The key to RPAS, UAS and drone detection

by David A Moschella David A Moschella on May 3, 2017
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Drones are all the rage.  These amazing machines offer fun capabilities like aerial photography and videography -- even racing! However, they can also be used in dangerous, intrusive and intentionally harmful ways.

So, there is a clear need to be able to detect, and in some cases deny access to, remotely piloted aerial systems (RPAS), also known as drones or unmanned aircraft systems (UAS). Whatever you call them, they're here to stay and will only get better, faster and cheaper.  

How could one detect, say, a quadcopter?  

A high-resolution active radar system operating in the low GHz regime could do the job quite nicely.  It would also be very expensive. Perhaps an optical, thermal or acoustic system could be employed, if bad weather operation were not needed.  Check this nice discussion of detecting, identifying and responding to RPAS incursions.  BTW, don't overlook the operator commanding the drone. S/he uses a remote controller sending RF signals to/from the UAS's control system.    

Therefore a lower cost approach to RPAS detection could be to exploit the control and telemetry RF emissions from drones and their operators. These signals can be geolocated using direction finding techniques, and their character can provide information about the type of drone in use -- in other words: signals intelligence (SIGINT).

Many RPAS systems employed by non-state actors are commercial-off-the-shelf platforms equipped with real-time video downlink and a self-forming WiFi network for control. Each can be exploited to detect the drone and the operator. 

IS drone video capture.png

To illustrate, let's explore link budgets of a not-at-all hypothetical scenario.  Say you are a good guy working to take back territory captured by IS and are bogged down in urban conflict. You need to know when the eyes-in-the-sky are active and generally where their operators are located. 

From an operational perspective, you'd like to detect RF emissions from the controller and drone at a safe standoff distance, beyond the reach of their cameras and ordinance.   This means detecting far beyond the operational radius of the remote operator's controller or an autonomously operating drone's range.  

From IS's perspective, two link budgets need to be maintained for operational effect, one for the video stream, the other for controller communications to the drone.   

You may recall these essential link budget parameters:

  • Radio frequency
  • Range and elevation of receiver (Rx) and transmitter (Tx)
  • Gains of power amplifier, Rx and Tx antennas
  • Receive and transmit RF chain losses
  • Receiver sensitivity
  • Multipath conditions, like earth reflection
  • Obstructions to line-of-sight propagation  
Drone and Operator Detection Visualizer-2.jpg

So let's take a general look at these link budgets using the values in the drawing above for a 200m high drone and an operator on the ground, and leave it as an exercise for the reader to explore the equations at your leisure.

For the 5.8 GHz drone video stream, using a ground multipath propagation model (ignoring obstructions) and adding a -10 dB fade margin, its typical 28 dBm transmitter with 2 dBiC omni antenna plus moderate RF losses in cables, etc., gives about a 2 km video link range when using a video feed viewer with 10 dBiC antenna gain and -85 dBm receiver sensitivity.  This is pretty good range of operation, but exploitable.  

Let's see what a product we offer could do to detect this video stream and at what distance.  Aaronia's Drone Detection System (DDS) is a very capable scanning antenna array and sensitive real-time spectrum analyzer to perform long range detection of drone and operator RF signals, isolating them to a particular sector.

Drone Detection System with RF Command Center.png

Its 6 dBi LPDA antennas are arrayed in a circle and switched by a fast multiplexer to a real-time spectrum analyzer (RTSA) with a -105 dBm receiver sensitivity.   

Focusing on the electronics and antennas of the drone operator's video receiver and the DDS, even giving up 7 dBi in the DDS antennas compared to the video receiver's high gain helical antenna (10 dBiC - {6dBi - 3 dBi CtoL}), the RTSA's superior sensitivity leaves a net increase of 13 dB in signal measurement, which translates to a detection range of at least ten times farther than the range of the operator's inferior video receiver (assuming the DDS receiver is operating above the local noise floor).  That's more than plenty of stand-off range.   

Performing similar analysis on the 2.4 GHz remote controller link shows a lower detection range limit as the video stream, but still at least five times the drone control range.  So our Drone Detection System is an effective means to inform and protect you and your crew from drone threats.  FYI, using multiple DDS systems networked together gives the ability to triangulate and geolocate these signals quite well. 

The bottom line and key enabler of drone detection at safe standoff ranges boils down to receiver sensitivity plus a really nice DDS system to provide line of bearing and a user interface to effectively interpret the collected information.  

Anyway, when choosing the right antenna for your system, try out our Customer Attuned Collaboration process, designed to produce successful outcomes through consideration of real-world use cases and system specifications to optimize the selection of components.   Let’s chat to assure the best solution for you.  

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Topics: Measurement, Announcement, Learning