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Characterization and Compensation of Hardware Impairments in Transmitters for Wireless Communications
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: 0000-0002-9352-0261
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Increasing demands for data rate, energy efficiency and reliability in wireless communications have resulted in the introduction of radio frequency (RF) multiple input multiple output (MIMO) transmitters. However, MIMO transmitters suffer from additional crosstalk impairments along with the power amplifier (PA) and I/Q imbalance distortions observed in single input single output (SISO) transmitters. Therefore, this thesis focuses on the characterization and compensation of these hardware impairments in RF SISO and MIMO transmitters.

PA distortions are often compensated using the Volterra series, but it suffers from high computational complexity. Therefore, a non-parametric method based on density estimation has been proposed in this thesis to estimate the PA transfer function, from which pruned Volterra models can be developed. The method is validated for a Doherty PA and achieves competitive error performance at a lower complexity than its competitors.

For MIMO transmitters, a characterization technique that uses multitone excitation signals has been proposed. Multitone signals yield non-overlapping tones at the outputs of the MIMO Volterra kernels. These kernel outputs are used to identify the dominant crosstalk impairments, from which block structure and base-band behavioral models are developed. The method is validated for 2x2 and 3x3 MIMO transmitters and it is shown that the derived models achieve a better complexity accuracy trade-off than the other pruned MIMO Volterra models considered in this thesis.

Finally, the thesis presents compensation models for joint static I/Q imbalance and MIMO PA distortions based on conjugate pair and real-valued basis functions. The models are augmented with sub-sample resolution to compensate for dynamic I/Q imbalance distortions. The proposed models are validated for a 2x2 RF MIMO transmitter and achieve a better complexity accuracy trade-off than the other state-of-the-art models considered in this thesis.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. , p. 65
Series
TRITA-EECS-AVL ; 2018:60
Keywords [en]
Power amplifier, RF transmitters, SISO, MIMO, crosstalk, Volterra series, Volterra kernels, behavioral modeling, DPD, Ramanujan sums, multitone signals, I/Q Imbalance, non-linearity, memory polynomial, density estimation, hardware impairments
National Category
Signal Processing
Identifiers
URN: urn:nbn:se:hig:diva-27935ISBN: 978-91-7729-924-0 (print)OAI: oai:DiVA.org:hig-27935DiVA, id: diva2:1250155
Public defence
2018-10-18, Hörsal 12:108, Kungsbäcksvägen 47, Gävle, 13:15 (English)
Opponent
Supervisors
Available from: 2018-09-21 Created: 2018-09-21 Last updated: 2018-09-24Bibliographically approved
List of papers
1. Density estimation models for strong nonlinearities in RF power amplifiers
Open this publication in new window or tab >>Density estimation models for strong nonlinearities in RF power amplifiers
2014 (English)In: Proceedings of the Asia-Pacific Microwave Conference 2014, 2014, p. 116-118Conference paper, Published paper (Refereed)
Abstract [en]

The paper presents a method for modeling strongnonlinear effects in power amplifiers based on the principlesof density estimation. The static nonlinear transfer function isobtained by averaging measured data. The performance obtainedwith density estimation is similar to the one using high ordernonlinear static polynomial models. The benefit of consideredmethod over the ones using polynomial models is that the formerestimates blindly the structure of the transfer function and doesnot suffer from numerical instabilities.

Series
Asia Pacific Microwave Conference-Proceedings
Keywords
power amplifier, density estimation, power amplifier modeling, nonlinearities, memory polynomials
National Category
Communication Systems
Identifiers
urn:nbn:se:hig:diva-17718 (URN)000380417700393 ()2-s2.0-84988258886 (Scopus ID)978-490233931-4 (ISBN)
Conference
Asia Pacific Microwave Conference (APMC) 2014, 4-7 November 2014, Sendai, Japan
Available from: 2014-10-23 Created: 2014-10-23 Last updated: 2018-11-26Bibliographically approved
2. Using Intrinsic Integer Periodicity to Decompose the Volterra Structure in Multi-Channel RF Transmitters
Open this publication in new window or tab >>Using Intrinsic Integer Periodicity to Decompose the Volterra Structure in Multi-Channel RF Transmitters
2016 (English)In: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 26, no 4, p. 297-299Article in journal (Refereed) Published
Abstract [en]

