在我們開始描述反無人機系統之前，我有兩個問題：

障礙的優點 射頻 偵測:

1. 訊號加密難以破解
2. 易受電磁干擾
3. FPV 難以定位

雷達偵測

什麼是 相控陣雷達：

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.

反 Uas 雷達主要探測 「低小慢 」目標，常使用 X、Ku 波段，綜合雙極化全相干、智能雷達資料處理、多源資料融合等技術，可實現全天候、主動化、多目標、精細化探測 「低小慢目標 」+「低空微氣象 」目標。

a的優點 radar偵測:

1. 掃描速度快，光束靈活可控
2. 偵測範圍遠
3. 目標容量大，可在空域中同時監控和追蹤數百個目標
4. 強大的抗干擾能力
5. 對複雜的目標環境有很強的適應能力
6. 高可靠性

障礙的優點 radar偵測:

1. 高成本
2. 設備複雜
3. 近距離有盲點
4. 光束掃描範圍有限

電子光學追蹤系統 (EOTS)

什麼是電子光學追蹤系統：

光電辨識追蹤設備結合了可見光和紅外成像技術，通過光學系統收集目標的光學信息，並將其轉換成電信號進行處理和分析，從而實現對目標快速、準確的辨識和追蹤。

a的優點 電子光學追蹤系統：

1. 高畫質攝影機、高精度
2. 強大的物件辨識能力
3. 即時影像傳輸
4. 自動追蹤目標

障礙的優點 電子光學追蹤系統：

1. 受環境影響
2. 技術複雜性
3. 強硬體依賴性
4. 光學攝影機較昂貴

計數器系統

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.

無人機干擾器

什麼是無人機干擾器：

利用高頻電磁波技術，將電磁波傳送至與UAV通訊頻段相同的頻段，干擾UAV接收遙控器上的指令，導致UAV無法正常解析遙控器上的指令及影像訊號，進而失去控制，並依預設程序返航或降落。

通常，我們會根據干擾器的結構將其分成幾類，即固定式干擾器、背包式干擾器和手持式干擾器。以下我列出了幾張與這些類型相對應的圖片。

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

a的優點 無人機干擾器：

1. 價格便宜。性價比高
2. 可涵蓋多個通訊頻段
3. 同時干擾多個目標

障礙的優點 無人機干擾器：

1. 干擾距離有限
2. 設備功率高
3. 不會對無人機造成直接損害，只能迫使無人機返回出發點或安全降落在原地。

Drone Spoofer

什麼是 drone spoofer：

藉由傳送誤導的 GPS 訊號，無人機無法準確取得位置資訊，導致其定位偏移或失去導航能力。

市場上主要有固定式的spoofing設備和可攜式的spoofing設備。全球衛星定位系統(GNSS)偽裝設備在結構上並沒有太大的差異，我們需要關注的是它涵蓋了幾種衛星定位系統的訊號。我們知道全球四大定位系統的主流：GPS、Beidou、Galileo、Glonass。一般而言，我們需要這四個系統的訊號。因為一般的 Uav 至少有兩個 GNSS 定位器，以 DJI 的 Uav 為例，很多可能有三個甚至四個定位器。因此，為了做到萬無一失，我們的欺騙裝置最好能涵蓋所有四種主要的 GNSS。

a的優點 drone spoofer：

1. 裝置功耗低
2. 它會直接影響無人機的飛行，甚至導致無人機墜毀。
3. 覆蓋範圍大於干擾器

障礙的優點 drone spoofer：

1. 價格相較於干擾器更貴
2. 無法應付無 GNSS 功能的無人機
3. 它會影響區內所有裝置的 GNSS 功能

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.