Ultra-Low Power Direct-Conversion 16 QAM Transmitter Based on Doherty Power Amplifier

This letter presents a fully-integrated umW,ltra-low power (ULP) direct-conversion transmitter. For an ULP modulation, a voltage-driven passive-mixer is optimized with a super source follower (SSF) having a low-output impedance. Also, a linear Doherty PA is proposed for a good back-off efficiency. For transmitting a 16-QAM signal with PAPR of 7.5 dB, the efficiency of the Doherty PA is 14% with the ACLR of -30.1 dBc and the EVM of 5.8% at the average output power of -7.66 dBm. The baseband buffer and the mixer including the non-overlapping 4-phase clock generator consumes 0.59 and 0.51 mW, respectively, and the measured power consumption of the transmitter chain is 2.59 mW. The transmitter is implemented using 28 nm CMOS process and occupies an active area of 0.525 mm
²
.