source waveforms, are vulnerable to strong interference, and rely on Doppler signatures, limiting their ability to detect subtle or slow-moving targets. Here, we introduce a metasurface-enabled PR (MEPR) concept that integrates a space-time-coding programmable metasurface to imprint distinct spatiotemporal tags onto ambient wireless wavefields. This mechanism transforms a PR into an active-like sensing platform without the need for source control, enabling interference suppression, signal enhancement, and accurate target localization and tracking in cluttered environments. A proof-of-concept implementation operating at 5.48 GHz confirms real-time imaging and tracking of unmanned aerial vehicles under interference-rich conditions, with performance comparable to active radar systems. These results establish MEPR as a solid foundation for scalable, adaptive, and energy-efficient next-generation integrated sensing and communication systems.