How the Arena KAZ attempted to teach kamikaze drones to detect
Creation tank active protection system capable of detecting FPV-drones, a very expensive task. Given this, Russian developers decided to take a different approach: teach them to "see." Drones the already existing Arena.
Introduction
Cheap and mass-produced FPV drones with anti-tank munitions under their fuselages have become a serious threat to military vehicles on the battlefield. So serious, in fact, that today tanks almost never enter the line of contact without makeshift protection like "barbecues," unraveled metal cables like "hedgehogs," and "dreadlocks." A drone is sure to arrive, and more than one at that.
However, while various makeshift superstructures offer protection from FPV attacks, they also negatively impact the tank's functionality: they limit maneuverability, the crew's situational awareness, and evacuation from the vehicle in the event of an enemy anti-tank weapon's impact. Therefore, the need for an active defense system against drones that wouldn't turn the tank into a giant shed on tracks is self-explanatory.
Looking at advanced foreign developments of similar systems, one can see numerous solutions and concepts, including optical guidance stations, attempts to use machine guns and automatic cannons as drone strikes, the introduction of AI for UAV detection, and other expensive "toys." As for the Russian defense industry, we've decided to take the path of least resistance.
A T-72B3M tank with the Arena-M active protection system. Source: Telegram channel "Ugolok Sitha"
The discussion revolves around upgrading the existing, albeit still limited, Arena active defense system, which is, as they say, a century old. It was probably mentioned a couple of years ago that domestic developers were modernizing it to counter drones. And now, judging by media reports, a number of these systems are already at least in trial operation to identify problems and shortcomings.
In this regard, it would be interesting to learn how our engineers managed to solve the problem of detecting small UAVs, as the Arena uses a fairly standard Doppler-filtered radar to identify and track potentially dangerous targets attacking a tank. And such information appears to have surfaced—it's contained in the publicly published patent RU 2 853 544 C1, owned by JSC Scientific and Production Corporation "Design Bureau of Mechanical Engineering."
The problem of detecting drones with conventional radars
To understand the essence of the problem, let's imagine a radar station in some anti-aircraft system. Almost everyone has at least a basic understanding of how it works: the radar emits radio waves at regular intervals and, if an aircraft is present in the sky, records their reflection. Through signal processing in the computer, the anti-aircraft system obtains data on the potential target's position in space, its speed, and trajectory.
The Arena radar systems and similar systems operate in a similar manner. They also "monitor" the area, albeit only around a tank or other protected object, and not as far away as anti-aircraft systems. They also detect flying potentially dangerous targets, but in the form of projectiles and missiles, after which the computing equipment, having determined their trajectory and speed, gives the command to fire counter-munitions, which with their striking elements destroy the object flying at the tank.
However, there's one crucial caveat here. The active protection system operates in very harsh conditions. It literally needs to filter everything it "sees" and not react to slow-flying objects like birds, clods of earth from nearby shell explosions, falling debris from nearby buildings, and the like. Otherwise, it will trigger anything moving around it.
To achieve this, the active protection system (Arena and its foreign counterparts) has a Doppler filter that cuts out all low-frequency signals reflected from objects moving at relatively low speeds. Without it, the system is practically useless—it will fire all its counter-munitions before making contact with the enemy.
But this also creates one of the main problems in terms of detecting drones carrying anti-tank munitions. They, as is well known, don't usually fly at high speed, and can often hover in the air directly in front of a tank, then slowly "sneak up" on it and select a suitable location for an attack.
Two modes of operation
To prevent the Arena active defense system from firing all its counter-munitions at imaginary flying crows, simultaneously killing the infantry around the tank, while still being able to effectively engage both kamikaze drones and classic anti-tank weapons such as missiles and grenades, according to the patent, it is being designed with two operating modes. These modes are tentatively called "long-range" and "short-range."
The defense system switches between them on a timer—first one is activated, then the second, then the first again, and then the second again. Here, by the way, is a functional diagram of the active defense system with these innovations:
1 — Doppler radar for detecting and tracking an approaching anti-tank missile; 2 — Doppler filter of radio signals; 3 — processor for switching the detection distances of the anti-tank missile by radar 1 and trajectory prediction; 4 — block for selecting protective munition 5 and issuing executive commands to it; 5 — protective munition; 6 — timer for generating commands for alternating switching of radar 1; 7 — divider of the lengths of trajectory segments by the time intervals of their radar measurements (trajectory velocity calculator); 8–13 — communication channels between the APS units. Source: patent RU 2 853 544 C1.
