Dual Channel continuos signal acquisition using NI PXIe 5641R

[atifyaqoob]

Hi,

I am doing a continuous signal acquisition using PXIe-5641R IF Transceiver and 2 x PXI-5600 Downconverters. I am basing my design on the example code "PXIe-5641R Stream to Disk"given in the instrument driver example programs folder. I have modified this application to add the external digitizer and also a queue which can keep the samples before recording on the hard drive.

Currently, I need to record both the antenna inputs at the maximum sample rate (25MS/s). But, unfortunately I am not able to do it. I can record the samples uptil 12.5MS/s and also at lower speeds, but it gives an error if the max sample rate is used. I have attached both the programs, the orginal example program and the modified version of it. The same problem occurs with both the programs!

Any help to fix this issue would be very much appreciated as I need that application to work asap!!

Thanks,

Atif

[atifyaqoob]

Hi,

Also, by using the FPGA programming interface for the dual channel continuous acquisition, I have made a project which also works fine uptil 12.5MS/s. The project is also attached here for reference. This program can actually record dual channel signals at 25MS/s as well but the recorded signal is no more continuous.

Apparently, there is no overflow of the buffers as observed from the overflow indications. But by analyzing the signal values, it is found that recorded signal is not continuous at this speed while it is perfectly ok uptil IQ rate of 12.5MS/s.

Any Help!!!!

Thanks,

Atif

[JerryAL]

Hi atifyaqoob

Unfortunately, you have maxed out the streaming rate for this specific module.  If you look at the module block diagram in the help file, you’ll see that there is a PCI link to the PCIe bus.  This limits total streaming bandwidth to about ~110 Mbytes per second.  This includes data streaming down to the module as well as the data streaming from the module the host computer. 

Streaming two channels at 12.5 MSps, which corresponds to 100 MBytes/s, is pretty much maxing out the module’s streaming ability.

Jerry

[atifyaqoob]

Hi Jerry

Thanks for the help!!

But, do you think we can achieve a streaming rate of 200 MBytes/s with any other module?

Thanks

Atif

[JerryAL]

Hi atifyaqoob- You probably should contact your local NI Sales representative to get the best option from where you are, what you have, and where you need to get to. My first guess with what I currently know that you have, 2 NI 5600 RF downconverters already would be to use a second NI 5641R.  You already have the code written, it will work on one channel on each module, etc.  The trade off is the cost of the second module.  I don’t know of a simple single module replacement that can be replaced as easily.  There might be a NI FlexRIO / Adaptor module combination that might work, this would require modifying your FPGA code a bit to deal with the lack of DDCs, etc.  There will probably be other modifications of your current host/FPGA code that would be required as well.

Jerry

[atifyaqoob]

Thanks Jerry for your help!

Atif