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Enhancing Radio Frequency System Performance by Digital Signal Processing
KTH, School of Electrical Engineering (EES), Signal Processing.
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis measurement systems for the purpose ofcharacterization of radio frequency power amplifiers are studied.Methods to increase the speed, accuracy, bandwidth, as well as toreduce the sampling requirements and testing cost are presented. Amethod intended for signal shaping with respect to peak-to-averageratio reduction and its effects-improvements on the radio frequencyfront-end performance is investigated.

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

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

A general method for designing multitone for the purpose ofout-of-band characterization of nonlinear radio frequency modulesusing harmonic sampling is presented. It has an application with thevalidation of power amplifiers behavioral models in theirout-of-band frequency spectral support when extracted fromundersampled data.

A method for unfolding the frequency spectrum of undersampledwideband signals is presented. It is of high relevance tostate-of-the-art radio frequency measurement systems which capturerepetitive waveform based on a sampling rate that violates theNyquist constraint. The method is presented in a compact form, iteliminates ambiguities caused by folded frequency spectra standingoutside the Nyquist band, and is relevant for calibration matters.

A convex optimization reduction-based method of peaks-to-averageratio of orthogonal frequency division multiplexing signals ispresented and experimentally validated for a wireless local areanetwork system. Improvements on the radio frequency power amplifierlevel are investigated with respect to power added efficiency,output power, in-band and out-of-band errors. The influence of thepower distribution in the excitation signal on power amplifierperformance was evaluated.

Place, publisher, year, edition, pages
SE-100 44 Stockholm, Sweden: Signal Processing, School of Eletrical Engineering, Royal Institute of Technology , 2010. , ix, 9 p.
Series
Trita-EE, ISSN 1653-5146 ; 2010:030
Identifiers
URN: urn:nbn:se:kth:diva-24536OAI: oai:DiVA.org:kth-24536DiVA: diva2:351369
Presentation
2010-08-20, 99:132, Kungsbäcksvägen 47 Gävle, SE-801 76, University of Gävle, 10:15 (English)
Opponent
Supervisors
Projects
KKS
Note
QC 20101001Available from: 2010-10-01 Created: 2010-09-14 Last updated: 2010-10-01Bibliographically approved
List of papers
1. Automated Multidimensional Characterization of Power Amplifier for Design and Production
Open this publication in new window or tab >>Automated Multidimensional Characterization of Power Amplifier for Design and Production
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2009 (English)In: Proceedings IEEE International Instrumentation and Measurement Technical Conference, IEEE , 2009, 144-148 p.Conference paper, Published paper (Refereed)
Abstract [en]

Designing, optimizing and producing modern power amplifiers (PA) requires new and fast RF (radio frequency) measurement techniques capable of characterizing its real behavior. PAs are a truly multidimensional device where many desired performance parameters are contradictory to each other. This is especially true for the generation of modern communication PAs that require high efficiency, high linearity as well as high bandwidth. This paper presents a software-defined measurement setup for fast and cost efficient multidimensional measurements based on highly accurate standard instruments and a PC. The test bed as well as the graphical user interface is presented along with a demonstration of its functionality. During tuning of tank networks, drain quiescent current, and bias conditions, 3-dimensional graphs can be selected for the most appropriate axes of trade-off parameters to display a true behavior of the PA under test subjected to real-world or close to real-world signals. The measurement system offers the possibility to monitor envelope-tracking dynamic power consumption up to 100 MHz plus the possibility to use high crest factors.

Place, publisher, year, edition, pages
IEEE, 2009
Series
IEEE Instrumentation and Measurement Technology Conference, ISSN 1091-5281
Keyword
Automated multidimensional measurements, power amplifier, time domain measurement, state-of-the-art test-bed, gain distortion-efficiency
National Category
Signal Processing
Identifiers
urn:nbn:se:kth:diva-24527 (URN)10.1109/IMTC.2009.5168432 (DOI)000277153600027 ()2-s2.0-70449895655 (Scopus ID)978-1-4244-3352-0 (ISBN)
Conference
I2MTC2009 - International Instrumentation and Measurement, Technology Conference, Singapore, 5-7 May 2009
Projects
KKS
Note
© 2009 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. QC 20100930Available from: 2012-02-03 Created: 2010-09-13 Last updated: 2012-02-03Bibliographically approved
2. Wideband Characterization of Power Amplifiers Using Undersampling
Open this publication in new window or tab >>Wideband Characterization of Power Amplifiers Using Undersampling
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2009 (English)In: 2009 IEEE MTT-S International Microwave Symposium Digest, 2009, 1365-1368 p.Conference paper, Published paper (Refereed)
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.

