IWR6843AOP：Heart Rate Measurement Inaccurate (Consistently Below 70 bpm) in Vital Signs Demo

I am encountering an issue with heart rate measurement accuracy while using the IWR6843AOP mmWave sensor for vital signs monitoring. I would appreciate technical support to help identify and resolve the problem.

Setup Details:

• Device: IWR6843AOP
• Demo Used:
  C:\ti\radar_toolbox_3_20_00_04\source\ti\examples\Industrial_and_Personal_Electronics\Vital_Signs\Vital_Signs_With_People_Tracking
• PC GUI (Visualizer):
  Radar Toolbox version 1.30.01.03 (Vital Signs Dashboard)
• Configuration: Using default example configuration (no modifications made)

Issue Description:
The system successfully detects a person and outputs both heart rate and respiration rate. However, the reported heart rate is consistently below 70 bpm, even when the subject has elevated their heart rate through light physical activity (e.g., stepping in place). The respiration rate appears reasonable and responsive.

For comparison, we simultaneously measured the subject's heart rate using a contact-based ECG electrode sensor, which showed a heart rate of approximately 80~90 bpm, while the IWR6843AOP radar system reported a value below 70 bpm.

Steps Taken So Far:

• Verified stable hardware connection and sensor operation.
• Ensured subject is seated still, 1–1.5 meters directly in front of the sensor.
• Confirmed the correct .cfg file is loaded (default from example).
• Tested with multiple subjects — same behavior observed.
• Environment is free of major reflective surfaces or RF interference.

Request for Support:

• Are there known limitations or configuration parameters that could affect heart rate accuracy?
• Should specific chirp parameters, FFT settings, or post-processing thresholds be adjusted for better HR estimation?
• Could there be a compatibility issue between radar firmware/toolbox version 3.20.00.04 and GUI version 1.30.01.03?
• Are there recommended debugging methods, logs, or internal signals (e.g., phase output, spectrogram) I should inspect?

I can provide the configuration file, screenshots, or recorded data if needed.

Thank you for your support.