Getting IQ data USRP and writing to file

[kumar16]

Hello,

I am trying to measure the power and IQ components of a modulated signal (using a USRP as TX) at the receiving end (using another USRP as RX). I do not have any issues on the TX side. Here are my question on the RX side.

* I was able to use a given VI to get the power, but my question is how do I write the max power in text file over time, i.e. how can I keep reading the power over a set interval and keep recording it in a text file?

* How can I get IQ data from the recieved power in a similar manner and record it to a text file locally over time as well.

I am new to this, so any help is greatly appreciated. Thank you very much.

[Sarah_Y]

Hi kumar16,

I have attached a simple VI that is used for recording an IQ signal.  It is called Record FM.vi, but it will work for any IQ signal.  It receives and fetches IQ data using the USRP.  It then writes the data that is acquired to a binary file.  You can change the file type if you like, but if you ever intend to play this file back using a USRP, it will need to be a .bin file.  This VI has not been optimized for maximum streaming rates.  If you need to get about 1 or 2 MS/s IQ rate, this VI will most likely not work for you.  You can remove the waveform graph from the loop to improve performance some if needed.  

A similar type of set up can be used to write your power data to a file.  However, the more processing that you do in the same loop that you have your fetch in, the worse your streaming performance will be.  You may need to consider a producer consumer architecture.

Hopefully this VI will serve as a good starting point for your application.  Let me know if you have any questions as you go along, I'd be happy to help.

[attique1987]

Hello,

I read your post and it really helped me but still I need some more assistance. Actually I am working on channel sounding techniques for which I am using USRP and LabVIEW at the receiver end. I need to record the continuously received IQ data into hard-disk and then to read it later for post processing, in order to find out the channel impulse responce.

Any type of help in this regard will be most welcome... Thanks

Best Regards

Attique

[ritvik93]

Hii,

I am currently building a RF channel emulator which emualates multipath and fading for satellite communciation. I want your help as to how can i get the IQ data from the usrp and save it as a file. I am working on GNU Radio and my i/p signal will be Kband signal.

Regards