4.3.2 Dual-Band Transceiver with Two Antennas and External SPDT

To address the workaround with the internal switch, add an external SPDT to decouple the frequency bands. For more details, see Figure 4-11.

The following figure demonstrates a dual-band transceiver setup where low-band and high-band inputs, RFIN_LB and RFIN_HB, and the RF output are managed with two antennas and an external SPDT switch (RFIN_LB + RFIN_HB + RF_OUT + 2 x ANT + Ext Switch).

An additional control signal is required for the external SPDT. In this example, the high-band frequency uses the external SPDT. Use the firmware feature RX_Active to control the external switch. Set antenna switching to SPDT_RX for the high band service and set SPDT_TX to high resistance. For the low-band frequency service, the firmware controls the internal SPDT. Matching for the LNA and antennas is straightforward, while matching for the PA must serve both frequency bands. Depending on the selected frequencies, find a suitable trade-off.