An all-digital universal RF transmitter [CMOS RF modulator and PA]

This paper presents a CMOS class-D PA with on-chip all-digital RF modulator. The IC is fabricated in a 0.18 μm digital CMOS process with MIM capacitors. The die size is a square 2.5 mm on each side. The active area used for the modulator (excluding the pads and bypass capacitance) is 0.315 mm². The class D PA shows 75 dB IM, -50 dB feedthrough, and puts out 19.6 dBm at >69% drain efficiency from a 1.8 V supply. The modulator operates in the IQ domain, without the use of bias control nor envelope modulation.