Change search
Refine search result
1234567 151 - 200 of 343
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • 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
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 151.
    Khan, Zain Ahmed
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering. Högskolan i Gävle.
    Zenteno, Efrain
    Universidad Católica San Pablo.
    Händel, Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering. KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems.
    Isaksson, Magnus
    Högskolan i Gävle.
    Identification of Third Order 3x3 MIMO Volterra Kernels using Multitone Excitation SignalsManuscript (preprint) (Other academic)
  • 152.
    Khan, Zain Ahmed
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering. Universidad Catolica San Pablo, Peru.
    Zenteno, Efrain
    Dept. Electronics and Telecommunications, Universidad Catolica San Pablo, Arequipa, Peru.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Isaksson, Magnus
    Dept. Electronics, Mathematics, and Natural Sciences, University of Gävle, Gävle, Sweden.
    Multitone design for third order MIMO volterra kernels2017In: 2017 IEEE MTT-S International Microwave Symposium (IMS), Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 1553-1556, article id 8058925Conference 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.

  • 153.
    Khan, Zain Ahmed
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. University of Gävle.
    Zenteno, Efrain
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. University of Gävle.
    Isaksson, Magnus
    University of Gävle.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Density Estimation Models for Strong Nonlinearities in RF Power Amplifiers2014In: 2014 Asia-Pacific Microwave Conference Proceedings, APMC 2014, 2014, p. 116-118Conference 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.

  • 154. Kumar, Sailesh G.
    et al.
    Sundar, Shyam S.
    Gupta, Amit K.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    An Experimental Study on a Pedestrian Tracking Device2015In: 2015 IEEE INTERNATIONAL CONFERENCE ON ELECTRONICS, COMPUTING AND COMMUNICATION TECHNOLOGIES (CONECCT), IEEE , 2015Conference paper (Refereed)
    Abstract [en]

    The implemented navigational algorithm of an inertial navigation system (INS), along with the hardware configuration, decides its tracking performance. Besides, operating conditions also influence its tracking performance. The aim of this study is to demonstrate robust performance of a multiple Inertial Measurement Units (IMUs) based foot-mounted INS, The Osmium MIMU22BTP, under varying operating conditions. The device, which performs zero-velocity-update (ZUPT) aided navigation, is subjected to different conditions which could potentially influence gait of its wearer, its hardware configuration etc. The gait-influencing factors chosen for study are shoe type, walking surface, path profile and walking speed. Besides, the tracking performance of the device is also studied for different number of on-board IMUs and the ambient temperature. The tracking performance of MIMU22BTP is reported for all these factors and benchmarked using identified performance metrics. We observe very robust tracking performance of MIMU22BTP. The average relative errors are less than 3 to 4% under all the conditions, with respect to drift, distance and height, indicating a potential for a variety of location based services based on foot mounted inertial sensing and dead reckoning.

  • 155.
    Landin, Per N.
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Gävle, Sweden; Chalmers University of Technology, Sweden; Vrije Universiteit Brussel, Belgium .
    Barbe, Kurt
    Van Moer, Wendy
    Isaksson, Magnus
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Two novel memory polynomial models for modeling of RF power amplifiers2015In: International journal of microwave and wireless technologies, ISSN 1759-0795, E-ISSN 1759-0787, Vol. 7, no 1, p. 19-29Article in journal (Refereed)
    Abstract [en]

    Two novel memory polynomial models are derived based on physical knowledge of a general power amplifier (PA). The derivations are given in detail to facilitate derivations of other model structures. The model error in terms of normalized mean square error (NMSE) and adjacent channel error power ratio (ACEPR) of the novel model structures are compared to that of established models based on the number of parameters using data measured on two different amplifiers, one high-power base-station PA and one low-power general purpose amplifier. The novel models show both lower NMSE and ACEPR for any chosen number of parameters compared to the established models. The low model errors make the novel models suitable candidates for both modeling and digital predistortion.

  • 156.
    Landin, Per N.
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Isaksson, Magnus
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Comparison of Evaluation Criteria for Power Amplifier Behavioral Modeling2008In: 2008 IEEE MTT-S INTERNATIONAL MICROWAVE SYMPOSIUM DIGEST, New York: IEEE , 2008, p. 1441-1444Conference paper (Refereed)
    Abstract [en]

    In this paper different evaluation criteria for power amplifier behavioral modeling are studied and evaluated using measuremed data. The figure-of-merits are calculated from complex-envelope data of a sampled power amplifier intended for 3G. Both time- and frequency domain methods are included in the study. It is found that a model evaluation criterion should have ability to capture both the linear and nonlinear distortion as well as the memory effects in the power amplifier. The normalized mean square error (NMSE) and the weighted error-to-signal power ratio (WESPR) are found to be the strongest candidates for capturing the in-band and the out-of-band errors, respectively. Both are also independent of power amplifier technology and stimuli input.

