Necessity of Anti-Drone systems (by Signalian)
Drones have gained attention as a threat to safety and security since their entrance into civilian technology, which has fueled the development of anti-drone (or counter drone) technologies. Drones are a broad category of vehicles that do not only include the popular recreational quadcopters that are constantly seen on television, but also vehicles such as hobby RC cars and unmanned military helicopters. UAVs are part of the UAS - unmanned aerial system. The UAS includes not only the UAV, but the physical controller, human operator, and even any satellites or computers needed for advanced processes; it is the whole system needed to complete the operation of the UAV.
Anti-drone systems are designed to protect against drone accidents or terrorism, but they will need to evolve in order to deal with future drone flight systems . UAVs have been used in a variety of military actions. Non-military UAVs have been accused of endangering airplanes, as well as persons and property on the ground. Due to the potential of an ingested drone to quickly damage an aircraft engine, safety concerns have been raised. Multiple near-misses and verified collisions have occurred involving hobbyist UAV pilots operating when violating the aviation safety standards. It is expected that unmanned aircraft systems (UAS) will be used increasingly for malicious purposes as they can carry cameras, weapons, toxic chemicals and explosives and are being used increasingly for terrorism, espionage and smuggling purposes.
Common Reasons of Drone incidents
1. Negligence
Individuals who are oblivious to or are unaware of the appropriate regulations and constraints. As a Result, they fly their drones across sensitive or forbidden terrain. They have a “clueless” thinking while having no intention of disrupting regular Aviation and its operations.
2. Gross negligence
a. Individuals who are reckless because they are aware of the appropriate regulations and constraints yet choose to break them for personal or professional advantage (e.g., aggressive spotters). Their actions can be described as “reckless”, as they disrupt civil aviation while completely ignoring the implications of their conduct.
b. Individuals who intentionally st rive to use drones to disrupt aerodromes and flight operations, regardless of whether they are aware of the applicable legislation and limits. These individuals may even act as a group to maximize their impact. While their actions may have unexpected repercussions for aviation safety, they do not seek to put human lives in jeopardy.
3. Criminal/terrorist motivation
Criminals and terrorists are persons who intentionally strive to utilize drones to interfere with the safety and security of civil aviation, regardless of whether they are aware of the applicable legislation and limits. These persons should be considered criminally motivated or even terrorists because their actions are purposeful and show no concern for human lives and property.
Drone detection Systems
Modern detection solutions guarantee a certain level of drone detection accuracy by integrating multiple detection systems. Each methodology has performance limitations in terms of detection range, functionality, weather dependency, etc. Drone detection exploits various features of flying drone. Drones commonly emit heat, sound, and RF signals to communicate with the remote operator. Detection system collects sensor data to confirm the presence of drones in nearby areas. Depending on the measure, it can specify the drones’ expected location.
1. Radio Frequency Systems
System : RF receiver
Advantages:
1. Capturing the communication spectrum and signals UAV and operators.
2. Low complexity and easy to implement
3. Could operate in all weather and day/night conditions
4. Easier to improve due to modular implementation of receivers and digital signal processing units used in implementation
5. Possibility to locate the pilot
6.
Disadvantages
1. Knowledge regarding UAV communication specifications (e.g., frequency bands, modulations, etc.) is required.
2. Difficult to accurately determine AoA
3. Difficult to use in urban areas due to fading and multipath phenomena
4. Vulnerable to malicious or illegal modified RF that will exceed receiver capabilities.
5. Unable to detect Autonomous flight.
Detection range : 3 km to 50 km.
The main disadvantage is the fact that with the help of radio frequency it is not possible to intercept drones that do not communicate with the pilot, on the other hand, there are currently very few such drones. Extensive use of the 2.4, 5, and 5.8 GHz bands is also a problem in densely populated areas, which can make it more difficult to identify drones. Some drones use directional antennas, which makes them virtually undetectable from the wrong direction. RF scanner detects the drones by signal analysis, drones using unknown control protocols or different frequency bands are challenging to detect. The advantage of this method is the fact that the systems do not have to transmit any signal, the device must be equipped only with a passive high-frequency signal sensor. This makes the construction of these devices simpler. Another significant advantage is that the systems can also locate the pilot who controls the drones.
2. Infrared radiation (HEAT)
System : Infrared Camera (IR Cam)
Advantages:
1. Covers all of the visible and IR spectrum (3 MHz–300 GHz)
2. IR cameras could operate in cloudy weather and in day or night
3. Could be assisted by computer-vision technologies
Disadvantages:
1. Provides 2D images
2. Limited performances by weather conditions and background temperature
3. Dependent on geo-reference data
4. LoS is required
5. Lower Accuracy
Detection range : 1 km to 15 km.
