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  • 51.
    Krishnan, Rakesh
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Robotics, Perception and Learning, School of Computer Science and Communication, KTH - Royal Institute of Technology, Stockholm, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    SHAPE Algorithm for Approximate Computation of Angular Velocities in Humeral Motion2017Inngår i: 2017 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), IEEE, 2017, s. 714-718Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Estimating human motion is an area of emerging interest in instrumentation and measurement. Importantly, in such applications the physicality of the solution is paramount. Therefore, our paper proposes the SHAPE algorithm to estimate angular velocities of a moving segment from a cluster of passive markers used in a standard motion capture system known as stereophotogrammetry. We demonstrate the efficacy of our formulation with reference to the well known shape-matching algorithm in computer graphics. It is shown that our method is superior over the shape-matching algorithm.

  • 52.
    Krishnan, Rakesh
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik. Robotics, Perception and Learning, School of Computer Science and Communication, KTH - Royal Institute of Technology, Stockholm, Sweden; BioMEx Center, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik.
    Gutierrez-Farewik, Elena
    KTH Engineering Sciences, Mechanics, Royal Institute of Technology (KTH), Stockholm, Sweden; BioMEx Center, Royal Institute of Technology (KTH), Stockholm, Sweden .
    Smith, Christian
    Robotics, Perception and Learning, School of Computer Science and Communication, KTH - Royal Institute of Technology, Stockholm, Sweden; BioMEx Center, Royal Institute of Technology (KTH), Stockholm, Sweden.
    A survey of human shoulder functional kinematic representations2019Inngår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 57, nr 2, s. 339-367Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    In this survey, we review the field of human shoulder functional kinematic representations. The central question of this review is to evaluate whether the current approaches in shoulder kinematics can meet the high-reliability computational challenge. This challenge is posed by applications such as robot-assisted rehabilitation. Currently, the role of kinematic representations in such applications has been mostly overlooked. Therefore, we have systematically searched and summarised the existing literature on shoulder kinematics. The shoulder is an important functional joint, and its large range of motion (ROM) poses several mathematical and practical challenges. Frequently, in kinematic analysis, the role of the shoulder articulation is approximated to a ball-and-socket joint. Following the high-reliability computational challenge, our review challenges this inappropriate use of reductionism. Therefore, we propose that this challenge could be met by kinematic representations, that are redundant, that use an active interpretation and that emphasise on functional understanding.

  • 53.
    Krishnan, Rakesh
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Robotics, Perception and Learning, School of Computer Science and Communication, KTH - Royal Institute of Technology, Stockholm, Sweden..
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Smith, Christian
    Robotics, Perception and Learning, School of Computer Science and Communication, KTH - Royal Institute of Technology, Stockholm, Sweden.
    How do we plan movements?: A geometric answer2016Inngår i: School and symposium on advanced neurorehabilitation (SSNR2016): Proceedings, 2016, , s. 2s. 16-17Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Human movement is essentially a complex phenomenon. When humans work closely with robots, understanding human motion using robot’s sensors is a very challenging problem. This is partially due to the lack of proper consensus among researchers on which representation to use in such situations. This extended abstract presents a novel kinematic framework to study human intention using hybrid twists. Thisis important as the functional aspects of the human shoulder are evaluated using the information embedded in thoraco-humeral kinematics. We successfully demonstrate that our approach is singularity free. We also demonstrate that how the twis tparameters vary according to the movement being performed.

  • 54.
    Krishnan, Rakesh
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Robotics, Perception and Learning, School of Computer Science and Communication, KTH - Royal Institute of Technology, Stockholm, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Smith, Christian
    Robotics, Perception and Learning, School of Computer Science and Communication, KTH - Royal Institute of Technology, Stockholm, Sweden.
    Human shoulder functional kinematics: Are we ready for the high-reliability computational challenge?2016Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In  this  preview  talk,  I  will  present  a  short  summary  of  our  ongoing  work  related  to  human shoulder functional kinematics.  Robot-assisted rehabilitation needs functional understanding of human kinematics in design, operation and evaluation of this technology. Human shoulder is an important  functional  joint  that  enables  fine  motor  skills  for  human  upper  arm  manipulation. Due  to  several  mathematical  and  practical  challenges,  the  shoulder  kinematics  is  often oversimplified. Moreover, there is a lack of agreement among different research communities on  the  suitable  kinematic  representation  when  connecting  humans  to  robots.  Currently,  it  is expected  that  this  computational  structure  used  in  such  applications  have  high-reliability. Therefore,  we  pose  the  question:  Are  we  ready  for  the  high-reliability  computational challenge?

