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  • 301. Völcker, Björn
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Frequency estimation by proper correlation lag constellations2000In: Proceedings Nordic Signal Processing Symposium, 2000, p. 449-452Conference paper (Refereed)
  • 302.
    Völcker, Björn
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Frequency estimation from proper sets of correlations2002In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 50, no 4, p. 791-802Article in journal (Refereed)
    Abstract [en]

    As a complement to the periodogram, low-complexity frequency estimators are of interest. One such estimator is based on Prony's method and rely on phase information of the auto correlations. Without prior knowledge of the frequency (e.g., a given frequency interval), the frequency cannot be unambiguously estimated from a single correlation only. In this paper, we introduce a new method of phase unwrapping using an arbitrary number (more than one) of correlations. From this arbitrary set of correlations, we propose a weighted average estimator. We derive the asymptotic performance and show how the correlation lags should be properly chosen. From a design aspect, there is often a restriction of using a fixed number of computations. In addition, we therefore propose a strategy to find a proper set of correlation lags subject to a given computational complexity. Finally, simulation results that lend support to the theoretical findings are included.

  • 303.
    Völcker, Björn
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    On design of correlation based frequency estimators2001In: 2001 IEEE WORKSHOP ON STATISTICAL SIGNAL PROCESSING PROCEEDINGS, NEW YORK: IEEE , 2001, p. 425-428Conference paper (Refereed)
    Abstract [en]

    As a complement to the Periodogram, low complexity frequency estimators are of interest. Different designs of these estimators may affect the performance significantly. In this paper we consider correlation based estimators and present a design strategy that outperforms most estimators in the same class. We give a closed form expression for the asymptotic performance together with a new method of phase unwrapping to resolve an introduced frequency ambiguity. Finally, we illustrate the performance through a design example.

  • 304.
    Völcker, Björn
    et al.
    KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Optimizing Correlation Based Frequency Estimators2002In: European Signal Processing Conference, ISSN 2219-5491, article id 7072095Article in journal (Refereed)
    Abstract [en]

    As a complement to the periodogram, low-complexity frequency estimators are of interest. One such estimator is based on Prony's method and rely on phase information of the auto-correlations. Both performance and computational complexity are functions of the choice of correlations used in the estimator and often we have a trade off situation. In this paper, frequency estimation from an arbitrary set of estimated auto-correlations is studied. We further introduce a design strategy by optimizing a performance criterion given a predetermined computational constraint. We illustrate this by numerical examples.

  • 305. Wahlström, J.
    et al.
    Jaldén, Joakim
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Skog, I.
    Händel, Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Alternative em Algorithms for Nonlinear State-Space Models2018In: 2018 21st International Conference on Information Fusion, FUSION 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 1260-1267Conference paper (Refereed)
    Abstract [en]

    The expectation-maximization algorithm is a commonly employed tool for system identification. However, for a large set of state-space models, the maximization step cannot be solved analytically. In these situations, a natural remedy is to make use of the expectation-maximization gradient algorithm, i.e., to replace the maximization step by a single iteration of Newton's method. We propose alternative expectation-maximization algorithms that replace the maximization step with a single iteration of some other well-known optimization method. These algorithms parallel the expectation-maximization gradient algorithm while relaxing the assumption of a concave objective function. The benefit of the proposed expectation-maximization algorithms is demonstrated with examples based on standard observation models in tracking and localization. 

  • 306. Wahlström, J.
    et al.
    Skog, I.
    Händel, Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Inertial Sensor Array Processing with Motion Models2018In: 2018 21st International Conference on Information Fusion, FUSION 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 788-793Conference paper (Refereed)
    Abstract [en]

    By arranging a large number of inertial sensors in an array and fusing their measurements, it is possible to create inertial sensor assemblies with a high performance-to-price ratio. Recently, a maximum likelihood estimator for fusing inertial array measurements collected at a given sampling instance was developed. In this paper, the maximum likelihood estimator is extended by introducing a motion model and deriving a maximum a posteriori estimator that jointly estimates the array dynamics at multiple sampling instances. Simulation examples are used to demonstrate that the proposed sensor fusion method have the potential to yield significant improvements in estimation accuracy. Further, by including the motion model, we resolve the sign ambiguity of gyro-free implementations, and thereby open up for implementations based on accelerometer-only arrays.

