Performance of a frequency compensated EER-PA with memoryless DPD

The Envelope Elimination and Restoration (EER) technique has attracted significant attention recently because of its high efficiency under back-off operation. Memoryless Digital Predistortor (DPD) is indispensable for an EER power amplifier (PA) because of the EER PA´s strong nonlinearity due to the dynamic power supply voltage. However, performance of the memoryless DPD is significantly degraded by the frequency response of the envelope amplifier in EER-PA. We have proposed a simple and useful EER-PA model to analyze the performance degradation of the memoryless DPD. Successful compensation of the third-order intermodulation distortion of two-tone signals has been demonstrated using the memoryless DPD and frequency response compensation based on this model. In this paper, we show that the proposed model is applicable not only to two-tone signals but also to OFDM test signals. An EER-PA with a split-band envelope amplifier has been developed for experimental verification. Measured adjacent channel leakage power ratio (ACPR) of the developed EER-PA was improved from -22.5 dBc to -42.5 dBc for a 1.4 MHz bandwidth OFDM test signal using the frequency response compensation and memoryless DPD.