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【Introduction】The number of smart home applications and connected devices continues to grow, and users’ daily lives are becoming more and more convenient. However, this results in high energy consumption, as these devices are often in long-term active or standby mode, ready to be used at any time, even when no one is present. Equipped with smart devices featuring Infineon’s XENSIV™ mmWave radar sensors, these devices are not only more energy efficient, but also smarter and more sustainable.
The growing popularity of smart buildings and smart homes is expected to grow significantly in the coming years: Currently, the number of smart homes in the world is estimated to exceed 200 million, and this number is expected to exceed 500 million in the next few years.
The number of smart homes worldwide is expected to exceed 500 million in the next few years
The intelligence of the house is inseparable from the increasingly digital devices, the clever functions of these devices have never been seen before. However, equipment costs also remain high: despite a steady decline in standby power consumption in the past, the demand for energy has continued to grow. Smart devices require energy even when they are “off” because they can only select standby mode to instantly respond to user input (eg via voice control) or to provide up-to-date information from the smart home or the web. In addition, many times the device does not have to operate at all in standby mode and therefore consume energy – mainly when no one is present.
To solve this problem and meet the requirements for digitalization and energy saving, Infineon makes full use of its own semiconductor solutions. Among them is the XENSIV™ radar sensor, which can be used in almost all smart home devices. Radar sensors are very sensitive to detect presence and readiness of equipment – similar to a screen saver that disables the PC monitor if there is no mouse or keyboard input for a certain amount of time, and immediately deactivates when new input is detected Reactivate. With this reliable presence and absence detection technology, Infineon mmWave radar supports the design of truly smart, energy-efficient devices.
User Presence Triggered Activity vs. Sustained Activity or Standby
A 2021 Statista survey in Germany shows that more than three-quarters of more than 3,000 Germans aged 18 to 64 own at least one smart home device. In the US, the statistics are very close.
The number of smart devices in U.S. households is growing rapidly, according to Statista
In China, the proportion of smart home device users is as high as 90%. These devices and their applications are diverse, including: lighting, security equipment; consumer electronics such as TVs, laptops, and sound bars; kitchen appliances and air conditioners. However, all equipment is increasing the demand for energy, and the energy saving effect is very poor, especially in the stage of rising energy costs, and customers prefer equipment that is energy efficient, sustainable and environmentally friendly. In addition, grid infrastructure is under increasing pressure.
One way to reduce energy consumption when no one is around is to put devices such as thermostats, smart speakers or digital assistants into “deep sleep mode” instead of putting them in normal standby mode. For some devices, this saves only a few watts or a fraction of the energy. But there are use cases where putting the device in deep sleep mode or turning it off temporarily can save more than 100 watts because there’s no need to use things like TV screens, laptops, sound systems, or air conditioners when no one is there. Using radar sensors, these devices can sense the presence or movement of people; if there are still no such pulses, radar-based smart devices can automatically switch to sleep mode, saving energy. Depending on the sensor and implementation, the radar module itself consumes only a few mW, up to 0.1 W, which is well below the power requirements of many Electronic devices in powered-on or standard standby mode.
How to use radar sensors to improve energy efficiency
To save energy, it’s time to rediscover how devices must always be available and connected—including power-hungry standby modes. We require that the device be active or standby only when the user really needs it, that is, when the user is present. That’s what we’re currently doing in “non-smart” homes, turning on the lights after entering the room, or manually turning on the air conditioner only when it’s too hot inside. However, in many devices, users are still not using or even disabling power-saving features such as timeouts. Mainly because those features related to advanced functionality often result in long startup times and lack of up-to-date information, especially after troublesome manual reactivation, and thus noticeably impact the customer experience.
But the new smart approach could solve many problems: Why must the thermostat’s Display be turned on, and why must the device itself be connected to the Internet in order to download weather data? Why is the camera of a home security system always on, recording data, preprocessing the data, and transmitting it to the cloud even when no one is moving in the monitored area? The best way to achieve a smarter way of device activation is to implement motion detection by deploying radar sensors to wake the device from deep sleep mode.
For example, a smart thermostat could be turned off by default and only the radar detection module activated. Whenever the radar detects movement in the room, the thermostat kicks in, updating the house’s standard data and weather data sourced from the internet. If someone enters a defined area, eg within 1 m, the Display will turn on. So the user can activate it without touching the screen and then wait for the data to update and the results to appear. This presence detection concept can be deployed in a variety of other smart home devices and appliances.
