A 10MHz-Bandwidth 2mV-Ripple PA-Supply Regulator for CDMA Transmitters

Abstract

Polar modulation has been proven to be an effective way to build high-efficiency high-linearity power amplifier systems. In a polar transmitter, high-efficiency non-linear power amplifiers can be used for linearly modulated waveforms. Because of envelope bandwidth expansion in polar modulated transmitters, the design of a wide-bandwidth high-efficiency supply modulator is one of the most challenging aspects of a polar transmitter. The most common technique for providing wide-bandwidth low-noise supply modulation in a linear system PA is by using linear low-dropout regulators, however at backed-off power levels their efficiencies are low. Envelope tracking is another common technique for transmitter design. Although this technique relaxes the bandwidth requirement of the supply modulator, it uses a less efficient linear power amplifier. A parallel combination of linear and switch-mode regulators for a polar PA is proposed. A similar topology for EDGE PA regulators has been proposed.