The CTE is from 16 µs to 160 µs and consists of an unwhitened sequence of 1s,
equivalent to a continuous tone nominally offset from the carrier by +250 kHz for the Bluetooth Low Energy 1 Mbps
PHY and +500 kHz for the 2 Mbps Bluetooth Low Energy PHY. The format of the CTE, when switching and/or
sampling, is shown in the following figure.
Antenna switching is performed during switch slots and the guard period. The AoA/AoD feature requires that one IQ sample is taken for each microsecond within the reference period, and once for each sample slot. Oversampling is possible by changing the sample spacing as described in IQ sampling. The switch slot and sample slot durations are either 1 or 2 µs, but must be equal. The format of the CTE and switching and sampling procedures may be configured prior to, or during, packet transmission and reception. Alternatively, during packet reception, these operations can be configured by reading specific fields of the packet contents.