  • 157.
    Landin, Per N.
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Isaksson, Magnus
    Högskolan i Gävle, Ämnesavdelningen för elektronik.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Parameter Extraction and Performance Evaluation Method for Increased Performance in RF Power Amplifier Behavioral Modeling2010In: International Journal of RF and Microwave Computer-Aided Engineering, ISSN 1096-4290, E-ISSN 1099-047X, Vol. 20, no 2, p. 200-208Article in journal (Refereed)
    Abstract [en]

    A frequency-weighted parameter extraction method based on the performance evaluation criterion weighted error spectral power ratio (WESPR) is proposed. Performance of models extracted using the normalized mean square error (NMSE) are compared to the performances of models extracted using the WESPR. The results show an increase in performance with a decrease in model complexity.

  • 158.
    Landin, Per N.
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Van Moer, W.
    Isaksson, M.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Peak-power controlled digital predistorters for RF power amplifiers2012In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 60, no 11, p. 3582-3590Article in journal (Refereed)
    Abstract [en]

    This paper investigates the issue of predistorter blow-up, i.e., uncontrolled peak expansion caused by the predistorter. To control the peak expansion, an extension of the multistep indirect learning architecture (MS-ILA) is proposed by adding a constraint that describes the allowed peak power of the predistortion signal. The resulting optimization problem is shown to be convex and an optimization method is formulated to solve it.

  • 159.
    Landin, Per Niklas
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Barbe, Kurt
    Vrije Universiteit Brussel.
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    Isaksson, Magnus
    University of Gävle.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Proofs of Derivations in Memory Polynomial Baseband Modeling of RF Power Amplifiers2011Report (Other academic)
    Abstract [en]

    This paper contains supporting derivations for the paperMemory Polynomial Baseband Modeling of RF Power Am-plifiers. All references to numbered equations, propositionsand assumptions are to the corresponding number inMemoryPolynomial Baseband Modeling of RF Power Amplifiers.

  • 160.
    Landin, Per Niklas
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Nader, Charles
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Björsell, Niclas
    Center for RF Measurement Technology, Univeristy of Gävle.
    Isaksson, Magnus
    Wisell, David
    Ericsson AB, Stockholm.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Andersen, Olav
    Ericsson AB, Gävle.
    Keskitalo, Niclas
    Center for RF Measurement Technology, University of Gävle.
    Wideband Characterization of Power Amplifiers Using Undersampling2009In: 2009 IEEE MTT-S International Microwave Symposium Digest, 2009, p. 1365-1368Conference 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.

  • 161.
    Landin, Per Niklas
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Nader, Charles
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    Björsell, Niclas
    University of Gävle.
    Isaksson, Magnus
    University of Gävle.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Overview of Synergetic OFDM Crest Factor Reduction and Digital Pre-Distortion for RF PAs2011Conference paper (Other academic)
    Abstract [en]

    Digital baseband pre-distortion (DPD) is used tolinearize nonlinear RF PAs, crest factor reduction (CFR) toincrease the maximum output power level of RF PAs. Togetherthey result in increased output power with maintained, or even,better linearity. This paper discuss some of the techniquesfor DPD and CFR methods currently under investigation.Measured results for a class-AB PA using OFDM signalsindicate a possibility to increase the power added efficiency(PAE) by at least 15%-points, from 30%to 45%, and a poweroutput increase of 6 dB while maintaining specified ACLRrequirements.

  • 162.
    Larsson, Robin
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Inertial Sensor Driven Smartphone and Automobile Coordinate System Alignment2017In: 2017 IEEE 20TH INTERNATIONAL CONFERENCE ON INTELLIGENT TRANSPORTATION SYSTEMS (ITSC), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    In this study a method is presented for estimating the orientation of an inertial measurement unit (IMU) located within an automobile, using only the measurements from the IMU itself. The orientation estimation problem is posed as a non-linear filtering probletn, which is solved using a marginalized particle filter. The performance of the proposed method is evaluated using a large collection of real-world data, collected by multiple drivers. The drivers used their own smartphones and had no restrictions on smartphone handling during drives. The orientation accuracy achieved with the proposed method is in the order of a few degrees; 50% of cases were below 5 degrees and 90% of cases were below 20 degrees.

  • 163.
    Lundin, Henrik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Andersson, Tomas
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Skoglund, Mikael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Analog-to-Digital Converter Error Correction using Frequency Selective Tables2002In: RadioVetenskap och Kommunikation (RVK), 2002, p. 487-490Conference paper (Refereed)
    Abstract [en]

    Error correction for analog-to-digital converters (ADCs) is considered. The frequency-dependent nature of ADC errors motivates the proposal of a novel scheme, incorporating look-up table correction and fast frequency estimation. The method is evaluated using experimental converter data, and the performance, measured in SFDR and SINAD, is found to be superior to that of non frequency-dependent correction methods.

