Analysis of Signal Processing Methods to Reject the DC Offset Contribution of Static Reflectors in FMCW Radar-Based...

Area of Science:

• Electromagnetics and Signal Processing
• Biomedical Engineering
• Wireless Health Monitoring

Background:

• Frequency-modulated continuous wave (FMCW) radars offer innovative wireless solutions for remote vital signs monitoring (respiration and heart rates).
• Static reflectors in FMCW radar systems introduce unwanted direct current (DC) offset, distorting vital signs data and reducing measurement accuracy.
• Accurate vital signs monitoring necessitates effective removal of DC offset for proper phase demodulation.

Purpose of the Study:

• To analyze and compare various DC offset calibration methods for FMCW radar vital signs monitoring.
• To determine the optimal DC offset calibration method for maximizing accuracy in physiological parameter measurement across different transmitting frequencies.
• To evaluate the performance of these methods in a realistic office environment using subjects.

Main Methods:

• Utilized two FMCW radar systems operating below 10 GHz and at millimeter wave (mmWave) frequencies.
• Applied four distinct DC offset calibration techniques to baseband radar signals derived from cardiopulmonary activities.
• Experimentally assessed the accuracy of each method by measuring respiration and heart rates of multiple subjects.

Main Results:

• Linear demodulation demonstrated superior performance for vital signs monitoring with FMCW radars operating below 10 GHz.
• Geometric fitting emerged as the most accurate method for mmWave FMCW radar vital signs monitoring.
• The choice of DC offset calibration method significantly impacts the accuracy of remote vital signs measurement.

Conclusions:

• The optimal DC offset calibration strategy for FMCW radar vital signs monitoring is frequency-dependent.
• Linear demodulation is recommended for sub-10 GHz systems, while geometric fitting is preferred for mmWave systems.
• Effective DC offset calibration is crucial for reliable and accurate remote physiological monitoring using FMCW radar technology.