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Gain correction FMCOMMS3

Question asked by vittal92 on Apr 12, 2016
Latest reply on Apr 12, 2016 by ACozma



We are working with FMCOMMS-3 and ZYNQ ZC702, and I have made the changes in the HDL core of the design to transmit and receive custom data by using custom IPs and asynchronous FIFOS for CDC.


I see the data at the receiver output (RX end post ADC), and as I was told during the previous discussions, the received data will NOT be same as the TX data, but that the data will be shifted and the shift for every value of the data is same (multiplied of divided by some integer value).


I have couple of questions --


1) If I am sampling the same data multiple times, I see that the data is not the same and there is some noise associated with it. Is this expected? Is there a way wherein I can use a filter and get rid of the noise?

For example, I am sending a step function in one of the channels (I/Q), and the received output is as shown below

It can be seen that at every step, the data is not constant but has some noise associated (I have attached the TX data (green in color) to see the difference) . The variation in magnitude at each consecutive step is close to +-100, and this is creating issues in my design. Is there a way wherein I can get this right?


2) If there is a solution for question 1, can I match the magnitude of the RX output to that with the TX (same magnitude without any shift) by changing any of the AGC parameters in the IIO software?


Your help is appreciated.
Thank you