A simplified approach to concurrent dual-band power amplifiers digital predistortion

Abstract

The increasing demand for wider bandwidth in the current wireless networks and the need to work simultaneously with different networks impose many design challenges for power amplifiers (PA) design and the digital predistortion (DPD) in many aspects. The analog-to-digital converter (ADC) sampling speed for conventional DPD has to be several times the original signal bandwidth in order to cover the out-of-band intermodulation components caused by a nonlinear PA, which leads to use high-speed ADCs that tend to be the most expensive components in a transmitter with DPD. The emerge of concurrent dualband (multi-band) PAs, two (multiple) ADCs are needed to deal with each band separately. Eliminating the need to repeat the components for each band is essential to lower the complexity and cost of the DPD design. In this paper, a method to compensate for the nonlinearities in a nonlinear concurrent dual-band transmitter is presented. The method uses only one branch to feedback the PA output signal instead of two (multiple) branches in the conventional architecture. Thus, It allows the use of only one ADC with only one down-converter, hence making a complexity reduction for the design of the DPD. The results show that the implementation of a dual-band DPD can be simplified using the proposed approach without sacrificing the DPD accuracy.