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Gain control issues with AD9364

Question asked by mmilosavljevic on Sep 13, 2017
Latest reply on Sep 18, 2017 by mmilosavljevic

Dear Support Team,

I have the custom board with the AD9364 and a demodulation core integrated with the AD HDL reference design. 

 

I have generated a test signal from an Arbitrary Waveform Generator to test my demod algorithm. The generated signal looks like in the figures below. 

 

The problem I have is that if I use the Manual gain mode on AD9364 and fixed power from signal generator I can demodulate almost all messages. However, with Slow attack mode the error rate is increased. It is even worst with the Fast attack mode. I tried to understand how those modes work and I think i do, but it is still not clear to me why would at least the slow attack introduce more errors? I can maybe see that happening if the power of the signal is changing causing gain changes in the Rx chain which in result can introduce phase shifts but here things are pretty much constant (at least thats what i can conclude).

 

If on the other hand I have same signal as below but introduce amplitude changes (i.e. for instance one of those below has amplitude below 1) then things are even worst. The fast attack mode is introducing a lot of errors while slow attack is slightly better compared to fast attack.  

 

Any suggestions would be appreciated.

 

Thanks

Milos

 

 

Zoomed in one of the above

 

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