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AD9371 strange spectrum for received sine wave

Question asked by why2 on Dec 23, 2017
Latest reply on Dec 26, 2017 by Vinod

We are testing AD9371 boards by transferring a 1MHz sine wave from one to another, configured with 80MHz sampling rates, 2.55GHz center frequency.

 

When two AD9371 boards connected to a single reference clock source (30.72MHz), We saw a relatively sharp peak in receiving spectrum. 

 

 

However, when two AD9371 boards connected to separate reference clock source with same frequency (30.72MHz), The spectrum is strange. The peak supposed to appear in the specific frequency spreads to adjacent channel.

 

 

Therefore, when we transfer OFDM signal with second ref clk configuration, the inter-carrier interference is very large because of the spectral leakage.

 

 

Here are our questions:

1. Why does this happen? Do you have any comment to figure out this problem? 

2. Intuitively, when using single reference clock, the frequency in TX and RX should be exactly the same. However, we observed about 1000Hz center frequency offset in our experiment. We are curious about it.

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