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Factors related to improvement of eye diagram

Akshaay

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Hi

I am designing a transmitter. I was simulating for the data i will be sending through the transmitter and found that for slow corners my jitter is high but the rise and fall times are same for all the data patterns. I want to know why jitter is more even when the rise/fall times are same?
I am new to design of tx, and eye diagram is totally new for me.Kindly help.

Thanks
 

Akshaay

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Hi

I am designing a transmitter. I was simulating for the data i will be sending through the transmitter and found that for slow corners my jitter is high but the rise and fall times are same for all the data patterns. I want to know why jitter is more even when the rise/fall times are same?
I am new to design of tx, and eye diagram is totally new for me.Kindly help.

Thanks
correction in subject: eye diagram
 

guntherleet

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Hey,

How you measuring the jitter? you sampling after a channel?
Eye diagram contain data about random jitter and deterministic jitter as well
 

martinnl

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Now I don't now how your transmitter looks like but for simplicity and illustration lets assume you have two amplifiers in series.

Your rise and fall time will mostly depend on the second amplifier while only jitter also comes from the first amplifier. So it is not strange that jitter increases while rise and fall time stays the same.

If I were you I would break down the problem and look at a single rising or falling edge. If you have Spectre RF available you can run a phase noise simulation and see where the jitter comes from. Otherwise try to inspect all intermediate signals and see how and why they change to identify the source of the jitter.
 

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