Series
IEEE MTT-S International Microwave Symposium, ISSN 0149-645X ; Vols 1-3
Keyword
Communication system performance, modeling, nonlinear systems, power amplifiers, radio transmitters
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-11674 (URN)10.1109/MWSYM.2009.5165959 (DOI)000273507400343 ()2-s2.0-70450273349 (Scopus ID)978-1-4244-2803-8 (ISBN)
Conference
2009 IEEE MTT-S International Microwave Symposium, IMS 2009; Boston, MA; United States; 7 June 2009 through 12 June 2009
Note

QC 20150713

Available from: 2009-12-02 Created: 2009-12-02 Last updated: 2015-07-13Bibliographically approved
3. Multi-tone design for out-of-band characterization of nonlinear RF modules using harmonic sampling
Open this publication in new window or tab >>Multi-tone design for out-of-band characterization of nonlinear RF modules using harmonic sampling
2010 (English)In: 2010 IEEE International Instrumentation and Measurement Technology Conference, I2MTC 2010 - Proceedings, IEEE , 2010, 620-623 p.Conference paper, Published paper (Refereed)
Abstract [en]

In this paper we evaluate the generation of a multi-tone set for characterizing the behavior of nonlinear radio frequency (RF) modules in its out-of-band when harmonic sampling is used as digitizer. The purpose is to provide the reader with a tool to select proper frequencies and record length for a given application and test-bed. The method is based on simulations and the use of Sidon sequences. The proposed method is applicable to sparse discrete frequency multi-tones.

Place, publisher, year, edition, pages
IEEE, 2010
Keyword
Harmonic sampling, multi-tone, power amplifiers, out-of-band errors, radio frequency measurement systems
National Category
Signal Processing
Identifiers
urn:nbn:se:kth:diva-24532 (URN)10.1109/IMTC.2010.5488231 (DOI)2-s2.0-77957831915 (Scopus ID)978-1-4244-2832-8 (ISBN)
Conference
2010 IEEE International Instrumentation and Measurement Technology Conference, I2MTC 2010; Austin, TX; United States; 3 May 2010 through 6 May 2010;
Projects
KKS
Note

QC 20150713

Available from: 2010-10-01 Created: 2010-09-13 Last updated: 2015-07-13Bibliographically approved
4. Unfolding the Frequency Spectrum for Undersampled Wideband Data
Open this publication in new window or tab >>Unfolding the Frequency Spectrum for Undersampled Wideband Data
2011 (English)In: Signal Processing, ISSN 0165-1684, E-ISSN 1872-7557, Vol. 91, no 5, 1347-1350 p.Article in journal (Refereed) Published
Abstract [en]

In this letter, we discuss the problem of unfolding the frequency spectrum for undersampled wideband data. The problem is of 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 problem is presented in a compact form by the inclusion of a complex operator called the CN operator. The ease-of-use problem formulation eliminates the ambiguity caused by folded frequency spectra, in particular those with lines standing on multiples of the Nyquist frequency that are captured with erroneous amplitude and phase values.

Place, publisher, year, edition, pages
Elsevier, 2011
Keyword
Aliasing, Ambiguities, Frequency Spectrum Reconstruction, Radio Frequency Measurement Systems, Undersampling, Wideband Signals
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-24535 (URN)10.1016/j.sigpro.2010.12.013 (DOI)000287905700032 ()2-s2.0-79551484125 (Scopus ID)
Funder
ICT - The Next Generation
Note

QC 20101001

Available from: 2010-09-14 Created: 2010-09-14 Last updated: 2017-12-12Bibliographically approved
5. Peak-to-average power reduction of OFDM signals by convex optimization: experimental validation and performance optimization
Open this publication in new window or tab >>Peak-to-average power reduction of OFDM signals by convex optimization: experimental validation and performance optimization
2011 (English)In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 60, no 2, 473-479 p.Article in journal (Refereed) Published
Abstract [en]

We evaluated the application of the convex optimization to peak-to-average power reduction on an orthogonal frequency division multiplexing (OFDM) 802.11a signal. A radio frequency power amplifier was excited with an OFDM signal, and the peak-to-average reduced counterpart and its performance figure of merits were measured and compared. A state-of-the-art radio frequency test system with high accuracy was used for this purpose. Improvements due to the optimization in the output power and power-added efficiency and the influence of the power distribution in the excitation signal on power amplifier performance were investigated. Improvements of 6 dB in output power and 6.5% in power-added efficiency were achieved on average near the operating region. The effect of preserving power-free guard subcarriers was introduced in the optimization algorithm and investigated regarding adjacent channel interference. An improvement of 9 dB from that aspect was observed using half of the power-free subcarriers, which reveals the importance of a guard interval.

Keyword
Communication system performance, convex optimization, dirty radio, power amplifiers, power-added efficiency (PAE), spectrum mask
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-24530 (URN)10.1109/TIM.2010.2050360 (DOI)000286008700014 ()2-s2.0-78651273904 (Scopus ID)
Projects
KKS
Funder
ICT - The Next Generation
Note

QC 20150727

Available from: 2010-09-30 Created: 2010-09-13 Last updated: 2017-12-12Bibliographically approved

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