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Re: calculate SNR and watch a binary file

From: Markus Feldmann
Subject: Re: calculate SNR and watch a binary file
Date: Thu, 26 Mar 2009 10:16:08 +0100
User-agent: Mozilla-Thunderbird (X11/20090103)

Francesco Potorti` schrieb:
I can save the spectrum as a binary file.
The file includes several 16 bit complex information.

How to watch this with octave and calculate
the SNR ?

i wrote a small script:
filename = "spectrum.m";
fid = fopen (filename, "r");
[val, count] = fread (fid, 100, "uchar", "native")

But i want to watch the original komplex values instead of int values.
How to ?

That depends on how the values are written to the file.

As i know my Spectrum Analyser produces I/Q Signals, so there should be
2*16 bit values. Each 16 bit value is complex.

What you wrote is either a typo or I do not understand it.  I suppose
you meant that each complex value is written as two 16 bit numbers.
If this is the case, do not use "uchar" but "int16".  Then try and see
if you get the correct numbers, probably the real and complex parts of
each sample.  If not, try to experiment and guess how the numbers are
written to the file.  Or else try to find some documentation on it :)

Thanks for your Answer,

in my Spectrum there is an unknown peak in the middle of the FFT-Plot
which exists every time. I think it will be created as byproduct
of a CIC decimation(Digital Down Converter) in my analyser.
Therefor i want to manipulate this complex values, but didn't know how
to ?

Any hints ?

Regards Markus

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