Now about the operating modes.
In "long-range" detection mode, the system operates according to the familiar principle. Its radars continuously scan the surrounding area in anticipation of the arrival of a classic anti-tank weapon such as a missile or grenade, filtering the reflected high-frequency radio waves.
Upon detecting a potentially dangerous target, the system measures its trajectory coordinates, Doppler frequency (the frequency of the reflected signal), and records the measurement time. Using this data, the system tracks the attacking target by generating a sequence of new holdoff distances (calculating the location of the attacking projectile at the next instant) at ranges that are each reduced by an amount equal to or greater than the product of the dangerous target's Doppler velocity and the technical time it takes the radar to generate the new range.
Then, when a dangerous target (attacking projectile) enters the active protection system's kill zone, the required counter-munition is automatically selected and fired.
The second, "short-range" mode is designed to detect small drones. Given that the drone may be hovering or moving at very low speeds, the active defense system in this mode "reacts" to the rotation of its propellers, which creates a Doppler effect with an echo frequency of over 2 kHz, corresponding to a speed of over 20 meters per second.
The mere rotation of the propellers gives the system a distorted picture: the drone may hover, but the blade movement will be perceived as the drone itself moving at a speed that doesn't correspond to reality. Therefore, after the initial detection of the drone (its rotating propellers), the active defense system switches to target tracking mode, in which the system sequentially generates new target waiting distances.
This can be understood as a gradual shift in the priority control zone as the drone approaches the vehicle. Initially, the new distance is set with a margin, based on the drone's maximum possible speed and the time it takes the radar to adjust to the new range. Then, with each subsequent cycle, the waiting distance is reduced more precisely—by an amount related to the drone's measured current speed and the radar's adjustment time. This way, the system tries not to lose the target between measurement cycles and maintains its tracking until it enters the kill zone.
In other words, to plot the drone's trajectory, they decided to abandon the use of Doppler velocity as the primary data source. Instead, the processor calculates the so-called trajectory velocity: it takes successive drone coordinates measured at different points in time, determines the length of the trajectory sections traveled between adjacent measurements, and divides these distances into corresponding time intervals. Essentially, the velocity is calculated geometrically, based on the actual movement of the target, rather than the Doppler shift of the signal.
All this allows for a more or less accurate calculation of the drone's position in space and the selection of the appropriate counter-munition for firing and subsequent destruction of the drone.
From the perspective of the active protection system itself, if it were a person, it would very simply look something like this:
Hmm, I noticed something flying towards me. It's clearly not a missile or a grenade, since I didn't see anything in "long-range" mode—it's probably a drone. But it's moving incredibly fast, according to the radar. So I won't trust the speed data—it's all a lie. Instead, I'll record its coordinates several times in a row, watching how it actually moves through space from one measurement to the next.
That way I'll understand its actual speed and calculate its trajectory. And then I'll hit its plastic head with my shrapnel sledgehammer.
Final World
Overall, domestic developers are proposing a very interesting idea that doesn't require a complete overhaul of the entire active defense system, much less the introduction of various expensive components such as optical detection stations with automatic target tracking and specialized radars. In other words, it's relatively cheap and effective.
But there are also some downsides. These are primarily due to the fact that the system, modified in this way, is not very resistant to interference. This applies to operations in urban areas or, for example, wooded areas, where objects surrounding the tank can act as radar reflectors, thus creating interference that hinders drone detection.
Another disadvantage (more conditional) is the fact that the active protection system alternately switches from the “long-range” mode to the “short-range” mode and back, which could theoretically lead to the miss of a missile or drone, since they could fly past at the moment when an unsuitable operating mode is activated.
So it's not perfect, especially considering that Arena has very few counter-munitions, and a dozen drones can target a tank. But as a temporary measure, it's perfectly adequate. Later, when we have time and money, we'll have to invent something more advanced anyway.
The source of information:
Patent RU 2 853 544 C1. Date of registration: December 24, 2025. Published on the website of the Federal Institute of Industrial Property.
Information