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AD9361 narrow bandwidth OFDM signal and LO frequency offset

Question asked by RobertYJ on Jul 9, 2017
Latest reply on Jul 10, 2017 by travisfcollins

Hi everyone,

 

In my project I have to use AD9361 FMCOMMS3 to transmit a OFDM signal with bandwidth 2MHz, 64 subcarriers, LO frequency 900MHz, then receive the signal by another AD9361.

 

With these conditions the subcarrier spacing is 2MHz/64 = 31.25KHz, but now I am facing some problem that carrier frequency offset is too large, and cause the receiver can not synchronize the signal by using long training symbol cross correlation.

 

I have tested when CFO < 12.5KHz(40% subcarrier spacing) the receiver can synchronize the signal well, and I also know this is caused by the different local oscillator have different frequency. So after the testing I found that the LO frequency have about 25KHz offset between transmitter and receiver.

 

I know I can adjust the reference clock or DCXO to fix this problem, but my supervisor ask me that he don't want to change the different reference clock or DCXO for different AD9361, he want to use the same parameter to all AD9361 and also suit my OFDM signal, and I really don't know how to make this happen.......

 

Can someone help me to figure out some method to achieve my supervisor's request? I will be very appreciate.

 

Thanks!!

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