A Variable Envelope Outphasing Concept for Transmitter Linearization

Outphasing transmitter is typically implemented by dividing amplitude-varying waveform into multiple power amplifier (PA) paths with zero peak-to-average-power ratios (PAPR) per path. This arrangement provides linear output for the combined signal with high amplifier efficiency. However, due to the combining of outphased signals, the output power of the combined signal is compromised. In this paper, we present a novel concept called variable envelope outphasing (VEOP), which allows the possibility of systematically distributing the time-varying amplitude of the signal to the common and outphasing parts. This provides a valuable tool to balance the linearity and output power and thus produce a high-PAPR signal as a sum of lower PAPR signals. The proposed VEOP concept is demonstrated through conductive measurements at 2.4 GHz. The experimental results show that the choice of PAPR distribution before and after the amplification stage through VEOP provides linearity and achieved output power trade-off.