Antenna amplifier module, component description

P82.62-3254-06

A2/72 Window antenna amplifier module 2

Location

Window antenna amplifier module 2 is glued on above the rear window heater.

Task

 Receiving signals

 Selection of signal sources

 Signal filtering and amplification

 Relaying signals

Receiving signals

Window antenna amplifier module 2 receives the following signals from the antenna structures in the rear window:

- Amplitude-modulated and frequency-modulated radio signals (AM, FM)

- Signal for radio remote central locking

Selection of signal sources

Window antenna amplifier module 2 automatically selects the ideal source for the FM signals (antenna diversity).

Signal filtering and amplification

Window antenna amplifier module 2 filters the frequency bands and amplifies the antenna signals.

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Relaying signals

Window antenna amplifier module 2 forwards the following signals

- Signal for radio remote central locking over coaxial cable to rear SAM control unit with fuse and relay module (N10/2)

- Radio signals (AM, FM) over coaxial cable to each audio unit

 Depending on equipment installed, one of the following audio devices is installed:

- Radio (A2), with code (523) MB Audio 20 radio

- Radio and navigation unit (A2/56), with code (525) MB Audio 50 APS radio

- COMAND operating, display and controller unit (A40/3), with code (527) COMAND APS with single DVD drive (with navigation)

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Design

The following components are integrated into the window antenna amplifier module 2:

- Amplifier for AM antenna

- Filter and amplifier with diversity system for FM antennas

- Receiver unit for radio remote central locking

The processed signals are picked up by the rear SAM control unit with fuse and relay module and from each audio unit over coaxial sockets.

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Extremely conductive silicone material is used as the electrical connection material between the antennas in the rear window and window antenna amplifier module 2. The silicone material is pressed against the silver surfaces of the antennas by spring force.

 The rear window is equipped with all the antennas irrespective of the special equipment.

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Function

 High-frequency signal filtering and amplification

 Radio remote central locking

 Antenna diversity

High-frequency signal filtering and amplification

The frequency bands (AM, FM) made up of the incoming signals from the antennas on the rear window are selected using electrical filters. These filters are designed differently, as the transmission frequencies vary from country to country.

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The filtered frequency bands are then selectively amplified.

Radio remote central locking

The signals for the radio remote central locking system are demodulated and digitized by window antenna amplifier module 2.

 During demodulation the useful signal is separated from the high-frequency carrier frequency (transmission frequency).

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Antenna diversity

The receiver-specific changeover between the FM antennas in the rear window is implemented during the following process:

- Window antenna amplifier module 2 routes the signals of the active FM antennas to the radio tuner in each audio unit.

- The integrated radio tuner uses the incoming FM signals to generate the reference signal.

- This reference signal is transferred to window antenna amplifier module 2 via a separate lead.

- Following demodulation, the diversity processor of window antenna amplifier module 2 checks whether the IF signal is free of interference. In the event of interference, a switch is automatically made to the next antenna in the rear window.

 The switchover speed depends on the frequency at which interference occurs. In the case of poor FM reception, this serves to prevent a continuous switchover from one antenna to the next; something which would also interfere with reception.