24GHz radar sensor is an advanced sensing technology that mainly detects the presence, motion speed, distance, and angle of target objects by transmitting and receiving microwaves with a frequency of approximately 24.125GHz. This sensor adopts planar microstrip antenna technology, which has the characteristics of small size, high integration, and sensitive induction. It is the core component of many applications, such as radar speedometers, water level measurement devices, automotive ACC (adaptive cruise control) systems, and automatic door sensing systems.

 

Principle

The working principle of 24GHz radar sensors can be divided into two main types: continuous wave (CW) Doppler radar and frequency modulated continuous wave (FMCW) radar.

• CW Doppler radar: By emitting a constant frequency signal and receiving a reflected signal, the frequency of the received signal will change due to the Doppler effect. By calculating the frequency difference between the transmitted signal and the received reflected signal, the velocity of an object can be determined. The dual channel designed sensor can output two intermediate frequency (IF) signals with a phase difference of 90 °, which enables the system to determine whether the target object is approaching or moving away from the sensor.
• FMCW radar: By using a transmission frequency that varies linearly with time (i.e. frequency modulation), when a signal is reflected back from an object, a frequency difference is generated between the received signal and the transmitted signal due to the time difference in the signal’s round-trip propagation. By measuring this frequency difference, the distance between the object and the sensor can be calculated.

 

Application

24GHz radar sensors have a wide range of applications, including but not limited to the following aspects:

• Traffic monitoring: vehicle flow statistics, speed monitoring, distance measurement, parking assistance, blind spot detection, collision avoidance control, etc. In addition, it is also used for obstacle detection, platform monitoring, and train speed testing in railway systems.
• Object detection: suitable for fields such as automatic door opening, sanitation facility sensing, security alarm, intelligent lighting control, and crowd counting.
• Sports speed measurement: can be used to measure the movement speed of athletes or objects, such as speed measurement for sports such as running, skiing, golf, etc.
• Industrial applications: liquid level monitoring, fluid flow rate measurement, mud density measurement, conveyor belt monitoring, and robot navigation.
• The Internet of Things (IoT): It plays a role in smart home intrusion prevention, smart grid, public safety systems, etc. Due to its strong anti-interference ability, it can respond to changes in object status in a timely manner.

24GHz Radar Sensor Case

1. Applications in the Internet of Things

Home intelligent intrusion prevention

24GHz radar sensors are used in home security systems to detect unauthorized intruders. By continuously scanning the designated area, the radar can identify moving objects and distinguish their direction and speed, triggering alarms or notifying the system. Compared with traditional infrared sensors, 24GHz radar is not affected by temperature changes and is less susceptible to interference from pets or other small objects, thereby reducing false alarm rates.

Airport intrusion prevention

In the security protection around the airport, 24GHz radar can work 24/7 without being limited by weather conditions, providing long-range perimeter protection. The radar system is linked with the video surveillance system, and once abnormal activity is detected, the target location can be quickly locked and corresponding safety measures can be activated.

Smart grid

When applied to smart grids, 24GHz radar sensors can monitor activities around power facilities such as utility poles, substations, etc., to prevent theft and vandalism. The combination of radar data and power grid management system helps to enhance the safety and reliability of the power grid.

Prison system

The surveillance of prison perimeter is also an important application of 24GHz radar. Radar can monitor the situation inside and outside the walls, detect attempted escape in a timely manner, and link with the security system inside the prison to ensure timely response.

2. Applications in Automotive Driving Assistance Systems

ACC adaptive cruise control system

The installation position of 24GHz radar sensors on cars is usually behind the front bumper, which can monitor the distance and speed of the vehicle ahead in real time. When the preceding vehicle decelerates, the ACC system will automatically adjust the vehicle speed to maintain a safe distance; When the road ahead is clear, accelerate back to the preset speed. In addition, the 24GHz radar can also be used in conjunction with emergency braking systems to further enhance driving safety.

Other ADAS functions

In addition to ACC, the 24GHz radar also supports blind spot monitoring (BSD), lane change assistance (LCA), rear cross traffic alert (RCTA) and other functions, providing drivers with comprehensive safety protection.

3. Traffic detection

Traffic flow monitoring

24GHz radar sensors can be installed on both sides of roads or bridges for real-time monitoring of traffic flow, average speed, and congestion. These data are crucial for traffic management, as they can help optimize signal control strategies, reduce traffic bottlenecks, and improve road capacity.

Road safety law enforcement

Traffic police can use portable 24GHz radar speedometers for mobile law enforcement, accurately measuring the speed of passing vehicles and cracking down on speeding behavior. Meanwhile, radar data can serve as a legal basis to support traffic violation penalties.

4. Sports speed measurement

Sports Training and Competition

24GHz radar sensors are widely used in the field of sports, such as measuring the swing speed of golf balls, detecting the shooting speed of soccer balls, and measuring the starting reaction time in track and field competitions. These sensors not only improve measurement accuracy, but also provide real-time feedback for athletes, helping to enhance training effectiveness.

5. Automatic door sensing

Automatic doors in commercial premises

In public places such as shopping malls and office buildings, 24GHz radar sensors are used in automatic door systems to detect pedestrian approaches and promptly open doors. Compared to infrared sensors, radar can penetrate obstacles such as clothing and packages, enabling detection at longer distances and improving user experience while also increasing security.