High efficiency power amplifier applying envelope elimination and restoration technique with a single stage envelope amplifier with ripple cancellation network

This paper presents the integration of a single stage envelope amplifier with a switched class E amplifier using the Kahn´s technique or envelope elimination and restoration (EER). This technique is based on the combination of a switched and high efficient power amplifier supplied by a hi gh efficient envelope amplifier to obtain a linear and highly efficient RF amplifier. This work is focused on the envelope amplifier, a synchronous buck converter with ripple cancellation network, and on the integration with the high efficiency switched class E amplifier. With the proposed design of the synchronous buck converter with ripple cancellation circuit it is possible to decrease the ratio between the switching frequency and the large signal bandwidth of the envelope amplifier, which is one of the most limiting design factors of this application. The predistortion technique has been applied to increase the linearity and the improvement has been quantified experimentally. A high total efficiency has been obtained both for a quadrature amplitude modulation (QAM) signal and for an orthogonal frequency-division multiplexed (OFDM) modulation, with higher peak to average power ratio(PAPR).