A 1–3 GHz I/Q Interleaved Direct-Digital RF Modulator As A Driver for A Common-Gate PA in 40 nm CMOS

We present a 1-3 GHz, 2×13-bit I/Q interleaved direct-digital RF modulator (DDRM) realized in 40 nm CMOS technology as a driver for an external common-gate (CG) power amplifier (PA). The proposed digital-intensive quadrature up-converter features a pair of novel current-steering mixing DACs with an additional leakage path to boost the efficiency of the external CG PA. The realized DDRM also employs IQ-interleaving, harmonic rejection, and dynamic biasing to improve its spectral purity, in-band linearity, and system efficiency. The proposed digital up-converter prototype provides standalone more than 19.6 dBm RF peak output power. Without using any digital pre-distortion, it achieves an ACLR of -44.5 dBc and an EVM of -35 dB, when applying an 80 MHz 256 QAM signal at 2.4 GHz.