Improving Digital Predistortion Mismatch Sensitivity Using Tunable Matching Networks

Sánchez-Pérez, César; Mingo, J. de; García-Dúcar, Paloma; Carro, Pedro L.; Valdovinos, Antonio

doi:10.1109/vetecs.2011.5956328

Cited by 5 publications

(10 citation statements)

References 14 publications

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“…These can be categorized into methods that keep the PA load impedance at its nominal value, and methods that deal with PA load variation. Implementations of the former methods are presented in [7], [8]. In [7], an adaptive tunable matching network (TMN) ensures the nominal load for the PA and thereby preserves linearity under antenna mismatch conditions.…”

Section: Introductionmentioning

confidence: 99%

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Preserving Polar Modulated Class-E Power Amplifier Linearity under Load Mismatch

Khodkumbhe

Huiskamp

Ghahremani

et al. 2020

2020 IEEE Radio Frequency Integrated Circuits Symposium (RFIC)

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Power amplifiers (PAs) need digital predistortion (DPD) linearization to handle high-order complex modulation schemes in next-generation communication systems. While load variation is inevitable, DPD is generally designed considering only the nominal load impedance for PAs. This paper presents a polar class-E PA with an on-chip waveform characterizer enabling adaptive digital predistortion (ADPD) to preserve the linearity of the PA under load mismatch. The presented ADPD corrects both AM/AM and AM/PM distortions, which are prominent in the demonstrated PA, while simultaneously correcting for slow memory effects without the need for complex memory DPD algorithms. Load-pull measurements demonstrate that target error vector magnitude (EVM) and adjacent channel power ratio (ACPR) can be maintained in a significantly larger area on the Smith chart going from 50 Ω optimized static DPD to our ADPD for a 2 GHz 1024 QAM signal with 1 MSym/s symbol rate.

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Section: Introductionmentioning

confidence: 99%

“…Implementations of the former methods are presented in [7], [8]. In [7], an adaptive tunable matching network (TMN) ensures the nominal load for the PA and thereby preserves linearity under antenna mismatch conditions. However, TMNs are lossy, bulky and hence not suitable for easy integration in ever-miniaturizing CMOS integrated circuits.…”

Section: Introductionmentioning

confidence: 99%

Preserving Polar Modulated Class-E Power Amplifier Linearity under Load Mismatch

Khodkumbhe

Huiskamp

Ghahremani

et al. 2020

2020 IEEE Radio Frequency Integrated Circuits Symposium (RFIC)

View full text Add to dashboard Cite

show abstract

“…These can be categorized into methods that keep the PA load impedance at its nominal value, and methods that deal with PA load variation. Implementations of the former methods are presented in [139], [140]. In [139], an adaptive tunable matching network (TMN) ensures the nominal load for the PA and thereby preserves linearity under antenna mismatch conditions.…”

Section: Discussionmentioning

confidence: 99%

“…Implementations of the former methods are presented in [139], [140]. In [139], an adaptive tunable matching network (TMN) ensures the nominal load for the PA and thereby preserves linearity under antenna mismatch conditions. However, TMNs are lossy, bulky and hence not suitable for easy integration in ever-miniaturizing CMOS integrated circuits.…”

Section: Discussionmentioning

confidence: 99%

Integrated measurement techniques for RF-power amplifiers

Huiskamp¹

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“…The PA LMM creates multiple signal reflections at the PA output port, generating frequency-dependent interactions between the forward and reflected RF waves, responsible for worsening the PA's linearity and memory effects (VUOLEVI;RAHKONEN, 2003). As described in (CRIPPS, 2006), LMM reduces the maximum PA output power, as well as the PA power efficiency ROERMUND, 2005), (SANCHEZ-PEREZ et al, 2011). Moreover, LMM at the fundamental band accentuates the PA output signal distortions (YE et al, 2010), whereas load impedance fluctuations at baseband and harmonics are the main responsible for the so-called NL memory effects (MOON; KIM, 2011), i.e., PA memory effects that only manifest under the NL regime.…”

Section: Pa Load Impedance Mismatch (Lmm)mentioning

confidence: 99%

Digital signal processing techniques for the compensation of analog circuit impairments in impedance mismatched radio-frequency transmitters.

Hemsi¹

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Esta tese investiga e propõe novos modelos para a compensação digital de imperfeições de rádio frequência (RFradio frequency) em transmissores sem fio de banda larga, mais especificamente para amplificadores de potência (PApower amplifiers) não-lineares e sujeitos a descasamento de impedância de carga (LMMload mismatch). Tais imperfeições em transmissores de RF, juntamente com o desbalanceamento entre as componentes em fase e quadratura (IQin-phase and quadrature) em moduladores digitais, são responsáveis por degradar o desempenho do transmissor, tanto em termos de pureza espectral, quanto em qualidade da modulação e taxa de erro de bit (BERbit error rate).Diversos cenários práticos em que PAs estão sujeitos a LMM motivam a pesquisa por modelos comportamentais não-lineares e com memória voltados a predistorção digital (DPDdigital pre-distortion) mais avançados, capazes de superar as limitações relatadas na literatura de modelos tradicionais e que sejam menos complexos do que as abordagens existentes para PA LMM.Nesta tese é proposta a aplicação do modelo polinomial Wiener-Hammerstein com realimentação (WHFB -Wiener-Hammerstein with feedback) como modelo comportamental simplificado para DPD no contexto de PAs sujeitos a LMM.A elevada dimensionalidade da estrutura WHFB proposta pode ser reduzida através de técnicas esparsas de estimação, tais como o operador de encolhimento e seleção absoluto mínimo (LASSOleast absolute shrinkage and selection operator) e extensões de LASSO em blocos, que são capazes de diminuir significativamente o número de coeficientes necessário, reduzindo, assim, o comprimento do filtro de DPD e, proporcionalmente, o custo da filtragem.Além disso, extensões de LASSO voltadas a blocos, como Group-LASSO e Sparse-group LASSO, são aplicadas no contexto de dimensionamento do modelo, ou seja, na tarefa de determinar valores adequados para seus parâmetros, o que, tradicionalmente, requer uma busca exaustiva.Os modelos WHFB denso e esparso são validados experimentalmente através de medições em um set-up de testes experimental e também comparados a outros, incluindo modelos baseados na decomposição em fatores paralelos (PARAFACparallel factors) e na expansão de Laguerre, demonstrando, assim, sua capacidade de compensar adequadamente PAs sujeitos a LMM.Finalmente, é proposta uma nova estratégia de redução do modelo de Volterra, que resulta em um polinômio de memória mais flexível e modular, em que os parâmetros são escolhidos independentemente para cada ordem de não linearidade. Esta abordagem flexível é capaz de descrever com precisão uma gama ampla de condições operacionais/ ambientais de PAs.

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Improving Digital Predistortion Mismatch Sensitivity Using Tunable Matching Networks

Cited by 5 publications

References 14 publications

Preserving Polar Modulated Class-E Power Amplifier Linearity under Load Mismatch

Preserving Polar Modulated Class-E Power Amplifier Linearity under Load Mismatch

Integrated measurement techniques for RF-power amplifiers

Digital signal processing techniques for the compensation of analog circuit impairments in impedance mismatched radio-frequency transmitters.

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