Class S Power Amplifier System for Radio Applications in the HF Band

This work presents the development and implementation of a class S power amplifier system for the use in radio applications in the HF band. The system consists of a bandpass Delta Sigma modulator and a class D power amplifier system. Both parts are designed separately, so a flexible combination of the subsystems is possible, but the focus of this work are the mutual influencing factors of the two subsystems. The complete class S system shows a maximum drain efficiency of 13.3% at a SQNR of 37.9 dB. For better reconstruction of the input signal a simple filter and impedance matching circuit is added at the output. The measurement of the filtered signal yields a drain efficiency of 7.8% at a SQNR of 33.2 dB.