  • 55.
    Krishnan, Rakesh
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Computer Vision and Active Perception Lab, School of Computer Science and Communication, KTH - Royal Institute of Technology, Stockholm, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Smith, Christian
    Computer Vision and Active Perception Lab, School of Computer Science and Communication, KTH- Royal Institute of Technology.
    Invariant Spatial Parametrization of Human Thoracohumeral Kinematics: A Feasibility Study2016Inngår i: 2016 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), IEEE Robotics and Automation Society, 2016, s. 4469-4476, artikkel-id 7759658Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we present a novel kinematic framework using hybrid twists, that has the potential to improve the reliability of estimated human shoulderkinematics. This is important as the functional aspects ofthe human shoulder are evaluated using the information embedded in thoracohumeral kinematics. We successfully demonstrate in our results, that our approach is invariant of the body-fixed coordinate definition, is singularity free and has high repeatability; thus resulting in a flexible user-specific kinematic tracking not restricted to bony landmarks.

  • 56.
    Krishnan, Rakesh
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Robotics, Perception and Learning, School of Computer Science and Communication, KTH - Royal Institute of Technology, Stockholm, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Smith, Christian
    Robotics, Perception and Learning, School of Computer Science and Communication, KTH - Royal Institute of Technology, Stockholm, Sweden.
    Segmenting humeral submovements using invariant geometric signatures2017Inngår i: 2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (Iros) / [ed] Bicchi, A., Okamura, A., IEEE, 2017, s. 6951-6958, artikkel-id 8206619Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Discrete submovements are the building blocks of any complex movement. When robots collaborate with humans, extraction of such submovements can bevery helpful in applications such as robot-assisted rehabilitation. Our work aims to segment these submovements based on the invariant geometric information embedded in segment kinematics. Moreover, this segmentation is achieved without any explicit kinematic representation.Our work demonstrates the usefulness of this invariant framework in segmenting a variety of humeral movements, which are performed at different speeds across different subjects. Our results indicate that this invariant framework has high computational reliability despite the inherent variability in human motion.

  • 57.
    Krishnan, Rakesh
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik.
    Cruciani, Silvia
    KTH, Stockholm, Sweden.
    Gutierrez-Farewik, Elena M
    KTH, Stockholm, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik.
    Smith, Christian
    KTH, Stockholm, Sweden.
    Reliably Segmenting Motion Reversals of a Rigid-IMU Cluster Using Screw-Based Invariants2019Inngår i: 2018 IEEE-RAS 18TH INTERNATIONAL CONFERENCE ON HUMANOID ROBOTS (HUMANOIDS), 2019, s. 88-95, artikkel-id 8624969Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Human-robot interaction (HRI) is moving towards the human-robot synchronization challenge. In robots like exoskeletons, this challenge translates to the reliable motion segmentation problem using wearable devices. Therefore, our paper explores the possibility of segmenting the motion reversals of a rigid-IMU cluster using screw-based invariants. Moreover, we evaluate the reliability of this framework with regard to the sensor placement, speed and type of motion. Overall, our results show that the screw-based invariants can reliably segment the motion reversals of a rigid-IMU cluster.

  • 58.
    Landin, Per
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Nader, Charles
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    Björsell, Niklas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Isaksson, Magnus
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Händel, Peter
    KTH Royal Institute of Technology.
    Overview of Synergetic OFDM Crest Factor Reduction and DigitalPre-Distortion for RF PAs2011Inngår i: RFMTC11, 2011Konferansepaper (Annet vitenskapelig)
    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.

  • 59.
    Landin, Per Niklas
    et al.
    Högskolan i Gävle, Radio Center Gävle.
    Nader, Charles
    Högskolan i Gävle, Radio Center Gävle.
    Björsell, Niclas
    Högskolan i Gävle, Radio Center Gävle.
    Isaksson, Magnus
    Högskolan i Gävle, Radio Center Gävle.
    Wisell, David
    Ericsson AB.
    Händel, Peter
    Högskolan i Gävle, Radio Center Gävle.
    Andersen, Olav
    Ericsson AB.
    Keskitalo, Niclas
    Högskolan i Gävle, Radio Center Gävle.
    Wideband Characterization of Power Amplifiers Using Undersampling2009Inngår i: 2009 IEEE MTT-S International Microwave Symposium, Boston: IEEE MTT , 2009, s. 1365-1368Konferansepaper (Fagfellevurdert)
    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.

