Digitally controlled envelope tracking power supply for an RF power amplifier

A new digital self-oscillating (DiSOM) modulator is presented in this paper. The advantage of the DiSOM is that it allows the sampling frequency of the digital compensator to be higher than the switching frequency, but it also has the ability to shape the quantization noise on the switching output due to clock frequency quantization. An envelope tracking power supply for an RF power amplifier (RFPA) can help improve system efficiency by reducing the power consumption of the RFPA. To show the advantage of the DiSOM over traditional counter based digital PWM modulators two designs were compared in both simulation and by experiment. The results shows that the DiSOM could give an increase in open loop bandwidth by more than a factor of two and reduce the closed loop output impedance of the power supply by a factor of 5 at the output filter resonance frequency.