I have a design where I need to connect two 1Gb Ethernet devices on one card. To save space & cost I want to capacitively couple the four pairs instead of using transformers.
I've done point-to-point 100Mb Ethernet like this and it works flawlessly. The technique was to couple the lines with 100nf caps and then add appropriate pull up/down resistors to properly bias the drivers/receivers.
I saw one reference to the fact that this won't work at 1Gb, but I can't find the reference again. I have found several references to doing it at100Mb, but they are all several years old.
Has anyone done this or heard about it?