Digital predistortion optimization using normalization gain adjustment in wideband systems

Digital predistortion (DPD) is a highly cost-effective technique to linearize high power amplifiers (HPAs) in wireless applications. In this paper we propose a normalization gain control in the predistortion function synthesis to provide further improvement in terms of correction and linearity performance. The linearity dependency of the linearized amplifier upon the normalization gain and the transmitted signal has been investigated. It is shown that he linearity performance of the predistorter depends on the normalization gain factor. Transmitted signal characteristics such as probability density function (pdf) or peak to average power ratio (PAPR) affect to DPD performance. Thus, different normalization gain factors will be suitable depending on the transmitted signal. Tests carried out in LTE downlink and uplink transmissions confirm that the DPD performance improves when an adjustment of the normalization gain is included in the predistortion extract process.