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Wideband Characterization of Power Amplifiers Using Undersampling
Högskolan i Gävle, Radio Center Gävle.
Högskolan i Gävle, Radio Center Gävle.
Högskolan i Gävle, Radio Center Gävle.ORCID-id: 0000-0001-5429-7223
Högskolan i Gävle, Radio Center Gävle.
Vise andre og tillknytning
2009 (engelsk)Inngår i: 2009 IEEE MTT-S International Microwave Symposium, Boston: IEEE MTT , 2009, s. 1365-1368Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

In this paper a radio frequency power amplifier is measured and characterized by the use of undersampling based on the generalized Zhu-Frank sampling theorem. A test system has been designed allowing the bandwidth of the stimuli signal to be 100 MHz in the characterization process. That would not be possible with any vector signal analyzer on the market. One of the more challenging problem within the proposed concept is the model validation process. Here, two different techniques for model validation are proposed, the multitone and the spectrum scan validation methods.

sted, utgiver, år, opplag, sider
Boston: IEEE MTT , 2009. s. 1365-1368
Serie
IEEE MTT-S International Microwave Symposium, ISSN 0149-645X
Emneord [en]
Communication system performance, modeling, nonlinear systems, power amplifiers, radio transmitters.
HSV kategori
Identifikatorer
URN: urn:nbn:se:hig:diva-5487ISI: 000273507400343ISBN: 978-1-4244-2803-8 (tryckt)OAI: oai:DiVA.org:hig-5487DiVA, id: diva2:236396
Konferanse
IEEE/MTT-S International Microwave Symposium, Boston, MA, 7-12 June 2009
Prosjekter
KKS SDMTilgjengelig fra: 2009-09-26 Laget: 2009-09-22 Sist oppdatert: 2018-11-26bibliografisk kontrollert
Inngår i avhandling
1. On Radio Frequency Behavioral Modeling: Measurement Techniques, Devices and Validation Aspects
Åpne denne publikasjonen i ny fane eller vindu >>On Radio Frequency Behavioral Modeling: Measurement Techniques, Devices and Validation Aspects
2009 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
Abstract [sv]

Effektförstärkare för radiofrekvensapplikationer utgör fortfarande ett av de största problemen i trådlösa kommunikationssystem. Detta beror på att dessa förstärkare är ickelinjära, har låg energieffektivitet och ger mycket distortioner. Bättre verktyg för att förstå och korrigera dessa beteenden är nödvändiga. Ett sådant verktyg är beteendemodellering. En beteendemodell kanses som en svart låda med insignal(er) och utsignal(er). In detta fall är dessasignaler samplade basbandssignaler och den svarta lådan är en matematisk relation mellan en insignal och en utsignal.

Avhandlingen behandlar några krav för beteendemodellering av nämnda system genom att presentera metoder för utvärdering och förbättring av modellernas prestanda. Detta åstadkoms genom att betrakta ett frekvensviktat felkriterium.

Ett högpresterande mätsystem är också nödvändigt för experimenten. Prestandan hos det tillgängliga systemet jämförs med prestandan hos ett allmänt erkänt mätsystem, en s.k. storsignalsnätverksanalysator, genom att betrakta prestandan hos beteendemodellerna som extraheras och validerasmed data från respektive mätsystem. Resultatet visar att det existerande mätsystemet har god prestanda.

Ett stort problem vid beteendemodellering är att kunna sampla med tillräckligt hög hastighet. Genom att använda Zhu-Franks generaliserade samplingsteorem vid beteendemodellering kan en del av detta problem undvikas. Teoremet medför att man kan sampla med en väsentligt lägre samlingsfrekvens än vad Nyquistteoremet säger. Modeller extraheras och prestandanutvärderas genom att använda kriteriet normalized mean square error (NMSE).

För stabil prediktion och korrektion av utsignalen måste robustheten hos de använda modellerna verifieras. En sådan studie som berör robustheten mot variationer i lastimpedansen har genomförts. Prestandan på direkta modeller försämras med 7 dB mätt som adjacent channel error power ratio (ACEPR). Prestanda på inversmodellen, implementerad som digital predistortion, försämras med upp till 13 dB mätt som adjacent channel power ratio(ACPR).

Abstract [en]

Radio frequency (RF) power amplifiers (PA) are still the most troublesome part of a wireless system due to their inherent nonlinearity, low powerefficiency and high distortions. Better tools are needed to understand and correct the undesirable behavior. Some of these tools are behavioral models. A behavioral model is often thought of as a black box with some inputs and some outputs. In the case here these inputs are sampled signals which means that the modeling amounts to finding a mathematical relationship between the input signal(s) and the output signal(s).