  • 307. Wahlström, J.
    et al.
    Skog, I.
    Händel, Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Inertial Sensor Array Processing with Motion Models2018In: 2018 21st International Conference on Information Fusion, FUSION 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 788-793Conference paper (Refereed)
    Abstract [en]

    By arranging a large number of inertial sensors in an array and fusing their measurements, it is possible to create inertial sensor assemblies with a high performance-to-price ratio. Recently, a maximum likelihood estimator for fusing inertial array measurements collected at a given sampling instance was developed. In this paper, the maximum likelihood estimator is extended by introducing a motion model and deriving a maximum a posteriori estimator that jointly estimates the array dynamics at multiple sampling instances. Simulation examples are used to demonstrate that the proposed sensor fusion method have the potential to yield significant improvements in estimation accuracy. Further, by including the motion model, we resolve the sign ambiguity of gyro-free implementations, and thereby open up for implementations based on accelerometer-only arrays. © 2018 ISIF

  • 308.
    Wahlström, Jens
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    La Rosa, Patricio S.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Nehorai, Arye
    The beta-Model-Maximum Likelihood, Cramer-Rao Bounds, and Hypothesis Testing2017In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 65, no 12, p. 3234-3246Article in journal (Refereed)
    Abstract [en]

    We study the maximum-likelihood estimator in a setting where the dependent variable is a random graph and covariates are available on a graph level. The model generalizes the well-known beta-model for random graphs by replacing the constant model parameters with regression functions. Cramer-Rao bounds are derived for special cases of the undirected beta-model, the directed beta-model, and the covariate-based beta-model. The corresponding maximum-likelihood estimators are compared with the bounds by means of simulations. Moreover, examples are given on how to use the presented maximum-likelihood estimators to test for directionality and significance. Finally, the applicability of the model is demonstrated using temporal social network data describing communication among healthcare workers.

  • 309.
    Wahlström, Johan
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skog, Isaac
    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.
    Detection of Dangerous Cornering in GNSS-Data-Driven Insurance Telematics2015In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 16, no 6Article in journal (Refereed)
    Abstract [en]

    We propose a framework for the detection of dangerous vehicle cornering events, based on statistics related to the no-sliding and no-rollover conditions. The input variables are estimated using an unscented Kalman filter applied to global navigation satellite system (GNSS) measurements of position, speed, and bearing. The resulting test statistic is evaluated in a field study where three smartphones are used as measurement probes. A general framework for performance evaluation and estimator calibration is presented as depending on a generic loss function. Furthermore, we introduce loss functions designed for applications aiming to either minimize the number of missed detections and false alarms, or to estimate the risk level in each cornering event. Finally, the performance characteristics of the estimator are presented as depending on the detection threshold, as well as on design parameters describing the driving behavior. Since the estimation only uses GNSS measurements, the framework is particularly well suited for smartphone-based insurance telematics applications, aiming to avoid the logistic and monetary costs associated with, e.g., on-board-diagnostics or black-box dependent solutions. The design of the estimation algorithm allows for instant feedback to be given to the driver and, hence, supports the inclusion of real-time value-added services in usage-based insurance programs.

  • 310.
    Wahlström, Johan
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Driving behavior analysis for smartphone-based insurance telematics2015In: WPA 2015 - Proceedings of the 2nd Workshop on Physical Analytics, ACM Digital Library, 2015, p. 19-24Conference paper (Refereed)
    Abstract [en]

    Insurance telematics programs are continuously gaining market shares in the automotive insurance industry. By recording data on drivers' behavior, the information asymmetry between the policyholder and the insurer is reduced, enabling a granular risk differentiation based on the true risk levels of the drivers. However, the growth of the insurance telematics industry is being held up by large logistic costs associated with the process of acquiring data. As a result, several market participants have started looking towards smartphone-based solutions, which have the potential of easing and improving the data collection process for both policyholders and insurers. In this paper, we present a unified framework highlighting the challenges of smartphone-based driver behavior analysis. Since all driver behavior analysis relies on access to accurate navigation data, we first address the intermediate step of smartphone-based automotive navigation. The considered topics include estimation of the smartphone's orientation with respect to the vehicle, classification of the smartphoneowner as a passenger or driver, and navigation in GNSSchallenged areas. Once a driver-specific high-performance navigation solution has been obtained, it can be used to extract information on the driver's behavior. We review the most commonly employed driving events, and discuss some of the difficulties inherent in detecting these events.

  • 311.
    Wahlström, Johan
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skog, Isaac
    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.
    IMU alignment for smartphone-based automotive navigation2015In: 2015 18th International Conference on Information Fusion, IEEE , 2015, p. 1437-1443Conference paper (Refereed)
    Abstract [en]

    Recent years have seen an increasing interest in making use of the smartphone as a cheap and viable navigation device for land-vehicles. However, smartphone-based automotive navigation suffers from the fact that the orientation of the smartphone’s inertial measurement unit, with respect to the vehicle, in general is unknown. In this study, we present a method for simultaneous vehicle navigation and smartphone-to-vehicle alignment. In addition to the state estimates obtained from applying a standard global navigation satellite system-aided inertial navigation system to estimate the smartphone dynamics, this will also provide us with estimates of the vehicle’s attitude. These estimates are used to improve the navigation solution, and also enables the estimation of additional vehicle, road, and driver characteristics, which requires knowledge of the vehicle’s attitude. The performance of the proposed method is evaluated with both simulations and experimental data.

