Microwave sensors operate on the Doppler principle.
They register and compare the frequency of transmitted and reflected signals.
People and objects cause disparities between the emitted and received frequencies as they move through the detection zone, thereby activating the sensor relay, causing the door to open.
Microwave Sensors have a large elliptical detection area. They can detect motion only, detect uni or bi-directional traffic, and can activate the swing-side of swing doors without detecting door movement.
Hotron supply various Automatic Door Sensors that use Microwave Technology: