UHF Class E/F₂ Outphasing Transmitter for 12 dB PAPR Signals

Abstract

This paper exploits the degree of freedom provided by the continuous class-E modes in order to reduce the impact of a FET on-state resistance when approximating the zero voltage switching (ZVS) operation along a wide range of resistive loads. A UHF class-E/F2 power amplifier (PA), which includes a lumped element drain terminating network to synthesize the optimal load modulation (LM) trajectory, has been designed to maintain an efficiency as high as possible along an output power control range above 10 dB. Based on this PA, an outphasing scheme in the 700 MHz frequency band has been implemented. It is shown to provide an efficiency higher than 60% up to an output power below 5% (-13 dB) of its peak value (47 W). Under mixed-mode operation and applying digital predistorsion (DPD), a 10 MHz LTE signal with a peak-to-average power ratio (PAPR) as high as 12.2 dB has been linearly reproduced with average efficiency and PAE values of 46.6% and 42.9%, respectively.

Load-Invariant Double Class-E/F2 Resonant Topology for UHF DC-DC Power Conversion

“…Following the analysis in [17] for the effect of the reactive 2 nd harmonic termination, efficiency contours obtained from simulations are plotted in Fig. 3a, both for the original class-E (open circuit termination) and the class-E/F2 (inductive termination resonating the output capacitance) modes under a high level CW excitation.…”

Outphasing Class-E/ F2 Power Amplifier using a Quadrature Hybrid as Non-Isolating Combiner

“…1) for a nearly infinite choke, a 1∠113.7º reflective termination at the second harmonic and open circuit conditions at the higher order ones, corresponding to those for a class-E/F2 amplifier [3]. An optimum load modulating (LM) trajectory exists [4], including the impedance points providing maximum efficiency for each output power level. Under theoretical assumptions, a 100% efficiency vs. output power profile would result from zero but variable slope voltage switching operation.…”

“…2b to a position centered along the LM trajectory represented in Fig. 1 [2,4]. In this way, the outphasing angle could offer control over the drain impedance at the fundamental in the desired region over the LP contours.…”

“…Exploiting the potential of its continuous modes [3], the power range to be covered with low losses may be extended beyond the 8-9 dB output power backoff (OPBO) limit typical of single load modulating techniques. In [4], the authors combined these concepts in a lumped element class-E/F 2 topology for the UHF band. Integrating two of those PAs with a series combiner and an impedance transformer, a 12.2 dB PAPR 10 MHz LTE signal was reproduced with an average efficiency above 45%.…”