mmWave Radar False Trigger Elimination: Target Exclusion Zones & Sensitivity Tuning

While legacy Passive Infrared (PIR) sensors fail when an occupant sits motionless at a desk, FMCW (Frequency-Modulated Continuous Wave) mmWave radar can detect the sub-millimeter thoracic displacement caused by breathing. However, this microscopic sensitivity makes mmWave prone to false positive occupancy events.

1. Primary Sources of Ghost Presence Triggers

• Ceiling Fan Micro-Doppler Shifts: Rotating blades generate high-frequency periodic Doppler signals that mimic human walking patterns.
• HVAC Airflow Drafts: Rapid thermal gradients oscillating across curtains or foliage create fluctuating dielectric boundaries that register as subtle motion.
• Multipath Radar Reflections: Large glass windows and mirrors reflect RF energy, creating a mirrored virtual target behind solid drywall.

2. The Systematic 4-Step Remediation Protocol

1. Configure Spatial Exclusion Zones: In sensors with multi-target tracking (such as the Aqara FP2 or LD2410), define bounding exclusion boxes around rotating fan arcs and HVAC supply diffusers.
2. Tune Range Gate Energy Thresholds: Increase the minimum micro-motion gate threshold on the specific distance bin corresponding to vibrating curtains from 10 to 35.
3. Hardware Tilt Angle Calibration: Mount radar units at 1.8 meters pitched downward at 15 degrees, directing the primary lobe towards seated chest height rather than ceiling fixtures.
4. Combine with Illuminance Gating: Enforce automation conditions requiring light levels to be below 10 lux before triggering illuminance-dependent lighting macros.