53 research outputs found
Four-Way Microstrip-Based Power Combining for Microwave Outphasing Power Amplifiers
A lossless multi-way outphasing and power combining system for microwave power amplification is presented. The architecture addresses one of the primary drawbacks of Chireix outphasing; namely, the sub-optimal loading conditions for the branch power amplifiers. In the proposed system, four saturated power amplifiers interact through a lossless power combining network to produce nearly resistive load modulation over a 10:1 range of output powers. This work focuses on two microstrip-based power combiner implementations: a hybrid microstrip/discrete implementation using a combination of microstrip transmission line sections with discrete shunt elements, and an all-microstrip implementation incorporating open-circuited radial stubs. We demonstrate and compare these techniques in a 2.14 GHz power amplifier system. With the all-microstrip implementation, the system demonstrates a peak CW drain efficiency of 70% and drain efficiency of over 60% over a 6.5-dB outphasing output power range with a peak power of over 100 W. We demonstrate W-CDMA modulation with 55.6% average modulated efficiency at 14.1 W average output power for a 9.15-dB peak to average power ratio (PAPR) signal. The performance of this all-microstrip system is compared to that of the proposed hybrid microstrip/discrete version and a previously reported implementation in discrete lumped-element form.Massachusetts Institute of Technology. Center for Integrated Circuits and SystemsMassachusetts Institute of Technology. Microsystems Technology Laboratories. GaN Energy Initiativ
The digital predistorter goes multi-dimensional: DPD for concurrent multi-band envelope tracking and outphasing power amplifiers
Over at least the last two decades, digital predistortion (DPD) has become the most common and widespread solution to cope with the power amplifier's (PA's) inherent linearity-versus-efficiency tradeoff. When compared with other linearization techniques, such as Cartesian feedback or feedforward, DPD has proven able to adapt to the always-growing demands of technology: wider bandwidths, stringent spectrum masks, and reconfigurability. The principles of predistortion linearization (in its analog or digital forms) are straightforward, and the linearization subsystem precedes the PA (a nonlinear function in a digital signal processor in the case of DPD or nonlinear device in the case of analog predistortion and counteracts the nonlinear characteristic of the PA. Some excellent overviews on DPD can be found in [1]-[4]. Let us now look at the challenges that DPD linearization has faced and will continue to face in the near future with 5G new radio (5G-NR).This work has been supported in part by the Spanish Government and FEDER under MICINN projects TEC2017-83343-C4-1-R and TEC2017-83343-C4-2-R and by the Generalitat de Catalunya under Grant 2017 SGR 813
UHF class E/F2 outphasing transmitter for 12 dB PAPR signals
This paper exploits the degree of freedom provided by the continuous class-E modes in order to reduce the impact of a FET on-state resistance when approximating the zero voltage switching (ZVS) operation along a wide range of resistive loads. A UHF class-E/F2 power amplifier (PA), which includes a lumped element drain terminating network to synthesize the optimal load modulation (LM) trajectory, has been designed to maintain an efficiency as high as possible along an output power control range above 10 dB. Based on this PA, an outphasing scheme in the 700 MHz frequency band has been implemented. It is shown to provide an efficiency higher than 60% up to an output power below 5% (-13 dB) of its peak value (47 W). Under mixed-mode operation and applying digital predistorsion (DPD), a 10 MHz LTE signal with a peak-to-average power ratio (PAPR) as high as 12.2 dB has been linearly reproduced with average efficiency and PAE values of 46.6% and 42.9%, respectively.This work was supported by Spanish Ministry of Science, Innovation and Universities through TEC2017-83343-C4-1-R project, co-funded with FEDER. D. Vegas also thanks for the BES-2015-072203 grant. The support provided by Prof. P. Gilabert and Prof. G. Montoro, UPC, on the GMP-LUT DPD is highly appreciated
Impacto e compensação da largura de banda vídeo em amplificadores de potência de elevado rendimento
The aim of this work is to determine, quantify and model the performance
degradation of wideband power amplifiers when subject to concurrent multiband
excitation, with a particular focus on the average efficiency variation.
