The purpose of this document is to create an awareness of radio frequency interference to wireless devices operating in the 2.4 GHz ISM band as a result of certain USB 3.0* devices and cables. This is a guide to customers of the USB 3.0 RFI mitigation options that are available.



2.4 GHz wireless devices

The 2.4 GHz ISM band is a widely used unlicensed radio frequency band for devices ... such as wireless routers, as well as wireless PC peripherals such as a mouse or keyboard. These devices may use standard protocols such as the IEEE 802.11b/g/n or Bluetooth*, or they may use proprietary protocols. The radios may use frequency hopping, frequency agility, or may operate on a fixed frequency. In order for a wireless radio receiver to detect the received signal correctly, the received signal power must be greater than the sensitivity of the radio. The sensitivity limit of the receiver is influenced by the minimum signal-to-noise ratio (SNR) required for demodulation. The receiver sensitivity, transmitted signal power, receive and transmit antenna gain, and wireless link path loss dictate the achievable wireless range by determining the signal and noise power at the receiver. As the distance between a transmitter and receiver is increased, the signal power at the receiver input decreases. At the same time, the increased presence of broadband noise in the longer link will decrease the actual signal-to-noise ratio at the receiver. This reduces the wireless range. The reduction of the available SNR at the receiver requires an increase in the minimum signal level to overcome the sensitivity limit of the receiver.