Energy-Efficiency Optimization of the High Power Amplifier for Multicarrier Systems:Analytical EVM Derivation
Résumé
"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."