Joint RF pre-distortion and post-distortion linearization of small cell power amplifiers

Abstract

In this paper a power amplifier (PA) linearization technique is proposed where an RF predistorter (RFPD) is used in conjunction with a linearization amplifier (LA) to achieve a more effective joint pre-distortion and post-distortion linearization. This approach is suitable for use with small cells PAs because its power and cost overhead are scalable with the power range and cost of the PA. To demonstrate the technique's linearization capability, a prototype of the linearization scheme was implemented and applied to a 6-W class AB PA with a centre frequency of 850-MHz. When stimulated with a 15-MHz bandwidth modulated signal, the PA's adjacent channel leakage ratio and error vector magnitude were improved by more than 13 dB and 5 percentage points, respectively, at peak power, and up to 18 dB and 5.2 percentage points, respectively, at power backoff with the proposed linearization scheme. Furthermore, similar linearization was achieved when the PA was driven with a 40-MHz bandwidth modulated signal.