NVIDIA Jetson Xavier NX DG-09693-001_v1.7 | 82
Chapter 15. USB 3.2 and Wireless
Coexistence
USB 3.2 supports a 5 Gbps (or multiple) signaling rate. The USB 3.2 specification requires USB
3.2 data to be scrambled and spread spectrum is required. The noise from the USB 3.2 data
spectrum has been found from around DC to 4 GHz and beyond. This noise can desensitize
nearby receivers operating in the cellular and WiFi 2.4 GHz band. This includes, for example,
WiFi 802.11b/g/n or Bluetooth
®
including Bluetooth mouse devices, Bluetooth keyboards, and
so on. This noise causes:
WiFi sensitivity degradation
Wireless link throughput drop
Wireless operation range degradation.
This chapter is focusing on USB 3.2, but other high-speed interfaces such as HDMI, DP, and so
on. can also cause issues with wireless subsystems. The issues and recommended mitigation
techniques would be similar.
15.1 Mitigation Techniques
Each design is different due to unique construction and relative location of USB 3.2 circuits
and connectors and receiving antenna. Depending on the level of noise generated, emitted,
radiated, and coupled to receiver antenna, some or all the recommendations might need to be
implemented to limit unwanted noise from radiating from the circuit.
The following mitigation techniques described will help minimize the USB 3.2 de-sense.
INCREASE THE USB 3.2 TO ANTENNA SEPARATION
During the placement phase of the design, care must be taken to identify the noise source and
try to physically increase the separation between the noise source and antenna. One of the
major noise sources is the USB 3.2 connector itself. If possible, the antenna or USB 3.2
location can be changed to increase physical isolation. In general, doubling the distance
between antenna and noise source, reduces the coupling by around 6 dB.
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