Custom Direction-Finding Solutions using the Silicon Labs Bluetooth Stack#

NOTE: This section replaces AN1297: Custom Direction-Finding Solutions using the Silicon Labs Bluetooth Stack. Further updates to this application note will be provided here.

Bluetooth 5.1 introduced support for Direction Finding by adding the option to send and receive Constant Tone Extensions (CTEs) after Bluetooth packets. This makes it possible to measure the phase of the incoming signal on different antennas. However, calculating the direction of the incoming signal from the measured phases is the responsibility of the application, and not of the Bluetooth stack. This document explains the interface between the stack and the application regarding phase measurements to enable implementing custom direction-finding solutions using Silicon Labs’ Bluetooth stack. The information in this document provides an alternative to using the Silicon Labs customizable reference implementation, and is intended for developers who have a deep understanding of direction-finding algorithms and prefer to develop their own solution.

Developers who prefer to start with the Silicon Labs customizable direction-finding solution should refer to Application Development with the Silicon Labs RTL Library instead of this document.

Key Points#

• Constant Tone Extension

• Antenna Switching

• IQ samples

• Phase compensation