RF switch-mode power amplifier with an integrated diplexer for signal reconstruction and energy recovery

A new RF switch-mode power amplifier architecture is proposed as an alternative to other switch-mode amplifier designs based on class D or class S circuits. Class D/S circuits have a number of implementation challenges including output baluns, high swing drivers, and protection diodes. In the proposed design, a single switching device is driven by a pulse train and matched to an output diplexer. The diplexer has complementary bandpass and bandstop filter characteristics where the bandpass filter is used for signal reconstruction and the bandstop filter is used to capture out-of-band energy and recycle RF power to enhance power efficiency. An experimental prototype of the driver, switch-mode amplifier and diplexer have been implemented to demonstrate the amplifier concept. A drain efficiency of 70% is measured over a frequency range of 400 MHz to 850 MHz at an output power of 10 W. Future extensions of the work will include implementations of the energy recovery circuit to recycle out-of-band RF load power.