Combining multiple counter-drone systems

A complete counter-drone system needs to follow a series of steps to successfully mitigate the possible threat from a hostile drone. These steps can be referred to as the Drone Kill Chain. Each link in the chain can utilize various technologies as shown below.

Drone kill-chain

Drone kill-chain

First the drone needs to be detected within the area of operations. Once detected it then needs to be precisely located, ideally in three dimensions. Knowing it is “somewhere over there” isn’t actionable intelligence. Next, the level of threat needs to be identified. Is the drone heading directly towards the installation? Is it carrying a payload? Is it weaponized? Is there a swarm of drones? Once the threat level has been determined, the security team has to decide on the appropriate countermeasure. This could be anything from having a chat with the drone operator who has accidentally strayed into the restricted area, to shooting down the drone with kinetic weapons. Lastly would be to assess the operation and feedback learning into the system.

CRFS can directly provide the first three links in this chain, detect, locate, identify, and help cue the other technologies.

Detect and locate

There are various methods used to detect drones, including our own RF detection used in RFeye DroneDefense. Each method has its advantages and disadvantages.



Radar has a long, illustrious history in tracking aircraft. Modern holographic systems can cope well with smaller devices such as drones. However, radar has drawbacks in terms of cost, “false alarms” for birds, ability to detect drones flying close to the ground and line-of-sight requirements, which can impair its effectiveness in urban environments.


Optical systems extend our own senses using superior optics and image enhancement. They are able to identify and track drones based on their visual signature, and, when using infrared (IR), by a drone’s heat signature. Optical systems give an unrivaled understanding of context. For example, by verifying if a drone is weaponized. They do, however, still need additional hardware to perform geolocations and can encounter difficulty in coping with bad weather and bright sunlight.


Acoustic sensors are programed to recognize the unique sounds produced by drone motors. They rely on a library of sounds from known drones, so if a drone isn’t in the library, it won’t be detected. Range from the target, background noise and strong winds can also influence the effectiveness of acoustic sensors.

RF detection

Our RFeye DroneDefense solution detects and geolocates the RF (radio frequency) signals emitted by the drone and the operator. Drones are usually operated by a radio control signal and often have on-board data link transmitters for real-time sensor download e.g. video feed, telemetry data. These signals can be detected several kilometers away and geolocated in three dimensions (long, lat, altitude). RF is also the only system type able to also locate the operator.

However, RF detection will only work when there are RF signals present. There are drones that can operate without any radio control signal and can fly using pre-programmed GPS waypoints. Although in this scenario the drone operator won’t be able to view the video feed from the drone or alter course.

Countermeasures – actions on

Once the drone has been detected and the threat level determined, it is then time to deploy the appropriate countermeasure. There are various systems available, and like detection methods, they all have their advantages and disadvantages.

  • Speak to or detain the operator – If the operator can be detected, this method is fairly effective for nuisance or accidental drone interference. However, if there is an immediate threat, there probably won’t be time to get to the drone operator.
  • RF Jamming – Jammers have been proven to be effective on drones directly operated via RF (obviously if the drone is using GPS waypoints, this is redundant). Jamming will cause the drone to either land where it is or return to the operator. The exact frequency to jam on can be determined via RF detection. Some jammers have limited range or need direct line of sight to be effective, other more powerful jammers may cause interference to friendly systems.
  • GPS jamming – This causes a similar effect to RF jamming, but the legality and consequences of interference may prohibit this method in sensitive areas e.g. airports.
  • RF Spoofing – This method endeavors to take control of the drone and lock out the operator. It can be extremely difficult to implement successfully on all makes of drones, and if the data link is encrypted, it becomes even harder.
  • Lasers, nets, projectiles – These try to destroy or physically disable the drone. They can be effective but may struggle to target a small, fast moving, agile target. Also, if the drone is missed, the net/projectile may cause damage or injury when it falls to earth.
© US Army 2018

Integrating the solutions

In these scenarios it is essential to have a comprehensive suite of sensors working together to maximize detection probability, minimize false alarms and optimize geolocations. As there isn’t a one size fits all solution for drone detection, CRFS is committed to working with systems integrators and primes in bringing together the “best of breed” in detection methods to deliver a robust solution.

Once a drone has been detected and located the system needs to alert the security team to its presence. RFeye DroneDefense can do that directly by displaying a visible warning and an audible alert. However, when part of a larger integrated systems using the client’s own Command and Control (C2) solution, data needs to be streamed into it. RFeye DroneDefense can stream the drone’s (or even multiple drones’) flight path (track data) and geolocation straight into the C2 system. This data can be used to guide the other sensor technologies on to the target location and cue the appropriate countermeasures.

For more information on how CRFS technology can work with an integrated system, visit the Systems Integrator page or get in touch.

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Further reading

What is 3D TDOA?

The basics of 3D geolocation

Drone Detection: Myths and Reality

Separating drone fact from drone fiction

Drones and Critical Infrastructure

Drones and border security