High-efficiency power amplifier using dynamic power-supply voltage for CDMA applications

Abstract

Efficiency and linearity of the microwave power amplifier are critical elements for mobile communication systems. This paper discusses improvements in system efficiency that are obtainable when a dc-dc converter is used to convert available battery voltage to an optimal supply voltage for the output RF amplifier. A boost dc-dc converter with an operating frequency of 10 MHz is demonstrated using GaAs heterojunction bipolar transistors. Advantages of 10-MHz switching frequency and associated loss mechanisms are described. For modulation formats with time-varying envelope, such as CDMA, the probability of power usage is described. Gains in power efficiency and battery lifetime are calculated. An envelope detector circuit with a fast feedback loop regulator is discussed. Effects of varying supply voltage with respect to distortion are examined along with methods to increase system linearity.

CMOS Linear Power Amplifier with Envelope Tracking Operation (Invited Paper)

“…It operates over a wide bandwidth, but is not efficient enough for high PAPR signals. In [17,18], a switched-mode power supply (SMPS) delivers high efficiency, but its bandwidth is too narrow to use in 4G systems, such as Mobile-WiMAX and 3GPP LTE. In [19 21], a hybrid switching converter that combines the advantages of the two modulators is used to achieve high efficiency and good linearity simultaneously as shown in Fig.…”

Design and Simulation of a Wideband Hybrid EnvelopeTracking Power Amplifier Using LDMOS Transistor

“…ET uses a linear PA and a controlled supply voltage, which tracks the input envelope. When the supply voltage tracks the instantaneous envelope modulation signal, it is called Wide Bandwidth ET (WBET) [6]- [9]; when the supply voltage tracks the long-term average of the input envelope power, it is called Average ET (AET) [10]- [11]; when the supply voltage switches to different step levels according to the input envelope power, it is called Step ET (SET) [12], [13]. In ET we dynamically bias the RF transistor so that the RF transistor working in the high efficiency compression region over a wide dynamic range of output power and improve the PA average efficiency.…”

CMOS Integrated Switched-Mode Transmitters for Wireless Communication

“…Su and McFarland (1998) have demonstrated a CMOS implementation of an EER system, including a delta-modulated supply, a limiter, and envelope detectors, driving a switched-mode PA, resulting in significant linearity and efficiency improvements. Envelope tracking (ET) describes a transmitter architecture where the Cartesian RF signal is amplified by means of a linear amplifier, with its supply controlled by the envelope of the signal (Hanington et al, 1999;Takahashi et al, 2008). One of the main advantages is that the bandwidth of the PA input signal is not expanded, but a linear amplifier generally has a lower efficiency than a SM amplifier.…”