A simple and effective RF predistorter for use in the HPAs of base stations in cellular mobile systems

This paper presents the design of using a simple mixer circuit, constructed with Schottky diodes as the nonlinear device, to generate the intermodulation (IM) products for predistortion of high-power amplifiers (HPAs) in the base stations of cellular mobile systems. The design has a simple structure and requires no external dc bias voltage. A complex polynomial is used to model the characteristic of the HPA and the predistorter generates the in-phase and quadrature components of the intermodulation distortion (IMD) products for predistortion of the HPA. Experimental results using a practical HPA show that, for a modulated CDMA (IS-95) signal, the predistorter can reduce the adjacent-channel-power ratio (ACPR) by 15 dB.