5652

[Sharmi]

Hi,

I am using NI 5663 with the 5652 SIgnal Generator, 5601 Down Converter and 5622 IF Digitizer, to receive a 1GHz signal.

I want to set a certain frequency for the 5652 which acts as the Local Oscillator. I can go to Measurement & Automation and set the desired frequency from the test panel and run it but once I close the window, the values are reset.

How can I make sure that 5652 is generating the desired frequency?

Could someone answer please?

Thanks so much,

Sharmi

[Sharmi]

Want to add a few points -

1. I am using 5673 to transmit a 1GHz signal and using RFSG SIngle Tone Generatiion vi for this.

2. To configure 5652 (which is acting as the local oscillator in the 5663 receiver part),for a particular frequency, I copied the RFSG SIngle Tone Generatiion vi and changed the resource name.( So now I have two vi's, one for transmitting the signal and the other to generate the local oscillator frequency)

3. For the downconersion I am using RFSA Acquire Continuous IQ vi.

4. When I run all the programs simultaneously I get an error in the above mentioned copied vi -

"niRFSG Check Generation Status.vi<ERR> The session handle is not valid" 

Can someone please tell me what is wrong here?

Thanks so much,

Sharmi

[Lea_D]

Hey Sharmi,

It looks like these are two different questions, so I'll try to address each of them separately. 

In regards to your first post, setting the frequency in the test panel with Measurement & Automation Explorer is just for quickly testing your device and taking readings. Unfrotunately, these settings are not designed to save once we shut it down. If you want it to save that frequency without having to re-enter it, you'll have to look at using a LabVIEW vi where you can set the default value or leave the test panel up.

In regards to the second post, I think there's a bit of confusion on the top level RFSG Single Ton Generation.vi. I opened up this VI and looked over it. It looks like you would open a session to the entire RFSG. Not just to the signal generator. 

Inside of Measurement & Automation explorer. If you click on your 5611, there will be a configure button in the top. Click on this and assign the 5652 LO and your I/Q signal generator to this. Then inside of the Single Tone Generation vi, open the session to the 5611. You can then use this example to set the output power and frequency and this top VI will take care of everything for you VSG.  You would also do this same assigning and top VI for the VSA as well.

Lastly, it looks like you've opened a service request for this same issue. Would you rather communicate about this issue through that service request or through the discussion forum? I hope this helps and please let me know if I can further clarify anything.

Lea D.

Applications Engineering | National Instruments

[Sharmi]

Hi  Lea,

Thanks so much for the reply.

Sorry for opening the SR.I understand that the applications engineers monitoring the forums are very busy, but I  was stuck with this problem the entire day and opened it when I got no reply here. I would like to communicate here.

In Measurement & Automation the LO and AWG are already associated. I did not understand why I need to open a session to 5611. I want to set/check the RF OUT of 5652 on the RFSA and not on RFSG. So, should I open a session to RFSA in the Single Tone Generation vi?

 I read in the PXIe 5601 guide that for a tuned RF frequency of 1GHz, the LO frequency is 187.5 MHz + 1GHz = 1.1875 GHz. Is it configured by default or I have to set the LO frequency to 1.1875 GHz? Because what I really find weird is, with my input  RF  frequency at 1GHz, when I view the downconverted I and Q channel frequencies I see the FFT peaks at 5000 and I don't know what is happening.

 Sorry for asking so many questions, I am really confused 😞

Thanks,

Sharmi

[Lea_D]

Hi Sharmi,

No problems on the SR. I just want to make sure you're getting the right information in a centralized location.

In regards to the question to opening the session to the 5611, this is just how you call a session to the VSG with all of the parts associated with it. I'm still confused on your application and what you're trying to do. It seems like you were origianlly getting an error when trying to generate a signal with the example Single Tone Generation.vi.

So RFSA is for RF Signal Aquisition... meaning your VSA (Vector Signal Analyzer) is your 5663 device. This device (which is a combination of three other devices) performs automated measurements. RFSG is for RF Signal Generation. You would use your VSG (Vector Signal Generator and your 5673E device) in order to generate data. 

That being said, the Single Tone Generation example on generating the tone. This means that you would be using it with RFSG. 

187.5MHz is already the frequency for the 5601.

I definitely think we should step back and look at your overall application with this device and in a way start over. What is the end goal of this? Are you working on a project with this, or are you just trying to use this device to learn some of the concepts? 

-Lea D

[Lea_D]

Hey Sharmi,

I just talked to someone also and wanted to give another quick note. The 187.5 is in it. When you associate everything to your RFSA and open a session to it. You should just be able to set your center frequency (1GHz in your case I think). The session would be opened up to the VSA. The LO would do that calculation automatically with the 187.5.

This help document  explains the LO calculations that are done depending on the input frequency.

[Sharmi]

Hi Lea,

Thanks so much for the reply.

I am working on a project which aims the following-

• Transmit an RF signal at 1GHz.
• Receive the RF signal, down convert it to baseband, digitize it and split the resulting signal into I and Q channels.
• View the outputs  for the two channels in time domain and also the frequency spectrum.

As for the original error with Single Tone Generation vi, I do not think I will need to use it now since you mentioned that 187.5 is the Intermediate Frequency by default.

So my question is why I do I see the spikes at 5000? Is it some kind of offset 

Please let me know if you need any more information.

P.S.. I have attached the signal acquisition vi and the results, just in case you want to have a look.

Thanks so much,

Sharmi

[Lea_D]

Hi Sharmi,

Thank you for attaching your code. I was able to look at this and hook it up on our hardware. Using the RFSG Soft Front Panel, I went ahead and created a 1GHz signal which I routed to a VSA. From here, I used your VI and was able to replicate the spike at 5000.

Looking further at this, it seems like this spike at 5000 changes depending on the number of samples that you put in that control. For example, you're getting a spike at 5000 when you do 10000 samples. You get a spike at 10,000 when you do 20,000 samples. You get a spike at 15,000 when you put in 30,000 samples. So that's how you can control this spike.

This code that you attached looks like an example, but I'm looking at the FFT done on the I and the Q data. This FFT has a constant attached to the input called "Shift?". The shift input is defaulted false, and when you set this to true, it shifts the data by the DC offset (so yes, this is an offset to answer your question).

When I do your same data and turn this constant to a false instead of true, then the spikes happen at 10,000 instead of 5000 which would be what I expect.

[Sharmi]

Hi Lea,

Thanks so much for the reply.

The code is a inbuilt RFSA example which I modifed according to the requirements.

Sharmi