Before we begin our description of an anti-drone system, I have two questions:

The disadvantages of RF detection:

1. Signal encryption is difficult to crack
2. Vulnerable to electromagnetic interference
3. The FPV is difficult to locate

Radar Detection

What is phased array radar:

Phased-array radar is phase-controlled electronically scanned array radar. Its ability of fast and precise beam conversion enables the radar to complete the scanning of the whole space within 1 minute. The so-called phased array radar is a radar array composed of a large number of identical radiation elements. Each radiation element is independently controlled by the wave controller and phase shifter in phase and amplitude, which can obtain accurate and predictable radiation pattern and beam direction.

The anti-Uas radar mainly detects “low small slow” targets, often using X and Ku band, and synthesizes dual-polarization fully coherent, intelligent radar data processing, multi-source data fusion and other technologies, which can realize all-weather, active, multi-target and fine detection of “low and small slow targets” + “low altitude micro-meteorological” targets.

The advantages of radar detection:

1. Fast scanning speed, flexible and controllable beam
2. Long detection range
3. The target capacity is large, and hundreds of targets can be monitored and tracked simultaneously in the airspace
4. Strong anti-interference capability
5. Strong adaptability to complex target environment
6. High reliability

The disadvantages of radar detection:

1. High cost
2. Equipment is complex
3. There are blind spots at close range
4. The beam scanning range is limited

Electron Optic Tracking System(EOTS)

What is electron optic tracking system:

Optoelectronic identification and tracking equipment combines visible light and infrared imaging technology, collects the optical information of the target through the optical system, and converts it into electrical signals for processing and analysis, so as to realize the rapid and accurate identification and tracking of the target.

The advantages of electron optic tracking system:

1. High definition camera, high precision
2. Strong object recognition ability
3. Real-time image transmission
4. Automatic target tracking

The disadvantages of electron optic tracking system:

1. Affected by the environment
2. Technical sophistication
3. Strong hardware dependency
4. Optical cameras are more expensive

Counter System

After detecting the drone through the detection system, it is necessary to solve the problem of how to defend the drone. The ways to defend Uavs are usually divided into two main categories, namely soft kill and hard kill. Soft kill is mainly achieved through electronic technology, while hard kill uses physical destruction. At present, the most common is soft-kill technology, because it is better cost performance and less difficult to implement. Soft kill technology applies electromagnetic wave technology to interfere with the remote control signal and video transmission signal of UAV by transmitting the same frequency signal. The technology was first used in drone jamming devices, and then spawned into drone spoofing devices.The market is flooded with drone jamming devices, and let’s discuss this one first. Then, let’s look at drone decoy devices.

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What is the drone jammer:

Using high-frequency electromagnetic wave technology, the electromagnetic wave is transmitted in the same frequency band as the UAV communication band, which interferes with the UAV receiving instructions on the remote control, resulting in the UAV being unable to parse instructions and video signals on the remote control normally, thus losing control and returning or landing according to the preset procedure.

Usually, we classify jammers into several categories according to their structure, namely stationary jammers, backpack jammers, and handheld jammers. Below I have listed a few images that correspond to each of these types.

You need to decide which structure of the interference device to choose according to your specific use case.

The advantages of drone jammer:

1. The price is cheap. High cost performance
2. It can cover multiple communication frequency bands
3. Jamming multiple targets simultaneously

The disadvantages of drone jammer:

1. The interference distance is limited
2. High equipment power
3. No direct damage is caused to the drone, which can only force the droneto return to its departure point or land safely in place.

Drone Spoofer

What is the drone spoofer:

By sending misleading GPS signals, the drone can not accurately obtain position information, resulting in its positioning offset or loss of navigation ability.

The market is mainly stationary spoofing equipment and portable spoofing equipment. There is not much difference in the structure of the GNSS spoof device, what we need to be concerned about is that it covers the signals of several satellite positioning systems. We know the mainstream of the four major global positioning systems: GPS, Beidou, Galileo, Glonass. In general, we need signals from all four systems. Because common Uavs have at least two GNSS locators, many of DJI’s Uavs, for example, may have three or even four locators. So in order to be foolproof, it’s best that our spoofing device covers all 4 major GNSS.

