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Behavioral Modeling and Linearization of Crosstalk and Memory Effects in RF MIMO Transmitters
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences. KTH.ORCID iD: 0000-0003-1183-6666
Chalmers University of Technology.
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences. ACCESS Linnaeus Centre, Signal Processing Lab, KTH Royal Institute of Technology.
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.ORCID iD: 0000-0003-2887-049X
2014 (English)In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 62, no 4, 810-823 p.Article in journal (Refereed) Published
Abstract [en]

This paper proposes three novel models for behavioral modeling and digital pre-distortion (DPD) of nonlinear 2$,times,$ 2 multiple-input multiple-output (MIMO) transmitters in the presence of crosstalk. The proposed models are extensions of the single-input single-output generalized memory polynomial model. Three types of crosstalk effects were studied and characterized as linear, nonlinear, and nonlinear & linear crosstalk. A comparative study was performed with previously published models for the linearization of crosstalk in a nonlinear 2 $,times,$2 MIMO transmitter. The experiments indicate that, depending on the type of crosstalk, the selection of the correct model in the transmitter is necessary for behavioral modeling and sufficient DPD performance. The effects of coherent and partially noncoherent signal generation on the performance of DPD were also studied. For crosstalk levels of ${-}{hbox{30}}$ dB, the difference in the normalized mean square error and adjacent channel power ratio was found to be 3–4 dB between coherent and partially noncoherent signal generation.

Place, publisher, year, edition, pages
2014. Vol. 62, no 4, 810-823 p.
Keyword [en]
Behavioral modeling; digital pre-distortion (DPD); multiple-input multiple-output (MIMO); nonlinear and linear crosstalk; power amplifiers (PAs); RF
National Category
Signal Processing
Identifiers
URN: urn:nbn:se:hig:diva-16413DOI: 10.1109/TMTT.2014.2309932ISI: 000334525600010Scopus ID: 2-s2.0-84898403156OAI: oai:DiVA.org:hig-16413DiVA: diva2:704701
Available from: 2014-03-13 Created: 2014-03-13 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Characterization and Linearization of Multi-channel RF Power Amplifiers
Open this publication in new window or tab >>Characterization and Linearization of Multi-channel RF Power Amplifiers
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The demands for high data rates and broadband wireless access requirethe development of wireless systems that can support wide and multi-bandsignals. To deploy these signals, new radio frequency (RF) front-ends are requiredwhich impose new challenges in terms of power consumption efficiencyand sources of distortion e.g., nonlinearity. These challenges are more pronouncedin power amplifiers (PAs) that degrade the overall performance ofthe RF transmitter.Since it is difficult to optimize the linearity and efficiency characteristicsof a PA simultaneously, a trade-off is needed. At high input power, a PAexhibits high efficiency at the expense of linearity. On the other hand, atlow input power, a PA is linear at the expense of the efficiency. To achievelinearity and efficiency at the same time, digital pre-distortion (DPD) is oftenused to compensate for the PA nonlinearity at high input power. In case ofmulti-channel PAs, input and output signals of different channels interactwith each other due to cross-talk. Therefore, these PAs exhibit differentnonlinear behavior than the single-input single-output (SISO) PAs. The DPDtechniques developed for SISO PAs do not result in adequate performancewhen used for multi-channel PAs. Hence, an accurate behavioral modeling isessential for the development of DPD for multi-channel RF PAs.In this thesis, we propose three novel behavioral models and DPD schemesfor nonlinear multiple-input multiple-output (MIMO) transmitters in presenceof cross-talk. A study of the source of cross-talk in MIMO transmittershave been investigated to derive simple and powerful modeling schemes.These models are extensions of a SISO generalized memory polynomial model.A comparative study with a previously published MIMO model is also presented.The effect of coherent and partially non-coherent signal generationon DPD performance is also highlighted. It is shown experimentally thatwith partially non-coherent signal generation, the performance of the DPDdegrades compared to coherent signal generation.In context of multi-channel RF transmitters, PA behavioral models andDPD schemes suffer from a large number of model parameters with the increasein nonlinear order and memory depth. This growth leads to highcomplexity model identification and implementation. We have designed aDPD scheme for MIMO PAs using a sparse estimation technique for reducingmodel complexity. This technique also increases the numerical stability whenlinear least square estimation model identification is used.A method to characterize the memory effects in a nonlinear concurrentdual-band PAs is also presented. Compared to the SISO PAs, concurrentdual-band PAs are not only affected by intermodulation distortions but alsoby cross-modulation distortions. The characterization of memory effects inconcurrent dual-band transmitter is performed by injecting a two-tone testsignal in each input channel of the transmitter. Asymmetric energy surfacesare introduced for the intermodulation and cross-modulation products, whichcan be used to identify the power and frequency regions where the memory effects are dominant.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. 45 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2015:001
National Category
Signal Processing
Identifiers
urn:nbn:se:hig:diva-18848 (URN)
Presentation
2015-01-23, 99132, Kungsbäcksvägen 47, Gävle, 10:00 (English)
Opponent
Supervisors
Available from: 2015-01-27 Created: 2015-01-26 Last updated: 2016-08-17Bibliographically approved
2. Characterization and Linearization of Multi-band Multi-channel RF Power Amplifiers
Open this publication in new window or tab >>Characterization and Linearization of Multi-band Multi-channel RF Power Amplifiers
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The World today is deeply transformed by the advancement in wireless technology. The envision of a smart society where interactions between physical and virtual dimensions of life are intertwined and where human interaction is mediated by machines, e.g., smart phones, demands increasingly more data traffic. This continual increase in data traffic requires re-designing of the wireless technologies for increased system capacity and flexibility. In this thesis, aspects related to behavioral modeling, characterization, and linearization of multi-channel/band power amplifiers (PAs) are discussed.

