A Pulse-Modulated RF Power Amplifier System with Output Direct Absorptive Band-Pass Filter Connection

This paper presents a pulse-modulated RF power amplifier system with the aliasing-free digital pulse-width modulation employing direct connection of an absorptive bandpass filter as the output reconstruction filter. This implementation is capable of keeping the system linearity by reducing the out-of-band spurs reflection back to the power amplifiers. A prototype transmitter system including the absorptive filter is constructed with commercially available components. Measurements using a 16-QAM 20-MHz bandwidth LTE signal at 836.5 MHz, it achieves 4 to 6-dB ACLRs linearity improvement as compared with direct connection of an output SAW filter and without using any calibration or pre-distortion.