A Two-Phase Switching Hybrid Supply Modulator for RF Power Amplifiers With 9% Efficiency Improvement

摘要

A hybrid supply modulator consisting of a parallel operation of a high-drive, low output impedance, wideband class-AB linear amplifier and a high-efficiency, wideband, low-ripple switching amplifier is presented for the application of polar transmitters. At system level, a two-phase switching is employed to lower the inductor current ripple so that both the output ripple and power loss are reduced. On-chip feed-forward bandpass filter is used to extend the tracking bandwidth of the switching amplifier, without hurting the stability of parallel control loop or the need to increase switching frequency. At circuit level, the output impedance of the linear amplifier is lowered by optimizing the design of super source-follower output stage. Inductor current sharing and two-phase ramp generator are implemented for realizing the two-phase switching scheme.