Question on digital tv receiver

[nedsana]

qpsk ad8333

Hallo folks,
I am new to digital communication and I've been studying it for some time.
I need to make project fora simple digital tv receiver, or a Set Top Box. I went through this forum and I found some very useful materials. But I still need to ask some questions to the professionals, so I could clarify my idea

The first thing I would like to ask is whether I can use an analog tv tuner like UV916? (I could not find any silicon chips so I think that a classic approach could do the work).

The more important question concerns the demodulator. I went through the DVB standard and some chips like TDA10021 and L64781, which perform the whole OFDM tasks except the MPEG decoding. And here arises my question: if I use a QAM/QPSK demodulator like AD848 or LT5517, which outputs the I/Q basebands, can I perform this OFDM procedure on a software level? Can these demodulators (AD848 or LT5517) cause a low quality of the picture?

Thank you in advance.

Nedsan.

 

[nedsana]

Ok, obviously I asked a stupid question.
I am interested in the devices which can be used for developing STBs.
It turns out that I can't find a proper demodulator for my purpose. Can you suggest me a device which can demodulate the IF signal (37~40MHz) from the tuner?
Thanks.

 

[pedro.alves]

Sorry, but your question isn't clear for me
do you like one tunner to convert the signal of the DVB to one IF=37~40MHz, and use one software to demodulate the signal OFDM?
If are this your problem: i will recommend you look components like: MAX3541, MC44S803, etc....

 

[nedsana]

Thank you for your answer PedroAlvares,
I will try to explain myself better.

As far as I understood it, the regular tuner boxes, like UV916 capture the RF signal (ranging ~ 50MHz - 900MHz) and the output is a signal with a frequency 35MHz ~ 40MHz (this depend on the standards of the different countries). The devices you suggested me, MAX3541 and MC44S803FS are tuners as well, and they seem to do the same job as UV916.

The device which I want to make needs to capture the DVB-T signals. So my question is:
Can I capture DVB-T signals with UV916? Can this cause low quality of the picture?

And another question:
Can you suggest me a demodulator for extracting the Q/I signals from QAM signal?
Here I will give some more details.
I need the demodulator to work with the IF signal form the tuner (this signal was 35MHz~40MHz). By now I have picked up AD8333 and MAX2450, but I am afraid that they work only with QPSK modulated signals. Can these be used for QAM demodulation? If not are you aware of any other chips for this purpose?

Thank you for your answer again. I hope getting some more clues on my task

Nedsana.

 

[pedro.alves]

why don't you use ADI Tuner Type Number: ADMTV102 with this Kit Legend Silicon Demodulator Type Number: LGS-8GL5, LGS-8G75