| A classical approach for the power management of a communication system is to use a high-efficiency switching power supply. A conventional switching power supply comprises semiconductor switches, and a low pass filter including inductors and capacitors. A feedback loop stabilizes the output voltage and provides a few kilohertz of bandwidth. Unfortunately, such a power supply is not adequate in today's communication systems. The size, the cost, and the battery life are becoming critical issues in portable electronic devices. Therefore, new methods of power management are required.; The two main approaches to improve the efficiency of systems including RF power amplifiers (RFPA) are the slow power control and the envelope tracking technique. Digital realization of these techniques eliminates the need for external discrete components, enhances the system performance, and eases implementation of more sophisticated control schemes.; For the slow power control, a new high efficiency, digitally controlled DC-DC converter is introduced that enhances the RFPA efficiency. The converter operates in two modes of continuous-conduction mode (CCM) and pulse-frequency modulation (PFM) for the high and low output power, respectively. Furthermore, sensorless optimization of dead-times for the switching converters including synchronous rectifiers is proposed. This novel approach enhances the efficiency of the switching converters without a significant increase in hardware.; The envelope tracking technique improves the efficiency of the communication systems including amplitude modulation. In this technique, the amplitude and phase signals are applied through different paths to a nonlinear, but highly efficient RFPA, in order to achieve RF power amplification with high linearity. A three-level buck converter is proposed to achieve favorable tradeoffs in terms of the switching ripple, efficiency, bandwidth, or decreasing filter element sizes in the envelope-tracking application for RFPAs. Linear-assisted switching amplifiers are alternate solutions for the envelope tracking technique. They are based on the idea of combining high efficiency of switching converters with wide-bandwidth capabilities of linear amplifiers. A band-separation frequency is found to maximize the efficiency of the linear-assisted switcher. The band-separation frequency is determined based on the efficiency characteristics of the amplifiers and the amplitude-distribution of the amplified signal. |
