2 Channel Onboard DDC

[maxwellb]

Hi,

I recently purchased a used PXI-5142 2-Channel 100 MS/s digitizer with onboard Digital Down Conversion (DDC) to replace an old PXI-5112 100 MS/s digitizer. I currently have it set up to acquire bursts of 100 MS/s data, which I then downconvert in software.

I was really excited about the onboard DDC capability of the card, but when I went to try and implement it, I realized that it can only downconvert one channel at a time. This makes that function mostly useless to me, because I am measuring a current and a voltage signal which must be precisely synchronized in time. It looks like I would need two cards to use onboard DDC, and at that price, I will stay with software.

Are there any NI digitizer boards which are capable of dual-channel simultaneous onboard DDC?

How fast is the DDC? Can it downconvert and empty the memory buffer fast enough to keep up with 100 MS/s sampling, allowing full rate acquisitions of indefinite length?

I have thought of one other option, which is to buy a FlexRIO card, a digitizer module, and the FPGA module. I could do the DDC on the FPGA. That would be around $10,000, which might end up being the cheapest way to go...

Thanks!

[Henrik_Volkers]

I don't have and know this this card, but the spec looks charming 😉

As far as I understood the spec page 23, you should be able to use the (single) DDC on both channels and store both channels in one complex value.

I have to wait for a >= 250M/s version for my signals...  for now it's analog downconversion ....

[maxwellb]

Thanks, Henrik! That would be great if I can. I'll have to take another look.

Why do you need a 250 MS/s version? FYI, I have successfully used software DDC on a 7 MHz signal being sampled at 3 MS/s.

[Henrik_Volkers]

We capture and process hetrodyne laser interferometer signals with 80MHz 'carrier' and  40Mhz bandwidth ...

Since we unwrap the phase and the amplitude is not as stable as we would like it, subsampling leads to difficulties..