This thesis considers some requirements for behavioral modeling of said systems by presenting methods for general performance evaluation and improvement by considering a frequency weighted error criterion. A high performance measurement system is also needed. The performance of the available system is compared to the performance of a well recognized system, the large signal network analyzer (LSNA). The results show that the existing measurement system can extract behavioral models with the same performance as the LSNA and can give lower performance validation errors.

Still the need for higher bandwidths drives the measurement systems to the limits, especially the digital parts. By utilizing the so called Zhu-Frank generalized sampling theorem, behavioral modeling of a PA is done by using data acquired at a sampling rate lower than the Nyquist rate. Models of a PA are extracted and the performance is evaluated using the normalized mean square error (NMSE) criterion. For prediction and correction of the output signals the stability of the models regarding changes must be investigated. One such study considering controlled variations on the output load of the PA is done and both the predictive and corrective capabilities of the models are evaluated. The predictive capability gets up to 7 dB worse measured as adjacent channel error power ratio (ACEPR) and the corrective, as digital predistortion, gets up to 13 dB worse measured as adjacent channel power ratio (ACPR).

sted, utgiver, år, opplag, sider
Stockholm: Skolan för elektro- och systemteknik, Kungliga Tekniska högskolan, 2009. s. 65
Serie
TRITA-EE 2009:056, ISSN 1653-5146
HSV kategori
Identifikatorer
urn:nbn:se:hig:diva-6699 (URN)978-91-7415-526-6 (ISBN)
Presentation
2009-12-10, Hörsal 99131, Kungsbäcksvägen 47, Gävle, 08:47 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2010-04-28 Laget: 2010-04-22 Sist oppdatert: 2018-03-13bibliografisk kontrollert
2. Enhancing Radio Frequency System Performance by Digital Signal Processing
Åpne denne publikasjonen i ny fane eller vindu >>Enhancing Radio Frequency System Performance by Digital Signal Processing
2010 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
Abstract [en]

In this thesis measurement systems for the purpose of characterization of radio frequency power amplifiers are studied. Methods to increase the speed, accuracy, bandwidth, as well as to reduce the sampling requirements and testing cost are presented. A method intended for signal shaping with respect to peak to-average ratio reduction and its effects-improvements on the radio frequency front-end performance is investigated.

A time domain measurement system intended for fast and accurate measurements and characterization of radio frequency power amplifiers is discussed. An automated, fast and accurate technique for power and frequency sweep measurements is presented. Multidimensional representation of measured figure of merits is evaluated for its importance on the production-testing phase of power amplifiers.

A technique to extend the digital bandwidth of a measurement system is discussed. It is based on the Zhu-Frank generalized sampling theorem which decreases the requirements on the sampling rate of the measurement system. Its application for power amplifiers behavioral modeling is discussed and evaluated experimentally.

A general method for designing multitone for the purpose of out-of-band characterization of nonlinear radio frequency modules using harmonic sampling is presented. It has an application with the validation of power amplifiers behavioral models in their out-of-band frequency spectral support when extracted from undersampled data.

A method for unfolding the frequency spectrum of undersampled wideband signals is presented. It is of high relevance to state-of-the-art radio frequency measurement systems which capture repetitive waveform based on a sampling rate that violates the Nyquist constraint. The method is presented in a compact form, it eliminates ambiguities caused by folded frequency spectra standing outside the Nyquist band, and is relevant for calibration matters.

A convex optimization reduction-based method of peaks-to-average ratio of orthogonal frequency division multiplexing signals is presented and experimentally validated for a wireless local area network system. Improvements on the radio frequency power amplifier level are investigated with respect to power added efficiency, output power, in-band and out-of-band errors. The influence of the power distribution in the excitation signal on power amplifier performance was evaluated.

sted, utgiver, år, opplag, sider
Stockholm: Skolan för elektro- och systemteknik, Kungliga Tekniska högskolan, 2010. s. 90
Serie
TRITA-EE 2010:030, ISSN 1653-5146
HSV kategori
Identifikatorer
urn:nbn:se:hig:diva-7312 (URN)
Presentation
2010-08-20, Hörsal 99131, Kungsbäcksvägen 47, Gävle, 10:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2010-08-18 Laget: 2010-08-09 Sist oppdatert: 2018-03-13bibliografisk kontrollert

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