Radar: The Unblinking Eye in Counter-Unmanned Aerial Systems (C-UAS)

With the proliferation and widespread availability of drone technology, the threat posed by "low, slow, and small" (LSS) targets has become increasingly severe, ranging from civilian aerial photography to malicious espionage, smuggling, and even battlefield reconnaissance. Countering drones hinges on the principle of "detect to defeat," and the key to detection lies with radar—this ever-vigilant, "unblinking eye." In modern Counter-Unmanned Aerial Systems (C-UAS), radar plays an indispensable and central role.

Compared to traditional aircraft, drones (especially consumer-grade multi-rotor models) present severe challenges for radar detection:

• Low: They fly at low altitudes, often below 1,000 meters, easily masked by ground clutter (such as buildings and trees).
• Slow: Their slow flight speed results in a minimal Doppler shift, making it difficult to distinguish them from slow-moving ground clutter.
• Small: They have a small Radar Cross-Section (RCS). Often constructed with composite materials and stealthy shapes, they reflect extremely weak radar signals.

These characteristics render conventional air defense radars largely ineffective against drones, drastically reducing their detection range or causing them to fail entirely.

To address these challenges, modern anti-drone radars incorporate several advanced technologies:

• High Resolution and Advanced Signal Processing: They operate at higher frequencies (e.g., Ku, Ka bands) and wider bandwidths to achieve superior range and angular resolution. Simultaneously, sophisticated Pulse-Doppler processing and Moving Target Indication techniques are used to extract the drone's faint movement signal from powerful ground clutter.
• Phased Array Technology: Electronically scanned phased array radars eliminate mechanically rotating antennas. Their beams can jump across sectors in microseconds, achieving a very high refresh rate for monitoring critical airspace and ensuring highly agile drones are not missed.
• Low Probability of Intercept (LPI) Features: To prevent detection and evasion by hostile drones, advanced anti-drone radars employ frequency agility and low sidelobe transmission, making their signals difficult to identify and locate.
• Pattern Recognition and Artificial Intelligence (AI): A single radar plot is insufficient for identification. Modern systems analyze flight paths, velocity changes, and micro-Doppler signatures (unique frequency modulations caused by rotor blade rotation). Coupled with AI algorithms, they can accurately distinguish drones from birds or debris, and even identify specific drone models.

Radar does not operate in isolation within a C-UAS. It acts as the sensory hub, integrating with electro-optical/infrared (EO/IR) trackers, radio frequency (RF) sensors, navigation spoofers, and kinetic effectors to form a complete "Detect, Track, Identify, Defeat" loop.

• Detection Phase: Radar performs wide-area, continuous search, providing initial target coordinates.
• Tracking and Identification Phase: Radar maintains precise track, cueing EO/IR systems for visual confirmation. RF sensors can locate the drone's control and video transmission signals.
• Neutralization Phase: Using real-time coordinates from radar, jammers can spoof navigation or suppress communications, forcing a return-to-home or landing. Kinetic effectors like directed-energy weapons can execute precise engagements.

In an increasingly complex air and space security environment, with emerging threats like drone swarms, radar technology—the cornerstone of C-UAS—continues to evolve towards greater precision, robustness, and intelligence. Only by possessing this keen, "unblinking eye" can we effectively weave an invisible, multi-layered protective shield over our cities and battlefields, securing the skies above.