The origins of this degradation are traced to two main transistor properties:
the output baseband current generation by the nonlinear transconductance,
and the input baseband current generation by the nonlinear gate-source
capacitance variation. Each mechanism is analised separately, first by providing
a qualitative and intuitive explanation of the processes that lead to
the observed efficiency degradation, and then by deriving models that allow
the prediction of the average efficiency dependence with the input signal
bandwidth. The resulting knowledge was used to improve matching network
design, in order to optimize baseband impedance terminations and
prevent the efficiency degradation. The derived models were experimentally
validated with several PA prototypes implemented with Gallium Nitride
HEMT devices, using both conventional and optimized baseband impedance
matching networks, achieving over 400MHz instantaneous bandwidth with
uncompromised efficiency. The consolidation of the wideband degradation
mechanisms described in this work are an important step for modelling and
design of wideband, high-efficiency power amplifiers in current and future
concurrent multi-band communication systems.O objetivo deste trabalho é determinar, quantificar e modelar a degradação
do desempenho de amplificadores de banda-larga quando submetidos a
excitação multi-banda concorrente, com particular ênfase na variação do
rendimento energético. As origens desta degradação são devidas a duas
das principais propriedades do transístor: a geração de corrente em banda-base
na saída pela variação não-linear da transcondutância, e a geração de
corrente de banda-base na entrada pela variação não-linear da capacidade
interna porta-fonte. Cada um destes mecanismos é analisado isoladamente,
primeiro por uma explicação qualitativa e intuitiva dos processos que levam
à degradação de eficiência observada e, em seguida, através da derivação de
modelos que permitem a previsão da degradação do rendimento médio em
função da largura de banda do sinal de entrada. O conhecimento resultante
foi utilizado para melhorar o desenvolvimento de malhas de adaptação, por
forma a otimizar as terminações de impedância em banda-base e prevenir a
degradação do rendimento. Os modelos desenvolvidos foram validados experimentalmente
em vários amplificadores de potência implementados com
transístores de tecnologia GaN HEMT, utilizando malhas de adaptação convencionais
e otimizadas, onde se obteve 400MHz de largura de banda instantânea sem degradação do rendimento. A consolidação dos mecanismos
de degradação descritos neste trabalho são um importante passo para a
modelação e projeto de amplificadores de elevado rendimento e largura-debanda
para os sistemas de comunicação multi-banda concorrente convencionais
e do futuro.Programa Doutoral em Engenharia Eletrotécnic
Theory and Implementation of RF-Input Outphasing Power Amplification
Conventional outphasing power amplifier systems require both a radio frequency (RF) carrier input and a separate baseband input to synthesize a modulated RF output. This work presents an RF-input/RF-output outphasing power amplifier that directly amplifies a modulated RF input, eliminating the need for multiple costly IQ modulators and baseband signal component separation as in previous outphasing systems. An RF signal decomposition network directly synthesizes the phase- and amplitude-modulated signals used to drive the branch power amplifiers (PAs). With this approach, a modulated RF signal including zero-crossings can be applied to the single RF input port of the outphasing RF amplifier system. The proposed technique is demonstrated at 2.14 GHz in a four-way lossless outphasing amplifier with transmission-line power combiner. The RF decomposition network is implemented using a transmission-line resistance compression network with nonlinear loads designed to provide the necessary amplitude and phase decomposition. The resulting proof-of-concept outphasing power amplifier has a peak CW output power of 93 W, peak drain efficiency of 70%, and performance on par with a previously-demonstrated outphasing and power combining system requiring four IQ modulators and a digital signal component separator
Transmissor RF de elevado rendimento com duas entradas digitais para sistemas 5G
In recent years, there has been a need to increase the capacity and speed of information
transmission, so the communication signals used in mobile communications
have been improved to meet the expectations. This will be even more significant
in future 5G systems, since due to the high expansion of wireless devices, current
4G systems are starting to push their limits, where only small improvements
can be achieved. Which complicates the design of transmitters, since these new
signals have a wider bandwidth and a large variation between their average and
peak value, causing amplifiers to operate most of the time in a zone where they
are not as efficient. For this reason, amplifier architectures not only aim to have
high efficiency when operating at maximum signal excursion, but also to increase
efficiency in the zone where they will operate most of the time. For this purpose,
there are architectures based on supply voltage modulation and load modulation
to improve the efficiency at lower powers. This work addresses load modulation
architectures, where Doherty and Chireix are the most prominent. In addition, with
the increase in digital signal processing capabilities, new amplification architectures
based on the load modulation technique have recently been proposed, but instead
of using only one RF input, they use two independent digitally controlled inputs.
