Rear window antenna module, component description - GF82.62-P-3131SXJ

MODEL 216.3, 221.0/1 with CODE (498) Japan version up to model year 08/YoM 07

Shown on model 221

Fig 1: Identifying Rear Window Antenna Module - Shown On Model 221

Courtesy of MERCEDES-BENZ USA

Location

The rear window antenna amplifier module is attached to the rear roof frame.

Task

To process all antenna signals received via the antenna structures in the rear window.

The following signals are processed:

Radio reception (AM and 4-way FM diversity)
Vehicle Information and Communication System (VICS) in FM band
Radio remote control central locking (FZV)
TV reception for analog and digital television

In order to decouple the rear window heater from the antenna function, the heating field is connected as follows:

On the left, the heating field is connected to ground via a block circuit in the rear window heater connection line.
On the right, the heating field is connected to the voltage supply of the heater via a block circuit in the C-pillar.

Design, shown on model 221

Fig 2: Identifying Rear Window Antenna Module Components - Shown On Model 221

Courtesy of MERCEDES-BENZ USA

Function

AM reception

The prerequisite for AM reception is that a phantom voltage (DC offset) of 0 volts is applied at the IF [ZF] input of the rear window antenna amplifier module. The FM diversity function is deactivated in AM mode.

The radio signals of the AM frequency band are picked up and amplified by the rear window antenna amplifier module and then transmitted to the audio tuner control unit (N93/1) at the HF-Out output via a coaxial cable.

FM reception (with 4-way FM diversity)

The prerequisite for FM reception is that a phantom voltage (DC offset) of 12 volts is applied at the IF [ZF] input of the rear window antenna amplifier module. AM mode is deactivated in intermediate frequency diversity mode.

Radio reception in the FM frequency band is realized via an antenna diversity with 4 antennas. The associated antenna signals are picked up at the rear window, amplified and transmitted to the audio tuner control unit at the HF-Out output via a coaxial cable.

The audio tuner control unit transmits an intermediate frequency signal to the rear window antenna amplifier module as a quality indicator (IF-IN input). On the basis of this indicator, the module switches the FM antenna with the best reception quality through to the tuner.

In order to improve the effect on reception caused by transmitted wave reflection with multipath reception, 4 FM receiving antennas (FM1 to FM4) are installed in different locations. An FM diversity module that is integrated in the rear window antenna module performs a quality evaluation of the current reception characteristics of the 4 FM receiving antennas.

Radio remote control central locking (FZV)

The signal from the central locking system receive antenna is picked up by the rear window antenna amplifier module.

The signal from the RRCL antenna is switched to the RRCL receiver that is integrated in the rear window antenna amplifier module.

The RRCL signal is demodulated in the RRCL receiver and then transmitted to the rear SAM control unit with fuse and relay module (N10/2) via the RRCL output of the rear window antenna amplifier module.

TV reception

The terrestrial TV stations are received in parallel via 4 TV antennas in the rear window by the rear window antenna amplifier module and amplified. Then the TV signals are relayed to the TV antenna selector (A2/79) via coaxial cables.