Antenna selection

Nordic Thingy:53 Hardware

The single-ended antenna output (ANT) of the nRF5340 SoC is connected to an RF switch (U17), which allows you to select either antenna A1 or antenna A2. The RF front end allows the nRF5340 SoC to transmit using only one antenna at a time, that is, A1 or A2. It is not possible to transmit with both antennas at the same time. The antenna selection is controlled through the SEL pin (P1.10).

Antenna A1 is connected to the ANT1 port of the nRF21540 RF FEM, which is connected to the RF1 port of the RF switch. The nRF21540 RF FEM supports TX output power gain up to +20 dBm on the A1 antenna. The A2 antenna is connected directly to the RF2 port of the RF switch. The maximum TX output power supplied to A2 is +3 dBm.

The following table shows antenna gain over frequency for the A1 and A2 antennas.

Table 1. Antenna gain for A1 and A2
Antenna 2402 MHz 2440 MHz 2480 MHz
A1 +1.10 dBi +1.15 dBi +0.55 dBi
A2 –0.17 dBi –0.11 dBi -0.20 dBi
Note: The RF switch adds approximately 0.5 dB insertion loss. The OR gate (U16) is not mounted.

The following schematics describe the antenna selection.

Figure 4. Antenna selection for Nordic Thingy:53 v0.8.0
Figure 5. Antenna selection for Nordic Thingy:53 v1.0.0
C2 6 1.2pF C2 7 1.2pF C2 3 100nF C2 4 10 µ F L 4 1.9n H L 5 1.9n H RF_O 1 RF_O 2 C2 5 1.0pF ANT 1 ANT 2 T R X A1 VDD_nRF215 4 0 RF A2 J 1 J 2 RF_O1_S W RF2_S W C2 8 N.C . C2 9 N.C . FE M _CT R L A1 WL A.0 1 A2 WL A.0 1 R 5 0 R L 6 1.8n H SPI M IS O M OS I SC K C3 2 9.5pF C3 0 6.8pF C3 1 1.8pF C2 0 1.5pF L 7 N.C . C2 2 N.C . M OD E RX_E N SE L T X_E N CS N FE M _CT R L nRF215 4 0 VSS 1 ANT _SE L 8 T X_E N 9 ANT 1 2 ANT 2 3 M OD E 4 VD D 5 VD D 6 RX_E N 7 T R X 10 PDN 1 1 SC K 12 M OS I 13 M IS O 14 CS N 15 VSS 16 VSS 17 U2 nRF21540-QDAAG 0 CT R L 4 RF2 3 RF1 1 RF C 5 VD D 6 G ND 2 U1 7 PE 4259 C4 9 100nF T P4 3 VDD_PE 4 2 SB6 RF1 RF2 R 2 49R 9 R 6 33k