  • 312.
    Wahlström, Johan
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Risk assessment of vehicle cornering events in GNSS data driven insurance telematics2014In: Intelligent Transportation Systems (ITSC), 2014 IEEE 17th International Conference on, IEEE conference proceedings, 2014, p. 3132-3137Conference paper (Refereed)
    Abstract [en]

    We propose a framework for the detection of dangerous vehicle cornering events, based on statistics related to the no-sliding and no-rollover conditions. The input variables are estimated using an unscented Kalman filter applied to global navigation satellite system (GNSS) measurements of position, speed, and bearing. The resulting test statistic is evaluated in a field study where three smartphones are used as measurement probes. A general framework for performance evaluation and estimator calibration is presented as depending on a generic loss function. Further, we introduce loss functions designed for applications aiming to either minimize the number of missed detections and false alarms, or to estimate the risk level in each cornering event. Finally, performance characteristics of the estimator is presented as depending on the detection threshold, and on design parameters describing the driving behavior. Since the estimation only uses GNSS measurements, the framework is particularly well-suited for smartphone-based insurance telematics applications, aiming to avoid the logistic and monetary costs associated with e.g., on-board-diagnostics or black-box dependent solutions. The design of the estimation algorithm allows for instant feedback to be given to the driver, and hence, supports the inclusion of real time value added services in usage-basedinsurance programs.

  • 313.
    Wahlström, Johan
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Smartphone-Based Vehicle Telematics: A Ten-Year Anniversary2017In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 18, no 10, p. 2802-2825Article in journal (Refereed)
  • 314.
    Wahlström, Johan
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Skog, Isaac
    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), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Khosrow-Khavar, Farzad
    Tavakolian, Kouhyar
    Stein, Phyllis K.
    Nehorai, Arye
    A Hidden Markov Model for Seismocardiography2017In: IEEE Transactions on Biomedical Engineering, ISSN 0018-9294, E-ISSN 1558-2531, Vol. 64, no 10, p. 2361-2372Article in journal (Refereed)
    Abstract [en]

    We propose a hidden Markov model approach for processing seismocardiograms. The seismocardiogram morphology is learned using the expectation-maximization algorithm, and the state of the heart at a given time instant is estimated by the Viterbi algorithm. From the obtained Viterbi sequence, it is then straightforward to estimate instantaneous heart rate, heart rate variability measures, and cardiac time intervals (the latter requiring a small number of manual annotations). As is shown in the conducted experimental study, the presented algorithm outperforms the state-of-the-art in seismocardiogram-based heart rate and heart rate variability estimation. Moreover, the isovolumic contraction time and the left ventricular ejection time are estimated with mean absolute errors of about 5 [ms] and 9 [ms], respectively. The proposed algorithm can be applied to any set of inertial sensors; does not require access to any additional sensor modalities; does not make any assumptions on the seismocardiogram morphology; and explicitly models sensor noise and beat-to-beat variations (both in amplitude and temporal scaling) in the seismocardiogram morphology. As such, it is well suited for low-cost implementations using off-the-shelf inertial sensors and targeting, e.g., at-home medical services.

  • 315.
    Wahlström, Johan
    et al.
    Univ Oxford, Dept Comp Sci, Oxford OX1 2JD, England..
    Skog, Isaac
    Linköping Univ, Dept Elect Engn, S-58183 Linköping, Sweden.
    Nordström, Robin Larsson
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Fusion of OBD and GNSS Measurements of Speed2018In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 67, no 7, p. 1659-1667Article in journal (Refereed)
    Abstract [en]

    There are two primary sources of sensor measurements for driver behavior profiling within insurance telematics and fleet management. The first is the on-board diagnostics system, typically found within most modern cars. The second is the global navigation satellite system, whose associated receivers commonly are embedded into smartphones or off-the-shelf telematics devices. In this paper, we present maximum likelihood and maximum a posteriori estimators for the problem of fusing speed measurements from these two sources to jointly estimate a vehicle's speed and the scale factor of the wheel speed sensors. In addition, we analyze the performance of the estimators by use of the Cramer-Rao bound, and discuss the estimation of model parameters describing measurement errors and vehicle dynamics. Last, simulations and real-world data are used to show that the proposed estimators yield a substantial performance gain compared to when employing only one of the two measurement sources.

