To identify the locations where noise occurred, the board was measured using an EMC tester capable of mapping the magnetic near field.
By performing various types of communication, broadband noise was propagated on the Thunderbolt 3 TX signal line, PCI Express Gen3 TX signal line, and DisplayPort signal line on the add-in card board.
It is thought that this broadband noise radiates in the space from the signal line and enters the wireless antenna.
Consequently, this results in drops in Wi-Fi reception sensitivity and sub-6 reception sensitivity.
This issue is also expected to occur in USB4, which has virtually the same electrical specifications as Thunderbolt 3.