The main advantage of these systems are low acquisition costs, small size, and very low maintenance. Another advantage is that the cameras provide the same quality performance regardless of the weather, such as temperature or precipitation. On the other hand, drone detection depends very much on how much heat the drone produces, as many drone models are made of plastic and equipped with electric motors, in which case the device is more likely to detect a bird than a drone. Likewise, the resolution of a thermal camera is usually relatively limited, so small drones at greater distances may not always be detected.
3. Optical Systems
System : Optical camera
Advantages:
1. Low cost and less regulatory limitations
2. Miniaturized Identification
Disadvantages
1. Highly affected by the weather
2. Vulnerable to obstacles
3. Low range
Detection range : 0.5 km to 3 km.
The main disadvantage of these systems is poor detection in case of bad weather (dark and foggy conditions). Other disadvantages include the difficulty of determining the speed and distance of the drone when moving towards the camera. Good lens maintenance on the camera is also essential to keep it clean and functional. The whole system is also performance-intensive, as it must be very fast to be able to have a larger range. The advantage is that it is possible to use already developed and deployed cameras, which can also have a long-range thanks to high-quality optical zoom.
4. RADAR
System : Tx/Rx Antenna
Advantages:
1. Long ranges
2. Determines UAV shape, distance, speed, and direction.
3. 2D (PESA) and 3D (AESA) modes
4. Constant observability
Disadvantages
1. system detects the presence of small, unmanned aircraft according to their radar signature (low RCS)
2. Cannot distinguish a drone from obstacles if the drone hovers in one position or flies at low speed
3. Interference causes degradation
Detection range : 0.5 km to 3 km.
The main disadvantage of conventional radar systems is the fact that they are not suitable for detecting small drones, especially when the drone is moving slowly or when flying at low altitudes or hovering on the spot. In addition, the dimensions of the drone and the way the drones move are very difficult for radars to differ from the movement of birds. Radars must also emit high-energy radiation for successful detection, which can be dangerous to health, which means that the use of radar in densely populated areas is inappropriate. Among the advantages could be the fact that if the radar is used in an environment where there are very few obstacles, it can detect drones over long distances. Unlike radio frequency detection, the radar is also able to identify the drone even if the drones do not communicate with the pilot and are completely autonomous in their motion. The advantage is the fact that the detection of drones by radar is possible in bad weather or light conditions.
5. SOUND
System : Acoustic receiver
Advantages:
1. Covers the spectrum of 20 Hz–20 kHz
2. Acoustic signature library could be updated easily from flight to flight
3. Lightweight and can be easily associated with other types of sensors.
4. Compatible with RF based sensors.
Disadvantages
1. Limited range
2. Vulnerable to ambient noise
3. Susceptible to decoys
4. Low accuracy
5. high signal detection complexity
Detection range : Less than 0.2 km
Sound detection systems probably have the most disadvantages of all the systems described. Their disadvantages are, for example, the high cost of many expensive microphones, short-range or the fact that they are very affected by weather and especially wind. The slowness of the whole system is also a big drawback, as the speed of sound is low, and the drone can fly a relatively long distance before the sound reaches the remote sensor. Another negative is the fact that most drones are already very quiet, and their development is moving towards less and less noisy models, and conversely, some (mostly urban) environments are very noisy, which continues to make detection difficult. On the contrary, the advantage is rather small. Sound detection can also detect drones that do not communicate with the pilot, as well as drones that are not at the exemplary angle of the device because sound can bypass some obstacles.
6. Hybrid Systems
Radar + Optical (vision)
Radar and optical (or thermal) cameras provide excellent complement-arity for drone detection. Vision based detection can easily track drones by controlling image zoom, tilt, and focus, but struggles with dynamic control over the target area; whereas radar detection provides omni directional wide area scanning with low drone identification and low scan frequency. Thus, radar scans the target area, and vision system controls external and internal camera parameters to accurately investigate suspicious points. This combination dynamically compensates for each other’s flaws, and hence many vendors adopt this structure.
Multiple RF scanners.
RF scanners can detect drones and additional information (type, control commands, and so on), but not always their location. If the drones are controlled only by pulse position modulation (PPM) or pulse width modulation (PWM) messages, they may not emit location information on an RF channel. Since RF scanners are generally cheaper than equivalent coverage of radar systems, some vendors dominantly use multiple RF scanners instead of radar.
Sound (acoustic) + Optical (Vision)
Combining vision and acoustic sensors is a traditional sensor fusion technique to improve detection accuracy. Vision based detection struggles to distinguish unfamiliar drone shapes, and acoustic based detection achieves low performance in noisy environments. The complementary design is effective in terms of weather resilience, environmental resilience, and detection accuracy, hence products commonly employ this design.
