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Characterization and Linearization of Multi-band Multi-channel RF Power Amplifiers
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH Royal Institute of Technology, Stockholm, Sweden.ORCID iD: 0000-0003-1183-6666
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: urn:nbn:se:hig:diva-23287ISBN: 978-91-7729-198-5 (print)OAI: oai:DiVA.org:hig-23287DiVA: diva2:1064153
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
List of papers
1. Concurrent dual-band power amplifier model modification using dual two-tone test
Open this publication in new window or tab >>Concurrent dual-band power amplifier model modification using dual two-tone test
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2016 (English)In: 46th Europena Microwave Conference (EUMC) 2016, 2016, 186-189 p.Conference paper, (Refereed)
Abstract [en]

A dual two-tone technique for the characterization of memory effects in concurrent dual-band transmitters is revisited to modify a 2D-DPD model for the linearization of concurrent dual-band transmitters. By taking into account the individual nonlinear memory effects of the self- and cross-kernels, a new2D modified digital pre-distortion (2D-MDPD) model is proposed,which not only supersedes the linearization performance but also reduces the computational complexity compared to the 2DDPDmodel in terms of a number of floating point operations(FLOPs). Experimental results show an improvement of 1.7 dBin normalized mean square error (NMSE) and a 58% reduction in the number of FLOPs.

Series
European Microwave Conference, ISSN 2325-0305
Keyword
IEEE Keywords Computational modeling, Numerical models, Dual band, Two dimensional displays, Radio frequency, Computational complexity
National Category
Signal Processing
Identifiers
urn:nbn:se:hig:diva-22558 (URN)10.1109/EuMC.2016.7824309 (DOI)000393581100048 ()2-s2.0-85015185570 (Scopus ID)978-2-87487-043-9 (ISBN)978-1-5090-1514-6 (ISBN)
Conference
46th European Microwave Conference (EuMC), 4-6 October 2016, London, UK
Available from: 2016-10-06 Created: 2016-10-06 Last updated: 2017-05-02Bibliographically approved
2. Combating the Dimensionality of Nonlinear MIMO Amplifier Predistortion by Basis Pursuit
Open this publication in new window or tab >>Combating the Dimensionality of Nonlinear MIMO Amplifier Predistortion by Basis Pursuit
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2014 (English)In: Proceedings of the 44th European Microwave Conference, 2014, 833-836 p.Conference paper, (Refereed)
Abstract [en]

A general description of nonlinear dynamic MIMO systems, given by Volterra series, has significantly larger complexity than SISO systems. Modeling and predistortion of MIMO amplifiers consequently become unfeasible due to the large number of basis functions. We have designed digital predistorters for a MIMO amplifier using a basis pursuit method for reducing model complexity. This method reduces the numerical problems that appear in MIMO Volterra predistorters due to the large number of basis functions. The number of basis functions was reduced from 1402 to 220 in a 2x2 MIMO amplifier and from 127 to 13 in the corresponding SISO case. Reducing the number of basis functions caused an increase of approximately 1 dB of model error and adjacent channel power ratio.

Keyword
Digital pre distortion (DPD), MIMO power ampli fiers, LASSO, basis pursuit, power amplifier linearization
National Category
Communication Systems Signal Processing
Identifiers
urn:nbn:se:hig:diva-17716 (URN)000392912200209 ()2-s2.0-84922721597 (Scopus ID)
Conference
The 44th European Microwave Conference (EuMC 2014), Roma, Italy, October 5-10, 2014
Available from: 2014-10-23 Created: 2014-10-23 Last updated: 2017-04-03Bibliographically approved
3. Behavioral Modeling and Linearization of Crosstalk and Memory Effects in RF MIMO Transmitters
Open this publication in new window or tab >>Behavioral Modeling and Linearization of Crosstalk and Memory Effects in RF MIMO Transmitters
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.

Keyword
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:nbn:se:hig:diva-16413 (URN)10.1109/TMTT.2014.2309932 (DOI)000334525600010 ()2-s2.0-84898403156 (Scopus ID)
Available from: 2014-03-13 Created: 2014-03-13 Last updated: 2017-01-11Bibliographically approved
4. Characterization of concurrent dual-band power amplifiers using a dual two-tone excitation signal
Open this publication in new window or tab >>Characterization of concurrent dual-band power amplifiers using a dual two-tone excitation signal
2015 (English)In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 64, no 10, 2781-2791 p., 7104121Article in journal (Refereed) Published
Abstract [en]

A method to characterize the memory effects in a nonlinear concurrent dual-band transmitter is presented. It is an extension of the conventional two tone test for power amplifiers to concurrent dual band transmitters. The output signal of a concurrent dual-band transmitter is affected not only by intermodulation products but also by cross-modulation products. In one frequency band, the transmitter is excited by a two tone signal which frequency separation is swept. In the second band the transmitter is concurrently excited by an other two tone signal with slightly wider frequency separation. The frequency difference of the two signals is fixed during the frequency sweep. The two tone test is made at different power levels. The upper and lower third-order inter- and cross-modulation products are measured. The asymmetry between the upper and lower third-order inter- and cross-modulation products are measures of the transmitter's memory effects. The measurement results show that the memory effects are more dominant in the third-order intermodulation products than in the cross modulation products. An error analysis and system calibration was performed and measurement results for two different devices are presented.

