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external signal FM demodulation

 Hello NI Developers!

 

I have a PCI-E DAQ board - Not NI board!

I also have a working driver for DMA data transfer.

 

My LabView version is 7.1 and I don't want to buy a modulation toolkit. 

 

Does anyone know about existing FM demodulation algorithms ?

 

Thank you

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Hi ACiDuser,

 

While I am not familiar with doing this personally, it seems like you should be able to manually implement some kind of algorithm based on the fact that frequency can be found by using some trigonometry with the I and Q data you retrieve. Finding the frequency is equivalent to differentiating the phase, and this phase can be found by simply taking the arctan of the product of the quadrature component ('Q') and the complex conjugate of the in-phase component ('I'). One good resource I came across when doing a quick search of software-defined radio can be found in this article. This article gives an explanation behind the algorithm used in the demodulation. I do not know of any existing algorithms implemented in LabVIEW beyond the Modulation Toolkit, though someone may have done this before. Hope this helps, and best of luck!

Daniel S.
National Instruments
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Hello!

 

Sorry for late response.

 

Thank you for provided resource. There are used many C functions. I wanted to build FM demodulating algorithm using only LabView software.

So now I'm looking for a good Math step-by-step explaination of FM demodulation method.

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In addition: I haven't any "Q" and  "I" data. We use only one RF channel and non-linear sampling method. So I know there would be a lot of complex math processing.
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Anyone saw this implementation? LabView FM Modulation/Demodulation

I can't understand how to get those VI to work. Could somebody please explain?

 

Thanks

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