High-efficiency linear amplification by dynamic load modulation
08 Jun 2003-Vol. 3, pp 1717-1720
TL;DR: Load modulation is a new technique in which amplitude-modulated signals are produced with high efficiency by dynamic variation of the load impedance of the power amplifier as discussed by the authors, which is achieved by a T network with a pair of highvoltage MOSFETs that act as a voltage-variable capacitor.
Abstract: Load modulation is a new technique in which amplitude-modulated signals are produced with high efficiency by dynamic variation of the load impedance of the power amplifier. The prototype MOSFET PA operates in class E and produces a peak output of 19 W at 30 MHz with an efficiency of 66 percent. Load modulation is accomplished by a T network with a pair of high-voltage MOSFETs that act as a voltage-variable capacitor. The envelopes of a variety of different signals are successfully generated. For a Rayleigh (multi-carrier) envelope with a 10-dB peak-to-average ratio, the average efficiency is twice that achieved in linear operation of the same PA.
Citations
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TL;DR: This paper presents a multi-band multi-mode class-AB power amplifier, which utilizes continuously tunable input and output matching networks integrated in a low-loss silicon-on-glass technology to achieve the desired source and load impedance tunability.
Abstract: This paper presents a multi-band multi-mode class-AB power amplifier, which utilizes continuously tunable input and output matching networks integrated in a low-loss silicon-on-glass technology. The tunable matching networks make use of very high Q varactor diodes (Q>100 @ 2 GHz) in a low distortion anti-series configuration to achieve the desired source and load impedance tunability. A QUBIC4G (SiGe, ft=50 GHz) high voltage breakdown transistor (VCBO=14 V, VCEO>3.6 V) is used as active device. The realized adaptive amplifier provides 13 dB gain, 27-28 dBm output power at the 900, 1800, 1900 and 2100 MHz bands. For the communication bands above 1 GHz optimum load adaptation is facilitated resulting in efficiencies between 30%-55% over a 10 dB output power control range. The total chip area (including matching networks) of the amplifier is 8 mm2
226 citations
Cites background from "High-efficiency linear amplificatio..."
...Whenchanged dynamically [21], [22], this phase variation appears as an AM-to-PM distortion and degrades the linearity of a dynamic...
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...This approach, known as dynamic load line modulation [21], [22], enables the PA to operate at its maximum efficiency at each point in time, yielding considerable efficiency improvements also for modulated signals with a high peak-to-average power ratio....
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TL;DR: This paper presents a new approach for power amplifier design using deep submicron CMOS technologies and a transformer based voltage combiner is proposed to combine power generated from several low-voltage CMOS amplifiers.
Abstract: This paper presents a new approach for power amplifier design using deep submicron CMOS technologies. A transformer based voltage combiner is proposed to combine power generated from several low-voltage CMOS amplifiers. Unlike other voltage combining transformers, the architecture presented in this paper provides greater flexibility to access and control the individual amplifiers in a voltage combined amplifier. In this work, this voltage combining transformer has been utilized to control output power and improve average efficiency at power back-off. This technique does not degrade instantaneous efficiency at peak power and maintains voltage gain with power back-off. A 1.2 V, 2.4 GHz fully integrated CMOS power amplifier prototype was implemented with thin-oxide transistors in a 0.13 mum RF-CMOS process to demonstrate the concept. Neither off-chip components nor bondwires are used for output matching. The power amplifier transmits 24 dBm power with 25% drain efficiency at 1 dB compression point. When driven into saturation, it transmits 27 dBm peak power with 32% drain efficiency. At power back-off, efficiency is greatly improved in the prototype which employs average efficiency enhancement circuitry.
198 citations
TL;DR: In this paper, the design of varactor-based tunable matching networks for dynamic load modulation of high power amplifiers (PAs) is presented, and the results show that the power-added efficiency of the load modulated PA is improved by an absolute value of 10% at 10-dB backoff.
Abstract: In this paper, the design of varactor-based tunable matching networks for dynamic load modulation of high power amplifiers (PAs) is presented. Design guidelines to overcome the common breakdown, and tunability problems of the varactors for high power applications are proposed. Based on the guidelines, using commercially available abrupt junction silicon varactors, a tunable matching network is built and measured. The matching network is then used for load modulation of a 1-GHz 7-W class-E LDMOS PA. Static measurements of the load modulated PA show that the power-added efficiency of the PA is improved by an absolute value of 10% at 10-dB backoff. This promising result proves, for the first time, the feasibility of load modulation techniques for high-power applications in the gigahertz frequency range.