When building a model of any system, it is advantageous to take into account the knowledge of the physics of the system and include into the model. This approach could help to improve the model performance. In this context, three novel behavioral models and DPD schemes for nonlinear MIMO transmitters are proposed.

To model and compensate distortions in GaN based RF PAs in presence of long-term memory effects, novel models for SISO and concurrent dual-band PAs are proposed. These models are based on a fixed pole expansion technique and have infinite impulse response. They show substantial performance improvement. A behavioral model based on the physical knowledge of the concurrent dual-band PA is derived, and its performance is investigated both for behavioral modeling and compensation of nonlinear distortions.

Two-tone characterization is a fingerprint method for the characterization of memory effects in dynamic nonlinear systems. In this context, two novel techniques are proposed. The first technique is a dual two-tone characterization technique to characterize the memory effects of self- and cross-modulation products in concurrent dual-band transmitter. The second technique is for the characterization and analysis of self- and cross-Volterra kernels of nonlinear 3x3 MIMO systems using three-tone signals.

Abstract [sv]

Världen av idag har omvandlats starkt av framsteg inom trådlos teknik. Framtidens smarta samhalle där samspelet mellan fysiska och virtuella dimensioner i livet är sammanflätade och där mansklig växelverkan mer ofta än inte sker med eller formedlas av maskiner - exempelvis smarta telefoner - kräver allt mer datatrafik. Denna ständigt ökande datatrafik kraver i sin tur utformning av trådlös teknik som kan rymma flera kanaler och flera frekvensband för att öka systements kapactitet och flexibilitet. I denna avhandling diskuteras aspekter relaterade till beteendemodellering, karakterisering, och kompensering av ickelinjär distortion i radiofrekvens (RF) effektforstarkare (PA) för multipla-insignaler-multipla-utsignaler (MIMO) och samtidiga signaler i dubbla frekvensband.

När man gör en modell av ett system är det fordelaktigt att ta hänsyn till kunskap om det fysikaliska systemet och använda denna information i modellen. Denna strategi skulle kunna bidra till att forbattra modellens prestanda och minska antalet modellparametrar. I detta sammanhang föreslås tre nya beteende- och DPD-modeller för ickelinjära MIMO sändare. Olika typer av överhörning i MIMO-sändare undersöks för att härleda enkla och kraftfulla modeller. Effekter av koherent och partiellt koherent signalgenerering på DPD-prestanda utvärderas också. För att modellera och kompensera ickelinjär distortion i galliumnitridbaserade (GaN) RF PA med langtidsminneseffekter föreslås två nya modeller for RF PA med en in- och en utsignal (SISO) tre nya modeller för RF PA för samtidiga signaler i olika frekvensband. Dessa modeller är baserade på teknik med expansion runt fasta polvärden och har oändligt minnesdjup. Modellerna visar betydande resultatförbättring i jämforelse med dem med ändliga impulssvar. En beteendemodell baserad på en fysikalisk modell av förstärkaren föreslås för en PA för samtidiga signaler i olika frekvensband. Dess prestanda undersöks som beteendemodell och för utjämning av ickelinjär distortion.

Tvåtonskarakterisering är som ett fingeravtryck vid karakterisering av minneseffekter i dynamiska ickelinjära system. I detta sammanhang föreslås två nya tekniker för karakterisering av sändare för samtidiga signaler med olika frekvens och och MIMO-sändare. Den första tekniken är en dubbel tvåtonskarakterisering för de individuella minneseffekterna i egen- och korsmoduleringsprodukter i sändare med samtidiga signaler i olika frekvensband. Den andra tekniken är för karakterisering och analys av egen- och korsvolterrakärnor hos ett ickelinjärt 3×3 MIMO-system med hjalp av tre-tonssignaler. I den föreslagna tekniken analyseras egen- och korskänor längs linjer i en frekvensrymd för att fastställa blockstrukturer hos det underliggande systemet. Den kunskap som erhållits med hjälp av denna karakeriseringsteknik har kunnat användas för att modifiera tidigare publicerade beteendemodeller.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. 59 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2016:185
National Category
Signal Processing
Identifiers
urn:nbn:se:hig:diva-23287 (URN)978-91-7729-198-5 (ISBN)
Public defence
2017-02-24, 99:133, Kungsbäcksvägen 47, Gävle, 10:15 (English)
Opponent
Supervisors
Available from: 2017-02-02 Created: 2017-01-11 Last updated: 2017-02-22Bibliographically approved

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