Energy efficient power amplification of multilevel constellations can be achieved by an amplification structure based on the constellation's decomposition as a sum of polar components, such as M BPSK (Bi-Phase Shift Keying), that are separately amplified. By doing this one can define highly efficient transmitters based on multiple amplifiers. However, amplifiers' imbalances might lead to substantial constellation distortion since phase and gain imbalances cause rotations and translations of the symbols associated to each amplification branch that are combined to generate the resulting constellation. Therefore, it becomes crucial the knowledge of the amplifiers' imbalances to overcome this problem at the receiver side. For that we propose and evaluate efficient two new methods for estimating amplifier imbalances. Simulation results demonstrate that the good performance attainable by the proposed estimate algorithms can be assured without significant increase in system and computational complexity.
- Multi-amplifier transmitters
- Multilevel constellations