171 citations
Cites background or methods from "High-efficiency linear amplificatio..."
...Static measurements are used to demonstrate the feasibility of this architecture with focus on high-power high-efficiency performance....
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...Dynamic load modulation (DLM) is one of the techniques that can be used to boost the PA efficiency when a variable envelope modulated signal is used [1]–[3]....
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...This is considered as an important advantage of this technique, allowing high overall transmitter efficiency and wideband operation [1]....
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TL;DR: In this article, a method for achieving high-efficiency linear transmitters by codesign of the RF power amplifier (PA), dynamic supply, and signal processing is presented, which achieves 52.5% composite power-added efficiency with high linearity for a W-CDMA signal with a 23MHz supply modulator bandwidth.
Abstract: This paper presents a method for achieving high-efficiency linear transmitters by codesign of the RF power amplifier (PA), dynamic supply, and signal processing. For varying amplitude signals, the average efficiency of the PA is improved by adding a supply modulator with requirements derived from nonstandard PA modeling. The efficient PA and supply modulator both introduce signal distortion. A targeted linearization procedure is demonstrated with reduced complexity compared to standard digital predistortion. Experimental results on a 2.14-GHz 81% efficient 40-W peak power GaN PA illustrate the codesign method by achieving 52.5% composite power-added efficiency with high linearity for a W-CDMA signal with a 23-MHz supply modulator bandwidth.
138 citations
References
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TL;DR: In this article, a wide variety of techniques, implementations, and active devices are presented to generate RF/microwave power for wireless communications, but also in applications such as jamming, imaging, RF heating, and miniature dc/dc converters.
Abstract: The generation of RF/microwave power is required not only in wireless communications, but also in applications such as jamming, imaging, RF heating, and miniature dc/dc converters. Each application has its own unique requirements for frequency, bandwidth, load, power, efficiency, linearity, and cost. RF power is generated by a wide variety of techniques, implementations, and active devices. Power amplifiers are incorporated into transmitters in a similarly wide variety of architectures, including linear, Kalm, envelope tracking, outphasing, and Doherty. Linearity can be improved through techniques such as feedback, feedforward, and predistortion.
1,335 citations
TL;DR: In this article, the average efficiency of a class-G PA depends upon both the supply-voltage transition point and the amplitude distribution of the signal, and the average efficiencies are computed for a number of signals that occur in AF amplification, full carrier amplitude modulation, and envelope modulation of a linear RF PA.
Abstract: Class-G operation is an inexpensive and yet effective means of increasing the efficiency of audio power amplifiers (PAs) and amplitude modulators A class-G PA consists of two or more parallel-connected class-B PAs with different supply voltages Low-voltage segments of the signal are amplified by the low-voltage component of the amplifier, thus reducing power dissipation and increasing efficiency The average efficiency of a class-G PA depends upon both the supply-voltage transition point and the amplitude distribution of the signal Average efficiencies are computed for a number of signals that occur in AF amplification, full- carrier amplitude modulation, and envelope modulation of a linear RF PA For typical peak-to-average ratios, an ideal, two-voltage class-G PA has average efficiencies in the range of 60 to 70 percent, in contrast to the 35 to 40 percent of an analogous class-B PA
103 citations
20 May 2001
TL;DR: The 20-W class-E power amplifier (PA) described in this article is electronically tunable from 19 to 31 MHz (ratio 1.67) and operates from 25 V. The PA achieves an efficiency of 61 to 71 percent and has nearly constant output power across the band.
Abstract: The 20-W class-E power amplifier (PA) described here is electronically tunable from 19 to 31 MHz (ratio 1.67). This PA employs a single RF-power MOSFET and operates from 25 V. The output-tuning network employs fixed inductors and high-voltage MOSFETs for variable capacitors. The PA achieves an efficiency of 61 to 71 percent and has nearly constant output power across the band. It has excellent amplitude-modulation linearity for Kahn-technique transmitters, with two-tone IMDs at -40.4 dBc.
18 citations
"High-efficiency linear amplificatio..." refers background in this paper
...Its inductive input prevents harmonic currents and only single adjustment is required to change frequency [ 3 ]....
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...An electronically tuned RF PA can be configured for frequency agility, adaptation to a variable load, or amplitude modulation [ 3 ],[4]....
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