Piecewise Pre-Equalized Linearization of the Wireless Transmitter With a Doherty Amplifier

This paper describes a predistorter (PD) based on piecewise pre-equalizers for use in multichannel wideband applications. The predistortion linearizer consists of piecewise pre-equalizers along with a look-up-table-based digital PD that together compensate for nonlinearities, as well as memory effects of power amplifiers (PAs). It takes advantage of multiple finite-impulse-response filters that significantly reduce the complexity when compared to memory polynomial methods. The proposed method was also compared with the conventional Hammerstein structure. A 300-W peak envelope power Doherty PA was first modeled by measured time-based samples in order to verify the adjacent channel power ratio (ACPR) performance in simulation using a multitone and single wideband code-division multiple-access (W-CDMA) carrier. Furthermore, the experimental results applying two W-CDMA carriers verify that the proposed method provided similar improvement to that of the memory polynomial approach. The experimental results verified the complexity reduction and superior ACPR performance over the conventional Hammerstein structure.