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Don't undestanding RX_SAMP_FREQ of AD9361

Question asked by jmcp on Apr 30, 2015
Latest reply on May 21, 2015 by dpu

Hi everybody,


I'm new in this field and there is something I would like to know (maybe the question is very easy to answer).


I am using the ZEDBOARD SDR KIT with the AD9361 of analog.


With the preset configuration:


RX_SAMP_FREQ = 30.72 MHz


RX_LO_FREQ = 2.4 GHz


I am injecting a 2.401 GHz, so the result of the mixer is a 1 MHz sine. I show 6000 samples of this sine at the console and I make the FFT in MATLAB.


It appears a peak in the 42 bin. If I make the following calc:


f= bin/N * fs --> f*N/bin = fs --> 1 MHz * 1024 / 42 = 24.381 MHz (NOT 30.72 MHz)..


I am missing something, but I don't know what.


Thanks for all!