A 2-GHz Reconfigurable Transmitter Using A Class-D PA and A Multi-Tapped Transformer.

This paper presents a 2-GHz reconfigurable transmitter designed for the high-bands uplink of an NB-IoT RF transceiver. The transmitter is formed by an active upconversion mixer, a fully differential class D Power Amplifier (PA). To do the coarse power gain reconfiguration of the TX a multi-tapped transformer is designed which offers multi secondary taps delivering various levels of power to the antenna. To do a fine-tuning of the output power level a capacitor bank is implemented at the primary side of the transformer. The capacitor bank is tuning the resonance frequency while is forming an LC tank with the primary side. The proposed TX is designed in an RF 65-nm CMOS technology. The output power is delivered to another external PA through an off-chip matching network. The designs deliver a reconfigurable output between 2 dBm to 10 dBm while it is receiving an IF signal with 0 dBm power. The TX consumes 60 mA current through a 3V VDD.