5441 streaming IQ rates

[TimS.]

Hello,

I am currently trying to develop an application that uses the PXI-5441 and PXI-5610 to stream I16 IQ files and there are a couple questions that I've thought of while programming. I know that when using the RFSG drivers the IQ rate must be (100MS/s)/n discrete values with the highest "n" being 1024. Every RFSG file reading application I've seen and developed so far uses the "RFSG resample and write" block to ensure that a signal is being played out at an RFSG valid IQ rate regardless of the file's IQ data rate. I've experimented with the RF Record and Playback example under www.ni.com/streaming and I noticed that there is no resampling done before IQ data is written to memory. Also, it seems as if more IQ rates than just (100MS/s)/n are valid when using the 5441 and the OSP. (i.e. I've entered an IQ rate of 2.11222 MS/s, picked at random, to the FGEN property node and the coerced value still says 2.11222 MS/s. However, with the RFSG property node the 2.11222 MS/s gets coerced to 2.17391 MS/s)

It is possible that I will be reading files, up to the 6.6MHz bandwidth limit, into my streaming application that do not follow the (100MS/s)/n rule. So my main questions are:

1. Can the PXI-5441 handle more sample rates than (100MS/s)/n, below 8.333MS/s, when the OSP is enabled? (i.e. IQ rate = 2.11222 MS/s, which is not a valid (100MS/s)/n rate)
2. If not, what would be a good way to resample the interleaved I16 IQ data to a valid IQ rate while streaming and would the overhead involved with this be too much to still stream data?
3. As a side question, I may also need to AM/FM modulate the IQ data while streaming. Has anyone done this successfully before? I haven't tried it yet but my main gut feeling is that trying to modulate the IQ data while streaming would cause the streaming to fail.

Please help out with any of the three questions if you have feedback.

Thanks,

Tim S.

P.S. I've attached an excel spreadsheet listing the valid PXI-5671 IQ rates

[hoffiz]

Hi,

Like you said the possible IQ rates are as stated in the help: “(100 MS/s)/n, where n = 12, 14, 16... 512,516,520... 1024 (for example, n is divisible by 2 between 12—512, and divisible by 4 between 512—1024). Using one of these IQ rates enables the DUC.” If you take a look at the list you attached 2.17391MS/s is 100MS/s/46 (i.e. n=46). The PXI-5441 can only handle the interpolations specified in the manual when the DUC is enable.  5441 Specifications page 29.

For your third question if the rate that you need is one available on the DUC you can use the Modulation Toolkit to aid yourself in the AM/FM modulation of your signal.

I hope it helps