A 0.85mm² 51%-Efficient 11-dBm Compact DCO-DPA in 16-nm FinFET for Sub-Gigahertz IoT TX Using HD₂ Self-Suppression and Pulling Mitigation

In this paper, we propose a sub-gigahertz transmitter (TX) with a physically merged digitally controlled oscillator (DCO) and digital power amplifier (DPA). The matching transformer of single-ended DPA is placed inside the DCO transformer to save ~50% of area. The resulting DCO pulling is compensated via a feedback path and an inter-winding cancellation capacitor suppresses the second harmonic. Fabricated in 16-nm FinFET CMOS, the DPA reaches 51% efficiency at 11-dBm output with < −55-dBc HD ₂ . The 1.8-GHz DCO exhibits −116-dBc/Hz phase noise (PN) at 1-MHz offset and draws 195 uW from 0.3-V supply. The error vector magnitude measured with a 2-MHz 64-Quadratic amplitude modulation (QAM) orthogonal frequency division multiplexing signal at 5-dBm average power is 3.7%.