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

MODEL 216.3, 221.0/1 except CODE (494) USA version except CODE (498) Japan version up to Model Year 8

Illustrated on model 221

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

Courtesy of MERCEDES-BENZ USA

Location

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

All antenna signals that are processed by the rear window antenna amplifier module are received via the antenna structures in the rear window.

Task

The tasks of the rear window antenna amplifier module are:

Radio reception (AM and 4-way FM diversity)
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

Fig 2: Identifying Rear Window Antenna Module Components

Courtesy of MERCEDES-BENZ USA

Functions

AM reception (long wave, medium wave, short wave)

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 national 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 evaluation, 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 amplifier 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. Processing of the signal depends on the vehicle equipment.

On vehicles except code (889) Keyless go

The RRCL [FZV] receiving antenna in the rear window is switched to the RRCL [FZV] receiver integrated in the rear window antenna amplifier module. The RRCL [FZV] receiver demodulates the RRCL [FZV] signal of the transmitter key (A8/1) and then transmits it directly to the rear SAM control unit with fuse and relay module (N10/2).

On vehicles with code (889) Keyless go

A distinction is made between the following 2 cases:

Open/close via transmitter key, without Keyless Go function
Open/close via Keyless Go function

Open/close via transmitter key, without Keyless Go function Requirement

A phantom voltage of 0 volts is applied to the Keyless Go contact at the rear window antenna amplifier module.

The RRCL [FZV] receiving antenna of the rear window is then switched to the RRCL [FZV] receiver integrated in the rear window antenna amplifier module. The RRCL [FZV] signal of the transmitter key is demodulated in the RRCL [FZV] receiver and then transmitted directly to the rear SAM control unit with fuse and relay module.

Open/close via Keyless Go function

Requirement

A phantom voltage of 5 volts is applied to the Keyless Go contact at the rear window antenna amplifier module.

The RRCL [FZV] receiving antenna is switched directly to the Keyless Go output and forwarded to the Keyless Go control unit (N69/5). In this case, there is no evaluation of the RRCL [FZV] signal in the rear window antenna amplifier module. The evaluation takes place in the Keyless Go control unit.

TV reception (analog)

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 combination tuner (analog/digital) (A90/1) via coaxial cables.

The antenna diversity function is a constituent of the TV combination tuner.

TV reception (digital)

It is also possible to receive the terrestrially broadcast digital television stations via the existing antenna structures. The "DVB-T" standard is supported.

Digital TV signals are processed in the same way as analog TV signals.

The TV combination tuner (analog/digital) automatically switches between analog and digital TV reception of the same channel depending on the current reception status. The user cannot influence this.

DVB-T is the abbreviation for D igital V ideo B roadcasting-T errestrial and means that more channels can be received with better, digital quality using a normal antenna. Several European countries already have DVB-T or are in the process of setting it up. It is transmitted via the same TV bands as the analog TV signals.