The advantages of drone spoofer:

1. Low device power consumption
2. It can directly affect the flight of the drone, and even cause the droneto crash.
3. The coverage is larger than that of jammer

The disadvantages of drone spoofer:

1. The price is relatively more expensive than jammer
2. Unable to cope with dronewithout GNSS capabilities
3. It affects the GNSS functionality of all devices in the area

How to Choose a Jammer

Currently, there are many different jammers on the market. However, according to the structure of the equipment, it can be divided into three categories, respectively, stationary jammer, backpack jammer, and handheld jammer. You need to choose the right type for different use cases. Stationary jammer used for installation in outdoor use, to establish a station defense area, can be used for a long time. However, backpack jammers and handheld jammers are usually used when performing temporary tasks and cannot be used for a long time, and the working time is limited by the battery life.  In addition, from the antenna of the interference device can be divided into omnidirectional interference and directional interference.  Under a specific design, directional jamming can also achieve 360° omnidirectional jamming. What you need to know is that the directional jamming distance will be better than the omnidirectional jamming distance. The advantage of omnidirectional jamming is that the signal is transmitted at 360°.  The above mainly analyzes the related characteristics of the jammer from the structure, and then I will introduce some key performances of the jammer from the technical point of view.

There are two key parameters here:

• Frequency(It refers to the frequency range of the interfering signal emitted by the device)
• Power(It refers to the power of the interfering signal transmitted by the device)

The operating frequency of the device is determined by the communication frequency of the drone. There are two links for UAV communication, one is the remote control signal link, and the other is the video transmission signal link. These two signal bands are the ultimate targets of jamming devices. Common UAV communication frequencies: 868M, 915M, 1.5G, 2.4G, 5.2G, 5.8G. To cope with interfering devices, some FPV use very rare signal bands, such as 1.2G and 3.3G. These frequencies are the frequencies that jamming devices need to use. 

Now let’s look at anther parameter – Power. Signal power is often related to our other important performance, which is the jamming distance. Obviously, the larger the power, the farther the signal travels. At present, common power values such as 10W, 20W, 50W, 100W. 20W is commonly used in jamming guns, 50W and 100W are commonly used in stationary jamming equipment. It might be different in practice, but it’s a common occurrence. Because the large power requirements for the power supply will be higher, will undoubtedly bring more volume and heavier weight. So, if you want more interference range, you need more signal power. In addition, different interference ranges are obtained by using omnidirectional and directional antennas.

In general, the signal gain of directional antennas is between 10 and 16db, while the gain of omnidirectional antennas is between 2 and 6db. But the beam Angle range of directional antennas is limited and may be less than 90°. However, the signal radiation of omnidirectional antenna is 360° in the horizontal direction. It’s more of a performance tradeoff, distance for Angle. From the energy point of view, it follows the conservation of energy. Of course, we can use technology to send directional signals in a 360° direction.

Omni-directional antenna beam

Directional antenna beam

By analyzing the above 2 key parameters, I think we can clearly understand what kind of jammer we need. For example, say you spot an unauthorized DJI drone within 500 meters and want to temporarily disrupt it. We can easily check that the communication frequency of DJI UAV is 2.4G and 5.8G, and 5.2G is also used in some areas. GPS positioning is often 1.5G. The jamming gun uses a directional jamming mode, and usually 20W of high-frequency signal power can effectively interfere to a distance of 500 to 1000 meters. So, all you need is a jamming gun containing 1.5G,2.4G,5.2G,5.8G, and 20W signal power for a single channel. It’s possible that the DJI drones in your area are not using the 5.2G frequency. You can also get rid of it, so you can save some money. This is the simplest example, but the reality is that it’s much more complicated, so most people choose to cover as much bands as possible. 

It is important to know that the interference distance described by many sellers is usually the limit distance determined by the ideal environment. However, in reality, the interference distance involves many factors, such as the natural environment, the electromagnetic environment, the fuselage direction of the UAV, the signal transmission route from the remote control to the UAV, and so on. Let’s look at the plot of the distance between the device signal and the drone and the distance between the remote control and the drone to understand the concept of interference distance more clearly.

At point Q, the strength of the drone signal and the device signal are equal, when the device is 1000 meters away from the drone. Within a distance of less than 1000 meters from D, the signal strength of the device is higher than that of the drone, that is, the signal of the drone is suppressed in this area. When D starts to increase, the device signal becomes weaker, while the distance between the drone and the remote control becomes closer, and the signal strength of the UAV is stronger. At this point, the drone signal cannot be suppressed and the drone cannot be interfered. If the departure point of the drone is farther away, the Q point position will move to the right, meaning that the device interference distance will increase. So usually the interference distance given is either a range or an extreme value.

By understanding the above, I believe you have been able to choose a suitable jamming device.