A wide band envelope modulator for envelope tracking RF power amplifiers

Polar modulation RF power amplifier is a good candidate to enhance the efficiency while maintaining the linearity for high PAPR signals. Among different architecture used for envelope modulator, hybrid switching envelope modulator is attracted the attention. Class AB power amplifier which is the main block of hybrid switching envelope modulator should have wide bandwidth and low output impedance in a wideband of frequency to compensate high switching noise ripples. In this paper a wideband supply modulator with sufficient low output impedance is designed in 0.18 μm CMOS technology. The bandwidth of the modulator is around 437 MHz which is much larger than previously reported in literature. Thanks to the low output impedance of the class AB architecture, the HSEM architecture is capable of reducing the switching frequency noise up to 100MHz, while consuming approximately the same power as other architecture.