This dissertation aims at implementing a Doherty-Chireix amplifier with two digital
inputs to achieve efficient amplification for the 1.7 to 2.4GHz frequency band. In
the end it was possible to design and implement a Doherty-Chireix power amplifier,
with 700MHz bandwidth, with a gain between 13.9-11.3dB, a maximum power of
45dBm, a PAE of over 60% and peak-to-average power ratio between 5.2-4.1dB.Nos últimos anos, tem havido uma necessidade de aumentar a capacidade e velocidade
de transmissão de informação, deste modo os sinais de comunicação utilizados
nas comunicações móveis têm evoluído por forma a corresponder as expectativas.
Tal será ainda mais significativo nos futuros sistemas 5G, já que devido à elevada
expansão de dispositivos sem fio, os atuais sistemas 4G estão a começar a atingir
os seus limites, onde apenas pequenas melhorias podem ser alcançadas. Isto vem
complicar o projeto dos transmissores, uma vez que estes novos sinais apresentam
uma maior largura de banda e uma grande variação entre o seu valor médio e de
pico, fazendo com que os amplificadores operem na maior parte do tempo numa
zona em que não são tão eficientes. Por esta razão, as arquiteturas de amplificação
nos dias de hoje não só visam ter um grande rendimento quando operam com a
máxima excursão de sinal, mas também o aumento do rendimento na zona onde
irão operar a maior parte do tempo. Nesse sentido existem arquiteturas baseadas
em modelação de tensão de alimentação e modelação de carga de modo a melhorar
a eficiência a potências mais baixas. Neste trabalho são abordadas arquiteturas de
modulação de carga, onde Doherty e Chireix são as que mais se destacam. Para
além disso, com o aumento da capacidade de processamento digital de sinal, recentemente
foram propostas novas arquiteturas de amplificação que se baseiam nestas
técnicas, mas em vez de utilizar apenas uma entrada de RF, usam duas entradas
independentes controladas digitalmente. Esta dissertação visa a implementação de
um amplificador Doherty-Chireix com duas entras digitais de modo a obter uma
amplificação eficiente para uma banda de frequências de 1.7 a 2.4GHz. No final foi
possível projetar e implementar um amplificador de potência Doherty-Chireix, com
700MHz de largura de banda, com um ganho compreendido entre 13.9-11.3dB,
potência máxima de 45dBm, uma PAE superior a 60% e peak-to-average power
ratio entre 5.2-4.1dB.Mestrado em Engenharia Eletrónica e Telecomunicaçõe
Advanced High Efficiency Architectures for Next Generation Wireless Communications
L'abstract è presente nell'allegato / the abstract is in the attachmen
Linear Operation of Switch-Mode Outphasing Power Amplifiers
Radio transceivers are playing an increasingly important role in modern society. The
”connected” lifestyle has been enabled by modern wireless communications. The demand
that has been placed on current wireless and cellular infrastructure requires increased spectral
efficiency however this has come at the cost of power efficiency. This work investigates
methods of improving wireless transceiver efficiency by enabling more efficient power
amplifier architectures, specifically examining the role of switch-mode power amplifiers in
macro cell scenarios. Our research focuses on the mechanisms within outphasing power
amplifiers which prevent linear amplification. From the analysis it was clear that high power
non-linear effects are correctable with currently available techniques however non-linear effects
around the zero crossing point are not. As a result signal processing techniques for suppressing
and avoiding non-linear operation in low power regions are explored. A novel method of digital
pre-distortion is presented, and conventional techniques for linearisation are adapted for the
particular needs of the outphasing power amplifier. More unconventional signal processing
techniques are presented to aid linearisation of the outphasing power amplifier, both zero
crossing and bandwidth expansion reduction methods are designed to avoid operation in nonlinear
regions of the amplifiers. In combination with digital pre-distortion the techniques
will improve linearisation efforts on outphasing systems with dynamic range and bandwidth
constraints respectively.
Our collaboration with NXP provided access to a digital outphasing power amplifier,
enabling empirical analysis of non-linear behaviour and comparative analysis of behavioural
modelling and linearisation efforts. The collaboration resulted in a bench mark for linear
wideband operation of a digital outphasing power amplifier. The complimentary linearisation
techniques, bandwidth expansion reduction and zero crossing reduction have been evaluated in
both simulated and practical outphasing test benches. Initial results are promising and indicate
that the benefits they provide are not limited to the outphasing amplifier architecture alone.
Overall this thesis presents innovative analysis of the distortion mechanisms of the
outphasing power amplifier, highlighting the sensitivity of the system to environmental effects.
Practical and novel linearisation techniques are presented, with a focus on enabling wide band
operation for modern communications standards
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