RF-DAC-based PA Pre-Distortion using Expanding Non-Linear RF-DAC Scaling

We present an RF-DAC-based transmitter that uses an expanding characteristic to linearize the PA. Implemented in 22nm FDSOI CMOS, the transmitter operates with a carrier frequency of 12.5GHz, achieving a sample rate of 7GS/s. Measurements with >3.5GSym/s wideband modulated 64QAM SC and OFDM signals show EVM<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RMS</inf> <3.83% and ACPR <−32.4dBc when using the RF-DAC-based predistortion. The 1dB compression point is increased by 4.2dB. For multi-GHz wideband modulated signals, a >0.6 percent unit EVM improvement and a >2.5dB ACPR improvement are observed.