Energy-efficiency optimization of the high Power Amplifier for multicarrier systems: Analytical EVM derivation

Abstract

The high Power Amplifier (PA) dominates the power consumption in LTE transceiver systems in macro base stations and requests focusing the energy efficiency improvements on this device. In this paper, the impact of the nonlinearities on the amplified multicarrier signal is analyzed considering both linearization and Peak-to-Average Power Ratio (PAPR) reduction techniques. Therefore, we provide the expression of the Error Vector Magnitude (EVM) of the amplified signal using polynomial predistortion and clipping techniques. The EVM expression is a series expansion that depends on the Power Amplifier (PA) and predistortion coefficients, as well as, the PAPR and the average power of both input and clipped signals. The simulation results show that the proposed expression presents perfect accuracy. Moreover, theoretical analysis of the trade-off between the power amplifier linearity and efficiency is investigated considering the performance of the clipping and predistortion techniques. Therefore, an analytical expression which gives the optimal Input Back-Off (IBO) maximizing the PA efficiency, with respect to an EVM constraint and a given predistortion complexity, is provided. Based on different application scenarios and using a real power amplifier characteristic, it is demonstrated that significant energy efficiency improvement can be achieved when the IBO is appropriately adjusted.