Analysis and Design of Outphasing Transmitter Using Class-E Power Amplifiers With Shunt Capacitances and Shunt Filters

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.

Historical Aspect of Load-Modulated Balanced Amplifiers

“…However, these switching-mode power amplifiers have poor linearity and are unsuitable to replace linear power amplifiers and can be used in advanced architectures with linearization techniques. The LMBA was initially developed to address bandwidth limitations associated with conventional load modulation techniques [12], [13] and to enhance efficiency in the back-off region. Despite its potential for efficiency improvement, the inclusion of an additional control amplifier and a phase shifter contributes to an increase in circuit size.…”

Development Review of Broadband and Multi-Band Outphasing Power Amplifiers for High-Efficiency Amplification

“…The high conversion efficiency of OPAs is achieved through phase modulation between two sub-amplifiers, which work in saturation conditions [2]. An efficient power amplifier (PA) solution can be adopted, such as class-E or class-F, by the two sub-amplifiers to boost the conversion efficiency [3][4][5][6]. Many studies have been conducted on OPAs, including circuit topology and design methods.…”