A 12-bit resolution, 200-MSample/second phase modulator for a 2.5GHz carrier with discrete carrier pre-rotation in 65nm CMOS

A digital-to-RF phase modulator based on a single current-steering DAC is presented, including a carrier pre-rotation scheme that prevents phase inaccuracy due to carrier feedthrough. The phase modulator has been fabricated in a standard 65-nm CMOS process and draws 1.9 mW from a 1-V supply. The modulator achieves 12-bit resolution at a measured 200 MSamples/second, state-of-the-art performance in both resolution and sampling speed. It has sufficient speed to allow for oversampling to shape the output spectrum and therefore reduce filtering requirements, as demonstrated through a 32x oversampled 8-PSK signal at 6.25 MSymbols/second with under 6.1% EVM.