A wideband linear direct digital RF modulator using harmonic rejection and I/Q-interleaving RF DACs

Abstract

This paper presents a wideband linear direct digital RF modulator (DDRM) in 40nm CMOS technology. It features an advanced 2^nd-order-hold interpolation filter and I/Q-interleaving harmonic rejection RF DACs. The 2×9-bit DDRM core occupies 0.21mm² and consumes only 110mW at 1 GHz. Within the 0.9–3.1GHz frequency range, the peak output power reaches +9.2dBm and the 3^rd/5^th harmonic rejection, C-IMD3, and OIP3 are respectively better than 30 dB, −44 dBc, and +25 dBm. The EVM and ACPR at 3 GHz for a 57-MHz 64-QAM signal are better than −30 dB and −45 dB, respectively, and ACPR remains as low as −44 dBc up to a wide bandwidth of 110 MHz.