It is often heard that fighters are locked by radar in news and television. As long as a fighter is locked by a radar, more radar will lock the fighter according to the information provided by the locked radar, which means once it is found, it is basically impossible to run away. What kind of experience would it be if radar technology were applied to security area to lock ground targets? Will it not be able to run away after locking? What kind of technology is this?
Principles of radar detection target
● Principle of radar range measurement
The signal transmitted by the radar transmitting antenna passes through space to the target point, and then reflects from the target to the radar receiving antenna. Its propagation time delay ，is distance of the target，is the propagation speed of electromagnetic wave in space.After mixing the received signal, a single frequency signal can be obtained. Its frequency expression is，is bandwidth，is frequency modulation period，Time delay( ) can be obtained by estimating the frequency of the received signal.Finally, the detection target distance can be obtained.
● Principle of radar velocity measurement
The target has a certain speed, which caused Doppler frequency.Its expression is ，whichis the target relative to the radar radial velocity，is electromagnetic wave wavelength. The durationof each pulse is relatively small, and the distance between adjacent pulses can be regarded as unchanged. Because of the existence of the target Doppler frequency, the phase of the target echo frequency received at each time has a certain change. According to the change rules, the Doppler frequency of the target can be measured, which obtain the velocity of the target. the sketch map of the 4 adjacent target echoes is given in the following figure.
● Principle of radar angle measurement
Compared with the target echo signal received by element 1 in the array antenna, for a certain distant (far field) target, the signal of element 2 propagates a longer distance. Since the distance is much smaller than the target distance, it is only cause the phase difference between the received signals of the two elements.
The path length of the received signal in element 2 is ，whichis the target signal.The propagation time required for this length is，For narrow-band signals(The transmitting signal bandwidth is much smaller than the signal frequency), the time delay of the same frequency corresponds to the difference of phase. The angle of the targetcan be measured by solving the phase difference between the two elements.
How does NSR300WVF lock multiple targets simultaneously?
Multiple targets will be detected at the detection end, and the distribution of targets may occur randomly, with different distances. There are targets with different speeds at the same distance (such as T7 and T8) and targets with different angles at the same distance (such as T4 and T5). meanwhile, false targets may appear at the detection end. It is a single frame detection, there are some differences between the true value and detection quantity of the distance, speed and angle of the target, so the real information of the target can not be directly taken as a single detection value.
For a single detection of the target information, it is necessary to match from the point to the trajectory, the detection point 'belongs' to the real target. This process need use the current information and previous track information. As shown in the following figure, the blue point is the target moves trajectory. Assuming that two dots N1 and N2 are currently detected, N1 can be determined as the current detection point of the trajectory by certain matching rules.
There are some errors in the detection, so it is necessary to smoothly filter the detected target information to reflect the real trajectory of the target, and it needs to be further judged whether the detected target is the real target or not. Therefore, the number of targets detected will be far greater than the target output.
After signal processing such as detection, matching and filtering, the real target trajectory can be displayed on the user interface. If there are multiple targets in the radar monitoring area, the ability to distinguish different targets can be achieved for the difference of distance, velocity or angle information between the targets, and radar can monitor any distinguishable target in the whole area theoretically. Due to the limitation of system parameter design and hardware calculation time, the maximum target tracking number of radar will be reduced.
Components of Nanoradar NSR300WVF system：
● Radar：24GHz-ISM-Band radar of FMCW modulation mode. It actively emits an electromagnetic beam at a speed of 8 times per second, and receives reflected echoes from the target to detect and acquire information such as the azimuth and distance of the target. It supports up to 32 targets simultaneous detection and tracking. At the same time, the radar supports ≥10 target synchronous outputs, giving the most accurate detection results in the shortest time. Using intelligent algorithms, it can actively learn, and adapt to environment to identify the target.
● PTZ Camera： Track the target in real time, double confirm target and active raise alarm.
● Management software：Simple operation, alarm zone setting, real-time viewing, recording and playback function; open structure, support flexible extension to multi-level networking mode; provide user-friendly alarm query statistics, alarm display, alarm details, corresponding solution, etc.
System features of Nanoradar NSR300WVF：
● All Day&All Weather Protection：7×24h real-time protection in all weather, adaptable to bad weather such as rain, snow, smog, dust, smoke, etc.
● Active Detection, 3D Protection：radar will active raise alarm and trigger video alarm to lock the target in real-time, record alarm video and assess to control center.
● Intelligent,Reliability,Low false alarm rate：mbed with intelligent algorithms, the system is of accurate detection performance and can effective filter trees and birds to reduce false alarms.
● Simple operation,Open architecture ,Good compatibility：The system has an open architecture and can flexibly access to multiple security platforms.It is widely used in judicial, airport, oilfield, ports and other key application scenarios.
Nanoradar, founded in 2012, is specialized in R&D, production and sales of millimeter-wave radar for applications such as drones, security, automotive, and special industrial. We covers radar at the frequency bands of 24 GHz, 77 GHz, and 79 GHz, with technical focusing on MIMO system. Nanoradar has successfully developed more than 10 models of MMW radar, which are sold to more than 10 countries such as the United States, South Korea, Britain, France, etc. Nanoradar was achieved three times annual sales growth and is one of the leading millimeter wave radar manufacturers in China.