TV tuner, function - GF82.60-P-3109-02TJ
Function requirements:
- On-board power supply applied
- Authentication positive
- Circuit 15R ON
Function
The TV tuner communicates internally with the COMAND operating, display and control module (A40/3). External communications are affected by MOST using the audio gateway control unit (N93/1) and other system components.
Basic TV tuner controls:
- 4-fold antenna diversity, divided into audio and video signals
- Audio antenna diversity
- Video antenna diversity
- NTSC receiver
- Signal processing
TV tuner modules for audio and video
The TV system operates with a total of 3 reception modules, 2 tuners being used for picture processing and 1 tuner for the sound signal. The PLL tuners used cover a reception range of 45 to 866 MHz. The reception area is internally divided into 3 bands: VHF low, VHF high and UHF. Each band has its own controllable pre-stage. The tuner outputs are designed symmetrically. The TV tuner box has 4 antenna inputs, into which signals of the ideally complementary car antennas are fed.
The antenna inputs are assigned to the 3 TV receiver units as follows:
- Ant 1, Ant 2, Ant 3, Ant 4 are assigned to the audio receiver unit.
- Ant 1, Ant 2 are assigned to video reception route 2.
- Ant 3, Ant 4 are assigned to video reception route 1.
Each reception unit can select the best suited input signal independently. Audio/picture antenna diversity work separately in order to avoid unpleasant disturbing noises or picture obliteration during mobile reception.
Multistandard signal processing
The signals mixed by the tuner on the intermediate frequency are demodulated during subsequent signal processing. Both positive as well as negative amplitude-modulated signals can be processed. The demodulation stage for the sound signal receives a narrow-band filtered intermediate frequency signal which is virtually without video shares and cannot cause any further sound interference. The audio signals are "AM" or "FM" depending on the TV standard. AM sound and FM sound are converted to a second, lower intermediate frequency and then demodulated.