Eye diagram measurements

[IADanilov]

eye diagram measurement

Hello!

Help me to understand some points of eye diagram measurements, please.

For example, in RapidIO standard specifications for transmitter and receiver eye diagrams are given, but there is no any explanation how to measure these diagrams.

I think receiver eye diagram is measured as following: receiver is connected via transmission media to signal source and oscilloscope is connected to receiver pins. Is it correct? If yes, there is another question: what kind of signal source is usually used? Is it "quasi ideal" source or some device satisfied to standard specification?

And how to measure eye diagram of transmitter? I can imagine two variants of measurement setup:
1. Transmitter is connected via transmission media and 100 Ohm resistor (required by differential termination) direct to oscilloscope without addition load.
2. Transmitter is connected via transmission media and 100 Ohm resistor to some load (receiver or capacitance).

Variant 1 is explicit. And in variant 2 there are two points, where oscilloscope can be connected to the transmitter pins or to the end of transmission media. What way of eye diagram measurment is correct?

Best regards.

 

[giri_lp]

eye diagram

Usually eye diagrams for Tx/Rx characterisation is done by a UI overlay tool. Say one UI(unit interval) of your signal is 100ps you need to make a oscilloscope capture of the Tx signal ( Real time mode) for sufficiently large sample space ( 1000, 10e6 UI) and then overlap the individual UI using a suitable algorithm to arrive at the eye diagram.

Scope manufacturers like Tek/Agilent usually provide their tools to find the eye measuremnts