VST synchronize SG & SA using configuration list

[yafoteer]

Hi - there may be an example for this but I can't find it.

I have a 5644R VST and want to do a fast gain measurement of multiband antennas across a wide band of freqs.  In labview 2014 I do this psuedo code:

initialize SA for spectrum, RBW of 3kHz

initialize SG for CW

initiate SG generation

loop

   load freq into SG

   load freq into SA, span of 100Hz

   read SA

repeat for all freqs

This takes about 30ms per freq, which seems fast but is slow for what I need.  That is slower than the VNA I am trying to frree up for other things.  Maybe setting the span to Zero Span would help but when I try to enter 0 in the Span input I get an error.

I want to try using configuration scripts on both the SG and SA to see if that speeds things up.  For this to work, the generator and analyzer have to be synchronized. There are examples involving synching RFSA and RFSG but they do not work with the 5644R.  How can I sync the SA and SG on the VST?

And, will this speed things up at all?  

TIA

Ed K

[AirFrantz]

Hello,

Using a configuration list would definitely speed this up a bit, as you would bypass the rfsa/rfsg driver when switching the frequency.  The only drawback would be that you may lose power stability when switching faster.  I believe the transition time is somewhere around 300us to be within .5dB of desired power, and 300ms to be within .1dB of the desired power.

To synchronize your config lists for the sa and sg, you would need to implement some sort of handshaking triggers(for use as script triggers or config list step triggers).  You can use 2 PXI_Trig lines for this.  One way could be to call the RFSG export signal on the sg side, and export the 'configuration settled event'.  Then on the sa, use this signal as a trigger to take your measurement and export either the 'End of Record' event or the 'Done' event to trigger your next configuration for the sg side.

[yafoteer]

That sounds pretty cool, so I started reading up about scripts and triggers.  There is a lot of info packed very densely into help files.  

For instance, there is a wait script command which waits on a trigger.  But I see no command that generates a trigger.  How is it done?

I am starting to work on it.  Any resources you can recommend?

What about using the FPGA instead of lists?  I know even less about doing that.  Can I keep it on the card?

Thanks

Ed

[AirFrantz]

Ed,

Unfortunately there are not a lot of good references for scripting with NI-RFSG, I think the Help file is where to find most of the info about it.  You will configure scripttriggers using the RFSG configure trigger VI, and define output triggers using the 'Export Signal' vi's in RFSA/RFSG.  Alternatively, you can also create markers in your scripts, and use the export signal vi to send these to physical lines.

I'm not so sure on the FPGA side of this, I would imagine that something would be possible but I'm not very familiar with it.

[yafoteer]

Jon - this plan works.  I found an example vi which I have modified heavily to do what you suggested, and it runs like a champ.  I can go as fast as 500uS/freq and still get the resolution I need.  Once I get the code pretty I will close the loop and post it here.  Thanks.