Challenges in the design of wideband GaN-HEMT based class-G RF-power amplifiers

Wolff, Nikolai; Heinrich, W.; Bengtsson, Olof

doi:10.1109/gemic.2016.7461587

Cited by 11 publications

(3 citation statements)

References 8 publications

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“…A look-up shaping function (SF) between the instantaneous output power and drain supply voltage is generated from measured CW PAE, gain and output power. The SF and discrete voltage spacing can be tailored for maximum PAE, flat gain or any other PA metric with a drain voltage dependence [6], [9]. The four SFs used in this work are plotted in Fig.…”

Section: Supply Modulation Resultsmentioning

confidence: 99%

A 10-W6-12GHz GaN MMIC Supply Modulated Power Amplifier

Nogales

Popović

Lasser

2022

2022 52nd European Microwave Conference (EuMC)

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This paper presents a gallium nitride (GaN) Monolithic Microwave Integrated Circuit (MMIC) PA with octave bandwidth, designed specifically for amplifying high peak-to-average power ratio (PAPR) signals with high efficiency from 6 to 12 GHz. Across the octave bandwidth, greater than 23.0% PAE is achievable over 10-dB of back off power using a dynamic supply voltage range from 6 to 20 V. We present the design and CW characterization of the PA as well as measurements using a 10-MHz multi-carrier noise-like signal and a 4-level discrete supply modulator comparing four different tracking functions. At 6.5 GHz a flat-gain, uniform voltage spacing function yields a 2.5 dB improvement in noise power ratio (NPR) over the static 20 V results with 3.8% points of PAE improvement, reaching 35.0 dBm of average output power. Furthermore, for a target NPR of 20 dB supply modulation yields a 9.7,% point improvement in PAE over the static case with a 1.5 dB increased output power.

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Section: Supply Modulation Resultsmentioning

confidence: 99%

A 10-W6-12GHz GaN MMIC Supply Modulated Power Amplifier

Nogales

Popović

Lasser

2022

2022 52nd European Microwave Conference (EuMC)

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“…The basis for estimating the crucial range of PBO is the power probability density distribution. If this function is multiplied with η drain as a function of output power and integrated over the output power range we obtain an average FS drain efficiency, which is to be maximized [13]. For a 10 dB PAPR signal, for example, high η drain must be reached in the PBO range from 4 to 15 dB.…”

Section: Optimizing Efficiency and Resonant Commutationmentioning

confidence: 99%

GaN digital microwave outphasing PA

Hoffmann

Wentzel

Flisgen

et al. 2020

Int. J. Microw. Wireless Technol.

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This paper presents a novel GaN-based digital outphasing power amplifier (PA) for the 800 MHz range. The PA reaches a maximum output power of 5.8 W at 30 V final-stage (FS) drain supply voltage. A novel output combiner circuit is used and efficiency is improved by resonant commutation of the FSs and optimized driver circuits for the two GaN push-pull FSs. 3D electromagnetic simulation of output network has been conducted to extract an equivalent circuit model and to access full information in terms of functionality and broadband impedance characteristics for optimized outphasing operation in the final design. Measured total efficiencies (ηtot) of 59 and 25% at 0 and 10 dB power back-off are achieved, respectively, fitting the simulation quite well. The proposed digital outphasing module is a promising candidate for fully digitized base-station architectures in future wireless communications.

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“…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. In order to understand the fundamental mechanisms behind gain variation, in this paper, the analysis will be conducted using exclusively static measurements.…”

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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Challenges in the design of wideband GaN-HEMT based class-G RF-power amplifiers

Cited by 11 publications

References 8 publications

A 10-W6-12GHz GaN MMIC Supply Modulated Power Amplifier

A 10-W6-12GHz GaN MMIC Supply Modulated Power Amplifier

GaN digital microwave outphasing PA

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

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