Repetitive Fixed Bandwidth Limitation and QAM Correction for EER Power Amplifier

Envelope elimination and restoration (EER) power amplifier architecture can achieve high efficiency and linearity. However, when used with modern modulation schemes such as orthogonal frequency division multiplexing (OFDM) and wideband code division multiple access (W-CDMA), it suffers from expanded bandwidth problem. This paper shows that, the straightforward bandwidth limitation results in poor efficiency of the power amplifier (PA). We propose a new repetitive bandwidth limitation technique which reduces bandwidth expansion of both the envelope and phase polar drive signals without compromising the efficiency of the PA. It has been found that the improvement in bandwidth of drive signals is proportional to the number of repetition. The bandwidth limitation often results in spectral splatter and error vector magnitude (EVM). To counter this, we employ a QAM correction technique which reduces the in band distortion.