  • 316. Wigren, T.
    et al.
    Händel, Peter
    Harmonic signal modeling using adaptive nonlinear function estimation1996In: Acoustics, Speech, and Signal Processing, 1996. ICASSP-96. Conference Proceedings., 1996 IEEE International Conference on, 1996, Vol. 5, p. 2952-2955Conference paper (Refereed)
    Abstract [en]

    It is well-known that sine waves produce harmonic overtones when passed through static nonlinear functions. This paper describes a new algorithm where an arbitrary periodic signal is estimated recursively. The estimated signal model is typically parameterised as a real sine wave with unknown frequency in cascade with a piecewise linear function. A recursive Gauss-Newton prediction error identification algorithm for joint estimation of the driving frequency and the parameters of the nonlinear output function can then be derived. The approach handles colored measurement disturbances and gives a direct measure of the size of the nonlinearity that corresponds to the harmonic spectrum. The Cramer-Rao bound (CRB) is also calculated in the paper

  • 317. Wikström, Maria
    et al.
    Ahnström, Ulrika
    Falk, Johan
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Implementation of an acoustic location-finding system for TDOA measurements2003In: Nordic Matlab Conference 2003, 2003Conference paper (Refereed)
    Abstract [en]

    An implementation of an acoustic test-bed for direction- and location-finding is presented. The test-bed allows evaluation and testing of time difference of arrival (TDOA) techniques. A correlation-based method is used to estimate the TDOA between two time-synchronized and spatially separated receivers. A hyperbolic line then represents all possible transmitter positions for the estimated TDOA, which gives an asymptotic direction to the transmitter. When using three or more receivers a location may be estimated. Measurement show that the test-bed performs satisfactory for direction- and location-finding and works as a flexible platform for evaluating TDOA estimations.

  • 318.
    Wisell, David
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Implementation Considerations on the Use of Zhu's General Sampling Theorem for Characterization of Power Amplifiers2007In: Conference Record - IEEE Instrumentation and Measurement Technology Conference, 2007, p. 612-615Conference paper (Refereed)
    Abstract [en]

    In this paper Zhu's generalized sampling theorem for sampling of the output signal of a nonlinear system is applied to the case of radio frequency power amplifier modeling. The paper deals in some detail with hardware implementational issues in order to optimize the hardware design in order to make full use of the benefits given by Zhu's generalized sampling theorem. It is shown that some design changes have to be done compared to more traditional receiver designs, such as removing the anti-aliasing filters. It is also shown that the behavioral ampler models that are extracted using data taken using Zhu's generalized sampling theorem have equal or better performance with regard to out-of-band spectral emissions than when the models are extracted using data taken using Nyquist sampling of the output signal of the amplifier.

  • 319.
    Wisell, David
    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.
    Simultaneous Measurement of Transmitter and Receiver Magnitude and Phase Ripple2009Report (Other academic)
    Abstract [en]

    This paper describes a method to simultaneously measure the amplitude and phase ripple of two band pass linear systems in cascade by changing the center frequency for one of the systems. Extensive measurements are presented to support the theory.

    The method has a wide applicability for measurements on RF power amplifiers, transmitters, receivers, etc. The accuracy of the method is in the order of a few hundredths of a dB and one degree for most realistic measurement set-ups.

  • 320. Wisell, David
    et al.
    Jaldén, Joakim
    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.
    Behavioral Power Amplifier Modeling Using the LASSO2008In: 2008 IEEE INSTRUMENTATION AND MEASUREMENT TECHNOLOGY CONFERENCE, 2008, p. 1864-1867Conference paper (Refereed)
    Abstract [en]

    In this paper we use regularization; in the form of the LASSO, as identification procedure in order to find the parameters of the parallel Hammerstein model for behavioral power amplifier modeling. It is shown that the LASSO chooses a subset of the parameters of the parallel Hammerstein model in a systematic way and thereby reduces the number of model parameters while maintaining the performance. The values of the parameters are also smaller than when the ordinary least-squares algorithm is used for the parameter extraction since the LASSO imposes a limit on the L1-norm of the parameters Thus, the problem with larger and sometimes very large, parameters that is often encountered in behavioral power amplifier modeling is avoided Experimental results from measurements on a power amplifier intended for the 3G WCDMA system is provided to support the theory.

  • 321.
    Wisell, David
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Ronnow, Daniel
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    A bandwidth extension technique for dynamic characterization of power amplifiers2006In: 2006 IEEE Instrumentation and Measurement Technology Conference Proceedings, 2006, p. 1972-1976Conference paper (Refereed)
    Abstract [en]

    In this paper a method for increasing the bandwidth of a test-bed for dynamic characterization of power amplifiers is described. The technique is readily implemented using commercially available instruments which makes it suitable for e.g. production testing The bandwidth extension technique is combined with coherent averaging of the measurements in order to simultaneously increase the bandwidth and dynamic range of the test-bed. In addition the errors in the obtained wideband signal are estimated. The method is evaluated experimentally on a basestation power amplifier for the 3G WCDAM system.