An instrumentation, measurement and post-processing technique is presented to characterize transmitters by multiple input multiple output (MIMO) Volterra series. The MIMO Volterra series is decomposed as the sum of nonlinear single-variable self-kernels and a multi-variable cross-kernel. These kernels are identified by sample averages of the outputs using inputs of different sample periodicity. This technique is used to study the HW effects in a RF MIMO transmitter composed by input and output coupling filters (cross-talk) sandwiching a non-linear amplification stage. The proposed technique has shown to be useful in identifying the dominant effects in the transmitter structure and it can be used to design behavioral models and compensation techniques.

Keywords
Amplifiers, behavioral modeling, concurrent, digital predistortion, linearization, MIMO, MIMO Volterra series
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:hig:diva-21555 (URN)10.1109/LMWC.2016.2525019 (DOI)000374561900025 ()2-s2.0-84979470032 (Scopus ID)
Available from: 2016-06-10 Created: 2016-06-09 Last updated: 2018-11-26Bibliographically approved
3. Finding Structural Information about RF Power Amplifiers using an Orthogonal Nonparametric Kernel Smoothing Estimator
Open this publication in new window or tab >>Finding Structural Information about RF Power Amplifiers using an Orthogonal Nonparametric Kernel Smoothing Estimator
2016 (English)In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 65, no 5, p. 2883-2889, article id 7109926Article in journal (Refereed) Published
Abstract [en]

A non-parametric technique for modeling the behavior of power amplifiers is presented. The proposed technique relies on the principles of density estimation using the kernel method and is suited for use in power amplifier modeling. The proposed methodology transforms the input domain into an orthogonal memory domain. In this domain, non-parametric static functions are discovered using the kernel estimator. These orthogonal, non-parametric functions can be fitted with any desired mathematical structure, thus facilitating its implementation. Furthermore, due to the orthogonality, the non-parametric functions can be analyzed and discarded individually, which simplifies pruning basis functions and provides a tradeoff between complexity and performance. The results show that the methodology can be employed to model power amplifiers, therein yielding error performance similar to state-of-the-art parametric models. Furthermore, a parameter-efficient model structure with 6 coefficients was derived for a Doherty power amplifier, therein significantly reducing the deployment’s computational complexity. Finally, the methodology can also be well exploited in digital linearization techniques.

Keywords
Power amplifier, non-parametric model, kernel, basis functions, power amplifier linearization, Digital pre distortion.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:hig:diva-19395 (URN)10.1109/TVT.2015.2434497 (DOI)000376094500004 ()2-s2.0-84970016798 (Scopus ID)
Available from: 2015-05-27 Created: 2015-05-27 Last updated: 2018-11-26Bibliographically approved
4. Digital Predistortion for Joint Mitigation of I/Q Imbalance and MIMO Power Amplifier Distortion
Open this publication in new window or tab >>Digital Predistortion for Joint Mitigation of I/Q Imbalance and MIMO Power Amplifier Distortion
2017 (English)In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 65, no 1, p. 322-333, article id 7600411Article in journal (Refereed) Published
Abstract [en]

This paper analyzes the joint effects of in-phase and quadrature (I/Q) imbalance and power amplifier (PA) distortion for RF multiple input multiple output (MIMO) transmitters in the presence of crosstalk. This paper proposes candidate models for the digital predistortion of static I/Q imbalanced sources exciting a dynamic MIMO Volterra system. The proposed models are enhanced using a novel technique based on subsample resolution to account for dynamic I/Q imbalance distortions. Finally, the computational complexity of the proposed models is analyzed for implementation suitability in digital platforms. It is shown that the error spectrum for the proposed models in subsample resolution reaches the noise floor of the measurements. The proposed models achieve a normalized mean squared error of -50 dB and an adjacent channel power ratio of -57 dB for signal bandwidths upto 65 MHz and crosstalk levels ranging to -10 dB. These results demonstrate the effectiveness of the proposed techniques in the joint mitigation of I/Q imbalance and PA distortion with crosstalk for a typical 2x2 MIMO telecommunication setup.

