Change search

Cite
Citation style
• apa
• ieee
• modern-language-association-8th-edition
• vancouver
• Other style
More styles
Language
• de-DE
• en-GB
• en-US
• fi-FI
• nn-NO
• nn-NB
• sv-SE
• Other locale
More languages
Output format
• html
• text
• asciidoc
• rtf
Estimation of Inverse Models Applied to Power Amplifier Predistortion
Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
2013 (English)Licentiate thesis, monograph (Other academic)
##### Abstract [en]

Mathematical models are commonly used in technical applications to describe the behavior of a system. These models can be estimated from data, which is known as system identification. Usually the models are used to calculate the output for a given input, but in this thesis, the estimation of inverse models is investigated. That is, we want to find a model that can be used to calculate the input for a given output. In this setup, the goal is to minimize the difference between the input and the output from the cascaded systems (system and inverse). A good model would be one that reconstructs the original input when used in series with the original system.

Different methods for estimating a system inverse exist. The inverse model can be based on a forward model, or it can be estimated directly by reversing the use of input and output in the identification procedure. The models obtained using the different approaches capture different aspects of the system, and the choice of method can have a large impact. Here, it is shown in a small linear example that a direct estimation of the inverse can be advantageous, when the inverse is supposed to be used in cascade with the system to reconstruct the input.

Inverse systems turn up in many different applications, such as sensor calibration and power amplifier (PA) predistortion. PAs used in communication devices can be nonlinear, and this causes interference in adjacent transmitting channels, which will be noise to anyone that transmits in these channels. Therefore, linearization of the amplifier is needed, and a prefilter is used, called a predistorter. In this thesis, the predistortion problem has been investigated for a type of PA, called outphasing power amplifier, where the input signal is decomposed into two branches that are amplified separately by highly efficient nonlinear amplifiers, and then recombined. If the decomposition and summation of the two parts are not perfect, nonlinear terms will be introduced in the output, and predistortion is needed.

Here, a predistorter has been constructed based on a model of the PA. In a first method, the structure of the outphasing amplifier has been used to model the distortion, and from this model, a predistorter can be estimated. However, this involves solving two nonconvex optimization problems, and the risk of obtaining a suboptimal solution. Exploring the structure of the PA, the problem can be reformulated such that the PA modeling basically can be done by solving two least-squares (LS) problems, which are convex. In a second step, an analytical description of an ideal predistorter can be used to obtain a predistorter estimate. Another approach is to compute the predistorter without a PA model by estimating the inverse directly. The methods have been evaluated in simulations and in measurements, and it is shown that the predistortion improves the linearity of the overall power amplifier system.

##### Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1605
##### National Category
Engineering and Technology
##### Identifiers
Local ID: LIU-TEK-LIC-2013:39ISBN: 978-91-7519-571-1 (print)OAI: oai:DiVA.org:liu-97355DiVA, id: diva2:647126
##### Note

The series name "Linköping Studies in Science and Technology. Licentiate Thesis" is incorrect. The correct sereis name is "Linköping Studies in Science and Technology. Thesis".

Available from: 2013-09-10 Created: 2013-09-10 Last updated: 2013-10-09Bibliographically approved

#### Open Access in DiVA

##### File information
File name FULLTEXT01.pdfFile size 6317 kBChecksum SHA-512
623bcb3ff84ba5fee00b3a3b302d134a3dc98cebe474afcc7e42f01970a95e0f450c5cc166c515cffe76db94cc7d939e5159b95a0ebfcbf09a641fd1600303c9
Type fulltextMimetype application/pdf
##### File information
File name COVER01.pdfFile size 35 kBChecksum SHA-512
Type coverMimetype application/pdf

#### Search in DiVA

Jung, Ylva
##### By organisation
Automatic ControlThe Institute of Technology
##### On the subject
Engineering and Technology

#### Search outside of DiVA

The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available
isbn
urn-nbn

#### Altmetric score

isbn
urn-nbn
Total: 731 hits

Cite
Citation style
• apa
• ieee
• modern-language-association-8th-edition
• vancouver
• Other style
More styles
Language
• de-DE
• en-GB
• en-US
• fi-FI
• nn-NO
• nn-NB
• sv-SE
• Other locale
More languages
Output format
• html
• text
• asciidoc
• rtf
v. 2.34-SNAPSHOT
|