Switching-mode linear RF power amplifier system

A novel linear RF power amplification system employing voltage switching class-D amplifiers is presented. All information in the amplitude and phase-modulated source signal are encoded in the transition timing of a two-level pulse train in a special way such that its spectrum contains a replica of the signal to be amplified. Subsequently, the binary digital signal is power amplified by a switching amplifier. A bandpass filter is used in the load circuit to reconstruct the amplified source signal and to remove unwanted spectral components. The proposed configuration is simple to implement and has the potential of achieving both high efficiency (typical of switching-mode amplifiers) as well as high linearity. An implementation using commercial GaAs FET devices is demonstrated at 800 MHz with a simulated average power efficiency of 23% at 2 W output load power and −50 dBc spectral growth for a 64-QAM modulated signal having a 10 MHz bandwidth.