How does a RF sensor work?
An RF sensor works by passively listening to the Radio Frequency spectrums in which drones communicate with their controller. The most common bands of communication are the 2.4 GHz and the 5.8 GHz bands. These are the bands used by a lot of drones on the market including DJI drones. Other bands like the 1.2 GHz, 1.3 GHz and a few others are also used in the drone industry to communicate between the drone and it’s controller.
A RF sensor passively listens for signals in these bandwidths. Once it detects a communication protocol, it references it to a database of communication protocols to identify the signals generated by a drone and it’s controller.
What is a RF Communication Protocol?
A RF Communication Protocol are the sequence of data packets that are sent back and forth in order for a drone to communicate with it’s controller. Data about where an operator wants to fly the drone (go left, go right) etc is sent through the protocol. In addition, there are various types of data that are encoded and sent through the protocol. Live video feeds from the camera, GPS location of the drone, altitude data, speed data, usually all data considered flight telemetry is being communicated back and forth over the RF spectrum.
Types of RF Sensors.
There are two categories of RF sensors that can be used to detect drones. Both passively listen to the RF Communication protocols. The first decodes the protocol to read all the data that is being sent back and forth. This sensor is able to give exact GPS co-ordinates, altitude and speed data, because it is decoding and reading it from the protocol. Decoding/hacking communication protocols is illegal in the United States and many other countries, so the use of sensors that decode is not viable. There is one exception, which is the DJI Aeroscope sensor.
DJI Aeroscope
DJI Aeroscope sensor works by decoding the information for only DJI brand drones. Because DJI is the drone manufacturer, they have control over the encryption of communication, and can legally decode the signal to detect and track only DJI brand drones.
Therefore, by using DJI Aeroscope, security teams can detect and track all DJI drones, and get accurate information like drone GPS location, pilot GPS location, altitude, speed etc.
Other RF Sensors
The second type of RF sensor identifies the pattern of the communication protocol. This type of sensor maintains an extensive database (usually obtained through testing) of all the drone makes and models and their RF Signatures. When a RF drone communication pattern is observed by the sensor, it is compared with the database and based on the signature, the right drone make and model is identified.
The advantages of this type of sensor is that they are not restricted to any one brand, and can identify any drone make and model, provided it’s categorized in the database.
The disadvantage of this sensor is that it only provides directional detection of a drone. Based on the signal strength observed by the sensor, it can give a general sense of direction (usually a 45 degree angle) and a general sense of distance from the sensor within that angle.
The directional tracking can be made more accurate by installing multiple RF sensors at various locations and triangulating the signal strength observed by them.
What drone information can a RF sensor provide?
DJI Aeroscope provides the following drone information:
- Drone GPS Location
- Pilot GPS Location (in some cases - Pilot needs to be connected to DJI App)
- Drone Make & Model
- Altitude & Speed
- Real Time Tracking (location updated every 2 seconds).
- Unique Drone ID Number
The second type of sensor only provides the following information:
- Drone Make & Model
- Directional Detection (Angle & Distance from Sensor)
- Real-Time Directional Tracking (Angle & Distance update as drone is flying in real time).
- Unique MAC address for WIFI drones
How far can a RF Sensor detect a drone?
A DJI Aeroscope can detect a drone up to 20 miles away, based on the sensor antenna configuration. Since DJI Aeroscope only tracks DJI drones, the exact frequencies are known to the manufacturer and the sensor antennas are fine tuned to only listen for those frequencies. This allows DJI Aeroscope to detect a drone over a large range.
The second type of RF sensors have to passively listen to all types of RF frequencies and compare them against a database. Because of this the second type of RF sensors can only detect a drone up 3 miles based on configuration.
Does an RF sensor give 360 degree coverage?
Yes, an RF sensor is omnidirectional. Unlike radar, an RF sensor is not emitting any signals. So it can listen to frequencies in all directions and detect a drone within it’s range.
Do RF sensors cause interference with other sensitive equipment?
No. Since RF sensors are passive and don’t emit any signals, they don’t interfere with any other communication devices or other sensitive devices.
How does the surrounding environment affect the use of RF sensors?
RF sensors work the best when there is little interference like over an open field. Urban settings where there are a lot of buildings and metal parts cause RF to bounce and provide incorrect information. For example, a drone between 2 buildings won’t be detected, because the signal is not making it’s way to the RF sensor. In this case, multiple RF sensors need to be installed to ensure proper coverage.
Our airspace security experts conduct a thorough walk-through and RF survey of your facility to identify blind spots and suggest the ideal places to install RF sensors to ensure maximum coverage.
How will the implementation of Remote ID help with RF drone detection?
The technology that DJI Aeroscope uses is very similar to the proposed Remote ID for drones. DJI Aeroscope cannot decode the protocol for other drone makes, but have made their protocol open to other manufacturers. If another drone manufacturer uses a DJI protocol, that drone will be detected by Aeroscope. Remote ID will work similarly. All drone manufactures will have to follow a common drone protocol to encrypt certain information like drone location, that will be known and can be legally decoded by the RF sensor. Once implemented, Remote ID will allow all RF sensors to behave like Aeroscope where accurate drone location is detected for all drone makes and models as compared to today’s directional detection capabilities.
