M
Myauk
- Jan 1, 1970
- 0
I have been studying the Tuner Front End Designs.
According to suggestions from previous discussions, I studied the
application notes and circuit diagrams of front end modules.
The following things are those that I am getting confused with:
1. According to my understanding, there are several allocated channels
for television according to CCIR, France, USA, or China Tables. Let's
say a tuner front end is connected to the antenna, the first thing it
needed to be done is to select a typical channel among the channels
available. I understand that 'tank circuit' is used with variable
capacitance to tune to the desired channel.
So I imagine that a tuning unit with varicap diode will do the
selection of channel. The capacitance is set by the voltage applied
(up to 33V range). And this voltage might be supplied by a typical DAC
and register where the values are set by I2C control.
But practically, when I studied the tuner application note, I found no
clue for setting the capacitance for tuner tank circuit.
What I found is something 'Charge Pump', Prescaler, Divider, 15 Bit
Counter, Phase Detector, Op-amp unit, detecting Local Oscillators,
(sorry if I presume wrongly) and the output VTU controls the tuning
part. (according to a tuner front end design using the IC: SN761678B
TV TUNER IC.
There I am confused!
Can anybody show me some links or explain to me about it so that I
could start learning?
Regards
According to suggestions from previous discussions, I studied the
application notes and circuit diagrams of front end modules.
The following things are those that I am getting confused with:
1. According to my understanding, there are several allocated channels
for television according to CCIR, France, USA, or China Tables. Let's
say a tuner front end is connected to the antenna, the first thing it
needed to be done is to select a typical channel among the channels
available. I understand that 'tank circuit' is used with variable
capacitance to tune to the desired channel.
So I imagine that a tuning unit with varicap diode will do the
selection of channel. The capacitance is set by the voltage applied
(up to 33V range). And this voltage might be supplied by a typical DAC
and register where the values are set by I2C control.
But practically, when I studied the tuner application note, I found no
clue for setting the capacitance for tuner tank circuit.
What I found is something 'Charge Pump', Prescaler, Divider, 15 Bit
Counter, Phase Detector, Op-amp unit, detecting Local Oscillators,
(sorry if I presume wrongly) and the output VTU controls the tuning
part. (according to a tuner front end design using the IC: SN761678B
TV TUNER IC.
There I am confused!
Can anybody show me some links or explain to me about it so that I
could start learning?
Regards