Is it possible to implement a modem using FPGAs?

[jaz396]

FPGA's??????????

Hello,
Is it possible to implement a modem using FPGAs? what is the limitation of using FPGAs in electronic design ? and what is the advantages of using them over the traditional design techniques ?

Thanx,

 

[hoangthanhtung]

FPGA's??????????

As I think, when you try to use FPGA to implement a modem,the limitation is FSK modulation/demodulation. FPGA is only pure digital so the RF block you have to use private IC, which is connected with FPGA. We can use FPGA for control signal, MUX channel block, generate line code or other.

This is my opinion. Bye

 

[Big Boy]

Re: FPGA's??????????

In fact, someone could be quite surprized what DSP functions could be done in an FPGA. Especially with the hardware multiplier in the newer FPGA.

The thing is that it come much harder, and people doesn't usually do this in FPGA, so you may have a real hard time finding pre-made cores.

To do it on FPGA, it come to much bore basic math concepts, which need to be implemented in FPGA. This can be real die-hard math, but is still theorically possible.

 

[mc_navman]

Re: FPGA's??????????

It would seem that the FPGA is going to be powerful enough you need to add ADC and DAC. It would be quite possible to do a 1200 or 2400 baud modem but if you want a high speed modem there are a few tricks involved and so it might be best just to get a chip from Rockwell (and they will have a reference design.)

Is this to make money selling cheap modems? if so give up. A 56k modem is not so simple and they are very cheap.

Whatever your purpose this would be a fair to large size project.

 

[Big Boy]

Re: FPGA's??????????

It is possible to do DAC and ADC apps, but you need simple external components (resistors, capacitors and comparator).

Implementing a DAC can be done as a delta-sigma DAC. An ADC can be implemented like the above DAC, plus a comparator (special form of op-amp).

Read Xilinx application notes XAPP154 and XAPP155 (on Xilinx site, or simpler to do a search in google for the above application notes).

Big Boy

 

[jaz396]

Re: FPGA's??????????

Hello ,
thank you guys for your help .
I just want to ask whether the new modem (if implemented using FPGA) would be smaller in size or I will end up with the same size of what is existing in the market or even larger .

thanks again ,

 

[mc_navman]

Re: FPGA's??????????

It seems improbable that an FPGA design could be smaller in physical size than an ASIC design which is what a Modem on the market is. On top of the actually FPGA you will need powersupplies for the core voltage and analog section. You will also need a PCI interface if you a thinking of using this in a PC. I suspect that the FPGA will use a lot more power also (and therefore produce a lot more heat.) If this project is for an exercise for uni then fine but if it is comercial then perhaps you need to worry about your company going out of business soon and start looking for a new job. I think I can buy a PCI modem for about US$10 so there is little room for making money.