  • 164.
    Lundin, Henrik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Andersson, Tomas
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Skoglund, Mikael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Analog-to-Digital Converter Error Correction using Frequency Selective Tables2002In: RadioVetenskap och Kommunikation (RVK), 2002, p. 487-490Conference paper (Other academic)
    Abstract [en]

    Error correction for analog-to-digital converters(ADCs) is considered. The frequency-dependent na-ture of ADC errors motivates the proposal of a novel scheme, incorporating look-up table correction andfast frequency estimation. The method is evaluated using experimental converter data, and the performance, measured in SFDR and SINAD, is found tobe superior to that of non frequency-dependent correction methods.

  • 165.
    Lundin, Henrik
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Look-Up Tables, Dithering and Volterra Series for ADC Improvements2014In: Design, Modeling and Testing of Data Converters / [ed] Carbone, Paolo and Kiaei, Sayfe and Xu, Fang, Berlin Heidelberg: Springer Berlin/Heidelberg, 2014, p. 249-275Chapter in book (Refereed)
    Abstract [en]

    This chapter gives an introduction and an overview to correction methods for analog-to-digital converters (ADCs), including methods that are implemented using look-up tables, the method known as dithering, and methods that are based on a mathematical model of the ADC.

  • 166. Lundin, Henrik
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Accurate prediction of analog-to-digital converter performance after post-correction2006In: 18th IMEKO World Congress 2006: Metrology for a Sustainable Development, 2006, p. 1002-1007Conference paper (Other academic)
    Abstract [en]

    Analog-to-digital converter additive post-correction using look-up-tables is considered. An accurate expression is provided that predicts the ADC performance after correction. The expression depends on differential nonlinearity, random noise variance, and the numerical precisionof the correction terms. The theory shows good agreement when compared with simulations and experimental converter data.

  • 167.
    Lundin, Henrik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Skoglund, Mikael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Adaptively calibrating analog-to-digital conversion with correction table indexing2000Patent (Other (popular science, discussion, etc.))
  • 168.
    Lundin, Henrik
    et al.
    Global IP Solutions.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bounds on the performance of analog-to-digital converter look-up table post-correction2009In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 42, no 8, p. 1164-1175Article in journal (Refereed)
    Abstract [en]

    Analog-to-digital converter additive post-correction using look-up tables is considered. The problem of successfully predicting the converter's performance after correction is treated in particular. An accurate expression is provided that predicts the ADC performance after correction. The expression depends on differential non-linearity, random noise variance, and the numerical precision of the correction terms. The theory shows good agreement when compared with simulations and experimental converter data. The results are useful when designing systems involving ADCs and post-correction, since the performance parameters can be obtained with knowledge of a few ADC intrinsic parameters and the correction system resolution.

  • 169.
    Lundin, Henrik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Skoglund, Mikael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    A criterion for optimizing bit-reduced post-correction of AD converters2004In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 53, no 4, p. 1159-1166Article in journal (Refereed)
    Abstract [en]

    Dynamic digital post-correction of analog-to-digital converters (ADCs) is considered. A generalized dynamic correction method is proposed and a framework for analyzing the related bit allocation problem is derived. Finally, this framework is employed in an optimization problem. The solution to the problem indicates which ADC output bits to use in order to maximize the signal-to-noise and distortion ratio in a post-correction system with a constraint on memory size. The proposed methods are accompanied by exemplary results obtained using experimental ADC data.

  • 170.
    Lundin, Henrik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Skoglund, Mikael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    A Framework for External Dynamic Compensation of AD Converters2002In: Proceedings 7th European Workshop on ADC Modelling and Testing, 2002, p. 135-138Conference paper (Refereed)
    Abstract [en]

    External calibration and compensation of analog-to-digital converters is considered. First, a dynamic correction scheme is proposed to comprise bit-masking. Next, a framework for analyzing the effects of bit-reduced table indexing is derived. This framework is finally applied in an optimization problem for bit allocation in the bit mask of the introduced correction scheme. Both the correction method and the optimization problem are exemplified using experimental ADC data. The results indicate that the considered correction scheme is superior to static schemes, and that the choice of bit mask is of great importance, motivating the analysis framework.

  • 171.
    Lundin, Henrik
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    ADC Post-Correction Using Limited Resolution Correction Values2005In: Proceedings IMEKO 10th Workshop on ADC Modelling and Testing, 2005, Vol. 2, p. 567-572Conference paper (Other academic)
    Abstract [en]

    Analog-to-digital converter additive post-correction using look-up-tables is considered. In a practical post-correction system, the correction values must be stored using limited (fixed-point) precision. In this paper the effects of limited precision in the correction values is investigated. A theory for approximating the SINAD after correction using fixed-point values is presented. The theory shows good agreement when compared with simulation results.