Place, publisher, year, edition, pages
IEEE Press, 2015
Keyword
Concurrent dual-band, power amplifier, characterization, linearization, nonlinear distortion, MIMO, DPD
National Category
Signal Processing
Identifiers
urn:nbn:se:hig:diva-18854 (URN)10.1109/TIM.2015.2427731 (DOI)000361487500019 ()2-s2.0-84959505984 (Scopus ID)
Available from: 2014-12-17 Created: 2015-01-27 Last updated: 2017-01-11Bibliographically approved
5. Measurement and analysis of frequency-domain Volterra kernels of nonlinear dynamic 3x3 MIMO systems
Open this publication in new window or tab >>Measurement and analysis of frequency-domain Volterra kernels of nonlinear dynamic 3x3 MIMO systems
2017 (English)In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 66, no 7, 1893-1905 p.Article in journal (Refereed) Published
Abstract [en]

Multiple-input multiple-output (MIMO) frequency-domain Volterra kernels of nonlinear order 3 are experimentally determined in bandwidth-limited frequency regions. How the effect of higher nonlinear orders can be reduced and how this affects the estimated errors are discussed. The magnitude and phase of the kernels areKramers-Kronig consistent. The self- and cross-kernels have different symmetries and the kernels are therefore determined and analyzed in different regions in the 3D frequency space. By analyzing the properties along certain paths in the 3D frequency space, the block structures for the respective kernels are determined. These block structures contain the significant blocks of the general block structures for third-order kernels. The device under test is a MIMO transmitter for radio frequency signals.

Place, publisher, year, edition, pages
IEEE Press, 2017
National Category
Signal Processing
Identifiers
urn:nbn:se:hig:diva-23216 (URN)10.1109/TIM.2017.2664482 (DOI)000403292600026 ()2-s2.0-85014208551 (Scopus ID)
Available from: 2016-12-05 Created: 2017-01-05 Last updated: 2017-06-30Bibliographically approved
6. Digital Predistortion of Single and Concurrent Dual Band Radio Frequency GaN Amplifiers with Strong Nonlinear Memory Effects
Open this publication in new window or tab >>Digital Predistortion of Single and Concurrent Dual Band Radio Frequency GaN Amplifiers with Strong Nonlinear Memory Effects
2017 (English)In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670Article in journal (Refereed) Epub ahead of print
Abstract [en]

Electrical anomalies due to trapping effects in Gallium Nitride (GaN) power amplifiers (PAs)give rise to long-term or strong memory effects. We propose novel models based on infinite impulse response (IIR) fixed pole expansion techniques for the behavioural modeling and digital pre-distortion of single-input-single-output (SISO) and concurrent dual-bandGaN PAs. Experimental results show that the proposed models outperform the corresponding finite impulse response (FIR) models by up to 17 dB for the same number of model parameters. For the linearization of a SISO GaN PA the proposed models give adjacent channel power ratios (ACPRs) that are 7 to 17 dBlower than the FIR models. For the concurrent dual-band case, the proposed models give ACPRs that are 9to 14 dB lower than the FIR models.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2017
National Category
Signal Processing
Identifiers
urn:nbn:se:hig:diva-23117 (URN)10.1109/TMTT.2016.2642948 (DOI)
Available from: 2016-12-20 Created: 2016-12-20 Last updated: 2017-03-28Bibliographically approved
7. 2D Extended envelope memory polynomial model for concurrent dual-band RF transmitters
Open this publication in new window or tab >>2D Extended envelope memory polynomial model for concurrent dual-band RF transmitters
2017 (English)In: International journal of microwave and wireless technologies, ISSN 1759-0795, E-ISSN 1759-0787Article in journal (Refereed) Epub ahead of print
Abstract [en]

The paper presents a 2D extended envelope memory polynomial (2D-EEMP) model for concurrent dual-band radio frequency (RF) power amplifiers (PAs). The model is derived based on the physical knowledge of a dual-band RF PA. The derived model contains cross-modulation terms not included in previously published models; these terms are found to be of importance for both behavioral modeling and digital pre-distortion (DPD). The performance of the derived model is evaluated both as the behavioral model and DPD, and the performance is compared with state-of-the-art2D-DPD and dual-band generalized memory polynomial (DB-GMP) models. Experimental result shows that the proposed model resulted in normalized mean square error (NMSE) of -51.7/-51.6dB and adjacent channel error power ratio (ACEPR) of -63.1/-63.4 dB, for channel 1/2, whereas the 2D-DPD resulted in the largest model error and DB-GMP resulted in model parameters that are 3 times more than those resulted with the proposed model with the same performance. As pre-distorter, the proposed model resulted in adjacent channel power ratio (ACPR) of -55.8/ -54.6 dB for channel 1/2 and is 7-10 dB lower than those resulted with the 2D-DPD model and2-4 dB lower compared to the DB-GMP model.

Keyword
Behavioral modeling and digital predistortion of multi-band amplifiers, Power Amplifiers, RF Front-ends
National Category
Signal Processing
Identifiers
urn:nbn:se:hig:diva-23455 (URN)10.1017/S1759078717000277 (DOI)2-s2.0-85018373558 (Scopus ID)
Available from: 2016-12-05 Created: 2017-02-02 Last updated: 2017-06-16Bibliographically approved

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