Antenna amplifier, function - GF82.62-P-3105-04A
Models 215, 220
Filtering and amplifying high frequency signals
The electrical filters select the desired frequency bands (AM, FM, TV,...) from the high frequency signals coming from the rear window antennas. These filters are designed differently depending on the national version (e.g.
,
,...) since the transmission frequencies depend on the specific country. The frequency bands filtered out are then amplified selectively and transmitted by the coaxial leads to the corresponding control modules, e.g.:
- Radio (A2) or COMAND operating, display and control module (A40/3n1) or
- Overhead control panel control module (N70)
Demodulation of RCL signals
The signals for the radio frequency central locking (RCL) are demodulated and digitalized by the rear window antenna amplifier module (A2/12) . The data prepared in this manner are transmitted to the overhead control panel control module (N70) by a separate data line and there stored on the CAN interior compartment.
During demodulation
the information signal (e.g. the RCL signal) is separated from the high frequency carrier (transmitter frequency).
Antenna diversity function
The diversity processor integrated into A2/12 switches over between the rear window FM antennas depending on the reception to achieve the best possible reception.
- First the radio (A2) or A40/3n1 receives the signals of the active FM antenna from the rear window antenna amplifier module (A2/12) .
- A2 or A40/3n1 generates the IF reference signal from the FM signals received and transfers it back to the rear window antenna amplifier module (A2/12) via a separate cable.
- After demodulation, the diversity processor in the rear window antenna amplifier module (A2/12) checks whether the IF signal contains no interference. If interference is present, it automatically switches over to the next of the four FM antennas in the rear window.
- The switchover speed depends on the frequency of the interference occurring. This prevents continuous switching between the antennas when FM reception is very poor which could cause interference itself.