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Getting different Eye diagram (density) for same diff Tx param with different channel

Question asked by aguntuk on Mar 13, 2018
Latest reply on Mar 15, 2018 by aguntuk

I am stuck with a basic eye diagram (density) of my Tx. I have created a channel with differential Tx/Rx and with serial link which consists of different lumped parameters and T-lines (in my case microstrip). I have same same Tx parameters for 2 setups but I am getting different eye diagram (density) from Tx_Out. I have put differential Eye probe at the output of the differential Tx for both the setups. here is the first setup screenshot in the below:




Tx parameter:                                                                                     Eye density (after Tx: Tx_Out)                                                                                                                                                                                             


Now here is the 2nd setup where I added more lumped parasitics but didn't change Tx parameter:



Tx parameter:                                                                   Eye density (after Tx: Tx_Out)


Now why did the eye density changed here in the 2nd setup as I did not change anything in the Tx side and the Eye probe is only after the Tx which means my added lumped components should not affect the Tx, but it seems like it affected? Any reason behind that and how to mitigate that? Did I do anything wrong?


Note: I have used 100 ohm as electrical load for both Tx & Rx. And I am using ADS Keysight 2015.01


Your suggestions or comments are highly appreciated.