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fmcomms1-ebz wideband signal test results

Question asked by Marchzh on Jul 31, 2013
Latest reply on Sep 24, 2013 by charlyelkhoury

Hi,

    I use the reference design of fmcomms1 with ml605, and send white gaussian noise signal data through DDR->DMA->DAC.  When I observed the air signal with the spectrum analyzer,what I observed is below:

   The parameters is : DAC sampling rate :100MHz, Tx frequecny :2.2GHz.

AWGN_frequency_response.jpg

 

   When I send DDR DDS data through DAC, which is sine wave data(20MHz), setting the DAC sampling rate = 591.52M(which is recommended) and Tx RF frequency = 3.0GHz,  there is still have harmonic. The picture I took photo is below:

20130801921.jpg

 

    My question is: Why are there harmonics? Where does it come from? Shouldn't the harmonics be filtered and removed before sending in antenna? Because the harmonics will affect other bands.

 

    Thanks.

     Zhonghua He

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