# A Review of Counter-UAS Technologies for Cooperative Defensive Teams of Drones
## 4 Neutralization Systems
### Neutralizers Using Mini Drones  
Aerial platforms, like mini drones, show some interesting characteristics, such as high maneuverability, flexibility and deployment speed, but have limitations in terms of SWaP constraints. Therefore, as already stated in the previous paragraphs, it is not feasible to integrate neutralizers like high-power electromagnetics and high-power lasers in these platforms. In addition, neutralizers based on projectiles are not applicable to mini drones, both for SWaP constraints and because they are typically designed to be used with the surface-to-air launcher installed in terrestrial platforms. Small projectiles could be installed on mini drones, but they can be assimilated to nets. All other shown neutralizers, electronic and kinetic-mechanical, can be used with mini drones, even if the use of low-power lasers requires accurate pointing, which could represent a critical issue to solve. In particular, in the case of collision UAVs, the platform is itself a neutralizer.  
The use of mini drones can help to maximize the effectiveness or efficiency of some neutralization techniques. An example is RF jamming: by exploiting the mobility of a drone equipped with a jammer, it is possible to approach the m-drone in order to reduce the power necessary to disturb the signal under attack. Let us assume, for example, that in the case of a jammer installed on a ground platform, the minimum distance between jammer and malicious drone is 100 m, and that in the case of a jammer installed on a mini drone, the aforementioned distance is 10 m. The signal produced by the jammer installed on the mini drone consequently undergoes an attenuation lower than 20 dB compared to the signal emitted by the ground platform jammer. This advantage could be partially or totally compensated considering that in the ground platform, a directive antenna can be used to amplify the power transmitted in a certain direction, but, as shown in the work reported in [103], an antenna system capable of offering some directivity can be installed also on mini drones. Furthermore, multiples drones, which simultaneously transmit a jamming signal, could be used in a cooperative way to increase the power of the resulting interfering signal. An example is shown [104], where the authors investigated the problem of simultaneous tracking and jamming of a rogue drone in a 3D space with a team of cooperative drones.  
Finally, a drone team can be used directly as a neutralization technique. In the work reported in [16], a drone-based system was proposed for the purpose of intercepting and escorting an m-drone outside a restricted flight zone. The system consists of a defensive swarm, which is capable of self-organizing its defense formation in the event of intruder detection and chasing the malicious drone as a networked swarm. The neutralization approach is as follows: the swarm forms a three-dimensional cluster around the m-drone in such a way that the m-drone has a minimum set of movement possibilities. Assuming that the m-drone is going to avoid collisions with the drones of the swarm to maintain its functioning, by moving the defensive drones in a cooperative way, it is possible to escort the m-done outside the restricted flight zone.