A novel inverse class-D output matching network and its application to dynamic load modulation

This paper presents a new inverse class-D output matching network suitable for dynamic load modulation. The proposed matching network can synthesis the optimum load impedance at the fundamental as well as the necessary terminations at the 2^nd and the 3^rd harmonic, additionally it allows separate control over the imaginary and real part of the admittance at the fundamental. For load modulation applications an adaptive λ/4 line will be presented. An inverse class-D GaN power amplifier at 1 GHz based on the new output matching network is designed and measured. The measured amplifier has a maximum power added efficiency of 74% and maximum output power of 40 dBm. Through using the adaptive λ/4 line the amplifier can achieve a PAE of more than 50% at an output power of 32 dBm, which gives an efficiency improvement of more than 25% over an 8 dB output dynamic range.