When a PIR motion sensor is used, the sensor will detect the thermal signal of any object whenever the object is within the range of the sensor. The PIR sensor detects the change in the amount of infrared radiation it senses, converts the change into a voltage, and then compares the voltage with the threshold limit to trigger the signal of enabling lighting or triggering an alarm.
Although PIR technology is usually used for the current main applications of human body sensing, many challenges are imposed on PIR technology due to its inherent limitations. For example, when applied to indoor lighting, PIR technology has a limited range compared with radar technology, more sensors are needed because of limited coverage, and it appears less aesthetic after installation because PIR needs to be visible from the outside.
When applied to automatic doors, PIR technology can only detect the motion, which means that PIR sensors cannot detect objects if these objects stand still, judge whether someone is entering a building, or distinguish whether a person or an animal has entered. When applied to smart street lighting, PIR technology is vulnerable to severe weather conditions, resulting in less reliability. In addition, due to the lack of object recognition capability, it means that it is easy to cause incorrect triggering and it is impossible to carry out directional measurement. Moreover, when applied to intrusion alarms, PIR technology also needs to be visible, resulting in a less aesthetic appearance, and is also vulnerable to severe weather conditions affecting reliability, and more sensors must be used due to the limited detection range and coverage.
It is more complex to use radar technology. Radar can determine the motion, speed, and even direction of an object using the Doppler principle. When detecting an object, the radar will emit a 24 GHz waveform and reflect the object in the sensor's field of view. The reflected wave is received by the radar transceiver. The received signal will have a frequency difference called the Doppler frequency, which will then be used to detect motion and speed.
Compared with the shortcomings of PIR technology, mmWave radar provides better technical characteristics, i.e. working within a distance of several centimeters to several hundred meters, operating without direct line-of-sight (e.g. through drywall or plywood), and having the ability to adapt to environmental conditions (e.g. darkness). For example, in respect of indoor lighting, mmWave radar has a long detection range, and can save energy by automatically turning off lighting. It can also be installed by being hidden behind pipelines.
When applied to automatic doors, mmWave radar can detect the traveling direction of the human body, so it can open the door only when necessary, and make the building more energy-saving by reducing the number of times of opening the door. When applied to smart street lighting, mmWave radar has a long detection range and can carry out precise object recognition. It operates at a frequency of 24 GHz and is less vulnerable to hot weather. When applied to intrusion alarms, mmWave radar has a long detection range, and its detection sensitivity can be adjusted for higher accuracy and reduced errors.
With the improvement of radar capability, the amount of information that can be obtained also increases. Current radar technology provides a wider range of functions, which means that mmWave radar can now further benefit specific applications even though PIR may have been the only feasible solution in the past. When designing the sensor system for detecting proximity or motion information, designers must consider the flexibility and cost of the type of technology they use.
As sensor performance will be affected by range, object sensitivity and environmental factors, etc, designers must determine the key features and design costs of these technologies. Although the cost of radar technology is continuously decreasing, and it is more compact and simpler to design, the cost of PIR is lower, so it is still necessary to decide which technology to adopt according to the system requirements of functional application, design method, and cost.
Infineon has introduced the XENSIV™ 60 GHz radar chip, which can track submillimeter motion with great accuracy at high speeds. This highly integrated radar sensor solution is characterized by small volume and low power consumption, bringing innovative and intuitive sensing functions to many applications. It can measure the speed, range, and angle in the horizontal and vertical directions for accurate position mapping and 3D tracking, and has a high resolution detection capability of up to 2.5 cm.
In addition, Infineon has also introduced a radar presence detection solution that can detect a human presence within the configured range. Through XENSIV™ 60 GHz radar and its advanced radar presence detection algorithm, this solution can provide extremely high accuracy in detecting micro and macro motions.
In addition to radar chips, Infineon also provides reference designs and development platforms. Sense2Go is a simple and compact development platform that can be used for intelligent motion sensors. The Sense2Go platform allows users to implement and test a variety of sensing applications in the 24 GHz ISM band, such as Doppler-based movement detection, Doppler-based direction of movement detection, Doppler-based speed estimation, and frequency modulated continuous wave (FMCW)-based distance measurement for stationary targets.
In order to explore this potential market, Arrow Electronics and Jorjin are cooperating in mmWave radar technology. Jorjin is a Taiwanese company active in AR and IoT. With more than ten years’ experience in wireless module development, Jorjin uses mmWave radar technology to supplement its existing portfolio of sensor products. Jorjin is an independent design house (IDH) with whom Arrow Electronics has cooperated for many years. Arrow Electronics is a global distributor of Jorjin, responsible for sales of MM5D91-00 mmWave radar sensor modules.
MM5D91-00
Jorjin has introduced the MM5D91-00 integrated mmWave radar sensor module based on the Infineon XENSIV™ 60 GHz radar chip. The module simplifies the implementation of mmWave sensors in the 61.0 to 61.5 GHz band. In combination with the processor system based on the ARM Cortex-M4F 150MHz, 1024KB flash memory and 288KB RAM, 1Tx/3Rx antenna and on-board regulator, it features a UART interface and GPIO, uses 3.6 to 5.5 V power input, and has three benefits, i.e. compact size (20 x 15 x 2.3 mm), high resolution, and low power consumption.
The module has a radar field of view of ±45° azimuth angle and ±40° elevation angle, and is not vulnerable to environmental factors such as temperature, wind, sunlight, and dust/debris. Macro detection can be carried out if the distance is less than 10m and micro motion can be detected if the distance is less than 5m. Therefore, mmWave radar technology can be extended to various new applications, such as smart home, office automation, security and gesture detection, providing low power consumption and high resolution presence detection solutions.
In addition to the module, Jorjin has also introduced the MM5D91E00 evaluation board, which is structured based on the MM5D91-00 radar sensor module to demonstrate the presence detection function of its 60 GHz radar sensor and its advanced radar presence detection algorithm. The MM5D91E00 evaluation board has an easy-to-configure UART port for end users to change parameters. The standard mode is available for setting of detection range, sensitivity, reset, etc. The detection range, sensitivity, and status settings are stored in flash memory and remain set after power reboot.
mmWave radar is a proven powerful sensor providing higher accuracy and better performance than PIR technology, and can be used in consumer electronics, health care, monitoring, driver assistance, and short-range positioning and vital sign tracking in industrial applications. With great development potential in market applications, it is worthy of insight into this technology by manufacturers interested in seizing business opportunities in these applications.
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