NIRFSG time event interval

[thoalfukar]

Hello All,

I using NIRFSG  for signal generation and specifically the List mode configuration. within that mode I have to specify the time interval for each power level, and that is done by calculating the time according to the number of required samples.

For example, if I want 10000 samples for each measurement the time interval for each power level would be = 10000 / sample rate (10MHz/sec). this would give me 0.001 micro sec time interval for each measurement.

The problem is when I checked the measured samples for each measurement I found they are not exactly as I expect. The attached picture shows that I insert a time interval for FOUR measurements each one with 11600 samples but I got a different number of samples for the measurement some of them higher and some of them less than 11600. 

I am not sure if there is time resolution limitation! Please if someone has an idea about what is happening I would really appreciate.

[spacedan]

Hello Thoalfukar, 

I will look around a bit and see if I can find anything. Meanwhile:

1) Could you describe your system/setup in its entirety? What other HW, SW etc. 

2) 10 000 / 10MHz is 1 ms, not 0.001 micro sec (in case you used this as configuration settings somewhere). 

3) What are the units of the axes in the picture you sent? 

[thoalfukar]

1) Could you describe your system/setup in its entirety? What other HW, SW etc. 

I am working on developing measurement system able to perform load-pull measurement and S-parameter of a DUT.

The system is configured by two chassis. One of them includes VSGs and the other one includes the VSAs. The chassis is synchronized by PFI caple and the 10MHz backplane signal. I am using list mode technique for the generation and the acquisition process. 

To perform such measurement I set a list of powers and measure the response of the device for each injected power. Because of the list mode setting, the time interval of each power level should be set to receive the required number of samples.

The problem I am facing is the number of samples is not match the time I set, and it is different from power level to another.  For example: If I want 10000 samples for each power level at 10MHz sampling rate, the time interval for each power level should be  10000/10MHz = 1 ms, but when I checked the received measured sampled I found they are not exactly 100000, as shown in the previously attached graph, some of them more some of them less for the same time interval. 

2) 10000/10MHz is 1 ms, not 0.001 micro sec (in case you used this as configuration settings somewhere). 

Yes, sorry Its 1ms

3) What are the units of the axes in the picture you sent? 

the X-axis is sample index

the y-axis is recived voltage 

Note: in the attached graph the required number of samples is 11600 samples

[spacedan]

Hi again,

Thanks for the detailed information.

1) Which VSGs and VSAs do you have?

2) Have the measurements in the graph (1-4) been performed with the same VSG/VSA? 

[thoalfukar]

Hi, 

thanks for reply,

the VSG: PXIe 5673E 

VSA: PXIe 5663E

YES, actually all these measurement by the same VSA and VSG

[spacedan]

Hi again,

Thank you. 

Would it be possible to post the code that you use? 

[thoalfukar]

I am so sorry Daniel  I couldn't reply directly to some issues. I am not sure how can I send the code as it's in different VIs as the whole projects contain several functions. do you know which part exactly you want to see then I can send only that VI?

Many thanks

Thoalfukar

[spacedan]

Hi Thoalfukar,

No worries. I am not sure which VIs I would need, I would have to rely on your judgment for that. But probably the VIs or VI where you configure the number of samples/time interval and so on of the devices.

I think that the next step for me is to escalate this internally to someone with a bit more experience in this area, but before I do that would you kindly answer the following:

1) When did the problem occur?

2) Is this behavior seen in every measurement you do?

3) What happens if you use another pair of VSA/VSG? 

[thoalfukar]

Thank you very much for your kind attention.

First of all,  I have checked the data again and I found that the overall number of samples is the same as the expectation exactly. For example, 10 measurements with (1.16ms) for each one, I should receive 58K samples, and that what I getting exactly, but still the measurements are different in the number of samples from one to another. 

Please see the attached excel file which shows the detailed graph and the data as well. 

Regarding the code please see the simplified VI that I am using within the massive code which I couldn't send. 

Regarding the other generator and receiver, yes it happens with every receiver. 

Thank you very much

best regards

Thoalfukar

[spacedan]

Dear Thoalfukar,

Thank you for the information, and I apologize about getting back to you with some delay.

I will go ahead and post the issue internally and get back to you with next steps.