Keywords
Digital predistortion (DPD), in-phase and quadrature (I/Q) imbalance, linearization, multiple input multiple output (MIMO), power amplifier (PA)
National Category
Signal Processing
Identifiers
urn:nbn:se:hig:diva-22675 (URN)10.1109/TMTT.2016.2614933 (DOI)000395460200033 ()2-s2.0-84992060969 (Scopus ID)
Note

© 2016 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.

Available from: 2016-10-28 Created: 2016-10-28 Last updated: 2018-09-21Bibliographically approved
5. Multitone design for third order MIMO volterra kernels
Open this publication in new window or tab >>Multitone design for third order MIMO volterra kernels
2017 (English)In: 2017 IEEE MTT-S International Microwave Symposium (IMS), IEEE conference proceedings, 2017, p. 1553-1556Conference paper, Published paper (Refereed)
Abstract [en]

This paper proposes a technique for designing multitone signals that can separate the third order multiple input multiple output (MIMO) Volterra kernels. Multitone signals fed to a MIMO Volterra system yield a spectrum that is a permutation of the sums of the input signal tones. This a priori knowledge is used to design multitone signals such that the output from the MIMO Volterra kernels does not overlap in the frequency domain, hence making it possible to separate these kernels from the output of the MIMO Volterra system. The proposed technique is applied to a 2×2 RF MIMO transmitter to determine its dominant hardware impairments. For input crosstalk, the proposed method reveals the dominant self and cross kernels whereas for output crosstalk, the proposed method reveals that only the self kernels are dominant.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2017
Keywords
Complexity theory, Crosstalk, Kernel, MIMO, Peak to average power ratio, Radio frequency, Transmitters
National Category
Signal Processing
Identifiers
urn:nbn:se:hig:diva-25431 (URN)10.1109/MWSYM.2017.8058925 (DOI)000425241500419 ()2-s2.0-85032467119 (Scopus ID)978-1-5090-6360-4 (ISBN)
Conference
2017 IEEE MTT-S International Microwave Symposium (IMS), 4-9 June 2017, Honolulu, USA
Available from: 2017-10-19 Created: 2017-10-19 Last updated: 2018-11-26Bibliographically approved
6. Extraction of the Third-Order 3x3 MIMO Volterra Kernel Outputs Using Multitone Signals
Open this publication in new window or tab >>Extraction of the Third-Order 3x3 MIMO Volterra Kernel Outputs Using Multitone Signals
2018 (English)In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 66, no 11, p. 4985-4999Article in journal (Refereed) Published
Abstract [en]

This paper uses multitone signals to simplify the analysis of 3×3 multiple-input multiple-output (MIMO) Volterra systems by isolating the third-order kernel outputs from each other. Multitone signals fed to an MIMO Volterra system yield a spectrum that is a permutation of the sums of the input signal tones. This a priori knowledge is used to design multitone signals such that the third-order kernel outputs are isolated in the frequency domain. The signals are designed by deriving the conditions for the offset and spacing of the input frequency grids. The proposed technique is then validated for the six possible configurations of a 3x3 RF MIMO transmitter impaired by crosstalk effects. The proposed multitone signal design is used to extract the third-order kernel outputs, and their relative contributions are analyzed to determine the dominant crosstalk effects for each configuration.

Place, publisher, year, edition, pages
IEEE, 2018
Keywords
Crosstalk; hardware impairments; multiple-input multiple-output (MIMO); multitone signals; Volterra kernels
National Category
Signal Processing
Identifiers
urn:nbn:se:hig:diva-27812 (URN)10.1109/TMTT.2018.2854186 (DOI)000449354500028 ()2-s2.0-85052719621 (Scopus ID)
Available from: 2018-09-01 Created: 2018-09-01 Last updated: 2018-11-28Bibliographically approved
7. Identification of Third Order 3x3 MIMO Volterra Kernels using Multitone Excitation Signals
Open this publication in new window or tab >>Identification of Third Order 3x3 MIMO Volterra Kernels using Multitone Excitation Signals
(English)Manuscript (preprint) (Other academic)
National Category
Signal Processing
Identifiers
urn:nbn:se:hig:diva-27934 (URN)
Available from: 2018-09-21 Created: 2018-09-21 Last updated: 2018-09-24Bibliographically approved

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