Class-D−1 Power Amplifier Using Cavity Filtering Balun for All-Digital RF Transmitters

This letter presents a novel Class- D^-1 power amplifier (PA) based on a dielectric filled cavity balun. Different from the conventional Class-D PA, the functions of signal combination, filtering, and output impedance matching are all integrated into the high Q filtering balun. This method not only provides a high efficiency and sharp roll-off for noise shaping but also reduces the design complexity. The effect of C ₃ₒ on efficiency is also analyzed. A simple neutralizing network is used to obtain additional efficiency enhancement. For demonstration, a filtering Class- D^-1 PA operating at 1. 82 GHz is fabricated and measured. With the measured result, the proposed PA shows an output power of 41 dBm and a drain efficiency of 71. 8% with a high-frequency selectivity.