After performing the above tests and failures are still observed, the issue is most likely on the DUT boards. Further action is to use copper tape to cover or shield the area on the boards that is suspected to be most sensitive. Copper tape needs to be strongly connected to earth ground so that the copper tape can absorb most of the emission noise. If the copper tape is not connected to earth ground properly, the copper take can act as an antenna source, amplifying the signals from the covered area:

• Shield around MAC pins to minimize the exposure of MAC pins to the radiation source if the MAC is not used for testing
• Shield area around the MDI lines with earth ground. If covering MDI lines helps with RI testing performance, here are some recommendations for further improvement on MDI lines:
  • Minimize vias around MDI lines
  • Minimize components or exposed pads on the MDI lines
  • If possible, bury the MDI traces during RI tests
  • Symmetry on the MDI lines
• Shield area around the Rbias pin and traces. If covering Rbias pin and traces helps with RI performance, please follow the recommendations below:
  • Rbias is the reference current to drive the PHY internally. Having the optimal layout around Rbias area can help with RI testing performance
  • Bury Rbias trace in inner layer
  • Minimize vias around Rbias
  • Minimize Rbias component size
• Shield the oscillator or clock signal to see if that helps with RI performance
• Shield around the power lines to see if that helps with RI performance