ni 5640r + phase changes elimination

[sree_405]

Hi sir/Madam,
I am Sreenivasulu.O
i generated some digital modulated signal using ni 56402 card.
in tat i am getting some phase changes.but in my generatoin i didn't add any phase change(for normal sine wave also i am getting) .
Tell me how to eliminate that phase changes.

i have one more doubt also please check this link(last post):
http://forums.ni.com/ni/board/message?board.id=ifrio&thread.id=657&view=by_date_ascending&page=2


I am using LabVIEW 8.2 and card NI-5640R(PCI based) v 1.1

Thanking you
Sreenivasulu.O


 

[sree_405]

Hi

I am Sreenivasulu.please add this also to my prevoise post.

i am getting phase changes when i am using sampling frequency is high(above 4MHz,my application is 50Mhz and 25 MHz)

if i am using less sampling frequency i am not getting any phase changes.

please help me to come out from this problem.still i am not getting why it happens like this.

Thanks

Sreenivasulu.O 

[JerryAL]

Hi  Sreenivasulu

Please look at this post and see if this is the issue you are having for phase:

http://forums.ni.com/ni/board/message?board.id=ifrio&thread.id=671

Jerry

[sree_405]

Hi Jerry Sir,

I seen your discussion with Vasu.
I am not using any  Memory blocks.i think it may take default value.please tell me that default value.

One more thing for continuous generating signal it(memory size)is not the problem.Because of DMA FIFO depth is low.i am using dacO fifo depth is 65536,so i am able to generate continuously up to 32k samples(I and Q).

But phase changes may be because of that memory block size.for me its not ter.
Tell me sir whats problem to getting phase changes.how i can eliminate.

only problem is i am getting phase changes. if i am using less sampling rate i am not getting any phase changes.


Here i am attaching my files,please go through this file and correct me.


Thanking you so much sir.

Sreenivasulu.O

[russian]

Hi Jerry,

Please check http://forums.ni.com/ni/board/message?board.id=ifrio&thread.id=61.

Best regards,
Nikita

[sree_405]

Hi Jerry Sir,

My wavefrom size is less then the maximim configured size of the memory.U r correct this waveform is just looping.But in this case also i ma getting pahse chnages.Here i am not clear about waveform is phase continuous or not.My gneretaed wavefrom isphase continuous. But i don't in loopng processe how it is.From myr last sample to the first sample it is taking looping, i thought here i am getting phase chnages.i thought here it is taking automatically phase continuous.if not tell me how i can provide phase continuous here.

Thanking you sir.

Sreenivasulu.O

[sree_405]

Hi Jerry sir,

I am Sreenivasulu.Still i am unable to removing the phase changes.
I am Unable to find the reason why phase changes are getting.


Please take a look into my project file and correct me.i am checking signal in CRO.
Here i am sending my testing conditions.I tested with this parameters.
Fc=8.6MHz,Fs=25MHz,test--'sree' and Fb=19200.

Please spend your some valueble time for me.


Thanking you sir

Sreenivasulu.O

[JerryAL]

Hi Sreenivasulu

I’ve started looking at your VI again.  But I was stopped pretty quickly.

First, what values should I put in the Beginning Text, fc, and fb controls?  I’d like to know what values you are using so I can see what is happening.  Using the default zeros doesn’t give much of a waveform.

Second, it looks like you are creating real data, data type double, and then converting it to a complex double.  You then split out the real and imaginary arrays from the complex values.  Then you download them.  I suggest that you look at the real and imaginary arrays and compare each to the original data double array.  When you do this, the values in the first array become the real values in the complex double array.  The imaginary parts of the array are all zeros.  When you split the complex array into its real and imaginary components, you have a real array identical to the original array, and the imaginary array of all zeros.  You download this to the FPGA as IQ data.  I’m not sure what you are trying to generate in your waveform, but since the imaginary array is all zeros, you are essentially AM modulating your IF carrier in the DAC.  What modulation scheme are you trying to implement?

Third, I’m still not clear on what you mean when you say you are seeing phase changes.  The phase of the IF carrier?  Can you send an image or something that shows this phase change clearly?  In a previous post, it looked like the phase change was due to a subset of the waveform being generated because the FPGA memory buffer was smaller than the waveform.  I’m assuming that you have made sure this is not happening now.  But I don’t know what you are referring to when you say you are getting phase change.

Jerry

[sree_405]

Hi Jerry Sir,

Thanks for your good information.
1.For testing i used this parameters value.
Text-'sree',fc=8.6MHz,Fb=19200 and Transmit frequency is zero,why because already i up converted in math script node.

2.Yes you are correct sir.Sorry sir i didn't observed that thing.Here i am getting imaginary values are zero.Here for generating modulated signal i am using Math script node.Here i am generated signal correctly,but in converting into complex signal i did a mistake.I am trying to rectifying this one sir.You can also suggest correct way.I need to generate 6 modulation schemes are 2-FSK,4-FSK,BPSK,QPSK,OOK and GMSK.I tried to use Modulation toolkit but in that OOK and GMSK are not there,that too i am unable to generate my own bit stream.

3.Here i am attaching phase changes snaps.i told you sir i am using NI 5640R IQ example project,in that not mention about memory size block, i thought default vales is 20k.I tried with 8k samples(I and Q sample pair),even though i am getting phase changes.I tried with NI 5640R analog input and output example project also,in that also same problem.


I told you sir,if it is sine wave i am not getting phase changes,that too when if i adjust wave form size to some fixed size like 7500,9000,10000,12000 Etc,
if it is 10001,12350 etc i am getting phase changes.For modulated signal i am unable to adjust that length,because it is depending upon Fc,Fs,Fb Etc.Eevn though if i adjust same as sine wave lengths i am getting same phase changes.

Here i am attaching two more VI.U try with this also and correct me.
i."test_sin.VI" you test with Fc-8.6MHz,Transmit frequency is zero and in mathscript node  Tb=0:ts:0.0003-no phase changes,Tb=0:ts:0.0004-phase changes are occurring.
ii."twofsk_mod_mtool(HOST)" in this i am unable to generate my own bit stream.
    Here also i am phasing that same problem imaginary values are became zero.
I didn't get why,here i am not doing any data type conversion.
Please a look into this also.
test conditions:samples per symbol-1400,fc=8.6MHz,Fb=19200,Fd=200khz and text-'sree'.

Thanking you so much sir.


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

[sree_405]

Hi Jerry Sir,
Here Sreenivasulu again.Please help me sir.i am getting good ans from you only sir.
If you help me i'll  solve this  problem with in couple of days.
Today i tried sir,i am unable to convert mathscript node signal into complex.
In mathscript node i am generating double real data,i am converting it into complex using "To Double Precision Complex"
why here imaginary  array are become zeros.I didn't get reason sir.

Here i am attaching one image(ToComplex.jpg) i got it from your LabVIEW MathScript support engineer.

I tried using modulation toolkit also.with out upconverting i am able to complex signal,if i upconverted the signal here also imaginary  array are become zeros.
Here i am attaching two more images related to modulation toolkit.

Please help me out from this isuue also.

Thanking you sir.