Radar technology has been widely adopted in anti-drone solutions for effectively tracking the target trajectory. For anti-drone applications, the key is to use high-resolution radar to detect small drones with RCS of around 0.01 m² within typical distance. Many radars, such as pulse radars, have been designed to detect large metal objects like airplanes and helicopters, which are not suitable for detecting objects with small RCS, low flying height, and slow flying speed. For evaluating anti-drone solutions, the following factors shall be considered.
Filtering out Ground Clutter Waves: Ground clutter waves will interfere with radar detection. Furthermore, objects such as trees and buildings will cause large-area false reflection which could overwhelm the drone signal reflection. Advanced radars will apply various technologies to filter out these clutter waves.
Azimuth Angle Coverage: The azimuth angle is the horizontal coverage angle of the radar. A typical coverage range is from 60° to 120°. Multiple radars could be deployed for a large-angle coverage, even 360° coverage. Single set of ND-BU001, ND-BU002 or ND-BU003 could achieve 360° all-round coverage.
Pitch Angle: The pitch angle is easily overlooked when evaluating anti-drone solutions. In the market, many radars have very narrow pitch angles (between 10°~30°), which will cause huge blind zone out of the pitch coverage. Although a 90-degree vertical coverage is usually not necessary, the ideal pitch angle for detection shall be around 40°~80°. The pitch angle coverage of both ND-BU001 and ND-BU002 have reached the ideal range.
2D and 3D: Compared to 2D radars, 3D radars have several advantages, of which the most notable is that altitude information of detected drones can be achieved. With this function, 3D radars could reduce clutter waves by filtering objects above a certain height, which will eliminate false alarms. Both ND-BU001 and ND-BU002 adopt 3D radar technology for powerful functions.
Frequency Bands: Anti-drone radar bands include X-band (also commonly used on ships), K-band (originally used for self-driving vehicles, while suitable for anti-drone solutions), Ku-band, and S-band (compatible with military deployments). The size of the radar also depends on the bands used. For example, usually the size of the K-band radar is smaller.
Mobile/Fixed Panel: Generally, the fewer moving part the better the radar. Because this can reduce the possibility of wear and damage. Some radars can be used in both “gaze” and rotation modes. Gaze mode provides better detection and tracking performance, while the coverage angle is less than that of rotation mode.
Besides, mainstream radar technology methods for drone detection include pulse (active), continuous wave (active), and passive mode. Each method has its own characteristics with advantages and disadvantages.
Active Radar-Pulse: The radar transmits a very short but high-power pulse, and waits for the reflected echo pulse from the target. The reduction in the time window between the transmitting pulse and echo pulse will affect the performance. The narrower the pulse width, the higher the distance resolution. Pulse radars could provide instantaneous high-power output, as such, they are generally designed for long-distance detection.
Active Radar-Continuous Wave: The radar continuously transmits radio frequency signals and receives the reflected echo simultaneously. Influenced by Doppler effect, the receiver could calculate the speed and trajectory of the target by measuring the frequency shift. The continuous wave radar can’t calculate distance without timing reference in the transmitting signal. Both ND-BU001 and ND-BU002 adopt active continuous-wave radars, specifically for detecting small-size drones with low speed at low altitude.
Passive Radar: The passive radar detects targets within the receiving area by using existing environmental broadcast, communication signals, or radio navigation signals. The transmitter and receiver are located at different locations, while the user can only control the receiver. Potential transmitting signals used for drone detection include FM, DVB, GSM, GNSS, and Wi-Fi. The passive radar is quite attractive to end users who prefer non-transmitting equipment, as its detection operation won’t be easily noticed or interfered. Equipped with passive radar technology, ND-BU003 has obvious advantages in performance and price.
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