ni 5640r + phase changes elimination

[Vinay_Kumar]

Hello Sree,

To maintain phase continuity during FSK, the bit sequence must have equal number of '0's and '1's. Can you try this out and see if the phase discontinuty has disappered?

--Vinay

[sree_405]

Hi Vinay,
Thanks for your reply.i am getting phase changes not only in FSK but also in ook,bpsk,qpsk,Etc .

any way thanks,if u have any idea please help me

Thanks
Sreenivasulu.O

[Vinay_Kumar]

Hi Sree,

For all the above mentioned modulation schemes, to maintain continuity in phase the number of samples plays a critical role since you are trying to write a particular waveform into the IF-RIOs memory and replay the same waveform again and again. You will have to ensure that the waveform written on to the memory is ending at a proper phase and not at any arbitrary phase.

I guess you are having Modulation toolkit and RFSG drivers installed on your machine. The toolkit provides examples which tackle the same phase discontinuity issue for various modulation schemes.

I hope you will get a better understanding of this problem/ solution when you look at these examples.

--Vinay

[sree_405]

Hi Vinay,
Thanks for your information.I am having Modulation toolkit but i don't have RFSG drivers.I think this RFSG drivers is not support to NI 5640R hardware.

How i can know waveform written on to the memory is ending with proper phase?

any way very thank you so much.I'll try with your information.


Sreenivasulu.O

[Vinay_Kumar]

Sree,

You can download the RFSG drivers from http://joule.ni.com/nidu/cds/view/p/id/956/lang/en
You will have to reinstall Modulation toolkit after installing the RFSG drivers to get these examples.

--Vinay

[sree_405]

Hi Vinay,

Thanks for your reply.

Even though i installed RFSG drivers,it won't be use full to me.Because in this link( http://joule.ni.com/nidu/cds/view/p/id/956/lang/en) only they specified it is supported to specific hardwares.I think it won't support to NI 5640R card.

Vinay i am requesting you please work with project files,then you came to know what is my exact problem.Already your forum support engineer Jerry is helping me very well.After Jerry you are the only person helping me.
In this thread you can find my all project files(twofsk_mod.zip and snapshots.zip) with well phase changes snap shots.

So,please Vinay help to come out from this issue.If you want i'll send my files again.

I am waiting for your reply.i think sat and Sunday  you have leaves.
i am expecting solution to my issue on Monday.Please don't delay it.


Thanking you sir

--
Thanks & regards
Sreenivasulu.O
Cell: +91-93948-22850

[Vinay_Kumar]

Hey Sree,

1. You need the RFSG drivers to get the Modulation toolkit examples. This is not with respect to 5640R.
2. I have already looked at your project files. You can easily make changes to your code by looking at the examples which you get with Modulation toolkit only if RFSG drivers are installed.
3. As always, I can point you to the right resources for answers. You will need to take it forward from there and customize the examples we provide according to your needs. If you are having issues with developing on LabVIEW FPGA, I would recommend that you contact your local sales representative for support resources and details about available training.

Hope this helps.

Regards,
Vinay

[sree_405]

Hi Jerry Sir,

I am Sreenivasulu.I sent phase changes snapshots.Please verify and reply me reason/solution.

 Thnaking you sir.

[JerryAL]

Hi Sree

I looked at the images you uploaded and I wouldn’t use the description as a phase change, I would call it distortion, or multiple instances of short distortions of the signal. 

I looked at the code you are using to create your waveforms, and I think that explains the distortions in the sine wave you are looking at.  I’m not sure what it is creating, but it probably generates something that is distorted.

The first issue is that you are not downloading IQ data, or at least IQ data that is doing what you think.  I’ve attached two VIs that are modified versions of the data you are creating.  Using the Modulation Toolkit VIs and the Mathscript node with your algorithm. 

I modified the MT version to create an FSK signal using a PN sequence.  (For some reason I wasn’t getting any data out of the block that takes your text.  I’m not an expert on that note of the syntax, so I removed it pretty quickly to get to the modulation part.)  It creates the IQ data you need to download to the IF-RIO.  I noticed though that you were setting it for a MHz of deviation, but the IQ rate was in the KHz.  I believe this violates Nyquist.  I lowered your FSK deviation, lowered your carrier frequency (which is only used to display the waveform, it is not used to add to the waveform that is downloaded to the ni5640R.)  It is now creating data that I would expect to work on the ni5640R.

In the VI with the Mathscript node, I could not get any data out of the node, so I’m not sure what the data is supposed to look like. 

I don’t think you have a grasp yet of what IQ data is.  The NI 5640R module only uses IQ data, not real data.  IQ data is basically centered at zero Hz, so there is no RF carrier frequency associated with it.  So up converting the data to an IF carrier before downloading does not make sense.  Also, when using the MT Fractional Resample.vi, the sample rate of the IQ data in must be high enough to meet Nyquist with the IF carrier you request.  I believe I provided a few references in a previous post to look at concerning IQ data.

Jerry

[sree_405]

Hi Vinay and Jerry_L,

This is Sreenivasulu after long time.

Here i am getting some compilation problem.

please see this link:http://forums.ni.com/ni/board/message?board.id=290&thread.id=972

Thanking you so much

Sreenivasulu.O

cell:09394822850