bandwidth issue

[Al-rawachy]

Dears,

as I read in the specification of RFSA 5633E, the maximum bandwith that can I get is 50 MHz. when I use IQ acquistion I use the IQ sample rate in order to change the bandwidth of the receiver, but unfortunately I couldn't get the 50 MHZ that been mentioned before!! any idea? Thanks in advance

Sincerely

[mbb25]

Bandwith is 50 MHz above 330 MHz center frequency.  Are you tuned above 330 MHz?  See also the 'Bandwidth' section of the specifications:

http://www.ni.com/pdf/manuals/374957b.pdf

[shawn.t]

Can you share your VI or a screenshot of your configuration?

[Al-rawachy]

Thank you for your feedback,

eah, actually I know that i have to use above 330 MHZ, I got 50 MHZ bandwidth only in the case og spectrum acquistion but in IQ acquistion I couldn't get that?  please have a loook for the attached result, as you can see I do power sweep from 1.01 GHZ to 1.035 GHZ with center frequency 1.01G. It can be seen that the result onlu shown until 2 MHz and the other values still with noise floor

Thanks in advance 

regards

[shawn.t]

If the indicator labelled 'data' is your acquisition waveform, then it looks like you are getting a 50 MHz IQ rate at least (it's dt is 20 ns ~ 50 MHz). What is the generator doing at this point? Are you generating a broadband signal (i.e. 50 MHz wide), or are you sweeping the generator with a CW tone over frequency? It looks like the latter according to your front panel. 

Also, are you trying to acquire the entire sweep with one acquisition, or are you trying to acquire once for every generator frequency? I see the front panel mentions list mode. Are you using list mode?

My gut says that you are getting a 50 MHz bandwidth acquisition, but something else in the configuration is leading to the results that you're seeing. Can you share your block diagram?

[Al-rawachy]

hi SHawn,

Yes I am using list mode with frequency sweep as mentioned in the front panal. Please H ave a look for the code. It looks complicated but I am sure you can understand it. thanks again

[mbb25]

I don't have hardware at the moment to try running your VI.  Also, there are several subVIs missing ("1Clear Error.vi", "1Voltage to Watt.vi", +4 more).

I agree with Shawn that the cause is just as likely on the generator side as the analyzer.  Perhaps running the following shipping examples will help you figure out which half of the setup has the problem:

   <LabVIEW>\examples\instr\niRFSG\RFSG Configuration List Frequency and Power Sweep (Timer Triggered).vi

   <LabVIEW>\examples\instr\niRFSA\RFSA Getting Started IQ.vi

I see you are also using multiple generators and multiple analyzers, synchronized with TClk.  Above examples aren't set up for that, but could allow you to isolate the problem/check for understanding using just 1 analyzer and generator.

[Al-rawachy]

there is no vi missing, all vi(s) needed you can get it from the subvi folder. Although I am using Ni tclk to synchronize more generators and receivers, I am using only one generator and one receiver at this moment. I've  seen those examples many times but I am still have something unclear regarding the bandwidth issue? thanks for your feedback

[mbb25]

So you are seeing the same behavior (only 2 MHz of bandwidth) using the shipping examples?  If the problem reproduces there, I'm stumped.  If not, the shipping examples should help you check your code.

[shawn.t]

What it looks like is that you're running the sweep on the generator correctly, but only fetching an acquisition on the first point. I think you can fix this by doing two things:

1. Use multi-record acquistion. Set the number of records to be equal to the number of steps in your frequency sweep. Each acquisition will return the number of samples configured so you'll need to store an array of waveforms, run your FFT on each one, and calculate your results for each step---not the entire sweep at once.
2. To do this, you need to synchronize the reference trigger of each acquisition with the start of the SG frequency step. You should be able to export the timer event from the SG to something like PXI_Trig0 and bring that in as the reference trigger on the SA. This is similar to how you're export the SG start event to PFI0 and importing the start trigger on PFI1. Oh, you may have to choose different lines for multiple instruments or you could choose one as the master for all SAs.