A circuit is disclosed with an external coupling port for coupling to an external antenna, for example. The circuit has an FDD receive path including a narrowband passband filter. The circuit has a TDD receive path bypassing the narrowband passband filter but relying on a same amplifier. The circuit also has an FDD transmit path including a narrowband passband filter. The circuit has a TDD transmit path bypassing the narrowband passband filter of the FDD transmit path but relying on a same transmit amplifier. A switching configuration allows the circuit to operate in TDD mode, alternating between the TDD receive path and the TDD transmit path and in the FDD mode wherein the FDD transmit and receive paths are simultaneously coupled to the external coupling port.