A new high efficiency RF switch-mode power amplifier architecture for pulse encoded signals

A new architecture for RF switch-mode power amplifiers is proposed. In this design, a pulse encoded signal switches a single RF power device with a broadband output match coupled to an output diplexer. The broadband termination impedance across the device minimizes switching losses. A complementary diplexer design is used to implement a bandpass reconstruction filter required for the pulse encoded signal as well as a broadband bandstop filter to separate out-of-band spectral power from the reconstructed output signal. The bandstop filter output terminal also provides an option to enhance power efficiency by incorporating an energy recovery circuit in a feedback loop to the DC power supply. The recovery circuit has the potential to significantly boost power efficiency under back-off conditions. Simulated results are presented for a 2 GHz 25 W GaN power device. For a sigma-delta encoded pulse train, the power efficiency is 65.5% at an output power of 43.7 dBm and for a pulse position modulated signal the power efficiency is 65.7% efficiency at an output power of 44.3 dBm.