RF switch characteristics that matter the most in an AoA application are the switching time, channel isolation, and number of channels. Switching time is important because the Bluetooth 5.1 specification requires 2-µs switch slots with the option of supporting quicker 1-µs switch slots.

Figure 2-4 Constant Tone Extension Structure Bluetooth Specification v5.1

Therefore, the RF switch must be able to switch and settle within the specified switch slot time (whether 2 µs or 1 µs). It is important to note that IQ sampling begins 0.125 µs into a 1-µs slot and 1.125 µs into a 2-µs slot and ends 0.875 µs into a 1-µs slot and 1.875 µs into a 2-µs slot.

Figure 2-5 IQ Sampling Window for 2-µs Sample Slots

Figure 2-6 IQ Sampling Window for 1-µs Sample Slots

Channel isolation is also an important specification because it directly affects the efficiency of the system. The better the isolation between the RF channels, the better the overall efficiency of the RF system. Lastly, the number of channels is important as it plays a large factor in switch cost. Table 2-1 shows several viable RF switches, most of which have been implemented on TI angle of arrival printed circuit boards (PCB).