  • 322.
    Wisell, David
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Rönnow, Daniel
    Department of Electronics, University of Gävle.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    A technique to extend the bandwidth of an RF power amplifier test bed2007In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 56, no 4, p. 1488-1494Article in journal (Refereed)
    Abstract [en]

    In this paper, a method for increasing the bandwidth of a test bed for dynamic characterization of power amplifiers (PAs) is described. The technique is readily implemented using commercially available instruments, which makes it suitable for, e.g., production testing. The bandwidth extension technique is combined with coherent averaging of the measurements in order to simultaneously increase the bandwidth and dynamic range of the test bed. The errors in the obtained wideband signal are also estimated. The method is evaluated experimentally on a base station PA for the third-generation wideband code division multiple access system and on a Doherty amplifier. A tenfold increase in bandwidth to a total of 144 MHz and a more than 10-dB increase in dynamic range to 78 dB were obtained in practice. In addition, the obtained wideband signal is used for behavioral amplifier modeling.

  • 323.
    Yajanarayana, Vijaya
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Dwivedi, Satyam
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    IR-UWB Detection and Fusion Strategies using Multiple Detector TypesManuscript (preprint) (Other academic)
    Abstract [en]

    Optimal detection of ultra wideband (UWB) pulses in a UWB transceiver employing multiple detector types is proposed and analyzed in this paper. We propose several fusion techniques for fusing decisions made by individual IR-UWB detectors. We assess the performance of these fusion techniques for commonly used detector types like matched filter, energy detector and amplitude detector. In order to perform this, we derive the detection performance equation for each of the detectors in terms of false alarm rate, shape of the pulse and number of UWB pulses used in the detection and apply these in the fusion algorithms. We show that the performance can be improved approximately by 4 dB in terms of signal to noise ratio (SNR) for perfect detectability of a UWB signal in a practical scenario by fusing the decisions from individual detectors.

  • 324.
    Yajanarayana, Vijaya
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Dwivedi, Satyam
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Multi Detector Fusion of Dynamic TOA Estimation using Kalman Filter2016Conference paper (Other academic)
    Abstract [en]

    In this paper, we propose fusion of dynamic TOA (time of arrival) from multiple non-coherent detectors like energy detectors operating at sub-Nyquist rate through Kalman filtering. We also show that by using multiple of these energy detectors, we can achieve the performance of a digital matched filter implementation in the AWGN (additive white Gaussian noise) setting. We derive analytical expression for number of energy detectors needed to achieve the matched filter performance. We demonstrate in simulation the validity of our analytical approach. Results indicate that number of energy detectors needed will be high at low SNRs and converge to a constant number as the SNR increases. We also study the performance of the strategy proposed using IEEE 802.15.4a CM1 channel model and show in simulation that two sub-Nyquist detectors are sufficient to match the performance of digital matched filter.

  • 325.
    Yajnanarayana, Vijaya
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Dwivedi,, Satyam
    KTH, School of Electrical Engineering (EES), Signal Processing.
    De Angelis, Alessio
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Design of impulse radio UWB transmitter for short range communications using PPM signals2013In: IEEE International Conference on Electronics, Computing and Communication Technologies (CONECCT), 2013, IEEE conference proceedings, 2013, p. 1-4Conference paper (Refereed)
    Abstract [en]

    There are several practical challenges in designing an ultra wideband (UWB) device for communication. From the physical layer perspective, signaling technique should be optimally designed to work in synergy with the underneath hardware to achieve maximum performance. In this paper we propose a new cost effective hardware architecture for UWB communication and propose a variant of pulse position modulation (PPM) method which achieves maximum bit rate under the practical constraints imposed by UWB hardware.

  • 326.
    Yajnanarayana, Vijaya
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Dwivedi, Satyam
    KTH, School of Electrical Engineering (EES), Signal Processing.
    De Angelis, Alessio
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Spectral efficient IR-UWB communication design for low complexity transceivers2014In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 2014, no 158Article in journal (Refereed)
    Abstract [en]

    Ultra wideband (UWB) radio for communication has several challenges. From the physical layer perspective, asignaling technique should be optimally designed to work in synergy with the underneath hardware to achievemaximum performance. In this paper, we propose a variant of pulse position modulation (PPM) for physical layersignaling, which can achieve raw bitrate in excess of 150 Mbps on a low complexity in-house developed impulseradio UWB platform. The signaling system is optimized to maximize bitrate under practical constraints of lowcomplexity hardware and regulatory bodies. We propose a detector and derive its theoretical performance boundsand compare the performance in simulation in terms of symbol error rates (SER). Modifications to the signaling, whichcan increase the range by 4 times with a slight increase in hardware complexity, is proposed. Detectors for thismodification and a comparative study of the performance of the proposed UWB physical layer signaling schemes interms of symbol error rates are discussed.

  • 327.
    Yajnanarayana, Vijaya
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dwivedi, Satyam
    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.
    Design of impulse radio UWB transmitter with improved range performance using PPM signals2014In: 2014 IEEE International Conference on Electronics, Computing and Communication Technologies (IEEE CONECCT), IEEE Computer Society, 2014, p. 1-5Conference paper (Refereed)
    Abstract [en]

    There are several practical challenges in designing an ultra wideband (UWB) device for communication. From the physical layer signaling perspective it is important to avoid the strong peaks in the transmitted signal to fully exploit the regulatory bodies power constraint requirements. This will result in increased range performance for the sensors. Design of the transmit impulse radio (IR) UWB signals under the practical constraints of hardware and regulatory body is a critical optimization issue in the UWB system design. In this paper, we propose a IR-UWB signaling, which is a variant of pulse position modulation (PPM) method and achieves an increased range performance under the practical constraints of hardware and Federal Communications Commission (FCC) regulations.

