Antenna amplifier module, function - GF82.62-P-3105-04PP

Filtering and amplifying radio frequency signals 

Electrical filters select the desired frequency bands (AM, FM, TV,..) from radio frequency signals received by the rear window antennas. These filters are laid out differently depending on the national version, because the transmission frequencies vary from country to country. The filtered frequency bands are then amplified selectively and routed to the following control modules via coaxial lines.

• Radio (A2)
• COMAND operating, display and control module (A40/3)
• EIS [EZS] control module (N73)

Radio controlled central locking 

The signals for the radio remote-controlled central locking system are demodulated and digitized by amplifier module 1, window antenna (A2/71).

The data prepared thus are sent over a separate data line to the electronic ignition switch control module (N73) and forwarded there to the CAN interior (CAN-B).

During demodulation, the useful signal is separated from the high-frequency carrier frequency (transmitter frequency).

Antenna diversity 

The purpose of the diversity processor integrated into window antenna amplifier module 1 (A2/71) is to switch over between the rear window FM and TV antennas in order to achieve the best possible reception. The following section describes the function of the FM antennas:

• First the radio (A2) or COMAND operating, display and control module (A40/3), receives the active FM antenna signals from amplifier module 1, window antenna (A2/71).
• The integrated radio tuner uses the incoming FM signals to generate the reference signal (intermediate frequency signal).

This reference signal is sent over a separate line to the window antenna amplifier module 1 (A2/71):

• The diversity processor of the window antenna amplifier module 1 (A2/71) checks after demodulation, whether the intermediate frequency signal is trouble-free or not. If interference is present then a switch is automatically made to the next antenna in the rear window.
• The switchover speed depends on the frequency with which interferences occur.

  This prevents continuous switching between the antennas in areas where the FM reception is very poor which could result in interference itself.