Why Millimeter-Wave Technology Stands Out Among Sensing Technologies

As a high-precision and reliable sensing technology, millimeter-wave radar modules are widely used in human detection, vital sign monitoring, behavior analysis, and other fields. The core principle of millimeter-wave detection is to utilize radio waves in the 1GHz to 300GHz frequency band. When interacting with the human body, subtle changes in the echo signals are extracted to non-intrusively obtain information such as position, movement speed, micro-motions, and vital signs.
Why Millimeter-Wave Technology Stands Out Among Sensing Technologies
1. High Resolution

Due to its high frequency and short wavelength, millimeter-wave technology can capture narrow beams with the same antenna size, resulting in excellent angular resolution. Additionally, its large bandwidth (several GHz) enables centimeter-level precision in distance measurement.
2. Strong Penetration

Millimeter waves can easily penetrate common obstacles such as tables, chairs, wood, plastic, and thin walls. However, they reflect well off human skin, making it possible to detect people hidden behind barriers or even through clothing.
3. Sensitivity to Micro-Motions

With ultra-high resolution, millimeter-wave radar is highly sensitive to tiny movements, capable of detecting displacements as small as millimeters or even micrometers. This makes it ideal for medical monitoring applications like respiratory and heart rate detection.
4. Robust Environmental Adaptability

Unlike optical sensors, millimeter-wave radar is unaffected by external lighting conditions. It operates reliably in harsh environments such as strong sunlight, rain, or fog.
Core Detection Principles of Millimeter-Wave Radar Modules

Millimeter-wave radar detects the human body based on two key physical principles:
1. Frequency-Modulated Continuous Wave (FMCW) for Ranging and Speed Measurement

Most mainstream millimeter-wave human detection radars use the FMCW体制. The radar transmits a linear frequency-modulated continuous wave signal (chirp signal) over time. When this signal hits the human body, it is reflected back and received by the antenna. The frequency difference between the transmitted and received signals—known as the beat frequency—enables detection:

    Distance Sensing: The beat frequency is proportional to the target distance. By analyzing the beat signal using Fast Fourier Transform (FFT), the precise distance between the target and the radar is calculated.
    Speed Sensing: When the human body moves relative to the radar, the echo signal generates a Doppler shift proportional to the radial velocity. By analyzing phase changes across consecutive frequency spectra, the body’s speed is accurately measured.

 Micro-Doppler Effect and Phase Detection

The micro-Doppler effect is critical for vital sign monitoring and behavior recognition. Human life activities involve subtle, periodic movements that produce unique echo patterns:

    Breathing causes centimeter-level periodic chest displacement, while heartbeat induces millimeter-level vibrations. These micro-motions create distinct sideband frequencies (micro-Doppler signatures) superimposed on the main Doppler shift.
    By performing long-term, high-resolution analysis of echo signals, these signatures are extracted to separate respiratory rate, heart rate, and other vital signs.

Typical Application Scenarios of Millimeter-Wave Radar Modules

    Smart Home: Elderly fall detection, sleep quality monitoring, respiratory/heart rate tracking, and gesture control.
    Security and Surveillance: Intrusion alarm systems and people counting.
    Healthcare: Non-contact continuous vital sign monitoring and sleep apnea screening.
    Automotive Sensing: In-cabin occupancy detection and driver status monitoring.
    Human-Computer Interaction: Gesture recognition.

IV. Current Limitations

    Cost: High-performance millimeter-wave chips remain more expensive than ultrasonic or infrared alternatives.
    Power Consumption: Millimeter-wave radars have slightly higher power requirements.
    Anti-Interference: Strong reflections from multiple targets or metal objects may cause false triggers.
    Algorithm Dependency: High-precision detection relies heavily on advanced signal processing algorithms.
    Regulatory Restrictions: Transmission power and frequency bands must comply with strict radio regulations in different countries.

By leveraging these principles and addressing its limitations, millimeter-wave radar continues to play a pivotal role in advancing IoT and smart sensing applications.