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Enhancing Radio Frequency System Performance by Digital Signal Processing
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Stockholm: Skolan för elektro- och systemteknik, Kungliga Tekniska högskolan , 2010. , p. 90
Series
TRITA-EE 2010:030, ISSN 1653-5146
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:hig:diva-7312OAI: oai:DiVA.org:hig-7312DiVA, id: diva2:337800
Presentation
2010-08-20, Hörsal 99131, Kungsbäcksvägen 47, Gävle, 10:00 (English)
Opponent
Supervisors
Available from: 2010-08-18 Created: 2010-08-09 Last updated: 2018-03-13Bibliographically 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: 2009 IEEE Instrumentation and Measurement Technology Conference Proceedings, Singapore: I&M Society , 2009, p. 144-148Conference 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. Power amplifiers 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
Singapore: I&M Society, 2009
Keywords
Automated multidimensional measurements, power amplifier, time domain measurement, state-of-the-art test-bed, gain-distortion-efficiency
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:hig:diva-5486 (URN)10.1109/IMTC.2009.5168432 (DOI)000277153600027 ()978-1-4244-3352-0 (ISBN)
Conference
26th IEEE International Instrumentation and Measurement Technology Conference, Singapore, 5-7 May 2009
Projects
KKS DSM
Available from: 2009-09-26 Created: 2009-09-22 Last updated: 2018-03-13Bibliographically 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, Boston: IEEE MTT , 2009, p. 1365-1368Conference 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.

Place, publisher, year, edition, pages
Boston: IEEE MTT, 2009
Series
IEEE MTT-S International Microwave Symposium, ISSN 0149-645X
Keywords
Communication system performance, modeling, nonlinear systems, power amplifiers, radio transmitters.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:hig:diva-5487 (URN)000273507400343 ()978-1-4244-2803-8 (ISBN)
Conference
IEEE/MTT-S International Microwave Symposium, Boston, MA, 7-12 June 2009
Projects
KKS SDM
Available from: 2009-09-26 Created: 2009-09-22 Last updated: 2018-03-13Bibliographically 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, Piscataway, NJ: IEEE Service Center , 2010, p. 620-623, article id 5488231Conference 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
Piscataway, NJ: IEEE Service Center, 2010
Series
IEEE Instrumentation and Measurement Technology Conference, ISSN 1091-5281
Keywords
Harmonic sampling, power amplifiers, out-of-band errors, radio frequency measurement systems.
National Category
Control Engineering Signal Processing Telecommunications
Identifiers
urn:nbn:se:hig:diva-6380 (URN)10.1109/IMTC.2010.5488231 (DOI)000287997200120 ()2-s2.0-77957831915 (Scopus ID)978-1-4244-2833-5 (ISBN)978-1-4244-2832-8 (ISBN)
Conference
International Instrumentation and Measurement Technology Conference (I2MTC), 3-6 May 2010, Austin, Texas
Projects
KKS SDM
Available from: 2010-02-12 Created: 2010-02-12 Last updated: 2018-03-13Bibliographically approved
4. 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, p. 473-479Article in journal (Refereed) Published
Abstract [en]

We evaluated the application of 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-art radio frequency test system with high accuracy was used for this purpose. Improvements due to optimization in 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 6dB 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 9dB from that aspect was observed using half of the power-free subcarriers, which reveals the importance of a guard interval.

Keywords
Communication system performance, power amplifiers, power added efficiency, spectrum mask, convex optimization, dirty radio.
National Category
Signal Processing
Identifiers
urn:nbn:se:hig:diva-6379 (URN)10.1109/TIM.2010.2050360 (DOI)000286008700014 ()2-s2.0-78651273904 (Scopus ID)
Projects
KKS SDM
Available from: 2010-04-13 Created: 2010-02-12 Last updated: 2018-03-13Bibliographically approved

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Nader, Charles

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