  • 60.
    Luque, Carolina
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Improved dynamic range for multi-tone signal using model-based pre-distortion2009Inngår i: Metrology and measurement systems, ISSN 0860-8229, Vol. 16, nr 1, s. 129-141Artikkel i tidsskrift (Fagfellevurdert)
  • 61.
    Luque, Carolina
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Improved dynamic range for multi-tone signal using model-based pre-distortion2008Inngår i: Proceedings of the 13th Workshop on ADC Modelling and Testing, 2008, s. 1003-1007Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Some test and measurement applications require higher dynamic range for multi-tone signals than a signal generator can generate. Moreover, for other applications it can be interesting to improve the performance of a “low cost” signal generator. The spectral purity of generated signals can be improved by using pre-distorted base-band signals. In this paper, a dynamic grey-box model is described. A pre-distorter is used in order to improve the dynamic range. The results, which are based on measurements, show an improved dynamic range for a three-tone signal of approximately 9 dB and an improved ACPR of 5 dB for a WCDMA signal.

  • 62.
    Luque, Carolina
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Model-Based Pre-Distortion for Signal Generators2008Inngår i: GigaHertz Symposium 2008: abstract book, Göteborg: Chalmers , 2008, s. 88-88Konferansepaper (Fagfellevurdert)
  • 63.
    Mattsson, Per
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik.
    Zachariah, Dave
    Department of Information Technology, Uppsala University, Uppsala, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik.
    Flexible Models for Smart Maintenance2019Inngår i: Proceedings 2019 IEEE International Conference on Industrial Technology (ICIT), IEEE, 2019, s. 1772-1777Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Smart maintenance strategies are becoming increasingly important in the industry, and can contribute to environmentally and economically sustainable production. In this paper a recently developed latent variable framework for nonlinear-system identification is considered for use in smart maintenance. A model is first identified using data from a system operating under normal conditions. Then the identified model is used to detect when the system begins to deviate from normal behavior. Furthermore, for systems that operate on separate batches (units), we develop a new method that identifies individual models for each batch. This can be used both to detect anomalous batches and changes in the system behavior. Finally, the two methods are evaluated on two different industrial case studies. In the first, the purpose is to detect fouling in a heat exchanger. In the second, the goal is to detect when the tool in a wood moulder machine should be changed.

  • 64. Medawar, Samer
    et al.
    Björsell, Niclas
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Händel, Peter
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Jansson, Magnus
    Dynamic characterization of analog-digital-converters2007Inngår i: Mosharaka International Conference on Wireless Communications and Mobile Computing, 2007Konferansepaper (Fagfellevurdert)
  • 65. Medawar, Samer
    et al.
    Händel, Peter
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Jansson, Magnus
    ADC characterization by dynamic integral nonlinearity2008Inngår i: Proceedings of the 13th Workshop on ADC Modelling and Testing, 2008, s. 1037-1042Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Wide band characterization of analog-digital converter integral nonlinearity (INL) based on parametric modeling and least-squares parameter t is performed. In particular, the variations in the INL due to the frequency of the ADC stimuli are modeled. The INL is divided into two main entities describing the static and dynamic behavior of the ADC, respectively. The static component is modeled by a high code component (HCF) of piecewise linear segments centered 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 implementation is considered and is applied to 12-bit ADC data at 210 MSPS.

  • 66.
    Medawar, Samer
    et al.
    Signal Processing Laboratory, ACCESS Linnaeus Center, Royal Institute of Technology, Stockholm, Sweden.
    Händel, Peter
    Signal Processing Laboratory, ACCESS Linnaeus Center, Royal Institute of Technology, Stockholm, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Jansson, Magnus
    Signal Processing Laboratory, ACCESS Linnaeus Center, Royal Institute of Technology, Stockholm, Sweden.
    Input Dependent Integral Nonlinearity Modeling for Pipelined Analog-Digital Converters2010Inngår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 59, nr 10, s. 2609-2620Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 67.
    Medawar, Samer
    et al.
    Signal Processing Lab, ACCESS Linnaeus Center, Stockholm, Sweden.
    Händel, Peter
    Signal Processing Lab, ACCESS Linnaeus Center, Stockholm, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Jansson, Magnus
    Signal Processing Lab, ACCESS Linnaeus Center, Stockholm, Sweden.
    Model order determination and segmentation of analog-digital converters integral non linearity2010Inngår i: 2010 IEEE International Instrumentation and Measurement Technology Conference, I2MTC 2010: Proceedings, 2010, s. 36-41, artikkel-id 5488188Konferansepaper (Fagfellevurdert)
    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).

