Aerial Amplifier and Aerial Diversity Module

Aerial Amplifier And Aerial Diversity Module

Aerial amplifier and aerial diversity module
The system consists of an aerial amplifier and a diversity module in the head unit. The aerial amplifier relays the amplified aerial signals to the head unit via 2 separate leads. The head unit then selects the best aerial signal using the diversity function.
By contrast, with the previous systems the aerial diversity module switched between the various aerials, amplified the signal and then passed it on to the head unit via a single lead.

Depending on national-market version, the configuration of the aerial amplifier can vary. Depending on the vehicle equipment level and national-market version, the aerial amplifier may contain the following aerials:
- FM/AM/weatherband aerial
- FM 2 aerial (depending on equipment level)
- DAB aerial (frequency range: band III)
- VICS aerial (VICS stands for Vehicle Information and Communication System, Japan)

Functional description
The first aerial lead carries the signals for AM, FM and weatherband. The second aerial lead carries the 2nd FM signal. There are also aerial leads for the DAB aerial (frequency range: III band) and the VICS aerial. All aerials in the aerial amplifier are remotely powered.
Remotely powered is an electronics term. Remotely powered means the device receives its power supply from remote systems (e.g. amplifier) via leads which are actually for the purpose of transmitting the signal. This makes use of the fact that the signal is transmitted as alternating current. The superimposed direct current power supply has no effect on the signal used.
Consequently a RAD_ON lead (Radio ON) for the power supply is no longer required.
In the US version, the aerial amplifier also supports Weatherband frequencies. Weatherband is transmitted on 7 channels in the frequency range 162.4 MHz to 162.55 25 MHz (25 kHz increments). The Weatherband tuner is incorporated in the head unit in the FM module.
The aerial amplifier amplifies the high-frequency signals (HF signals) from the individual aerials. The amplified aerial signals are transmitted to the head unit via separate leads. In the FM band, the head unit then selects and uses the better of the two signals for FM reception.







System overview
The system overview shows the following functional network:







The aerials in the rear window are connected to the aerial amplifier by 3 leads.
The rear window heater element is supplied with power via the rear window heater wave trap circuit.
The wave trap reduces the transmission of interference pulses in the aerials in the rear window from the vehicle electrical system. With an unprotected aerial system, those interference frequencies enter the aerial system from the vehicle's electrical system through the power supply to the rear window heater.

Diagnosis instructions

Failure of the component
The head unit has a self-diagnosis capability. The head unit can detect the following aerial system statuses by means of the current flow of the remote power supply:
- No aerial connected (broken circuit)
- Passive aerial without aerial amplifier connected
- Active aerial with aerial amplifier connected
- Short circuit to earth

If a fault occurs on the aerial amplifier, the following behavior can be expected:
- Fault entry in the headunit

A function check on the aerial amplifier can be performed using the diagnosis system.


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