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

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 0.21mm
²
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.