Gb/s USB: RFI risk analysis and test methodologies

Gb/s speed USB signals running at 5 Gbps or 10 Gbps can radiate and interfere with wireless communication receivers integrated in mobile computer designs. There are several coupling paths for the radiation, including the connectors and cables between the USB hosts and devices. The radiation causes radio frequency interference (RFI) to integrated wireless receivers and can results in degraded wireless performance such as data throughput and poor user experience. Effective shielding of the cables and connectors is critical for reducing the radiation due to the high speed signaling. In this paper, a simple new test fixture and measurement method for characterizing shielding effectiveness of a USB cable which can lead to cost-effective cable designs with optimized shielding are discussed.