The New World of the Internet of Things: “When Human Presence Sensing Meets Millimeter-Wave Radar Technology”
Human-body presence-sensing millimeter-wave radar The technology is a method for human body detection that utilizes electromagnetic waves in the millimeter-wave frequency band.
In public spaces such as restrooms, offices, and corridors, oversight or poor management often leads to lights being left on. This not only increases the overall energy consumption of these areas but also results in unnecessary electricity waste. In restrooms, lights may remain on even when no one is using the facility—especially during bright daylight hours, when this waste becomes particularly noticeable. In offices, employees may forget to turn off the lights due to being busy or eager to leave, leaving entire rooms or specific zones brightly lit even when unoccupied. Corridors, serving as passageways between different areas, typically have lighting that runs for extended periods; if not promptly switched off, they too contribute significantly to energy loss. Such unintentional wastefulness not only drives up electricity usage but also exacerbates resource scarcity, placing an undue burden on the environment.

Accordingly, millimeter-wave radar–based human‑presence sensors have emerged, enabling functions such as lights turning on when a person enters and off when the person leaves. When someone enters the illuminated area, the millimeter-wave radar detects their presence and automatically switches the light on; once the person departs, the radar deactivates the light after a set delay, thereby achieving energy savings. Moreover, by analyzing a person’s movement patterns and positional data, the radar can adjust the light’s brightness and color, providing users with a more comfortable lighting environment.

I. Technical Principle
Millimeter-wave radar detects and locates the human body by transmitting millimeter-wave signals and receiving the signals reflected back from the human body. Its operating principle is based on the Doppler effect and the principle of target reflection. When a millimeter-wave signal illuminates the human body, the body’s motion induces a Doppler frequency shift in the reflected signal. By detecting and analyzing this Doppler shift, the radar can determine the human body’s motion state and positional information. Additionally, millimeter-wave radar can estimate the distance and bearing of the human body by processing the strength and time delay of the reflected signals.
II. Technical Features
High‑precision detection: Millimeter-wave radar offers highly accurate sensing capabilities, enabling precise measurement of human motion and positional information. Compared with conventional infrared sensors, millimeter-wave radar is unaffected by environmental factors such as temperature and lighting, delivering greater reliability and stability.
Non-contact detection: Millimeter-wave radar employs a non-contact sensing method, posing no harm to humans. Moreover, this non-contact approach allows the radar to be installed in specialized locations—such as walls or ceilings—without compromising the aesthetic appeal of the home.
Multi‑target detection: Millimeter‑wave radar can simultaneously track multiple targets and distinguish their motion states and positional information. This enables millimeter‑wave radar to support more intelligent control in smart homes, such as lighting and air‑conditioning management in multi‑person scenarios.
Strong anti-interference capability: Millimeter-wave radar exhibits robust resistance to interference, effectively mitigating disruptions from other electronic devices. Moreover, through advanced signal-processing techniques, it can suppress environmental noise, thereby enhancing detection accuracy.

Hengyi Technology’s 60 GHz millimeter-wave radar, a sensor for both manned and unmanned applications, can detect the presence of stationary, slightly moving, or actively moving personnel targets, offering high range accuracy and a low false-alarm rate. Compared with infrared, video, and laser technologies, it is less affected by fog, smoke, dust, and nighttime conditions, ensuring reliable operation in all weather. Even in challenging environments such as humid restrooms, it maintains excellent detection performance.

Overall, human‑presence millimeter‑wave radar, with its high‑precision sensing, non‑contact operation, multi‑target detection capabilities, and strong anti‑interference performance, is playing an increasingly vital role in smart home, intelligent security, and other fields.