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Betty Boop
Posts: 66
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RF Synchronization Suite

Hello! :smileyvery-happy: I’m currently trying the sample codes included in the RF Synchronization Suite. However, I’m having a hard time understanding the effect of the “phase offset” on the IQ data which I generate (or acquire).

 

For the generation part, I’m testing the sample code named “PXIe-5673 Phase Coherent Arb Waveform Generation with NI-TClk Example”. If for example, I entered 0° as my phase offset for channel 1 and then entered 10° as my phase offset for channel 2, does that mean that my data for channel 1 is AMPLITUDE1∠0° and my data for channel 2 is AMPLITUDE2∠10° in polar form? If so, do I enter these values before running the code, or while running the code (and after which I click the “Update Phase Offsets” button)?

 

Thank you very much for your time! God Bless! :smileyvery-happy:

Member
Andy_Hinde
Posts: 112

Re: RF Synchronization Suite

Hi Betty,
The Phase Offset control manipulates the phase of the onboard signal processor (OSP) of the arb component of the PXIe-5673.It doesn't change the phase of the actual IQ data/waveform downloaded to the arb, but does allow you to change the phase of the RF output (on the fly) as it is generated.

However, these changes should be viewed in a relative sense between channels. We can't guarantee what the phase of a single channel is since phase is a relative metric and the absolute phase of a single channel is just telling you a relationship between the RF output and the frequency reference being used for that channel. However, if you are comparing phase between multiple channels as in your phase-coherent use case, you can adjust the phase difference between two or more channels.

If you generate two signals out of two PXIe-5673s, you can adjust their phase relationship by changing the phase offset of one of the channels. Normally you would leave the first channel unchanged and simply change the Phase Offset of the second channel, but you could also do this vice versa.

The answer to your question though is that you're not setting an absolute phase relation ship of an individual channel starting from a 0 degree point. If both channels have Phase Offset set to 0, you shouldn't assume both channels are phase-aligned at the same phase, and that this phase is 0 degrees. Both channels will come up outputting RF signal with an unknown phase relationship to the reference, and an unknown phase delta between them. You can then use the Phase Offset controls tweak the outputs from this starting point.

Please let me know if this answers your question, and if you have any further ones. I'll also invite you to look at some updated phase coherency code posted on our RF Multi-Channel page on NI Comunity (feel free to join this page for updates!). This is what we consider our latest and greatest phase coherency code at the moment, and we need to go update the RF Synchronization Suite software to remove any mismatch. One thing you will notice is that this newer example set doesn't expose the Phase Offset control the way the examples you are looking at do. You can add this by using the same NI-RFSG attribute Phase Offset if you like.

 

RF Multi-Channel parent page:

https://decibel.ni.com/content/groups/rf-multichannel?view=overview

 

Phase Coherency Examples child page:

https://decibel.ni.com/content/docs/DOC-19433

 

Regards,

Andy Hinde

RF Systems Engineer

National Instruments

Member
Betty Boop
Posts: 66
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Re: RF Synchronization Suite

Thank you for your response! :smileyvery-happy: Actually, I’m currently working on a code for direction finding application. As we know, the direction can be calculated through the phase difference (unique propagation delay to each receiver). I’m sort of confused whether the ‘phase offset’ in the sample code affects this phase difference (that is, adjusting the phase offsets of both channels implies adjusting the phases of the two generated signals that are involved in the computation of the phase difference), or is the ‘phase offset’ plainly for the alignment of the channels? Thank you very much! God Bless! :smileyvery-happy:

Member
Andy_Hinde
Posts: 177
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Re: RF Synchronization Suite

Hi Betty,

There are phase offset controls in both the generation and acquisition code, which manipulate the OSPs of the vector signal generaotrs (VSGs) and vector signal analyzers (VSAs).

 

I'm not sure I understand the distinction you are communicating in your prior post about phase offset, can you elaborate?

 

Regards,

Andy Hinde

RF Systems Engineer

National Instruments

Member
Betty Boop
Posts: 66
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Re: RF Synchronization Suite

Thank you for your response! :smileyvery-happy: I'm tasked to generate and acquire 2 signals which resemble real RF signals, provided that the I/Q data of each signal can be manually adjusted. However, I'm having problems implementing this using the RF Synchronization Suite. I tried downloading NI RF Phase-Coherent Multi-Channel that you recommended, but some VIs are missing (as seen in the attached pictures). Where can I get them?:smileyvery-happy: Thank you! :smileyvery-happy:

Member
Andy_Hinde
Posts: 177
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Re: RF Synchronization Suite

Hi Betty,

You need to download and install the NI-Sync driver. These reference examples support multichassis expansion, which requires the use of NI PXIe-6674T or NI PXI-6672 modules, both of which are programmed via NI-Sync. You won't be using this feature, but the driver needs to be installed to open the examples nontheless.

 

NI-Sync 3.3:

http://joule.ni.com/nidu/cds/view/p/id/2496/lang/en

 

Regards,

Andy Hinde

RF Systems Engineer

National Instruments

Member
Betty Boop
Posts: 66
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Re: RF Synchronization Suite

I have just finished installing NI-Sync and there were no missing VIs unlike before. Thank you! :smileyvery-happy: I am going through the codes and I'm just wondering where I could manually adjust the I/Q data that I generate because I could not find it? :smileysad:

Member
Andy_Hinde
Posts: 177
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Re: RF Synchronization Suite

Hi Betty,

In Case (25) Configure Generators, within the sub-case Arb, you will see where some default arb waveforms are generated in software and downloaded to signal generator memory. This is the code that gets run when Arb is selcted from the front panel selector. You can generate your own IQ data here, or read it from a file for example as well.

 

Regards,

Andy Hinde

RF Systems Engineer

National Instruments

Member
Betty Boop
Posts: 66
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Re: RF Synchronization Suite

Thank you! :smileyvery-happy: May I just ask where can I get the missing VIs in the attached pictures?:smileyvery-happy:

Member
Betty Boop
Posts: 66
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Re: RF Synchronization Suite

Hi, Sir! Are these the right toolkits to download for the missing VIs?

 

1) NI Spectral Measurements Toolkit 2.6.1 - Windows Vista/XP x86/Server 2003 R2 (32-bit)/Server 2008 R2 (64-bit)/7

2) LabVIEW Modulation Toolkit 4.3.1

 

Thank you, Sir! :smileyvery-happy: