400 Mb/s ADC

I think we will try atmel...Jeff

hmmm...interesting idea

When did Atmel start making flash ADCs? Can someone actually buy these now? How much do they cost?

see:

for our "merely" 250 Msps particle physics project.

Paul Smith Indiana University Physics

could be

though

Yep, have been around for quite some time.

My guess is maybe $500 for the 1 G sample 8 bit devices.

How many do you need?

Maxim also has the MAX104 (1 Ghz,) and MAX108 (1.5Ghz) and other lower speeds in the range 500Mhz and up.

It sounds like you *really* want to do the FFTs on PCs, rather than on an outboard DSP. (for your application that might make sense, as you're only building one or a few of these things, and software development will be hugely easier) You might try "striping" the data across multiple PCs. After the ADC, block the data into 64K "packets", and have 2 or 3 links to FPGA "NICs" that receive blocks of 64k samples (plus maybe a sequence number) and DMA them over PCI.

Even if you do try to convert to SCSI or Fibre Channel and use standard adapters, you might still want to consider the striping idea.

I worked on something similar that never got built. We wanted to record the output of multiple 200MHz 12 Bit ADC and store it in a harddrive. There was some company that sold an optical interface harddrive that could manage the speed but we had decided to use multiple harddrive and split the data among the drives to achieve the desired throughput similar to what RAID drives do. As for FFT's they are done way faster in a FPGA than in any processor including DSP processors. The only problem is the cost of the FPGA if you need really big FFT's (4K 24 bit wide). The card I was working on was basically an RF spectrum analyzer for a missile so things needed to be done in a hurry. The harddrive thing was for a prototype so we wanted to store the RF we were seeing without processing it.

Ray

here's a reasonable place to start digging:

John

One of the articles listed a price of $795 for the 2 Gspl/s converter in 1000's Peter Wallace

It doesn't necessarily have to be a big FPGA, it depends on the size of the FFT as well as the required latency and throughput. Size can also be reduced by working with mixed fixed and floating point. I've done a number of FFT designs in FPGAs, some of which are in rather small devices. There is a 4K point example in an old 5v Virtex shown on the gallery page of my website.

dM> ... throughput similar to what RAID drives do. As for FFT's they

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--Ray Andraka, P.E. President, the Andraka Consulting Group, Inc.

"They that give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -Benjamin Franklin, 1759