Passive Entry: Notes

The graphic below shows the functional principle of "Passive Entry".

Fig 1: Signal Path For Comfort Access In F01/F02 Passive Entry System

Courtesy of BMW OF NORTH AMERICA, INC.

COMPONENTS DESCRIPTION CHART

Index	Explanation
1	Outside door handle electronics module (TAGE)
2	TAGE request to the CAS
3	Prompt about Comfort Access antenna
4	Comfort Access antenna
5	ID transmitter
6	Rear window antenna
7	Remote control receiver in the diversity module
8	Car Access System 4 (CAS 4)
LIN-Bus	Local Interconnect Network bus
f₁	Low frequency in the kHz range
f₂	High frequency in the MHz range
K-CAN2	Body CAN2
CA/FBD	Comfort Access/remote control services

Passive Entry enables access to the vehicle without the ID transmitter being actively operated.

For example, if the outside door handle is pulled, this triggers a pulse in the sensor. The outside door handle electronics analyze the sensor and inform the Car Access System that vehicle access is requested.

The Car Access System prompts the ID transmitter to identify report to the vehicle. For this, a low-frequency signal is emitted by Comfort Access via the antennas. Transmission is via the 125 kHz antennas.

The 125-kHz signal serves only to wake the ID transmitter. The ID transmitter responds with its transmission frequency. Subsequent communication is now bi-directional, i.e. in two directions. The Car Access System sends or receives all further information via the LIN bus.

The remote control receiver is equipped with both a receiver unit and a transmitter unit. It establishes the connection with the ID transmitter via the rear-window antenna. For that reason, only the high frequency range is now used.

Bi-directional communication has the advantage that data can be requested from or sent to the ID transmitter. The Car Access System has sole responsibility for this communication.

If the ID transmitter is able to be authenticated, the Car Access System initiate the request, e.g. unlocking the vehicle. The junction box electronics execute the unlocking.

The transmission frequency of the ID transmitter varies for the US is 315MHz.

NOTE: When it is not required, the ID transmitter is in sleep mode. This reduces its energy consumption. For sleep mode to be ended, the ID transmitter requires a wake-up signal. The wake-up signal can be sent by the Car Access System via the Comfort Access antennas. Pressing one of the buttons on the ID transmitter also wakes it.