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Why does AD9361 cross-board connection appear distortion by insert sin wave when using driver code which is provided by official website

Question asked by weiwade on Dec 27, 2017
Latest reply on Feb 5, 2018 by larsc

I use AD9361 board on warp virtex6 FPGA and design a pure sin wave to AD9361 Tx1 in hardware and write NO-OS driver code make it work. By operating spectrum analyzer to observe the output of the AD9361 Tx1 as a contour sine wave as Figure1. I confirm that the output of Tx1 is correct and it is what I want.

 

I make one ad9361 Tx1 connect to Rx1(one ad9361 board).Do the same thing which is mentioned in the first paragraph,and you can see that the waveform of Rx1 on chipscope in Figure 4 is the same as  Figure 1.

 

However, I make A ad9361 Tx1 connect to B ad9361 Rx1(two board cross-board connection) and do the same. I find that the waveform of B ad9361 Rx1 on chipscope distorts as Figure 2 and Figure 3 (Figure 2 is in 2.4G synthesis frequency.Figure 3 is in 1G synthesis frequency.).There are different distorted  level in different synthesis frequency.

 

I wonder know that how to figure out the distortion on cross-board connection through modify driver code? Or do you have any  simple test about  cross-board connection , and I can observe the undistorted wave precisely.

 

Thanks.

Figure 1The surrounding is connect with A ad9361 Tx1 and B ad9361 Rx1.The bigger picture is enlarged to see, you can see obvious sine wave obviously.The small one is zoomed out ,but in general the ampltude      Figure 2The surrounding is connect with A ad9361 Tx1 and B ad9361 Rx1.The bigger picture is enlarged to see, you can see obvious sine wave obviously.The small one is zoomed out .     Figure 3The surrounding is connect with A ad9361 Tx1 and B ad9361 Rx1.The bigger picture is enlarged to see, you can see obvious sine wave obviously.The small one is zoomed out.    Figure4

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