Low-Cost RFin–RFoutPredistorter Linearizer for High-Power Amplifiers and Ultra-Wideband Signals

Abstract

The 5G and beyond systems require the highly efficient linear power amplifier (PA) at the base station to deliver promised data rate in a power efficient manner. To facilitate higher data rates in future 5G communication, the demands for the wideband signals are continuously increasing, which creates adversity in employing digital predistortion (DPD) for the linearization of RF PA in ultra-wideband systems. System bandwidth constraint of the conventional DPD does not provide sufficient linearization of wideband signals. In this paper, we present two types of predistorter, first is RFin-RFout analog predistorter, in which linearization is performed by RF components in the analog domain, and the second is hybrid RF predistorter which takes the advantage of advanced DSP platform for improving the performance of RFin-RFout analog predistorter. The proposed predistorters eliminate the constraint on the system bandwidth of the conventional DPD. The requirements of data converters and reconstruction filters are relaxed in the analog predistorter (APD) architecture, whereas hybrid digitally controlled (HDC) APD eliminates the need of analog components by compensating the delay digitally. In order to validate this concept, a ZX60V-63+ PA from minicircuits is tested with 160-MHz eight-component carrier-long term evolution signal. The proposed APD architecture is able to deliver an adjacent channel power ratio (ACPR) of -46.4 dBc with an ACPR improvement of 13.4 dB at 1-dB back-off. Furthermore, with digital intervention, modified model, HDC-APD further provides a significant improvement in the linearization performance and delivers an ACPR of -53.5 dBc with an ACPR improvement of 20.5 dB.