Overview
mmWave (millimeter-wave) presence detection works by emitting radio waves and analyzing how they reflect off objects—including people—in the environment. While mmWave is highly capable in detecting micro-motions (such as breathing), it is also highly sensitive to reflections from walls, furniture, and other nearby surfaces.
Because of this, there is always a tradeoff between sensitivity and false detections. Increasing sensitivity allows the device to pick up smaller movements or detect presence farther away, but it also increases the likelihood of reflecting off unintended surfaces and causing false positives.
This support document explains why this tradeoff exists, how it affects your Inovelli mmWave device, and how to tune sensitivity settings for best results.
Why Sensitivity Matters
Increasing mmWave sensitivity changes two primary detection characteristics:
Detection Range Increases
Higher sensitivity allows the radar to detect smaller movements or detect motion at longer distances.Noise Floor Increases
When sensitivity is too high, the radar can interpret environmental reflections as motion. Examples:Reflections off glass, mirrors, or metal appliances
Radar energy bouncing around corners or in tight hallways
Moving curtains, HVAC airflow, ceiling fans, or robotic vacuum cleaners
This leads to a predictable effect:
More sensitivity = more detection range, but also more detected “noise.”
How Reflections Cause False Positives
mmWave sensors don’t just detect motion directly in front of them—they detect changes in phase and amplitude in the returning signal. In a real room, radar waves bounce many times before returning to the sensor.
When sensitivity is high, the device may misinterpret:
Reflected motion of a person walking outside the room
Reflections that “leak” around doorways
Subtle movement of objects within the radar field
Multi-path reflections off glossy or angular surfaces
This is why raising sensitivity too far can cause:
The room to stay “occupied” after someone has left
Presence detection through walls or glass
Random or intermittent occupancy triggers
Real-World Example
Let’s say you install the sensor in a bathroom.
Low sensitivity:
It only detects someone moving inside the room.
Presence may drop if the user sits still too long.
Medium sensitivity:
The device reliably detects small movements, including someone in the shower behind a curtain.
False positives remain unlikely.
High sensitivity:
The radar picks up reflections bouncing off tile and mirrors.
Someone walking past the bathroom may trigger occupancy.
After leaving, the room may remain occupied due to residual reflections.
This example illustrates the need to tune sensitivity for each environment.
Guidelines for Setting Sensitivity
1. Start with Medium Sensitivity
This provides the best balance for most rooms. Adjust upward only if detection is unreliable.
2. Increase Sensitivity for Large or Open Rooms
Use higher settings if:
The room is large
The user is often seated or motionless
The sensor is mounted farther away from typical movement
3. Decrease Sensitivity in Highly Reflective Environments
Lower settings help when the room has:
Mirrors
Glass shower enclosures
Stainless steel appliances
Tile walls or floors
Narrow hallways or alcoves where reflections accumulate
Tips for Minimizing False Detections
Avoid pointing directly at mirrors or windows
These are the most common sources of bounce-back reflections.Do not aim through doorways
Sensitivity increases the chance of detecting someone outside the room.Optimize Range (P101 - P106) Make sure the X, Y, and Z range are accurate based on the room size.
Summary
mmWave technology is extremely powerful, but it must be tuned for each environment. The key concept is:
Higher sensitivity improves presence detection but increases reflections—and therefore false positives.
Finding the optimal balance involves adjusting sensitivity based on:
Room size
Layout
Surfaces
Desired detection range
With proper tuning, Inovelli mmWave products can provide highly accurate presence detection with minimal false triggers.