Asynchronous Nonlinear Power-Tracking Supply for Power Efficient Linear RF PAs

In the world of portable wireless electronics, battery life and therefore power efficiency are key parameters, and RF power amplifiers (PAs) are severe limiting agents in this regard because of their power-intensive demands. Spectral density is also critical to extend the effective bandwidth of a wireless transmitter, which is why linear PAs are popular, in spite of their inherently low power efficiency levels. An asynchronous power-tracking scheme is therefore proposed to more efficiently power-condition the supply of linear RF PAs and extend overall battery life performance. The RF supply is comprised of a high power but slow-responding voltage regulator with a lower power but fast-responding parallel nonlinear clamping circuit. Simulations with a SiGe HBT class-A RF PA show that the proposed circuit consumes 10-15% less total power and achieves 1.5% better overall power efficiency than the state-of-the-art power-tracking scheme while meeting the same error-vector magnitude (EVM) performance.