  • 68.
    Medawar, Samer
    et al.
    Signal Processing Lab, ACCESS Linnaeus Center, Royal Institute of Technology.
    Händel, Peter
    Signal Processing Lab, ACCESS Linnaeus Center, Royal Institute of Technology.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Jansson, Magnus
    Signal Processing Lab, ACCESS Linnaeus Center, Royal Institute of Technology.
    Pipelined Analog-Digital Converters Integral Nonlinearity Modeling for Post-Correction2010Inngår i: 17th Symposium IMEKO TC4 - Measurement of Electrical Quantities, 15th International Workshop on ADC Modelling and Testing, and 3rd Symposium IMEKO TC19: Environmental Measurements / [ed] Linus Michaeli, Jan Saliga, 2010, s. 585-590Konferansepaper (Fagfellevurdert)
    Abstract [en]

    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 out of the ADC digital output for compensation. Static compensation is performed by adjacent sets of gains and offsets. Each set compensates an output code k range. The frequency content of the INL dynamic component is used to design a set of filters 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). Performance improvements in terms of spurious free dynamic range (SFDR), signal-to-noise and Distortion ratio (SINAD), intermodulation istortion (IMD) are obtained.

  • 69.
    Medawar, Samer
    et al.
    Signal Processing Laboratory, ACCESS Linnaeus Center, Royal Institute of Technology, Stockholm, Sweden.
    Händel, Peter
    Signal Processing Laboratory, ACCESS Linnaeus Center, Royal Institute of Technology, Stockholm, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Jansson, Magnus
    Signal Processing Laboratory, ACCESS Linnaeus Center, Royal Institute of Technology, Stockholm, Sweden.
    Postcorrection of Pipelined Analog–Digital Converters Based on Input-Dependent Integral Nonlinearity Modeling2011Inngår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 60, nr 10, s. 3342-3350Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 70.
    Medawar, Samer
    et al.
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Händel, Peter
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Royal Institute of Technology (KTH), Stockholm, Sweden.
    Murmann, Boris
    Stanford University.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Jansson, Magnus
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Dynamic Calibration of Undersampled Pipelined ADCs by Frequency Domain Filtering2013Inngår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 62, nr 7, s. 1882-1891Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Integral nonlinearity (INL) is used for the postcorrection of pipeline analog-digital converters (ADCs). An input-frequency-dependent INL model is developed for the compensation. 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 signal frequency. The INL model is subtracted from the digital output for postcorrection. The static compensation is implemented with a look-up-table. The dynamic calibration is performed by a bank of frequency domain filters using an overlap-add structure. Two ADCs of the same type (Analog Devices AD9430) are compensated for in the first three Nyquist bands. The performance improvements in terms of spurious-free dynamic range and intermodulation distortion are investigated. Using the proposed method, improvements up to 17 dB are reported in favorable scenarios.

  • 71.
    Medawar, Samer
    et al.
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Murmann, Boris
    Stanford University.
    Händel, Peter
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Jansson, Magnus
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Static Integral Nonlinearity Modeling and Calibration of Measured and Synthetic Pipeline Analog-to-Digital Converters2014Inngår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 63, nr 3, s. 502-511Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The integral nonlinearity (INL) modeling of pipeline analog-digital converters (ADCs) is investigated in this paper. The INL is divided into two distinct entities: a low code frequency component (LCF) 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 (SFDR) 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 resultsshow that the developed HCF models can achieve virtually complete calibration of the considered ADC.

  • 72.
    Nader, Charles
    et al.
    Högskolan i Gävle, Radio Center Gävle.
    Altahir, Hibah
    Högskolan i Gävle, Radio Center Gävle.
    Andersen, Olav
    Ericsson AB.
    Björsell, Niclas
    Högskolan i Gävle, Radio Center Gävle.
    Condo, Edith
    Högskolan i Gävle, Radio Center Gävle.
    Keskitalo, Niclas
    Högskolan i Gävle, Radio Center Gävle.
    De La Rosa, Hector
    Freescale Semiconductor Nordic AB.
    Automated multidimensional characterization of power amplifier for design and production2009Inngår i: 2009 IEEE Instrumentation and Measurement Technology Conference Proceedings, Singapore: I&M Society , 2009, s. 144-148Konferansepaper (Fagfellevurdert)
    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.

  • 73.
    Nader, Charles
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Händel, Peter
    Royal Insstitute of Technology, Signal Processing Lab.
    Unfolding the frequency spectrum of undersampled wideband data2011Inngår i: Signal Processing, ISSN 0165-1684, E-ISSN 1872-7557, Vol. 91, nr 5, s. 1347-1350Artikkel i tidsskrift (Fagfellevurdert)
    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. (C) 2010 Elsevier B.V. All rights reserved.

