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This letter proposes a three-level buck converter for tracking applications such as envelope-tracking in radio frequency power amplifiers (RFPAs). It is shown that the three-level buck converter can offer advantages in terms of switching ripples, losses, bandwidth, or the size of magnetic components compared to a standard buck or a two-phase buck converter. Experimental results illustrate improved efficiency and ripple rejection in an RFPA envelope-tracking application representative for low-power battery-operated systems. [ABSTRACT FROM AUTHOR]

This paper describes design and implementation of a digitally controlled dc/dc converter that provides a dynamically adjustable supply voltage for a radio frequency power amplifier (RFPA). The techniques employed in the design include a combination of constant-frequency continuous conduction mode (CCM) and a variable-frequency discontinuous conduction mode to achieve very high converter efficiency over a wide range of output power levels. The variable-frequency converter control is accomplished using a current-estimator circuit, which eliminates the need for current sensing. A field-programmable gate array (FPGA)-based digital controller implementation allows programmability of the mode transition and other controller parameters. In the complete experimental system, which consists of the digitally controlled dc/dc converter and a class-E RFPA operating at 10 GHz, experimental results show that the overall system efficiency is significantly improved over a wide range of RFPA output power levels. [ABSTRACT FROM AUTHOR]

Multifunctional RF front ends need to transmit different types of signals while maintaining efficiency and signal quality. This paper addresses efficient transmitter power amplifiers (PAs) for signals with varying peak-to-average ratios, requiring simultaneous efficiency and linearity. Linearity characterization of class-E high-efficiency PAs operating in envelope elimination and restoration (EER) mode is discussed. Specifically, a 67 % -efficient 10-GHz MESFET PA is characterized in terms of its AM-AM, AM-PM conversion and intermodulation products. Measurements of intermodulation distortion are compared with harmonic-balance simulations using TriQuint's Own Model provided by the device manufacturer. It is shown experimentally and through simulations that the amplifier in the EER mode has improved linearity while maintaining high-efficiency operation. [ABSTRACT FROM AUTHOR]

This paper describes the design, implementation, and characterization of a high-efficiency 10-GHz amplifier with dynamic drain bias control that maintains high efficiency over a range of output power levels. The power amplifier (PA) operates in class-E switched mode with 67% drain efficiency at an output power of 20.3 dBm, 0.7 dB less than the specified maximum power for the device. A coupler and detector at the output of the PA provide a feedback signal to the drain-bias controller based on a 96% efficient Buck dc-dc converter. When compared with a PA with constant drain bias (4 V), the average efficiency of the PA with dynamic biasing is improved by a factor of 1.4. Over an output power between 15-20 dBm, the drain bias varies from 2 to 4 V, and the efficiency improves from 22% to 65% at the lower power level. The efficiency includes the losses in the dc-dc converter. [ABSTRACT FROM AUTHOR]