  • 172.
    Lundin, Henrik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Skoglund, Mikael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Minimal Total Harmonic Distortion Post-Correction of ADCs2003In: International Workshop on ADC Modelling and Testing, 2003, p. 113-116Conference paper (Refereed)
    Abstract [en]

    Dynamic digital post-correction of AD converters is considered. A generalized dynamic correctionmethod is proposed and a framework for analyzing therelated bit allocation problem is introduced. Finally, thisframework is employed in an optimization problem. Thesolution to the problem indicates which ADC output bitsto use in order to maximize the THD in a post-correctionsystem with a constraint on memory size.The proposed methods are accompanied by exemplaryresults obtained using experimental ADC data.

  • 173.
    Lundin, Henrik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Skoglund, Mikael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    On external calibration of analog-to-digital converters2001In: 2001IEEE Workshop on Statistical Signal Processing Proceedings, NEW YORK: IEEE , 2001, p. 377-380Conference paper (Refereed)
    Abstract [en]

    External calibration and compensation of analog-to-digital converters is considered. Two novel methods are presented. Both methods employ multiple calibration frequencies in order to improve the wide-band performance of the converter. Also, a dynamic table indexing is introduced to further improve the performance. A recursive sine-wave reconstruction filter algorithm is developed for calibration purposes. The proposed methods are evaluated using experimental converter data. Results indicate that the dynamic indexing provides good correction performance, also at frequencies not used during calibration. Thus, wide-band calibration can be achieved.

  • 174.
    Lundin, Henrik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Skoglund, Mikael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    On External Calibration of Analog-to-Digital Converters2001In: IEEE Workshop on Statistical Signal Processing, IEEE , 2001, p. 377-380Conference paper (Refereed)
    Abstract [en]

    External calibration and compensation of analog-to-digital converters is considered. Two novel methods are presented. Both methods employ multiple calibration frequencies in order to improve the wide-band performance of the converter. Also, a dynamic table indexing is introduced to further improve the performance. A recursive sine-wave reconstruction filter algorithm is developed for calibration purposes. The proposed methods are evaluated using experimental converter data. Results indicate that the dynamic indexing provides good correction performance, also at frequencies not used during calibration. Thus, wide-band calibration can be achieved.

  • 175.
    Lundin, Henrik
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On the estimation of quantizer reconstruction levels2005In: Instrumentation and Measurement Technology Conference, 2005. IMTC 2005. Proceedings of the IEEE, VDE Verlag GmbH, 2005, Vol. 1, p. 144-149Conference paper (Refereed)
    Abstract [en]

    We consider the problem of estimating the optimal reconstruction levels of a quantizer, such as an analog-to-digital converter. A probabilistic transfer function model is applied for the quantizer. Two different assumptions are made for the transfer function, and an estimator based on order statistics is applied. The estimator turns out to give give better results in terms of mean square error than the commonly applied sample mean. The Cramer-Rao lower bound for the estimation problem is also considered, and simulation results indicate that the derived estimator is asymptotically efficient.

  • 176.
    Lundin, Henrik
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    On the estimation of quantizer reconstruction levels2006In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 55, no 6, p. 2176-2182Article in journal (Refereed)
    Abstract [en]

    We consider the problem of estimating the optimal reconstruction levels of a fixed quantizer, such as the amplitude quantization part of an analog-to-digital converter. A probabilistic transfer function model is applied for the quantizer. Two different assumptions are made for the transfer function, and an estimator based on order statistics is applied. The estimator turns out to give better results in terms of mean square error than the commonly applied sample mean. The Cramer-Rao lower bound for the estimation problem is also considered, and simulation results indicate that the derived estimator is asymptotically efficient.

  • 177.
    Lundin, Henrik
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Optimal index-bit allocation for dynamic post-correction of analog-to-digital converters2005In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 53, no 2, p. 660-671Article in journal (Refereed)
    Abstract [en]

    Signal processing methods for digital post-correction of analog-to-digital converters (ADCs) are, considered. ADC errors are in general signal dependent, and in addition, they often exhibit dynamic dependence. A novel dynamic post-correction scheme based on look-up tables is proposed. In order to reduce the table size and, thus, the hardware requirements, bit-masking is, introduced. This. is to limit the length of the table index by deselecting index bits. At this point, the problem of which bits to use arises. A mathematical analysis tool is derived, enabling the allocation of index bits to be analyzed. This analysis tool is applied in two optimization problems, optimizing the total harmonic distortion and the signal-to-noise and distortion ratio, respectively, of a corrected ADC. The correction scheme and the optimization problems are illustrated and exemplified using experimental ADC data. The results show that the proposed correction scheme improves the performance of the ADC. They also indicate that the allocation of index bits has a significant impact on the ADC performance, motivating the analysis tool. Finally, the optimization results show that performance improvements compared with static look-up table correction can be achieved, even at a comparable table size.

