STM32WL – Can TX and TX_HP use separate matching networks at different frequencies with one shared antenna, without an RF switch?

[Ryo T]

Hello,

 

I am designing a circuit using the STM32WL3R with a single shared antenna for two transmit frequencies.

 

My requirements are:

- 315 MHz: TX output, low RF power (approximately -40 dBm)

- 433 MHz: TX_HP output, high RF power (approximately +12 dBm)

- One shared antenna

- Separate matching networks for 315 MHz and 430 MHz

 

I would like to avoid an external RF switch if possible.

 

1. Can both matching networks be permanently connected to the shared antenna feed point, while enabling only one PA path at a time?

2. When TX is transmitting at 315 MHz, what is the RF impedance of the disabled TX_HP output? Can the TX_HP output and its matching network affect the 315 MHz matching?

 

I would appreciate any recommendations regarding the RF topology and matching network design.

 

Thanks.