In addition, if the reverse principle of vacancy detection is applied, the energy saving potential can be improved. In this case, devices such as TVs, speakers, smart lights, and air conditioners can be turned off if no movement is detected in the room for a period of time, which can significantly reduce power consumption. Since vacancy detection does not activate the device immediately, but rather deactivates it in a targeted manner when no one is there for a period of time, the sensor module itself can remain deactivated and a check is performed every few seconds or minutes. As a result, such sensor modules can save a lot of energy for the entire system with very little consumption on their own. Buildings with HVAC systems especially benefit from this, since most energy is wasted for heating and cooling, even when no one is present. To make matters worse, most of the time these devices run frequently and for long periods of time . However, a true smart home deactivates these systems when no one is there for a period of time. This feature is gaining popularity in lighting systems, but not yet in air conditioners and other equipment such as monitors, kitchen appliances, computers, speakers, and sound systems.
Nonetheless, users can also benefit from vacancy detection in other applications such as televisions. For example, the Infineon BGT60LTR11AIP radar sensor has been used in the Samsung Frame TV 2021 to switch the TV from art mode to sleep mode if no one is nearby for a user-specified time. This not only saves energy, but also extends the life of the display.
Infineon mmWave radar sensor BGT60LTR11AIP supports the design of truly smart, energy-efficient devices
Samsung Frame TV 2021 will switch from art mode to sleep mode if no one is detected for a user-specified time
Radar sensors are the most suitable sensing choice for smart home devices
Of all the motion detection solutions available, radar sensors are the most sensitive for the smallest movements, even those invisible to the naked eye. The sensitivity of PIR sensors cannot be compared. Also, radar does not rely on body heat like PIR sensors because it uses active sensing technology. This ensures that people with little or no movement are detected. However, one of the biggest advantages is the ability to penetrate non-conductive materials. While infrared, ultrasonic, camera or other image-based sensors must not cover or require holes in the product housing, radar sensors can be completely hidden within the device. As a result, you don’t have to make any compromises in product design, and you can avoid extra manufacturing steps and the cost of changing the housing as a result.
Another possibility is camera-based motion detection, such as for cameras, TVs, laptops, or other devices already equipped with suitable image sensors. However, the power consumption of the imaging system is very high, good lighting conditions may be required, and image processing is required to detect motion in the video, which undoubtedly increases the energy requirements. You could also blame the lack of privacy, as the camera system intrudes into private space – so users don’t fully trust it.
In addition, falling consumer electronics prices have increased cost pressures on components. Therefore, 3D ToF (time of flight) and camera sensors are often too expensive for presence detection. A powerful PIR solution not only affects the product housing design, but also requires additional Fresnel lenses, amplifiers, controllers, etc., which increases the BOM (Bill of Materials) cost. The Infineon BGT60LTR11AIP radar sensor requires minimal support components, especially in autonomous operation, and therefore has minimal impact on system cost. Radar sensors are small and can therefore also be integrated into small and thin electronic devices.
In addition, radar sensors are also very durable in dusty, smoky, or humid environments, where some laser-based ToF sensors or other image sensors may struggle to detect.
Additional Smart Features Supported by Radar Sensors
Users are often unaware that improper device operation can also lead to unnecessary power consumption. They may inadvertently waste energy without turning off equipment or adjusting settings when they leave temporarily. However, with the help of the radar sensor, the adjustment is made automatically at this point, so that the user does not waste energy even if he does not think about it.
In addition to being used as presence or absence detectors, radar sensors can add other functions to smart devices, such as in air conditioning systems. In these types of applications, radar sensors are most efficient when used in combination with temperature and CO2 sensors, so the system activates as needed – such as when someone is in the room, when the CO2 concentration is too high, or when the temperature exceeds predefined limits. While other sensing technologies typically only provide binary information such as presence or departure, radar sensors can check the number of people in the room in advance and adjust accordingly, and even check the location and distance of people to control the direction of airflow.
There are many other possible use cases, such as sound systems that track the position of the listener and continuously optimize volume and sound parameters accordingly. Or a child-friendly TV that measures the viewer’s distance and warns if a child’s eyes get too close to the screen. It can also be used in devices for the elderly or those in need of care, such as an alarm system to ask for help in the event of a fall. As a result, radar sensors not only save energy and improve people’s comfort, but also contribute to personal care and safety in a smart environment, all with ease.
 Martani, Claudio, et al.: ENERNET: A study of the dynamic relationship between building occupancy and energy consumption. Energy and Buildings, 2011, http://senseable.mit.edu/papers/pdf/20120401_Martani_etal_EnernetStudying_EnergyBuildings.pdf
 Norford, LK, et al.: Two-to-One Differences Between Measured and Predicted Performance of “Low-Energy” Office Buildings: Moderating Insights Based on the DOE-2 Model. Energy and Buildings, 1994, https://www.sciencedirect.com/science/article/abs/pii/0378778894900051?via%3Dihub
Has a background in Physics (M.Sc.) and completed an MBA before joining the Infineon Radar team in 2020. As product marketer and manager, he is responsible for the various series of Infineon 24G radar and mmWave radar sensors. Among them, Bernd mainly promotes all industrial, consumer and IoT related radar applications, including smart home and smart building systems.