I have a passive backplane with usb connectors intended for usb 3.0.
What is the required eye size of input, output to the backplane if it should be compliant to USB3.0 (not a usb-if member)?
Is it correct to only simulate the backplane itself or must s-parameters be used for reference host, device together with backplane to measure the eye (https://www.usb.org/ document-librar...annel-models)?
I have seen that USB 3.1 Channel Loss Budgets mention total loss 20db for complete system leaving at most 7.5dB for the backplane at usb3.0 2.5GHz? However, the usb-31
reference channel display host s21=-15dB and device s21= -20dB which I don’t seem to match since total must be less than 20dB (single ended, diffrential)?

Also, when connecting this backplane to any general equipment e.g. between a pc and a usb3 device is the device equalization automatically adapted to best performance or do all standard devices have their own fixed and pre-set equalization (or devices Learning their best setting during the init phase)? What is typically the limits of S21, S11 and limits of mode conversion Scd, Sdc? Generally, if a too high attenuation is present do the usb switch to usb 2 mode or does it disconnect?

Grateful for detailed feedback and references