Hello everyone,
I am using USRP2 with XCVR2450 daughter card with Windows XP and MATLAB
R2011a in 2.4GHz ISM band.
I am trying to implement a simple spectrum analyzer (based on energy
detection) with MATLAB’s SDRu package (NOT Simulink!!!). I started with
a
demo provided with the SDRu package (sdruFRSGMRSReceiver.m) and changed
it
to implement a simple fftplot. I am using fftplot.m given on following
link:
Here is my code:
---------USRP2 parameters---------------
USRP_SAMPLE_RATE = 100e6;
params.USRPDecimationFactor = 4;
params.USRPGain = 5;
params.FrontEndSampleRate =
USRP_SAMPLE_RATE/params.USRPDecimationFactor;
params.USRPFrameLength = 1024;
------------SDRu initilization-------------
if strcmp(findsdru, ‘No devices found’)
hSDRu = comm.SDRuReceiver( …
‘CenterFrequencySource’, ‘Input port’, …
‘Gain’, frsRx.USRPGain, …
‘DecimationFactor’, frsRx.USRPDecimationFactor, …
‘SampleRate’, frsRx.FrontEndSampleRate, …
‘FrameLength’, frsRx.USRPFrameLength, …
‘OutputDataType’, ‘single’)
usrpAvailable = false;
else
hSDRu = comm.SDRuReceiver(‘192.168.10.2’, …
‘CenterFrequencySource’, ‘Input port’, …
‘Gain’, frsRx.USRPGain, …
‘DecimationFactor’, frsRx.USRPDecimationFactor, …
‘SampleRate’, frsRx.FrontEndSampleRate, …
‘FrameLength’, frsRx.USRPFrameLength, …
‘OutputDataType’, ‘single’)
usrpAvailable = true;
end
% Get the carrier frequency for the selected channel
fc = convertChan2Freq(channel);
------------main loop of my program-----------------
% Loop until it reaches the target stop time.
timeCounter = 0;
StopTime = 10
while timeCounter < StopTime
[data, len] = step(hSDRu, fc);
figure
plotfft (data, frsRx.FrontEndSampleRate)
timeCounter = timeCounter + 1;
end
Using this code, I never see any signals in my plots, which are actually
there as I can see from a spectrum analyzer which I have at my desk. In
my
plot I see only one peak at center frequency.
My USRP2/MATLAB setup, SD card, UHD etc are all properly configured and
working fine since I have tested with MATLAB’s demos.
My first question, is it correct way to configure the USRP2 using
MATLAB. I
mean I am only setting gain, decimation, samplerate, and frame length-
Is
anything else is required.
Otherwise, should I do something between reading data from USRP2
(i.e.[data,
len] = step(hSDRu, fc);
) and fftplot(). I mean I am directly computing FFT using data read
from
USRP2, Is it correct OR should something else be done to prepare this
data???
In [data, len] = step(hSDRu, fc), ‘len’ is always 0 even though I am
getting
some complex numbers in ‘data’, can you please comment why this is so.
Best Regards
–
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