A fully-integrated digital-intensive polar Doherty transmitter

This paper presents an advanced 2.3-2.8 GHz fully-integrated digital-intensive polar Doherty transmitter realized in 40nm standard CMOS. The proposed architecture comprises CORDIC, digital delay aligners, interpolators, digital pre-distortion (DPD) circuitry in combination with frequency-agile wideband phase modulators followed by the digital main and peak power amplifier (PA) operating in quasi-load insensitive class-E using an on-chip power combiner. At 2.5 GHz, its maximum output power is +21.4 dBm. Drain efficiency is 49.4% at peak power, and 33.7% at 6-dB power back-off. Applying DPD for a 20-MHz 64-QAM signal, the measured EVM is better than -30 dB while the average drain efficiency is 24%.