Simplified Analysis and Design of Outphasing Transmitters Using Class-E Power Amplifiers

The outphasing technique can enhance a transmitter efficiency at power levels other than peak-envelope power. Its analysis is straightforward for various power amplifier classes. However, when using class-E power amplifiers, the outphasing analysis requires several steps in order to achieve performance prediction. In this paper, a simplified analysis and design of class-E outphasing transmitters is proposed as an alternative method that predicts efficiency and output power as a function of input drive phase difference based on classic design equations of the class-E amplifier. It is shown that the efficiency at backoff power can be optimized by the asymmetric combiner electrical lengths and the design parameters are then simplified so that they can be used in an actual prototype.