Wideband Cartesian RF-DAC-Based Predistorter using Nonlinear RF-DACs and IQ Expansion

Paper in proceeding, 2026

We here present an RF-DAC-based PD featuring IQ expansion, a linearization concept using segmented non-linear RF-DACs combined with increased expansion in the IQ direction. The proposed predistorter, realized within the RF-DACs themselves, is very hardware efficient, only requiring a small
amount of additional hardware compared to a conventional RF-DAC. The proposed RF-DAC-based PD, realized in a 22nm CMOS technology, is used to linearize a PA integrated on the same chip. With IQ expansion, we measure a peak compression ripple of ±0.2 dB across the full range with a peak output power <2.3 dB below the PA Psat. Modulated measurements with up to 4 GSym/s 64QAM SC signals show an EVM <4.05% and ACPR <−30.1 dBc, achieving an EVM improvement of >0.3 percent unit.