  • 328.
    Yajnanarayana, Vijaya
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dwivedi, Satyam
    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.
    IR-UWB detection and fusion strategies using multiple detector types2016In: IEEE Wireless Communications and Networking Conference, WCNC, Institute of Electrical and Electronics Engineers (IEEE), 2016, article id 7565140Conference paper (Refereed)
    Abstract [en]

    Optimal detection of ultra wideband (UWB) pulses in a UWB transceiver employing multiple detector types is proposed and analyzed in this paper. To enable the transceiver to be used for multiple applications, the designers have different types of detectors such as energy detector, amplitude detector, etc., built in to a single transceiver architecture. We propose several fusion techniques for fusing decisions made by individual IR-UWB detectors. In order to get early insight into theoretical achievable performance of these fusion techniques, we assess the performance of these fusion techniques for commonly used detector types like matched filter, energy detector and amplitude detector under Gaussian assumption. These are valid for ultra short distance communication and in UWB systems operating in millimeter wave (mmwave) band with high directivity gain. In this paper, we utilize the performance equations of different detectors, to device distinct fusion algorithms. We show that the performance can be improved approximately by 4 dB in terms of signal to noise ratio (SNR) for high probability of detection of a UWB signal (> 95%), by fusing decisions from multiple detector types compared to a standalone energy detector, in a practical scenario.

  • 329.
    Yajnanarayana, Vijaya
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dwivedi, Satyam
    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.
    Multi Detector Fusion of Dynamic TOA hstimation using Kalman Filter2016In: 2016 IEEE International Conference on Communications (ICC), Institute of Electrical and Electronics Engineers (IEEE), 2016Conference paper (Refereed)
    Abstract [en]

    In this paper we propose fusion of dynamic time of arrival (TOA) from multiple low complexity detectors like energy detectors operating at sub-Nyquist rate through Kalman filtering. We show that by having a multi-channel sub-Nyquist receiver with each channel having an energy detector can match the performance of a single channel digital receiver with matched filter. We derive analytical expression for number of sub-Nyquist energy detector channels needed to achieve the performance of digital implementation with matched filter and demonstrate in simulation the validity of our analytical approach. Results indicate that number of energy detectors needed will he high at low SNRs and converge to a constant number as the SNR increases. We also study the performance of the proposed strategy using IEEE 802.15.4a CM1 multipath channel model and show in simulation that two sub-Nyquist detectors are sufficient to match the performance of digital matched filter.

  • 330.
    Yajnanarayana, Vijaya
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Joint Estimation of TOA and PPM Symbols Using Sub-Nyquist Sampled IR-UWB Signal2017In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, no 4, p. 949-952Article in journal (Refereed)
    Abstract [en]

    Impulse radio ultra wideband (UWB) signals are used in various applications which require joint localization and communication. Due to the large bandwidth of the UWB signal, the estimation of time of arrival (TOA) and data symbols requires high sampling rates. This letter describes a sub-Nyquist rate receiver, which can jointly estimate TOA and data symbols. We first represent the received UWB signal in a new domain in which it is sparse. Then, we design physical layer waveforms and estimation algorithms to exploit this sparsity for joint estimation of TOA and pulse position modulation data symbols. The performance of the receiver is compared against the maximum likelihood (ML)-based receiver using an IEEE 802.15.4a CM1 line of sight UWB channel model. The proposed algorithm yields performance similar to the ML-based algorithms with only a fraction of sampling rate at high SNRs (> 25 dB).

  • 331.
    Yajnanarayana, Vijaya
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Performance evaluation of IR-UWB detectors and fusion techniques for UWB transceiver platforms2018In: International Journal of Ultra Wideband Communications and Systems, ISSN 1758-728X, Vol. 3, no 4, p. 177-191Article in journal (Refereed)
    Abstract [en]

    In this paper, we analyse the performance of a multi-pulse impulse radio based ultra-wideband (IR-UWB) detector in an AWGN setting and provide different fusion strategies for fusing these detector outputs. To enable the transceiver to be used for multiple applications, the designers have different types of detectors such as energy detectors, amplitude detectors, etc., built in to a single transceiver architecture. In this paper, we derive the detection performance equation for commonly used detectors in terms of false alarm rate, shape of the pulse, and number of UWB pulses used in the detection and apply these in the fusion algorithms. We show that the performance can be improved by approximately 4 dB in terms of signal to noise ratio (SNR) for high probability of detection of a UWB signal (95%), by fusing decisions from multiple detector types compared to a standalone energy detector, in a practical scenario.