  • 178.
    Lundin, Henrik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Skoglund, Mikael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Optimizing dynamic post-correction of AD converters2003In: IMTC/O3: PROCEEDINGS OF THE 20TH IEEE INSTRUMENTATION AND MEASUREMENT TECHNOLOGY CONFERENCE, VOLS 1 AND 2, 2003, p. 1206-1211Conference paper (Refereed)
    Abstract [en]

    Dynamic digital post-correction of AD converters is considered A generalized dynamic correction method is proposed and a framework for analyzing the related bit allocation problem is derived Finally, this framework is employed in an optimization problem. The solution to the problem indicates which ADC output bits to use in order to maximize the SINAD in a post-correction system with a constraint on memory size. The proposed methods are accompanied by exemplary results obtained using experimental ADC data.

  • 179.
    Lundin, Henrik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Skoglund, Mikael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Optimizing Dynamic Post-Correction of AD Converters2003In: Proceedings IEEE Instrumentation And Measurement Technology Conference, IEEE , 2003, p. 1206-1211Conference paper (Refereed)
    Abstract [en]

    Dynamic digital post-correction of AD converters is considered. A generalized dynamic correction method is proposed and a framework for analyzing the related bit allocation problem is derived. Finally, this framework is employed in an optimization problem. The solution to the problem indicates which ADC output bits to use in order to maximize the SINAD in a post-correction system with a constraint on memory size. The proposed methods are accompanied by exemplary results obtained using experimental ADC data.

  • 180.
    Lundin, Henrik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Skoglund, Mikael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Post-Correction of Analog-to-Digital Converters2003Manuscript (preprint) (Other academic)
    Abstract [en]

    A dynamic post-correction method for ADCs is presented. The method utilizes bit-masking, and a tool for analyzing the effects thereof is proposed. This tool is used to calculate optimal bit allocations, in order to minimize the THD of the corrected ADC. An example based on experimental ADC data is presented.

  • 181.
    Lundin, Henrik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Skoglund, Mikael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Post-Correction of Analog-to-Digital Converters2003In: Proceedings Northern Lights Workshop on Sensors, Signals and Systems, 2003Conference paper (Other academic)
  • 182.
    Lundin, Henrik
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Signal Processing Results on Dynamic ADC Post-Correction2005In: Proceedings of GigaHertz, 2005Conference paper (Refereed)
    Abstract [en]

    —In this paper we give a brief introduction to some issues and results regarding ADC post-correction. The emphasis is on signal process-ing aspects of post-correction, including dynamics, estimation and round-off effects.

  • 183.
    Lundin, Henrik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Svedman, Patrick
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Zhang, Xi
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Skoglund, Mikael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Zetterberg, Per
    KTH, Superseded Departments, Signals, Sensors and Systems.
    ADC imperfections in multiple antenna wireless systems - An experimental study2004In: 9th IMEKO Workshop on ADC Modeling and Testing, IWADC 2004, Held Together with the 13th IMEKO TC4 Symposium on Measurements for Research and Industrial Applications, IMEKO-International Measurement Federation Secretariat , 2004, p. 84-89Conference paper (Refereed)
    Abstract [en]

    This paper investigates some of the effects that ADC imperfections may have on wireless communication systems. First, an experimental communication system for wireless multiple-input multiple-output (MIMO) is described. In this test bed, an ADC behavioural model has been implemented. The resulting performance of the communication system, in terms of bit error rate, is assessed when the parameters of the ADC model are altered. The results show that, for this system, the ADC resolution is the key parameter while the non-linearity errors are of minor importance.

  • 184.
    Medawar, Samer
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Björsell, Niclas
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dynamic Characterization of Analog-Digital-Converters Non-Linearities2007In: Proceedings Mosharaka International Conference on Wireless Communications and Mobile Computing, 2007Conference paper (Refereed)
    Abstract [en]

    A characterization of a state of the art pipeline ADC is presented. Measurements are performed on a wide set of frequencies. The integral non linearity (INL) is modeled by high code and low code components, HCF and LCF. The HCF component is to be deprived of any dynamic behavior, and varies piecewise linearly in certain intervals. Hence, the LCF represents the dynamic behavior that should varies the frequency of the test signal. Employement of the method presented in [1] on measured data is performed and complemented with modifications stimulated by the behavior of measured data.

  • 185.
    Medawar, Samer
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    On the Calibration of Wideband Analog-Digital Converters2013In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 62, no 8, p. 2353-2355Article in journal (Refereed)
    Abstract [en]

    The characterization of analog-digital converter (ADC) error is investigated in this letter. More specifically, the ADC static and dynamic errors are clearly identified in a wideband characterization. Improvements obtained by static calibration are presented, and the limitations of dynamic calibration are also investigated.

