GF82.62-P-3121TXA Left Antenna Amplifier Module, Component Description

GF82.62-P-3121TXA Left Antenna Amplifier Module, Component Description

Component Identification:

Location
The left antenna amplifier module (A2/64) is installed behind the left C-pillar paneling.

Task
The left antenna amplifier module has the following tasks:
^ To decouple the power supply of the rear window's heating range in terms of high frequency
^ To filter and amplify the FM and AM signals of the rear window antenna.
^ To supply the amplified FM and AM signals, depending on the vehicle equipment, to the audio gateway control unit (N93/1) or the MB Audio 20 radio (with code 523 MB Audio 20 radio).
^ To supply the strongest of the 4 FM signals to the audio gateway control unit (diversity function).
^ To filter the TV1/TV2 signals of the rear window antennas, to amplify them, and to supply them to the TV tuner (A2/10) on vehicles up to 31.5.06 or to the TV combination tuner (analog/digital) (A90/1) as of 1.6.06.
^ To filter, demodulate, and digitize the signals for the radio frequency locking (RFL [FFZ]) received by the rear window antenna, and to supply them to the rear SAM control unit with fuse and relay module (N10/2).

Only if equipped with:
- With code 761 Radio remote control with reduced range without panic button
- With code 762 Radio remote control without panic button
- With code 763 Radio remote control with panic button

^ To filter the authorization signal of the Keyless Go function and to supply it to the rear SAM control unit with fuse and relay module (only with code 889 Keyless Go).

Design
The following components and functions are integrated in the left antenna amplifier module:
^ Filter and amplifier for AM signals
^ Filter and amplifier for TV1 and TV2 signals
^ Filter, amplifier, and a diversity system for the FM1, FM2, FM3, and FM4 signals
^ Filter, demodulator, and digitization function for the radio frequency locking signal
^ Filter for the authorization signal of the Keyless Go function
^ A trap circuit to decouple the power supply of the heating range in terms of high frequency

Function
Filtering and amplifying the AM, FM, TV, and radio frequency locking signals
The FM (FM1 to FM4) frequency bands, the AM frequency band, and the TV (TV1 and TV2) frequency bands are filtered and amplified in the left antenna amplifier module. Additionally, the radio frequency locking signal is filtered.

Antenna diversity feature (FM)
The diversity function serves for reduction of reception interference.

The task of the diversity function integrated in the left antenna amplifier module is to switch between the FM antennas (FM1 to FM4) of the rear window depending on the reception in order to allow best possible reception. First, the audio gateway control unit receives the signals of the active antennas from the left antenna amplifier module.
The audio gateway control unit uses the incoming FM signals to generate the IR reference signal. This reference signal is transmitted to the left antenna amplifier module via a separate line. The diversity feature checks whether the IR signal is free of interference after demodulation. If interference is present, the system automatically switches over to the next of the 4 FM rear window antennas.
The switchover speed depends on the frequency at which interference occurs. This prevents continuous switching between the antennas in areas where FM reception is very poor which in turn would result in interference.

Demodulation/digitization of the radio frequency locking signals
The demodulator is located in the left antenna amplifier module. During demodulation, the useful signal (radio frequency locking signal) is generated from the received HF signal and then digitized. The signals processed in this way are supplied to the rear SAM control unit with fuse and relay module via a separate line.

Antenna diversity function (TV)
The diversity feature serves for reduction of reception interference. The diversity feature is integrated in the TV tuner, with code 860 TV tuner (up to 31.5.05) or TV combination tuner (analog/digital), with code 863 Digital/ analog TV tuner (as of 1.6.05).