Modeling and analysis of the frequency dependence of class-E outphasing

Digital Predistorters Go Multidimensional: DPD for Concurrent Multiband Envelope Tracking and Outphasing Power Amplifiers

“…The frequency dependent characteristic of the non-isolating combiner, including the compensating reactances, and the reactive elements in the device model usually impose strong limitations to its bandwidth. As a way of illustration, if designed with class-E switched-mode PAs (a highly attractive operating class in terms of efficiency performance), the efficiency contours rotate counterclockwise with the increasing frequency, while the mutual load modulation trajectories offered by a passive (Foster) combiner rotate in the expected clockwise sense [40]. In a pure outphasing operation, the constant-envelope phasemodulated signals to be handled by the constitutive branches may have a bandwidth several times wider than the original signal to be reproduced.…”