Ultrasonic sensor

Combined transmit and receive mode 

In the combined transmit and receive mode, the ultrasonic sensors first of all transmit a package of ultrasonic impulses in succession. Subsequently, the ultrasonic sensors pick up the echo impulse that is reflected by an object in the pickup range.

This echo impulse is amplified in the ultrasonic sensor and forwarded as a digital signal to the junction box electronics (JBE). The JBE uses the runtime of the echo impulse to calculate the distance to the object.

Receive mode 

In the receive mode, an ultrasonic sensor picks up the echo impulses sent by neighboring ultrasonic sensors. The JBE can thus evaluate the signals from up to 3 ultrasonic sensors ("trilateration" = the neighboring sensors also "listen"). This signal evaluation of a number of ultrasonic sensors is used to calculate the minimum distance between the vehicle and the object.

Fig 1: Identifying Ultrasonic Sensor And Pin Plug Connection

Courtesy of BMW OF NORTH AMERICA, INC.

All the ultrasonic sensors have their own electronics. The front and rear ultrasonic sensors have a joint power supply and earth contact at the control unit.