Technical Analysis: Military Lessons of Anti-Drone Radar Technology - Chapter Two

1. 2 Military Lessons

Russia's special military operation in Ukraine has triggered intense confrontations between drones and C-UAS in warfare. Recently, the Ukrainian military has conducted significant practices regarding drone attacks in the ongoing conflict, providing valuable insights and lessons. Drones equipped with advanced sensors, cameras, and precise positioning capabilities have excelled in engagements with heavy armored vehicles and infantry, allowing the Ukrainian military to counter the Russian forces on the battlefield. Ukraine's drone operations demonstrate the characteristics of asymmetric warfare by adopting innovative tactics to challenge a more powerful opponent while greatly reducing the risk of direct combat involvement. Furthermore, a more significant change is the flexible and widespread militarization of civilian drones.Asymmetric WarfareDrones available for less than $10,000 offer a wide range of application possibilities, including information gathering, ambush planning, artillery target designation, and tracking troop movements and aircraft takeoffs and landings. These drones provide Ukraine with a cost-effective means to challenge Russia's military advantage, disrupting their forces and undermining their morale. For example, in the ongoing war with Russia, the domestically produced R18 drone used by Ukraine has caused approximately $130 million in various enemy material losses, equivalent to destroying about $670 worth of military assets for every dollar spent on producing the drone. The R18 drone can drop grenades from an altitude of 100 to 300 meters, effectively hovering above the target. It uses Soviet-style anti-tank grenades RKG-3 or RKG-1600 as bombs, equipped with thermal imaging, making its attacks unpredictable and highly effective.Micro DronesVideo footage shows a multirotor drone tracking and attacking a group of Russian tanks. Ukraine's drone technology highlights its adaptability and innovation in response to the changing nature of warfare. By embracing emerging technologies, Ukraine demonstrates the ability to gain strategic advantages through new means, potentially inspiring other countries to follow suit. Meanwhile, the demand for C-UAS solutions on the modern battlefield is becoming increasingly urgent.Anti-tank GrenadesNote: Source https://dronedj.com/2022/09/16/aerorozvidka-ukraine-drone-r18/.

(a) R18 multirotor military drone developed by Ukraine

Note: Source https://www.youtube.com/watch?v=4PqOSWzI_x8. (b) Russian tanks from the drone's perspective

Note: Source https://www.youtube.com/watch?v=4PqOSWzI_x8.

(c) Russian tanks destroyed by drones

Fig. 2 Ukrainian drones attacked Russian tanks and other military targets

(T-72A T-80B T-72B)

Fig. 2 Ukraine drone eliminated Russian tanks

(T-72A T-80B T-72B) & infantry vehicle 2 anti-drone radar

Traditional air traffic control radar, ground-based air defense radar, etc., are not suitable for detecting small drones. For example, Russia's S300 air defense system is primarily designed for high-speed large aircraft and ballistic missiles, making it ineffective at detecting and tracking small drones. Although these systems perform excellently in detecting, tracking, and dealing with fast-moving and large targets, they are less efficient when handling small, slow-moving, and low-flying drones.

Traditional air defense radar employs various strategies to reduce interference from small and slow-moving targets, including: 1) increasing the beam elevation angle to prioritize high-altitude targets; 2) raising the speed threshold to focus on fast-moving targets; 3) increasing the signal detection amplitude threshold to emphasize large targets with strong echo scattering. Consequently, these adjustments may miss small drone targets. These drones are made of composite materials and exhibit similar temperatures to the surrounding atmosphere, and their relatively low speed (about 150 km/h) further complicates detection, as they move at speeds comparable to clouds. When air defense radar systems attempt to eliminate cloud interference, they also filter out low-speed targets like drones, as these targets fall outside the radar's intended detection range. This filtering is crucial to prevent false alarms caused by various non-threatening objects, such as birds. To effectively address the shortcomings of traditional radar systems in detecting drones, there is an urgent need to develop dedicated drone detection radars (or anti-drone radars). These anti-drone radars should be designed to target the characteristics of small, slow, low-flying drone targets, enabling reliable detection and tracking of drones in various operational environments to counter drone threats.Many countries around the world are actively advancing the development, procurement, and deployment of anti-drone radars to capitalize on the expanding anti-drone market. Although there are differences in radar frequency bands, system designs, and other technical aspects, these systems generally follow basic radar principles. Table 1 provides some well-known anti-drone radars available on the market. Despite differences in radar parameters, their design concepts and resilient performance largely remain consistent.Note: 1) Product parameters can be found on the respective company websites; 2) The nominal range is based on common drone targets, such as the DJI Phantom 4 drone, which has an RCS of about 0.01 m²; 3) Specific identification features are not visible, only features shown in the data are listed.Anti-drone radars are primarily designed to monitor airspace below 1000 m Above Ground Level (AGL), capable of detecting clutter from ground and aerial objects (see Fig. 2). Low-altitude airspace is generally below 1000 m, while ultra-low-altitude airspace is below 100 m. For example, in pulse Doppler radar, the LSS characteristics of drones significantly affect the radar system's detection (as shown in Fig. 3).First, the 'low altitude' of drones requires anti-drone radars to have the capability to detect various active targets, including people, vehicles, birds, and drones, in ground, low-altitude, and ultra-low-altitude environments. Some anti-drone radars attempt to reduce the impact of ground clutter by adjusting the radar's elevation angle. However, this method has challenges in detecting drones.

