Contactless Vital Sign Monitoring with Millimeter-Wave Radar

1. Background: Limitations of Existing Monitoring Approaches

Contact-based monitoring devices—such as ECG electrodes, finger-clip pulse oximeters, and wearable wristbands—depend on the person being monitored to actively wear them. Over extended periods of use, this often leads to declining compliance, skin discomfort, forgetting to wear the device, or outright resistance, particularly among elderly individuals and post-operative patients. Camera-based visual monitoring achieves physical non-contact but introduces privacy concerns due to image capture, and its effectiveness depends on lighting conditions, limiting its suitability for privacy-sensitive or low-light settings such as bedrooms.

Against this backdrop, contactless vital sign monitoring based on millimeter-wave radar has emerged as one of the technical approaches capable of balancing monitoring continuity, user compliance, and privacy protection.

2. Technical Principles

2.1 Fundamentals of Millimeter-Wave Radar Sensing

Millimeter-wave radar continuously emits high-frequency electromagnetic wave signals through its antenna. When these signals encounter an object within the detection range—including the human body—they are reflected back. The radar receives the reflected signal and compares it against the transmitted signal to derive information such as the target's distance and angle. Alinket's ASK824 employs a 24GHz millimeter-wave radar with Frequency-Modulated Continuous Wave (FMCW) modulation, offering a detection range of 0.3 to 2.5 meters, with a horizontal field of view of 60° and a vertical field of view of 80°.

2.2 Principles of Vital Sign Signal Extraction

Heartbeats and breathing cause periodic, minute displacements of the chest and body surface. Although these displacements are far too small to be observed with the naked eye, they cause a subtle phase difference between the radar's transmitted and reflected signals. By continuously capturing the periodic pattern of this phase variation, the radar demodulates it into respiration rate and heart rate data. At the same time, by analyzing the overall magnitude and distribution of the reflected signal, the system determines whether the subject is moving and whether they are in or out of bed.

2.3 Technical Comparison with Other Monitoring Methods

3. Product Implementation: ASK824 Technical Specifications

Data collected by the device is transmitted in real time via WiFi and the MQTT protocol to Alinket's Contactless Vital Sign Monitoring Management Platform. The platform provides a real-time dashboard, historical trend analysis, tiered permission management, and AI-assisted health analysis (for reference only; it does not constitute a diagnostic conclusion) — together forming a complete technical chain from the sensing layer to the application layer.

4. Application Scenarios

Building on these technical characteristics, the solution is applicable to the following scenarios:

• Cardiac Risk Alerting: Continuously tracking heart rate trends to provide early indication of abnormal fluctuations;

• Sleep Monitoring: Recording respiration and movement during sleep without contact, without disrupting sleep quality;

• Chronic Disease Rehabilitation Care: Providing continuous monitoring for chronic disease patients or those in post-operative recovery who require long-term observation of vital sign trends;

• Smart Elderly Care Support: Deployed in care facilities and home care settings to help caregivers and family members keep track of an older adult's condition;

• Smart Home: Serving as part of a household health management setup, working alongside other health monitoring devices.

5. Conclusion

The core value of contactless vital sign monitoring lies in making "continuous monitoring" and "not disrupting daily life" no longer conflicting goals. By virtue of being contactless, lighting-independent, and image-free, millimeter-wave radar offers a technical path that balances monitoring continuity with user experience across healthcare, elderly care, and home health management scenarios.

It should be noted that the technology and products described are intended to assist monitoring and provide reference information; they do not constitute a medical diagnosis. Specific health assessments should still be made by qualified medical professionals.