  • 186.
    Medawar, Samer
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Björsell, Niclas
    Department of Electronics, University of Gävle, SE-801 76 Gävle, Sweden.
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    ADC Characterization By Dynamic Integral Nonlinearity2008In: 13th Workshop on ADC Modelling and Testing, 2008, p. 1037-1042Conference paper (Refereed)
    Abstract [en]

    Wide band characterization of analog-digital converter integral nonlinearity (INL) based on parametric modeling and least-squares parameter fit is performed. In particular, the variations in the INL due to the frequency of theADC stimuli are modeled. The INL is divided into two main entities describing the static and dynamic behavior of theADC, respectively. The static component is modeled by a high code component (HCF) of piecewise linear segmentscentered around zero. A static low code (LCF) polynomial inherent to the INL data is added to the segments to complete the static part of the model. The INL dynamic part is modeled by an LCF polynomial. Method implementationis considered and is applied to 12-bit ADC data at 210 MSPS.

  • 187.
    Medawar, Samer
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Björsell, Niclas
    University of Gävle.
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Input-Dependent Integral Nonlinearity Modeling for Pipelined Analog-Digital Converters2010In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 59, no 10, p. 2609-2620Article in journal (Refereed)
    Abstract [en]

    Integral nonlinearity (INL) for pipelined analog-digital converters (ADCs) operating at RF is measured and characterized. A parametric model for the INL of pipelined ADCs is proposed, and the corresponding least-squares problem is formulated and solved. The INL is modeled both with respect to the converter output code and the frequency stimuli, which is dynamic modeling. The INL model contains a static and a dynamic part. The former comprises two 1-D terms in ADC code that are a sequence of zero-centered linear segments and a polynomial term. The 2-D dynamic part consists of a set of polynomials whose parameters are dependent on the ADC input stimuli. The INL modeling methodology is applied to simulated and experimental data from a 12-bit commercial ADC running at 210 mega samples per second. It is demonstrated that the developed methodology is an efficient way to capture the INL of nowadays ADCs running at RF, and it is believed that the methodology is powerful for INL-based ADC postcorrection in wideband applications.

  • 188.
    Medawar, Samer
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Björsell, Niclas
    Center for RF Measurememt Technology, University of Gävle, SE-801 76 Gävle, Sweden.
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Model Order Determination and Segmentation of Analog-Digital Converters Integral Non Linearity2010In: 2010 IEEE INTERNATIONAL INSTRUMENTATION AND MEASUREMENT TECHNOLOGY CONFERENCE I2MTC 2010, PROCEEDINGS, IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA: IEEE , 2010, p. 36-41Conference paper (Refereed)
    Abstract [en]

    Analog-digital converter (ADC) integral nonlinearity (INL) modeling is investigated. The model is comprised of two entities: a low code frequency (LCF) component modeled by an L-order polynomial, and a static high code frequency component (HCF), modeled by P linear disjoint segments centered around zero. Both model components are functions of the ADC output code k. A methodical way of estimating the LCF polynomial order L and the set of segments (number of and their borders), is suggested. The method computes the polynomial order L and the set of segments (number and borders) that minimizes the root mean square (RMS) distance between the INL data and its model. The method is applied to measured INL sequences of a 12-bit Analog Devices pipeline ADC (AD9430).

  • 189.
    Medawar, Samer
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Björsell, Niclas
    University of Gävle.
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Pipelined analog-digital converters integral nonlinearity modeling for post-correction2010In: 17th Symposium IMEKO TC4 - Measurement of Electrical Quantities, 15th International Workshop on ADC Modelling and Testing, and 3rd Symposium IMEKO TC19 - Environmental Measurements, 2010, p. 585-590Conference paper (Refereed)
    Abstract [en]

    An input-dependent integral nonlinearity (INL) model is developed for pipeline ADC post-correction. The INL model consists of a static and dynamic part. The INL model is subtracted from the ADC digital output for compensation. Static compensation is performed by adjacent sets of gains and offsets. Each set compensates a certain output code range. The frequency content of the INL dynamic component is used to design a set of filter blocks that performs ADC compensation in the time domain. The compensation scheme is applied to measured data of two 12-bit ADCs of the same type (Analog Devices AD9430). Significant performance improvements in terms of spurious free dynamic range (SFDR) are obtained.

  • 190.
    Medawar, Samer
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Björsell, Niclas
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Post-correction of pipelined analog-digital converters based on input dependent integral nonlinearity modeling2011In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, ISSN 0018-9456, Vol. 60, no 10, p. 3342-3350Article in journal (Refereed)
    Abstract [en]

    The integral nonlinearity (INL) is used for the postcorrection of analog-digital converters (ADCs). An input-frequency-dependent INL model is developed for the postcorrection. The model consists of a static term that is dependent on the ADC output code and a dynamic term that has an additional dependence on the input frequency. The concept of ADC digital output postcorrection by INL is first introduced. The INL model is subtracted from the digital output for postcorrection. The static compensation part is made by adjacent sets of gains and offsets, where each set corrects a range of output codes. The dynamic information, i.e., the frequency dependence of the INL dynamic component is used to construct a set of filter blocks that performs ADC compensation in the time domain. The compensation scheme is applied to the measured data of two ADCs of the same type (Analog Devices AD9430). Performance improvements in terms of spurious-free dynamic range, signal-to-noise and distortion ratio, intermodulation distortion, and noise are obtained. The dynamic compensation part, due to its frequency dependence, can be generalized; hence, a postcorrection block model can be used for compensating multiple ADCs of the same type.

