LabView

[sine_help]

thanks for reply actually i have acquired a spectrum  88Mhz to 108MHz ,there different signals in it . i select a particular signal without knowing its carrier frequency and i want to detect exact carrier frequency of that signal for demodulation. that detection should independent of data from NI 5600.

[GovBob]

I'm a bit confused by your statement "i select a particular signal" ? How do you select it? It's kind of hard to understand what you are doing and trying to accomplish using just words. Showing some code would work better.  Have you seen this example code?

http://zone.ni.com/devzone/cda/epd/p/id/921

It might be close to what you are doing.

Hope this helps.

[sine_help]

here i have attached a vi through which you can understand what i mean. i have recorded a spectrum centered at 100M with span 20M Fs 100M which contain different signals. each signal corresponds to a particular fm station. i want to cut  or filter a specific peak or station. and want to display it on another graph which shows that signal on 100M according to x axis. then find exact carrier frequency that should be 100M through different algorithms of frequency estimation availible eg Maximum Likelihood (ML) & Approximate ML,Phase Weighted Averagers etc. i want to know is there any VI that contain such algo or where i can get this please help me.

[sine_help]

please any one can answer my problem,

[Smootastic · Accepted solution]

Hi sine help,

I have found two VIs that do Frequency Estimation.  You can find the Power&Freq Est and Buneman Est VIs in Signal Processing»Spectral Analysis.  The help file for these VIs will give you a good idea of how it works.  Is this what you were looking for? 

[sine_help]

hi Kyle S

            thanks for help and Power&Freq Est  vi is working fine . but problem in it is accuracy if i want accuracy of 100Hz or less in detected carrier frequency eg if signal is 15MHz result should be 14.9999971 MHz  or arround this. how can i get such accuracy using Power&Freq Est Vi.  or do you have other algo such as maximum likelihood etc which have better accuracy . please help me to improve my accuracy. 

Best Regards,

[Smootastic]

Hi sine help,

How accurate are your values now?  What is your window function?  Does changing the window affect the accuracy? 

[sine_help]

 hi Kyle S

  in  niScope EX OSP  Downconversion example what is purpose of frequency translation(ie ON in that vi) how can i get real data.. because in block diagram of OSP ,frequency translation  makes I &Q data. i want data without any multiplication or bypass that frequency translation

block.  only active block will be DDC . is there any possibilty that can get data directly from ADC and bypass frequency translation and DDC block. can you send me example vi that fetch real data ( bypass frequency translation) and DDC enabled.

[sine_help]

MY digitizer is PXI 5142 please so answer the problem according to this digitizer

[Smootastic]

Hi sine help,

This question would be better answered on the High-Speed Digitizer forum (http://forums.ni.com/ni/board?board.id=150).  Those monitoring that forum have better knowledge of your PXI-5142 and the example you're looking at.