A 900 MHz voltage-mode class-S power amplifier

This paper presents a class-S power amplifier with voltage-mode class-D topology for the 900 MHz band. The design is based on a GaN-HEMT MMIC and realized as a hybrid module. For a typical 3.6 Gbps single-tone BPDSM input signal, the measured output power exceeds 1 W with an efficiency of 21%. In order to study the impact of coding efficiency, a periodic square-wave input signal was investigated as well. In this case, output power increases to 3 W. Efficiency rises to 43 % peaking at 59% for an output power of 0.8 W. For the voltage-mode version, these are the highest class-S output-power values in the 900 MHz band reported so far.