  • 74.
    Nader, Charles
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Händel, Peter
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    OFDM PAPR Reduction by Convex Optimization: A Power Amplifier Point-of-View2010Inngår i: 2010 IEEE International Microwave Workshop Series on "RF Front-ends for Software Defined and Cognitive Radio Solutions": IMWS 2010 - Proceedings, 2010Konferansepaper (Fagfellevurdert)
    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. Improvements in power added efficiency, in-band errors, out-of-band spectral emissions are investigated for their relevance and a study of the power distribution in the excitation signal is evaluated.

  • 75.
    Nader, Charles
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Händel, Peter
    Kungliga Tekniska högskolan.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Peak-to-average power reduction of OFDM signals by convex optimization: experimental validation and performance optimization2011Inngår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 60, nr 2, s. 473-479Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 76.
    Nader, Charles
    et al.
    Högskolan i Gävle, Radio Center Gävle. Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Landin, Per Niklas
    Högskolan i Gävle, Radio Center Gävle. Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Radio Center Gävle. Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Isaksson, Magnus
    Högskolan i Gävle, Radio Center Gävle. Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Wisell, David
    Ericsson AB.
    Händel, Peter
    KTH, EES, Signal processing lab.
    Andersen, Olav
    Ericsson AB.
    Keskitalo, Niclas
    Högskolan i Gävle, Radio Center Gävle.
    Wideband Power Amplifiers Characterization by Undersampling: Zhu-Frank Sampling Theorem2009Konferansepaper (Annet vitenskapelig)
  • 77.
    Nader, Charles
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Landin, Per Niklas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Van Moer, Wendy
    Vrije Universiteit Brussel .
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Händel, Peter
    Royal Institute of Technology, Signal Processing Lab.
    Rönnow, Daniel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Peak-power Controlling Technique for Enhancing Digital Pre-distortion of RF Power Amplifiers2012Inngår i: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 60, nr 11, s. 3571-3581Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we present a method to limit the generation of signal peak power at the output of a digital pre-distorter that is applied to a RF power amplifier (PA) operating in strong compression. The method can be considered as a joint crest-factor reduction and digital pre-distortion (DPD). A challenging characteristic of DPD when applied to a PA in strong compression is the generation of relatively high peaks due to the DPD expansion behavior. Such high peaks generation, which may be physically unrealistic, can easily damage the amplification system. Such a phenomenon, referred in this study as DPD-avalanche, is more noticed when the signal exciting the PA is compressed due to crest-factor reduction. The suggested method for controlling such DPD-avalanche is based on shaping the input signal to the DPD in such a way to keep the pre-distorted signal peak power below or near the maximum allowed peak power of the PA. The suggested method is tested experimentally on a Class-AB and a Doherty PA when excited with a wideband orthogonal frequency-division multiplexing (OFDM) signal. Scenarios for an OFDM signal with and without crest-factor reduction are evaluated. Measurement results when using the proposed DPD-avalanche controller show smooth deterioration of the in-band and out-of-band linearity compared to steep deterioration when no controller is used. In addition, the suggested controller offers a higher operating power range of the DPD while fulfilling out-of-band distortion requirements and preserving low in-band error.

  • 78.
    Nader, Charles
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Landin, Per
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Van Moer, Wendy
    Vrije Universiteit Brussel .
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Händel, Peter
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Isaksson, Magnus
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Peak-to-average power ratio reduction versus digital pre-distortion in OFDM based systems2011Inngår i: 2011 IEEE MTT-s International Microwave Symposium, Institute of Electrical and Electronics Engineers Inc , 2011, s. 5972830-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we evaluate the effect of applying peak-to-average power ratio (PAPR) reduction and digital pre-distortion (DPD) on RF power amplifiers when an OFDM signal is used. The cases where PAPR and DPD are applied separately and combined, are studied and investigated. Good performance is shown when combining both pre-processing techniques up to a certain operating point where DPD performance deteriorates. Solutions to improve the DPD performance at strong compression are suggested.