1) X-band radar is the most widely used frequency band among these systems; 2) Micro-Doppler and kinematic characteristics are the main identification features; 3) The maximum detection range for drone targets is within 6 km.

Many countries around the world are actively developing, acquiring, and deploying counter-drone radar systems to capitalize on the growing anti-drone market. Although there are differences in radar frequency bands, system designs, and other technical aspects, these systems generally follow basic radar principles. Table 1 provides some well-known counter-drone radar systems on the market. Although the radar parameters differ, the design approach and flexibility are largely consistent:

Note: ① Product parameters can be found on the websites of various companies; ② The nominal distance is for common drone targets, taking the DJI Elf 4 drone as an example, with an RCS of approximately 0 01 ㎡ ;③ The specific identification features are not visible, only the features displayed in the data are listed.

The anti drone radar is mainly designed to monitor airspace below 1000 meters above ground level (AGL) and can detect clutter from ground and airborne objects (see Figure 2). Low altitude airspace is generally below 1000 meters, while ultra-low altitude airspace is below 100 meters. Taking pulse Doppler radar as an example, the LSS characteristics of unmanned aerial vehicles significantly affect the detection of the radar system (as shown in Figure 3).

Firstly, the "low altitude" of drones requires anti drone radar to have the ability to detect various active targets including ground, low altitude, and ultra-low altitude, such as people, vehicles, birds, and drones. Some anti drone radars attempt to reduce the impact of ground clutter by adjusting the pitch angle of the radar. However, this method involves drone detection

① X-band radar is the most widely used frequency band among these systems;

② Micro Doppler and kinematic features are the main identification features;

③ The maximum detection range of drone targets is within 6 km.

The risk of high 'leakage alerts' exists because most small drones typically operate in ultra-low altitudes below 100 m. Therefore, an efficient counter-drone radar must have the capability for automatic target recognition. Secondly, the 'small size' of drones requires radar detectors to have sufficient detection sensitivity to extract weak signals and achieve a wide detection range. This prerequisite demands a high level of detection and recognition reliability. Finally, the 'slow speed' of drones poses challenges for radar tracking, which may mislead optical/infrared sensors and the countermeasure units in C-UAS solutions. This situation requires radar scanning to have a high update rate and fast recognition speed.

(b) Counter-drone detection targets

(c) Time for C-UAS to acquire targets [8]

Fig. 3 Typical counter-drone radar operation scenarios

Fig. 3 Typical counter-drone radar operation scenarios [8]

In summary, to establish a reliable and efficient counter-drone radar, it must possess strong automatic target recognition capabilities. By addressing these challenges and integrating appropriate capabilities, counter-drone radar can enhance its performance and play a significant role in counter-drone operations. In 2023, the European Commission released a new manual aimed at helping businesses and public sectors mitigate the threats posed by unmanned aircraft systems [8-9]. This manual emphasizes that C-UAS systems need to detect, track, confirm, and counter drone threats within a 2-minute time window (Fig. 3(c)). For example, assuming a drone's flight speed is 60 km/h, at a flight distance of 2 km, the time is approximately 120 seconds. Therefore, the response time for C-UAS systems is only 120 seconds, while the response time for counter-drone radar is even shorter.More exciting content in the next issue...

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