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Re: [Discuss-gnuradio] Change of complex binary file format for Matlab.

From: Sangho Oh
Subject: Re: [Discuss-gnuradio] Change of complex binary file format for Matlab.
Date: Thu, 13 Jan 2011 02:23:05 -0500

Thanks a lot.
I found the problem. I should have used 'int16' instead of 'int' nor 'float'.
I think I have better spectrum shape for 20Mhz signal using UHD compared to gnuradio  

But I  found high frequency portion is somewhat suppressed than the original samples transmitted.

One question is that whether it is possible to demodulate 20Mhz signal using Gnuradio. I think many are trying to demodulate 802.11 packets, but still cannot found any one succeeded. 

The maximum sampling that Gnuradio can provide rate is  25Mhz with decimation 4. But I am curious about whether it is possible to demodulate the 20Mhz signal without 2x or 4x oversampling. 


On Thu, Jan 13, 2011 at 12:31 AM, Josh Blum <address@hidden> wrote:

> I am trying to use "rx_samples_to_file.cpp" in UHD to save samples received.
> UHD seems save samples in complex integer format in c++.


> However, it is not possible to read that format from Matlab.

I'm not a huge matlab fan, but I am sure that it can read integers from
a file. http://tinyurl.com/6kyxdk4

> I have checked the Matlab utilities in Gnuradio, but they were not useful.

Its looks like you are not very familiar with matlab, so I suggest (out
of my person preference) that you take this time to learn python+scipy
http://www.scipy.org/ For one, its free. And I have always found myself
more productive with python, and I have found the plotting widgets and
mathematics that come with scipy give me everything I need.

> Is that any simpler way to change the formats of the saving file so that
> Matlab can easily read?

You can change the example easily to write binary floats. And with a
tiny bit more effort and a for loop you can write a text formatted file
as well.

> Another question is that why the saved samples are integer format? not
> float?

To save disk space and IO overhead for large captures or high data
rates. You will appreciate this if you change the example to output a
text format.

Good luck,

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From: Sangho Oh
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