  • 79.
    Nader, Charles
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Landin, Per
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    Björsell, Niklas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Händel, Peter
    KTH Royal Institute of Technology.
    Performance Evaluation of Peak-to-Average Power Ratio Reduction and Digital Pre-Distortion for OFDM Based Systems2011Inngår i: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 59, nr 2, s. 3504-3511Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 80.
    Nader, Charles
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Van Moer, Wendy
    Vrije Universiteit Brussel .
    Barbé, Kurt
    Vrije Universiteit Brussel .
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Händel, Peter
    Characterizing the out-of-band nonlinear behaviour of RF devices: the key to success2011Inngår i: 2011 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), New York: IEEE conference proceedings, 2011, s. 790-794Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a measurement recipe to characterize the out-of-band nonlinear behavior of RF devices when harmonic sampling is used as a digitizing technique. A major challenge to consider when using harmonic sampling is the overlapping of the aliased spectral bins of the digitized waveform. This challenge is more pronounced when using modulated excitation signals. In addition, the excitation signal used should mimic the real behavior of signals used in today's wireless systems. Hence, this paper provides the reader with a tool to select the proper excitation signal, sampling frequency and record length in order to achieve an accurate characterization of the nonlinear behavior of RF devices.

  • 81.
    Nader, Charles
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    Barbé, Kurt
    Vrije Universiteit Brussel.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Händel, Peter
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Evolved Harmonic Sampling: a Tool to Reduce the Digital Bandwidth Requirement of RF Receivers2011Inngår i: RFMTC11, Gävle, 2011Konferansepaper (Annet vitenskapelig)
  • 82.
    Nader, Charles
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Van Moer, Wendy
    Vrije Universiteit Brussel .
    Barbé, Kurt
    Vrije Universiteit Brussel .
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Händel, Peter
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Harmonic Sampling and Reconstruction of Wide-band Undersampled Waveforms: Breaking the Code2011Inngår i: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 59, nr 11, s. 2961-2969Artikkel i tidsskrift (Fagfellevurdert)
  • 83.
    Nader, Charles
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Van Moer, Wendy
    Vrije Universiteit Brussel .
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Barbé, Kurt
    Vrije Universiteit Brussel .
    Händel, Peter
    Royal Insstitute of Technology, Signal Processing Lab.
    Reducing The Analog and Digital Bandwidth Requirements of RF Receivers for Measuring Periodic Sparse Waveforms2012Inngår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 61, nr 11, s. 2960-2971Artikkel i tidsskrift (Fagfellevurdert)
  • 84.
    Nader, Charles
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Van Moer, Wendy
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Händel, Peter
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Wideband Radio Frequency Measurements: From Instrumentation to Sampling Theory2013Inngår i: IEEE Microwave Magazine, ISSN 1527-3342, E-ISSN 1557-9581, Vol. 14, nr 2, s. 85-98Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Whether listening to broadcast radio or testing developed wireless devices, for civilian or military applications, based on terrestrial or spatial links, a radio frequency (RF) receiver with good measurement capabilities that preserves the received signal information is required. Todays RF measurement receivers with wideband capabilities are split into two groups based on the measurement strategy they adopt. Both groups produce a time domain waveform with both amplitude and phase information that is constructed either from a transformation of its frequency contents or directly from its time-domain samples.

  • 85.
    Panigrahi, Smruti Ranjan
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik.
    Bengtsson, Mats
    KTH Royal Institute of Technology, Stockholm, Sweden .
    Data Fusion in the Air With Non-Identical Wireless Sensors2019Inngår i: IEEE Transactions on Signal and Information Processing over Networks, ISSN 2373-776X, Vol. 5, nr 4, s. 646-656Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, a multi-hypothesis distributed detection technique with non-identical local detectors is investigated. Here, for a global event, some of the sensors/detectors can observe the whole set of hypotheses, whereas the remaining sensors can either see only some aspects of the global event or infer more than one hypothesis as a single hypothesis. Another possible option is that different sensors provide complementary information. The local decisions are sent over a multiple access radio channel so that the data fusion is formed in the air before reaching the decision fusion center (DFC). An optimal energy fusion rule is formulated by considering the radio channel effects and the reliability of the sensors together, and a closed-form solution is derived. A receive beamforming algorithm, based on a modification of Lozano's algorithm, is proposed to equalize the channel gains from different sensors. Sensors with limited detection capabilities are found to boost the overall system performance when they are used along with fully capable sensors. The additional transmit power used by these sensors is compensated by the designed fusion rule and the antenna array gain. Additionally, the DFC, equipped with a large antenna array, can reduce the overall transmit energy consumption without sacrificing the detection performance.