NEUTRALIZING / DESTROYING The Drone
Drone neutralization schemes exploit various drone features, including flight mechanisms and communication systems. Neutralization methods can be mainly classified as destructive or nondestructive. However, most non-destructive methods may be quickly obsolete due to robust drone security and navigation solutions. Although drone jamming remains the most popular choice for current systems, its inherent aggressiveness and anti- jamming developments strongly suggest the necessity for alternative approaches. Geofencing for drones may prevent unintended accidents from legitimately authorized drones, but deliberate attacks may need to be defended physically, e.g. killer drones or drone capture.
In summary, anti-drone systems should include multiple neutralization solutions and utilize them appropriately to improve defense reliability. Specially, destructive and non-destructive methods should be separately treated in system design, and must be carefully selected
1. Electromagnetic pulse (EMP)
Its a beam generated with the goal to damage the internal electronics of the target drone.
Pros
1. Could burn or interfere with the internal electronics of the drone disrupting its operation.
2. Could operate in both narrow band and wide band domains.
Cons
1. Accurate direction of jamming is necessary
2. Difficult to know the effectiveness of jamming
2. Interceptor drones
An Interceptor drone or collision Drone is a drone used to force the target drone to land or return home.
Pros
1. Searching and tracking capabilities
2. Could carry weapons and ammunition.
Cons
1. Requires a relatively close approach to the target
2. Can have a considerable delay to launch
3. Laser
Lasers are directed rays used to destroy the target or blind the camera, a dazzler
Pros
1. Could operate at low powers (dazzlers) to blind the UAVs cameras or high power, which could burn/destroy the target
2. Easy to track the target
3. Cheaper and safer than projectiles or another physical countermeasure.
Cons
1. Sensitive to weather conditions
2. It is necessary to have an accurate measurement of the target’s position;
3. High power lasers could interfere with other systems.
4. Magnetic
Magnetics are use powerful magnets in order to create a magnetic field around a protected area
Pros
1. Cost effective
2. Could respond to multiple threats.
Cons
1. Small protected area
2. Could interfere with other systems
5. Prey birds
Eagles or falcons specially trained to attack the enemy’s drone [
Pros
1.Does not require complex technology.
2. Fewer humans are required
Cons
1. Applicable only to slower and small UAVs.
2. Could harm the falcons
6. Weapons/Projectiles/shooting nets/water cannons
Shooting nets—a net is launched towards the target drone to prevent the propellers from rotating
Projectiles—large-caliber ammunition used to destroy the target
Missiles—conventional ammunition, could be guided or unguided
Guns—conventional weapons and ammunition
Water cannons—a stream of water is directed towards the target drone
Pros
1. Effective against any type of UAV
2. Work in all weather conditions
3. Quick reaction method, mobile.
Cons
1. Might cause collateral damage
2. High costs but Confirmatory destruction
3. Requires professionally trained operators
7. RF/GNSS jamming
To disrupt the communication of the target drone with the control station and/or global navigation satellite system (GNSS)
Pros
1. Could neutralize grouped targets simultaneously, degrading their received signal-to-noise ratio (SNR
2. GNSS frequencies and bands are widely known and relatively easy to jam
3. The directivity diagram of the jamming signal can be oriented and directed as desired.
Cons
1. Ineffective against autonomous UAVs
2. Ineffective against drones that use inertial navigation systems/sensors (INS)
3. Ineffective against UAVs that use encrypted communications
4. Effective only for short distances
5. The jamming could interfere with other sensible equipment.
8. Spoofing
Spoofing are decoys the drone by using imitation GNSS and control signals in order to take over the command
Pros
1. DSP and AI algorithms could copy and reproduce the control communication signal with high accuracy in a relatively short time;
2. Could exploit the vulnerabilities of various systems of UAVs.
Cons
1. It is necessary to have a consistent analysis of the targeted UAVs regarding their operational frequencies
2. Spectrum sensing systems are desirable.
9. Hijacking to capture
Hijacking a drone to take control and land it for capture
Pros
1.Enable safe landing
2. Available for follow-up investigation
3. Ground and aerial solutions available
Cons
1. Only available for drones using known protocols
2. Difficult to target and hit
3. Possible damage during landing/crush
References:
1. Drone Detection and Defense Systems: Survey and a Software-Defined Radio-Based Solution by Florin-Lucian Chiper, Alexandru Martian * , Calin Vladeanu , Ion Marghescu, Razvan Craciunescu and Octavian Fratu.
2. Survey on Anti-Drone Systems: Components, Designs, and Challenges Seongjoon Park, (Graduate student member, IEEE), Hyeong Tae Kim, Sangmin Lee, Hyeontae Joo, and Hwangnam Kim, (Member, IEEE)
3. Anti-drone systems in Journal of Global Science.
