I've been reading a bunch, including the USB 3.0 spec, and I still don't get it. The transmit data lines are both capacitively coupled, so at the connector, SSTX are 0 V average?
Yet the voltage level diagram shows single-ended signals with a 0.3 VDC bias, is this before or after the coupling caps?:
Wouldn't this produce negative voltages on the receiver? Aren't the receiver ICs single supply? Is there a DC bias on either input or output? I read the part about how "8b/10b coding is DC-free", but I don't think that matters; it's like sending a 50% duty cycle square wave?
This is the closest I can find to an equivalent circuit (for a TI redriver):
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