  • 86.
    Panigrahi, Smruti Ranjan
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik. School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik.
    Bengtsson, Mats
    School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Sweden.
    Distributed detection with non-identical wireless sensors for industrial applications2019Inngår i: Proceedings of the IEEE International Conference on Industrial Technology, IEEE, 2019, s. 1403-1408Konferansepaper (Fagfellevurdert)
    Abstract [en]

    There has been very little exploration when it comes to design distributed detection techniques and data fusion rules with non-identical sensors. This concept can be utilized in many possible applications within industrial automation, surveillance and safety. Here, for a global event, some of the sensors/detectors in the network can observe the full set of the hypotheses, whereas the remaining sensors infer more than one hypotheses as a single hypothesis. The local decisions are sent to the decision fusion center (DFC) over a multiple access wireless channel. In this paper, a fusion rule based on minimization of variance of the local mis-detection is proposed. The presence of sensors with limited detection capabilities is found to have a positive impact on the overall system performance, both in terms of probability of detection and transmit power consumption. Additionally, when the DFC is equipped with a large antenna array, the overall transmit power consumption can be reduced without sacrificing the detection performance. 

  • 87.
    Panigrahi, Smruti Ranjan
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. School of Electrical Engineering, KTH Royal Institute of Technology, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Bengtsson, Mats
    School of Electrical Engineering, KTH Royal Institute of Technology, Sweden.
    Feasibility of Large Antenna Arrays towards Low Latency Ultra Reliable Communication2017Inngår i: 2017 IEEE INTERNATIONAL CONFERENCE ON INDUSTRIAL TECHNOLOGY (ICIT), 2017, s. 1289-1294, artikkel-id 7915549Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Industrial automation and safety applications demand low latency and ultra reliable communication. Currently deployed wireless communication technologies are mostly developed for non-critical applications and hence, they are not suitable for these kind of applications. On the other hand, cable based communication is widely popular in industries, even though it has limitations towards cost of installment and is susceptible towards mechanical wear and tear. This paper reviews the feasibility of large antenna arrays at the receiver to achieve low latency and ultra reliable communication for up-link scenarios. The suitability of both coherent and non-coherent multiple input multiple output (MIMO) receivers are investigated. Non-coherent MIMO receiver is found to be a promising option as signal to noise power ratio (SNR) is fairly reasonable in achieving the desired reliability. The effect of antenna correlation at the transmitter and at receiver on reliability are also looked into. Its influence on the system performance is very nominal. Moreover, in certain scenarios, antenna correlation at the transmitter gives a significant improvement in system performance. Furthermore, having a single antenna at the sensors is found not to be a limiting factor in achieving the desired performance goal.

  • 88.
    Qin, X.
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Measurement of horses gaits using geo-sensors2015Inngår i: 2015 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), 2015, s. 330-333Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The aim of this thesis is to determine the horse's gait types using the acceleration values measured from the horse. Measurements were taken at a race track in Gävle, Sweden. A total of five Nanotrak sensors were used, four on the different parts of the horse, and one on the hand of the horse's driver; a car was driven parallel to the horse and the motions of the horse was recorded by a camera in order to synchronize with the data measured by the sensors. In total four sets of measurements were recorded. The software to process the data was Matlab, and the main mathematical tool to analyze it was Short Time Fourier Transform (STFT), different windows were evaluated as well as the data length. The method for classification of horse's gaits was categorized as amplitude of the fundamental frequency component. The method shows promising results with a misclassification below one percent. However, higher sampling rate, more measurements and more analysis are needed to be done in the future to find a proper way to automatic determine the horse's gaits. 

  • 89.
    Rönnow, Daniel
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Laporte-Fauret, Baptiste
    Bordeaux INP, Enseirb-Matmeca Bordeaux, France.
    Determination of elongation of electrically smallobjects in building structures by polarimetric synthetic aperture radar2017Inngår i: I2MTC 2017 - 2017 IEEE International Instrumentation and Measurement Technology Conference: Proceedings, Torino: IEEE, 2017, s. 1520-1524, artikkel-id 7969898Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Short range synthetic aperture radar (SAR) wasused to study electrically small objects. A metallic rod and a metallic sphere could not be separated in the SAR images. Polarimetric SAR images were analyzed and images corresponding to different antenna orientations were obtained by applying rotation matrices to radar data. The target intensity varied with the rotation angle. Elongation and orientation of the objects could be determined from the ratio of minimum andmaximum intensity. Upper and lower limits for measurable elongation depend on measurement errors.

