Discrete-level envelope tracking for broadband noise-like signals

Lasser, Gregor; Duffy, Maxwell R.; Vance, Jason; Popović, Zoya

doi:10.1109/mwsym.2017.8059042

Cited by 15 publications

(5 citation statements)

References 11 publications

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“…But as the focus of this work was primarily on VHF power converters the results are promising, especially against the background of the very high switching frequency compared to other supply modulator solutions so far [4,7,11]. However, in fact, for ET systems in the 30 GHz range with targeted modulation bandwidths up to GHz the digital PA approach as a supply modulator is a real alternative but needs a lot of redesign and optimization.…”

Section: Envelope Tracking Supply Modulator Characterizationmentioning

confidence: 97%

“…The modulator showed a total efficiency of 67% for 500 MHz switching frequency. In the X-band [11] very efficient ET systems with 41% power-added efficiency (PAE) providing high modulation bandwidths up to 250 MHz have been realized. These systems use discrete level supply modulation with up to 8 levels of discretization [11].…”

Section: Introductionmentioning

confidence: 99%

“…In the X-band [11] very efficient ET systems with 41% power-added efficiency (PAE) providing high modulation bandwidths up to 250 MHz have been realized. These systems use discrete level supply modulation with up to 8 levels of discretization [11]. With regard to that another focus of this paper is to realize a GHz switching supply modulator for continuous ET supporting modulation bandwidths beyond 500 MHz with the same chip used for the DC/DC converter.…”

Section: Introductionmentioning

confidence: 99%

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A highly efficient GHz switching GaN-based synchronous buck converter module

Wentzel

Hilt

Würfl

et al. 2020

Int. J. Microw. Wireless Technol.

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The paper presents a highly efficient GaN-based synchronous buck converter suitable for switching in the lower GHz range. The module includes a very compact 2-stage GaN half-bridge converter MMIC (monolithic microwave integrated circuit) for low parasitic inductances between switches and drivers and a hybrid output network with core-less inductors to avoid ferrite losses. At 1 GHz switching frequency the buck converter achieves with pulse-width modulated (PWM) input signals power loop conversion efficiencies up to 78% for 40 V operation and output voltages up to 33 V. For 100 MHz the power loop efficiencies peak at 87.5% for 14.5 W conversion to 25 V. By changing the output network to a 2nd order low-pass with 700 MHz cut-off frequency the module has been characterized for the use as a supply modulator in very broadband envelope tracking systems with modulation bandwidths of up to 500 MHz. For 1 GHz switching frequency the power-added efficiency peaks at 74% for a 90% duty-cycle PWM input signal. The novelty of this work is that for the first time a buck converter design proves highest flexibility supporting different applications from very compact DC converters to microwave power amplifier efficiency enhancement techniques as well as efficient high frequency switching up to 1 GHz.

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Section: Envelope Tracking Supply Modulator Characterizationmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A highly efficient GHz switching GaN-based synchronous buck converter module

Wentzel

Hilt

Würfl

et al. 2020

Int. J. Microw. Wireless Technol.

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“…The pulse width limitation means that the DSM control signal needs to be modified from the ideal discretization of a continuous SM shaping function for higher bandwidth signals. To prevent signal clipping for short, high amplitude pulses, the drain supply pulses for these levels are stretched to comply with the maximum switching clock [18,29,30]. With these limitations in mind, testing is done with a 50 and 100 MHz signal with a SF based on four uniformly distributed drain voltages between 10 and 20 V for a flat gain response of 28 dB, as shown in [27].…”

Section: Distortion Mitigation In Dsmmentioning

confidence: 99%

Distortion mitigation for 100 and 250 MHz discrete supply modulation of a three-stage K-band MMIC PA

Duffy

Lasser²,

Popović³

2020

Int. J. Microw. Wireless Technol.

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Abstract This paper presents a high-efficiency linear GaN K-band transmitter for broadband high peak-average power ratio (PAPR) signals. A GaN MMIC 18.5–24 GHz three-stage power amplifier with over 4 W peak output power, 20 dB saturated gain, and 40% peak PAE is supply-modulated with a four-level discrete dynamic supply GaN MMIC. For 100 MHz signals with ${\rm PAPR}\gt 10\, {\rm dB}$ , we demonstrate an average efficiency improvement from 14 to 20% with a simultaneous linearity improvement in noise power ratio (NPR) from 23 to 26 dB through a shaping function focused on gain linearization. For 250 MHz signal bandwidth, there is no observed degradation in NPR and the efficiency is improved by 5 percentage points. For discrete supply modulation, the switching transients between levels are experimentally investigated for wideband signals.

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“…The measurements were conducted in a static and CW environment. Using static measurements to extrapolate dynamic operation has been shown to be a good starting point for predicting behaviour [11], [15], but can be limited, especially for GaN HEMT devices exhibiting trapping behaviour and thermal memory. In such devices, behaviour can be expected to change during dynamic, modulated operation [14], [20], [21], further impacting the gain variation.…”

Section: Impact On Envelope Tracking Pasmentioning

confidence: 99%

Analysis of Gain Variation With Changing Supply Voltages in GaN HEMTs for Envelope Tracking Power Amplifiers

Alt

Hirshy

Jiang

et al. 2019

IEEE Trans. Microwave Theory Techn.

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Envelope tracking (ET) is a promising power amplifier (PA) architecture for current and future communications systems, that uses dynamic modulation of the supply voltage to provide high efficiency and potentially very wide bandwidth over a large dynamic range of output power. The dynamic nature of the supply voltage can lead to a problematic variation in transistor gain however, particularly in GaN HEMTs. This paper describes and analyses this behaviour and the detrimental effect it can have on ET PAs. Contributing factors and origins of gain variation are described in detail along with how, for the first time, meaningful comparisons can be made between different devices. Using these guidelines, gain variation is shown to be a widespread issue effecting most GaN HEMTs presented in literature. To allow an analysis of the intrinsic device behaviour, an extended transistor model is developed that takes the effect of gate and source field plates into account. This model is refined using measurement data and used to demonstrate the fact that the parasitic gate-drain capacitance (C GD ) is the main contributor to the small-signal gain variation; a significant part of the overall gain variation. Based on this knowledge, possible strategies to reduce gain variation at the transistor technology level are proposed, allowing the optimisation of GaN HEMTs specifically for ET PAs. One identified strategy involves reducing the length of the gate field plate, and is shown to be a viable approach to reduce the gain variation in GaN HEMTs, albeit at an increased RF/dc dispersion.

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Discrete-level envelope tracking for broadband noise-like signals

Cited by 15 publications

References 11 publications

A highly efficient GHz switching GaN-based synchronous buck converter module

A highly efficient GHz switching GaN-based synchronous buck converter module

Distortion mitigation for 100 and 250 MHz discrete supply modulation of a three-stage K-band MMIC PA

Analysis of Gain Variation With Changing Supply Voltages in GaN HEMTs for Envelope Tracking Power Amplifiers

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