need to know about digital upconverters

[R110]

Hi all
I need to know about digital upconverters ( both base band to RF and IF to RF upconversion) . I want to know about the principles of it's operation and the effects of this part (in a digital transmitter) on the other parts , and also the effects of the other parts ( e.g. power amplifier ) on upconverter. I study about DVB-T transmitters and I focused on this part.

Why should we convert it from BB to IF and then to RF , Why not directly from BB to RF.in the second case we can have fully digital upconverters in the configuration of the trasmitter and it would be more reliable ( by using digital filters ) and may be more economical! . but there is another question , why most of the DVB_t transmitter manufacturers use another kind of configuration ( BB to IF and then If to RF) ? Is it because of technological constraints or something else?

as use see I have lots of questions in this area and I'm looking for a kind gentle person to get understood.

If you are one , just let me know to leave you no time to scratch your head

have a nice time
Ramin

 

[mgpc]

I need to review some of the my books but the jist of the problem with up-conversion, as I recall from very long time ago, is that if you do not go through an intermediate frequency, then your conversion circuit may interfere with the antenna(?). This doesn't sound logical to me at this point but I'm certain it has something to do with unwanted radiation.

This is a very fundamental problem in all RF circuits and this problem exists since the early 1900s. So I presume all good digital communication book will have a short section on the topic.

I'll have to double check on the accuracy of my statement and will get back to you later.

MGPC

 

[elcielo]

I want gap-filler(transposer) document.
plz help me.

 

[dll_embed]

The second way of upconverter is Zero IF structure. It is a very hot topic in the industry. There is some challenge with this structure. I recall some of them are:
1. DC coupling
2. LO leakage.
3. interference rejection.
etc.

And there is a good ieee paper explaining all the issues related with the structure. I can't remember the name exactly. If you want i can help to find and upload it.

regards

 

[ninhawk]

hi dll_embed:

please upload the paper about Zero IF upconverter and other references if you have.

 

[elcielo]

www.analog.com

AD9857

AD9772
AD9774
AD9777

etc..

 

[dll_embed]

Hi,

After searched the forum, i found this paper has been uploaded. Please follow the url below for the paper i mentioned.

**broken link removed**