R1, C1 and D1 form a slow-start, fast response mass-energy store for large ripples. The actual values of each are not critical with the larger values causing the unit to put less drag on the port (10 uF with “0” resistance is the official specification).

L1, C1 and L2, C2 form either a first to fourth order LC filters network and their exact values have to be calculated ahead of time. L2 can be linked if it’s not required.

USB can be assume to have an internal impedance of 10 ohms or less but the load impedance dramatically affects the values and this can’t be known without mesurement. So the exact parts values depend on the noise frequency and load impedance.

LC Filter Design Tool markimicrowave.com functions well because it allows you to map the impedances. Throwing random values will work but the right ones will work better. This project can also be used to partly buffer a single USB port if noise reduction is not required.

The board has a copper pour on three of the four layers for noise reduction with the balanced USB pair squirelling through the the core.out of harm's way with a parallel trace on the top side for the return current.