Mitigation and Identification of the Cause of Radiated Emissions in an 8 Gbps High-Speed System

This paper studies the impact of signal integrity issues related to rise/fall time and delay imbalance in differential traces of an 8 Gbps high-speed system in generation of excess radiated emissions at 8 GHz. Since modification of layout and system specifications are not possible at the final stages of system development, a custom-designed Frequency Selective Surface (FSS) absorber is used to reduce the emissions. The effectiveness of this solution is determined in comparison with a commercially available microwave absorber. This evaluation is conducted by observing the return loss and coupling between active sources on a mock-up system board and measuring radiated emissions outside the enclosure box containing the system board. An improved EMC scan set up is developed in-house for over the air radiation pattern measurements. The experimental results closely match simulations and all prove the superior performance of the custom-designed FSS absorber.