Linearization of Concurrent Tri-Band Transmitters Using 3-D Phase-Aligned Pruned Volterra Model

Abstract

This paper reports a novel digital predistortion (DPD) scheme for concurrent tri-band power amplifiers (PAs). The proposed tri-band DPD is based on a pruned Volterra model that takes into account the impact of the phase distortion observed in multi-band PAs as well as the compound amplitude distortion. By taking into account the phase variation effects across a wide frequency band, the proposed 3-D phase-aligned Volterra DPD can effectively compensate for the crosstalk effects between the fundamental frequencies, their harmonics, and intermodulation products due to the nonlinearity the tri-band PA exhibited. The performance of the proposed DPD is validated using a broadband Class-AB PA driven concurrently by three independent carrier-aggregated long-term evolution signals at separation frequencies around 100 MHz. The measurement results validate the accurate performance of the proposed 3-D phase-aligned pruned Volterra DPD in suppressing the in-band and cross-band intermodulation effects, and shows improvement over a basic 3-D tri-band DPD model that neglects phase variation effects across frequency.