  • 191.
    Medawar, Samer
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Murmann, Boris
    Stanford University, EE School, Integrated Circuits.
    Björsell, Niclas
    University of Gävle.
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Dynamic Calibration of Undersampled Pipelined ADCs by Frequency Domain Filtering2013In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, Vol. 62, no 7, p. 1882-1891Article in journal (Refereed)
    Abstract [en]

    Integral nonlinearity (INL) is used for the post-correction of pipelineanalog-digital converters (ADC)s. An input-frequency-dependentINL model is developed for the compensation. The model consistsof a static term that is dependent on the ADC output code and adynamic term that has an additional dependence on the input signalfrequency. The INL model is subtracted from thedigital output for post-correction. The static compensationis implemented with a look-up-table (LUT). The dynamic calibration isperformed by a bank of frequency domain filters using an overlap-add structure.Two ADCs of the same type (Analog Devices AD9430) are compensated in the first three Nyquist bands.The performance improvements in terms of spurious-free dynamic range(SFDR) and intermodulation distortion (IMD) are investigated. Using the proposed method, improvements up to 17 dB are reported in favorable scenarios.

  • 192.
    Medawar, Samer
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Approximate Maximum Likelihood Estimation of Rician K-Factor and Investigation of Urban Wireless Measurements2013In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 12, no 6, p. 2545-2555Article in journal (Refereed)
    Abstract [en]

    We consider the problem of estimating the K-factor of a Rician fading wireless channel based on observations of the envelope only, i.e., without phase-information. An approximate Rician power density function (pdf) is introduced to overcome the complexity of the exact pdf. A closed-form maximum-likelihood estimator is derived based on this approximate Rician pdf, while a maximum-likelihood estimator based on the exact Rician pdf appears to be infeasible. An improved estimator is also proposed that features less bias and less variance than the first estimator. The performance of the latter estimator is compared to moment-based estimators that were previously proposed in the literature and is found to have superior performance to closed-form moment estimators, especially for low sample numbers and/or large K-values. The estimator is applied to real wireless macro-cell urban-area measurements. The results show generally low K-factors (below 3dB), with occasional higher values in particular circumstances.

  • 193.
    Medawar, Samer
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Ricean K-factor estimation and investigation of urban wireless measurements2012In: 2012 IEEE International Conference on Wireless Information Technology and Systems, ICWITS 2012, IEEE , 2012, p. 6417686-Conference paper (Refereed)
    Abstract [en]

    We consider the problem of estimating the K-factor of a Ricean fading wireless channel based on observations of the envelope only. An approximate Ricean power density function (pdf) is introduced to enable the derivation of a closed-form maximum-likelihood K-factor estimator. A further improved estimator is also proposed, featuring less bias and variance than the first one. The latter estimator outperforms closed form estimators found in the literature especially for low number of samples and/or large K-values. The estimator is applied to real wireless macro-cell urban-area measurements.

  • 194.
    Medawar, Samer
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Murmann, Boris
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Björsell, Niclas
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Static Integral Nonlinearity Modeling and Calibration of Measured and Synthetic Pipeline Analog-to-Digital Converters2014In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 63, no 3, p. 502-511Article in journal (Refereed)
    Abstract [en]

    The integral nonlinearity (INL) modeling of pipeline analog-to-digital converters (ADCs) is investigated in this paper. The INL is divided into two distinct entities: a low code frequency (LCF) component and a high code frequency (HCF) component. Two static models are developed to represent the INL data. In both models, the LCF component is represented by a low-order polynomial. The HCF modeling is performed using two different basis functions: sinc and Gaussian. The structure of both HCF models is motivated by the pipeline architecture of the ADC under investigation. The model coefficients are estimated by applying the least-squares method to the measured INL data from two samples of a commercial pipeline ADC. The estimated HCF models are compared to each other and to previous models presented in the existing literature. In addition, the modeling methods are applied to synthetic HCF data generated by a pipeline ADC simulation model constructed in MATLAB. The INL models are then used to calibrate the synthetic ADCs, and the improvements in spurious free dynamic range are compared to those obtained when the ADCs are compensated by the INL data. Furthermore, the capability of the HCF modeling to calibrate a given ADC is tested by using the HCF model to compensate a synthetically generated ADC output in which only the measured HCF sequence and noise are added to the quantization process. The results show that the developed HCF models can achieve virtually complete calibration of the considered ADC.

