Format of captured data

GNU Radio
1

I am receiving 16-bit data from USRP (data is in the range of -32768 to
32767) in Windows. Now I want to apply some demodulation algorithms to
these
samples but I am a bit confused.
According to the following thread, each data sample that is coming from
USRP
is a complex baseband value. However, a complex baseband value should be
of
32 bit (and not 16-bit) as it comprises of 16-bit I and Q each.
http://www.ruby-forum.com/topic/182559

So the data samples that I am getting are in the form of I0,Q0,I0,Q0…
or
a sum: (I + Q)?
If these are in the form of I0,Q0 … then how do we keep a track that
which
one is an I and which one is a Q?

2

On Wed, May 27, 2009 at 1:50 PM, Ujala Q. [email protected]
wrote:

If these are in the form of I0,Q0 … then how do we keep a track that which
one is an I and which one is a Q?

If you use usrp_c() source, then the real part of the complex values
are the I values and the imaginary parts are Q values. They are each
16 bits.

Karthik

3

Hi,I am not using GNU Radio, I am simply taking 16-bit data samples from
the
USRP in a small C++ interfacing program for Windows using
“usrp_standard.h”.
Now, I want to write my own FM demodulation code for these samples as I
am
not using GNU Radio, I won’t be using any signal processing blocks,
therefore I cannot use usrp.source_c [s] block.

So in this case, what is my 16-bit sample representing? An I or Q or (I
+
Q)?