Envelope tracking technique with bang-bang slew-rate enhancer for linear wideband RF PAs

This paper deals with the design of power efficient switching regulators intended for linear power amplifiers employing envelope tracking techniques in wideband wireless standards. The bottlenecks in existing envelope tracking solutions involve a tradeoff between ripple voltage, slew rate and bandwidth. The slew rate limitation is identified as the main challenge and a `bang-bang' slew-enhancement technique is proposed for overcoming it. This approach enables the use of efficient supply modulators in wideband power amplifiers. The proposed scheme does not significantly degrade PA efficiency and improves the stability of the switching regulator. The prototype has been implemented using the TSMC 0.18 μm technology; schematic simulation results in Cadence^® demonstrate the feasibility of the proposed technique.