  • 195.
    Moghadam, Nima N.
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Correlation of distortion noise between the branches of MIMO transmit antennas2012In: Personal Indoor and Mobile Radio Communications (PIMRC), 2012 IEEE 23rd International Symposium on, IEEE , 2012, p. 2079-2084Conference paper (Refereed)
    Abstract [en]

    Despite the tremendous research effort spent on MIMO systems - very few papers address the impact of hardware imperfections. In this paper we analyze the distortion noise of the transmitter branches of a MIMO transmitter. In particular we analyze the cross-correlation of the distortion noises for the case that the transmitted signals are correlated. This case arises when there is just a single stream being transmitted with beamforming or in the case of multiple streams and linear precoding. We analyze the problem in two ways: using analytical derivations and using measurements on our testbed. In the analytical case we assume a transmitter impaired by a 3rd order non-linearity. For this scenario we find that the absolute correlation coefficient of the distortion noises is given by the absolute value of the correlation coefficients of the input signals to the power of three, while the phase is the same as that of the input signal. Our measurements also show good agreement between measurements and analytical results. It seems to suggest that the distortion noises can be regarded as practically independent whenever there are two or more modulation streams being transmitted (spatial multiplexing). In a single-stream scenario, the distortion noise will tend to have the same spatial distribution as the desired signal.

  • 196.
    Nader, Charles
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. University of Gävle, Sweden; Vrije Universiteit Brussel,, Belgium.
    Björsell, Niclas
    University of Gävle, Sweden.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Unfolding the Frequency Spectrum for Undersampled Wideband Data2011In: Signal Processing, ISSN 0165-1684, E-ISSN 1872-7557, Vol. 91, no 5, p. 1347-1350Article in journal (Refereed)
    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.

  • 197.
    Nader, Charles
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Gävle, Sweden.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Gävle, Sweden.
    Björsell, Niclas
    Center for RF Measurement Technology, University of Gävle.
    OFDM PAPR Reduction by Convex Optimization: A power amplifier point-of-view2010In: 2010 IEEE International Microwave Workshop Series on "RF Front-ends for Software Defined and Cognitive Radio Solutions", IMWS 2010 - Proceedings, IEEE , 2010, p. 81-84Conference paper (Refereed)
    Abstract [en]

    In this paper we evaluate the application of convex optimization for PAPR reduction on OFDM 802.11a signal type. A radio frequency power amplifier is measured and characterized while excited by both original and optimized OFDM signals. A state-of-art test setup was used for the purpose. Figure of merits such as power added efficiency, in-band errors, and out-of-band spectral emissions are investigated for their relevance and a study of the power distribution in the excitation signal is evaluated.

  • 198.
    Nader, Charles
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Björsell, Niclas
    University of Gävle, Radio center for measurement technology.
    Peak-to-average power reduction of OFDM signals by convex optimization: experimental validation and performance optimization2011In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 60, no 2, p. 473-479Article in journal (Refereed)
    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.

  • 199.
    Nader, Charles
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Landin, Per
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Björsell, Niclas
    Center for RF Measurement Technology, University of Gävle.
    Isaksson, Magnus
    Center for RF Measurement Technology, University of Gävle.
    Wisell, David
    Ericsson AB, Stockholm.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Andersen, Olav
    Keskitalo, Niclas
    Ericsson AB, Gävle.
    Wideband power amplifier charaterization by undersampling: Zu-Frank sampling theorem2009Conference paper (Refereed)
    Abstract [en]

    In this paper a power amplifier is measured and characterized by the use of the generalized Zhu-Frank sampling theorem. A specially designed test-bed has been used allowing the bandwidth of the stimuli signal to be 100 MHz in the characterization process.

  • 200.
    Nader, Charles
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Landin, Per Niklas
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Van Moer, Wendy
    Vrije Universiteit Brussel, ELEC department.
    Björsell, Niclas
    University of Gävle, Radio center for measurement technology.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Performance Evaluation of Peak-to-Average Power Ratio Reduction and Digital Pre-Distortion for OFDM Based Systems2011In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 59, no 12, p. 3504-3511Article in journal (Refereed)
    Abstract [en]

    In this paper, we evaluate the effect of applying peak-to-average power ratio (PAPR) reduction and digital pre-distortion (DPD) on two types of radio frequency power amplifiers when an orthogonal frequency division multiplexing (OFDM) signal is used. The power amplifiers under test are a standard class-AB amplifier and a Doherty amplifier. The PAPR reduction methods are based on a state-of-the art convex optimization formulation and on the standard clipping and filtering technique. The DPD method consists of modeling the behavior of the power amplifier using a parallel Hammerstein model, and then extracting the inverse parameters based on the indirect learning architecture. To achieve better DPD performance, extracting the DPD parameters based on multiple-step iterations is investigated. The cases where PAPR reduction and DPD are applied separately and combined are studied and investigated. Power amplifier figures of merit are evaluated. Good performance is shown when combining both pre-processing techniques up to a certain operating point where DPD performance deteriorates due to generation of strong peaks in the signal. In addition, a difference in the power amplifier behavior is reported and analyzed.

1234567 151 - 200 of 343
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • 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