  • 332.
    Yajnanarayana, Vijaya
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Magnusson, Klas E. G.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Brandt, Rasmus
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dwivedi, Satyam
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Optimal Scheduling for Interference Mitigation by Range Information2017In: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 16, no 11, p. 3167-3181Article in journal (Refereed)
  • 333.
    Zachariah, Dave
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    De Angelis, Alessio
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dwivedi, Satyam
    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.
    Schedule-based sequential localization in asynchronous wireless networks2014In: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, Vol. 2014, no 1, p. 16-Article in journal (Refereed)
    Abstract [en]

    In this paper, we consider the schedule-based network localization concept, which does not requiresynchronization among nodes and does not involve communication overhead. The concept makesuse of a common transmission sequence, which enables each node to perform self-localization andto localize the entire network, based on noisy propagation-time measurements. We formulate theschedule-based localization problem as an estimation problem in a Bayesian framework. This pro-vides robustness with respect to uncertainty in such system parameters as anchor locations and timing devices. Moreover, we derive a sequential approximate maximum a posteriori (AMAP) estimator.The estimator is fully decentralized and copes with varying noise levels. By studying the fundamentalconstraints given by the considered measurement model, we provide a system design methodology which enables a scalable solution. Finally, we evaluate the performance of the proposed AMAPestimator by numerical simulations emulating an impulse-radio ultra-wideband (IR-UWB) wireless network.

  • 334.
    Zachariah, Dave
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    De Angelis, Alessio
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dwivedi, Satyam
    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.
    Self-Localization of Asynchronous Wireless Nodes With Parameter Uncertainties2013In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 20, no 6, p. 551-554Article in journal (Refereed)
    Abstract [en]

    We investigate a wireless network localization scenario in which the need for synchronized nodes is avoided. It consists of a set of fixed anchor nodes transmitting according to a given sequence and a self-localizing receiver node. The setup can accommodate additional nodes with unknown positions participating in the sequence. We propose a localization method which is robust with respect to uncertainty of the anchor positions and other system parameters. Further, we investigate the Cramer-Rao bound for the considered problem and show through numerical simulations that the proposed method attains the bound.

  • 335.
    Zachariah, Dave
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skog, Isaac
    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.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bayesian Estimation With Distance Bounds2012In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 19, no 12, p. 880-883Article in journal (Refereed)
    Abstract [en]

    We consider the problem of estimating a random state vector when there is information about the maximum distances between its subvectors. The estimation problem is posed in a Bayesian framework in which the minimum mean square error (MMSE) estimate of the state is given by the conditional mean. Since finding the conditional mean requires multidimensional integration, an approximate MMSE estimator is proposed. The performance of the proposed estimator is evaluated in a positioning problem. Finally, the application of the estimator in inequality constrained recursive filtering is illustrated by applying the estimator to a dead-reckoning problem. The MSE of the estimator is compared with two related posterior Cramer-Rao bounds.

  • 336.
    Zenteno, Efrain
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Amin, Shoaib
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Isaksson, Magnus
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Combating the Dimensionality of Nonlinear MIMOAmplifier Predistortion by Basis Pursuit2014In: Proceedings of the 44th European Microwave Conference, 2014, p. 833-836Conference paper (Refereed)
    Abstract [en]

    A general description of nonlinear dynamic MIMOsystems, given by Volterra series, has significantly larger complex-ity than SISO systems. Modeling and predistortion of MIMOamplifiers consequently become unfeasible due to the largenumber of basis functions. We have designed digital predistortersfor a MIMO amplifier using a basis pursuit method for reducingmodel complexity. This method reduces the numerical problemsthat appear in MIMO Volterra predistorters due to the largenumber of basis functions. The number of basis functions wasreduced from 1402 to 220 in a 2x2 MIMO amplifier and from127 to 13 in the corresponding SISO case. Reducing the numberof basis functions caused an increase of approximately 1 dB ofmodel error and adjacent channel power ratio.

  • 337.
    Zenteno, Efrain
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Amin, Shoaib
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Isaksson, Magnus
    Univ Gavle, Dept Elect Math & Nat Sci, S-80176 Gavle, Sweden..
    Ronnow, Daniel
    Univ Gavle, Dept Elect Math & Nat Sci, S-80176 Gavle, Sweden..
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Combating the Dimensionality of Nonlinear MIMO Amplifier Predistortion by Basis Pursuit2014In: 2014 44TH EUROPEAN MICROWAVE CONFERENCE (EUMC), IEEE , 2014, p. 833-836Conference paper (Refereed)
    Abstract [en]

    A general description of nonlinear dynamic MIMO systems, given by Volterra series, has significantly larger complexity than SISO systems. Modeling and predistortion of MIMO amplifiers consequently become unfeasible due to the large number of basis functions. We have designed digital predistorters for a MIMO amplifier using a basis pursuit method for reducing model complexity. This method reduces the numerical problems that appear in MIMO Volterra predistorters due to the large number of basis functions. The number of basis functions was reduced from 1402 to 220 in a 2x2 MIMO amplifier and from 127 to 13 in the corresponding SISO case. Reducing the number of basis functions caused an increase of approximately 1 dB of model error and adjacent channel power ratio.