  • 90.
    Siddiq, Musab
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Synthetic Instruments: an overview2008Inngår i: Nordic Test Forum 2008, 2008Konferansepaper (Fagfellevurdert)
  • 91.
    Van Moer, Wendy
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Vrije Universiteit Brussel.
    Barbe, Kurt
    Vrije Universiteit Brussel.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    A novel spectral subtraction technique for cognitive radios2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the past a lot of work has been done to remove noise from speech. Most of the presented techniques were derived from Boll's spectral subtraction technique. Roughly speaking the spectral subtraction techniques consists of estimating the noise power during the periods when no speech is present and subtracting this estimate of the noise power from the signal when speech is present. This spectral subtraction technique could be a very good in-band de-noising technique for communication signals measured by cognitive radios. However, there is one major drawback: one can never turn off the spectrum so that no communication signals are present. This paper presents an extended version of the spectral subtraction technique which does not require `speech free?? periods, but can determine the noise power from the empty frequency bins in the spectrum. The presented method is based on an autoregressive (AR) model, which is linear in the parameters. Simulation results show that the presented technique is as performing as the original spectral subtraction techniques without the need to turn off the signals.

  • 92.
    Van Moer, Wendy
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Hamid, Mohamed
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Barbe, Kurt
    Vrije Universiteit Brussel, ELEC.
    Nader, Charles
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Saving lives by integrating cognitive radios into ambulances2012Inngår i: Medical Measurements and Applications Proceedings (MeMeA), 2012 IEEE International Symposium on, Budapest, 2012, s. 1-4Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A brain stroke is defined as a disturbance in the blood supply of the brain. This can be due to either an obstruction in the blood vessels of the brain or a rupture in the blood vessels which causes a leakage of blood in the brain. In many cases, a stroke results in the death of the patient within 24 hours. Hence, it is crucial that the neurologist has immediately contact with the patient in the first 30 minutes after the stroke. This means that a direct broadband communication link between the ambulance and the hospital is needed in order to transmit all necessary physiological parameters, such as blood pressure and glucose level as well as video images. In this paper, we present a new architecture of a wireless communication link between the ambulance and the hospital based on the concept of cognitive radios. The sender/receiver module in the ambulance will allow measuring the wideband spectrum and search for a suitable empty frequency band to send the data.

  • 93.
    Voet, Kevin
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Vrije Universiteit Brussel, Brussels, Belgium; Signal Processing Lab, Royal Institute of Technology, Stockholm, Sweden.
    Händel, Peter
    Signal Processing Lab, Royal Institute of Technology, Stockholm, Sweden.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Van Moer, Wendy
    Vrije Universiteit Brussel, Brussels, Belgium.
    Mirrored parallel Hammerstein predistortion for multitone generation2011Inngår i: 2011 IEEE INTERNATIONAL INSTRUMENTATION AND MEASUREMENT TECHNOLOGY CONFERENCE (I2MTC), 2011, s. 814-817Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper discusses the approach tested for digital pre-distortion of radio frequency vector signal generators, where joint mitigation of impairments is considered stemming from the inphase/quadrature modulator, local oscillator, and power amplifier. A predistorter structure, linear in its parameters, was taken and the parameters were estimated by the least-squares method. The proposed method is validated by demonstrating improvement in the performance of the Rohde & Schwarz SMU200 by about 8 dB reduction in mirror-frequency interference, 17 dB reduction in leakage from the local oscillator, and 6 dB improvement in inter-modulation products. Thus, the tested approach is considered useful for several instrumentation and measurement applications.

  • 94.
    Voet, Kevin
    et al.
    Vrije Universiteit Brussel.
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Händel, Peter
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Nonlinear Measurement Instruments: a Comparative Study2011Inngår i: RFMTC11, Gävle, 2011Konferansepaper (Annet vitenskapelig)
  • 95.
    Yang, Tingxiao
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    Zenteno, Efrain
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Royal Institute of Technology, KTH. Signal Processing Laboratory, Stockholm, Sweden .
    Björsell, Niclas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Measurement imperfections impact on the performance of digitally predistorted power amplifiers2014Inngår i: 2014 IEEE International Instrumentation and Measurement Technology Conference (I2MTC) Proceedings, 2014, s. 230-233Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents an study of the impact of analog to digital converter (ADC) impairments on digital pre-distortion (DPD) techniques when applied to RF power amplifiers (PA). The DPD technique is described by a memory polynomial model while the ADC impairments are modeled by quantization noise, random jitter, and the integral nonlinearity (INL); thus, summarizing systematic and random nature of ADC imperfect measurements. It is observed that increased jitter will have a negative impact on the modeling but not so much on the output performance from the pre-distorted PA. Moreover, the ENOB can be used as metric for both the quantization noise and integral nonlinearity and there is a value of ENOB which, if exceeded, do not improve the DPD performance; in this paper it is about 8 bits.

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