10.7 A 0.26mm2 DPD-Less Quadrature Digital Transmitter With <−40dB EVM Over >30dB Pout Range in 65nm CMOS

Digital transmitters (DTX) or digital power amplifiers (DPA) based on RF digital-to-analog converters (DAC) are optimal for wireless transmitters in CMOS due to the small chip area, low power consumption, and ability to evolve with scaling of the transistor feature size. A DTX integrates all functions of a conventional transmitter into a single RFDAC that directly converts digital bits to RF signals (Fig. 10.7.1) [1]-[3]. It consists of digital circuits (e.g., switches, logic gates, etc.) and passive devices rather than traditional mixed-signal, frequency mixing, gain and output stages. Due to switching operation the power scales ∞CV
²
f, which benefits from CMOS scaling. In this work, a quadrature switched-capacitor (SC) DTX is presented that can achieve <; -40dB EVM for >30dB output power (POUT) range, utilizing no external phase modulator or digital pre-distortion (DPD). The DTX utilizes three linearization techniques and can transmit a 1024-QAM signal with up to 40MHz bandwidth.