  • 338.
    Zenteno, Efrain
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Isaksson, Magnus
    University of Gävle, Department of Building, Energy and Environmental Engineering .
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    A Bandwidth Extension forTechnique Radio Frequency Measurements Using Pilot TonesArticle in journal (Other academic)
  • 339.
    Zenteno, Efrain
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. University of Gavle.
    Isaksson, Magnus
    University of Gävle.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Output Impedance Mismatch Effects on the Linearity Performance of Digitally Predistorted Power Amplifiers2015In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 63, no 2, p. 1-12Article in journal (Refereed)
    Abstract [en]

    This paper analyzes the effects of load impedance mismatch in power amplifiers which linearity has been enhanced using various digital predistortion (DPD) algorithms. Two different power amplifier architectures are considered: a class AB and a Doherty amplifier and three model structures for the DPD model are compared: memoryless polynomial (MLP), general memory polynomial (GMP) and Kautz-Volterra functions (KV). This paper provides a sensitivity analysis of the linearized amplifiers under load mismatch conditions and reports the performance when dynamic parameter identification for the DPD is used to compensate for the changes in the load impedance. In general,power amplifiers linearity is sensitive to load impedance mismatch. Linearity may degrade as much as 10 dB (in normalized mean square error) according to the magnitude and the phase of the reflection coefficient provided by the load impedance. However, depending on the amplifier design, the sensitivity toload impedance mismatch varies. While the Doherty amplifier studied show significant linearity degradations in the in-band and out-of-band distortions, the out-of-band distortions of the studied class AB were less sensitive to the load impedance mismatch. In adaptive DPD schemes, the performance obtained in the MLP model does not benefit from the updating scheme and the performance achieved is similar to a static case, where no updates are made. This stresses the memory requirements in the predistorter. When employing the GMP and the KV models in an adaptive DPD scheme, they tackle to a larger extent the linearity degradations due to load impedance mismatch.

  • 340.
    Zenteno, Efrain
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Gävle, Sweden; Universidad Católica San Pablo, Peru.
    Isaksson, Magnus
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Pilot tone aided measurements to extend the bandwidth of radio frequency applications2016In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 90, p. 534-541Article in journal (Refereed)
    Abstract [en]

    A technique to extend the effective measurement bandwidth of a non-coherent vector receiver is presented. This bandwidth extension technique relies on the use of a pilot signal (known a priori), which is added on the signal of interest and is measured in a single receiver. Compared to other bandwidth extension techniques referred as stitching techniques, the proposed approach avoids error propagation in the measurement bandwidth and simultaneously enables the measurement of signals that do not contain energy in certain spectral bands. The pilot signal is created in digital stages, which tackles to large extent the requirement of the a priori knowledge of this signal. Further, the pilot signal is designed to minimize estimation errors of the proposed technique, providing enhanced performance. It is analytically shown that the error incurred by the proposed method is always lower than the error from the measurement noise. Measurement results show the method functionality with an error in the range of -50 dB of the signal measured. Finally, the usefulness of the proposed technique is illustrated by measuring the input and output of an amplifier with dynamic range in excess of 80 dB over 290 MHz using an 18 MHz bandwidth receiver. This measurement could not have been performed by existing stitching techniques.

  • 341.
    Zenteno, Efrain
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. University of Gävle, Sweden.
    Isaksson, Magnus
    University of Gävle, Sweden.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Pilot Tone Aided Measurements to Extend the Bandwidth of Radio Frequency ApplicationsManuscript (preprint) (Other academic)
  • 342.
    Zenteno, Efrain
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Gävle, Sweden; Universidad Catolica San Pablo, Peru.
    Khan, Zain Ahmed
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Gävle, Sweden.
    Isaksson, M.
    Händel, Peter
    University of Gävle, Sweden.
    Using Intrinsic Integer Periodicity to Decompose the Volterra Structure in Multi-Channel RF Transmitters2016In: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 26, no 4, p. 297-299, article id 7440846Article in journal (Refereed)
    Abstract [en]

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

  • 343.
    Zenteno, Efrain
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. University of Gävle, Sweden.
    Khan, Zain
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Isaksson, Magnus
    Univerity of Gävle.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Finding Structural Information about RF PowerAmplifiers using an Orthogonal Non-Parametric Kernel Smoothing Estimator2015In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 65, no 5, p. 2883-2889Article in journal (Refereed)
    Abstract [en]

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

4567 301 - 343 of 343
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