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How to implement FMCW in USRP N210

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Hi All, 


This is my first message in NI forums and I am new at signal generation and processing. My intention is to generate FMCW signal by using USRP N210. I am doing my intern and need to create block diagram in Labview communication design suit.


As far as I know FM-CW is frequency modulated the continuous signal. In general, known FM modulation changes the phase of the carrier with a message signal where the carrier frequency is fixed. Right? But FMCW has carrier signal with changing frequency Am I right? If so, how can I change the carrier frequency with respect to time?


Then what to do with the message signal?


Can you please enlighten me?


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Message 1 of 8
Accepted by topic author firstking

Hi firstking,


Can you give a little bit more detail of what you’re trying to accomplish? This sounds like a chirp signal and I’m assuming you want a sine wave.


What range do you want to change the frequency over? Each USRP has a certain bandwidth that you can change the carrier frequency over before having to retune the local oscillator (LO).


Which daughterboard are you using with the N210? This will determine the total frequency range, but I believe most configurations with the N210 have a 40MHz BW.


Here are a couple resources for a chirp signal.


Also, the carrier frequency and LO can be changed by making use of property nodes.

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Message 2 of 8

Hi, Matt thanks for your reply. Those are very helpfull links. 


I have N210 from Ettus Research and SBX - 40MHz BW version daugtherboard. My intention is to make an fmcw radar. 


I wonder why I need to hcange the LO frequency.


And secondly, how can I see frequency change with respect to time so that I can make a base structure for a fmcw radar.



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Message 3 of 8
Accepted by topic author firstking

Hey firstking,


While I'm unsure about the best method to accomplish your application, I think a spectrogram might help you with visualizing the frequency change with respect to time referencing your last question.


 STFT Spectrogram (G Dataflow) -


Waterfall Plot (Spectrogram) Example -


In addition, you might want to check out the the Software Defined Radio code exchange and try posting on more specific forums to get better visibility.


SDR Code Exchange -


LabVIEW Communications Discussion Forum -


RF Measurement Devices -


Hope that helps!


Application Engineer, RF and Communications
National Instruments
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Message 4 of 8

Hi firstking!

I am also working on FMCW Radar Implementation now-a-days. Kindly suggest me literature that will help me in this regard.



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Message 5 of 8

Hey sayyar,


I'm not sure what firstking did to find his true answer but as my previous post suggest I would highly suggest posting in one of those other more relevant forums and maybe link this post in order to get better visibility and possibly even community members who have done this before.


I haven't so I'm sorry I can offer more technical advice.


Best of luck!

Application Engineer, RF and Communications
National Instruments
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Message 6 of 8

Hi firstking,

I am also working on the same project but unable to do it. Can you please help me in this project if you have completed this project?

Thanks in advance.



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Message 7 of 8

 I am working on my Project and I wanted to design FMCW radar in labview using USRP 2921 kit I want to discuss with you regarding Labview software as I am unable to access some of blocks in labview such as FFT, LPF,Windows blocks which is mentioned in image and I have attach in these,I just want to know how could I access those block and which version labview software is used in these Screenshot_2023-09-05-12-44-30-66_c37d74246d9c81aa0bb824b57eaf7062.jpgScreenshot_2023-09-05-12-44-05-10_c37d74246d9c81aa0bb824b57eaf7062.jpg

paper . I would be really thank you if you help me. 

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Message 8 of 8