Abstract
In this paper, a novel outphasing power amplifier (PA) based on class-E amplifiers with shunt capacitances and shunt filters is proposed. The new design provides high drain efficiency for both peak and back-off power levels. A mathematical model for the class-E power amplifier with shunt capacitance and shunt filter is presented. The proposed model enables derivation of load circuit parameters that provide optimum drain efficiency for the peak and back-off power levels using closed form mathematical expressions. Based on this model, an outphasing power amplifier is designed and subsequently implemented using microstrip transmission lines and a GaN HEMT devices. The fabricated power amplifier prototype is optimized for 2.14 GHz and provides drain efficiency of over 60% for back-off power levels up to 8.5 dB. The amplifier demonstrates a 44.3% drain efficiency for 64QAM OFDM modulated signal with 20 MHz bandwidth. Adjacent channel leakage ratio (ACLR) of −39.5 dB and error vector magnitude (EVM) of 0.9 % were achieved after the application of a memory polynomial linearization algorithm.
Highlights
P ROVIDING high data throughput and maintaining high energy efficiency are two of the main requirements for modern wireless communication systems
In this paper we present detailed analysis of load modulation properties of the class-E power amplifier (PA) with shunt capacitance and shunt filter
That the peak power solution is very similar to the analysis presented in [44], [45], the solution is modified in order to enable extension of the analysis for the back-off power case
Summary
P ROVIDING high data throughput and maintaining high energy efficiency are two of the main requirements for modern wireless communication systems. Each branch PA sees a constant load impedance and very high linearity can be provided As it was shown in [25], isolated combiners demonstrate low average efficiency for signals with high PAPR. The input impedance of nonisolated combiners depends on the outphasing angle and on the level of input signal This load modulation can significantly improve the average efficiency of the transmitter. It was shown that in order to maintain high efficiency of class-E PA under back-off output power, it is necessary to violate the ZVDS condition while fulfilling the ZVS condition. This analysis was used in order to design an outphasing PA in [21].
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