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  • 1.
    Björsell, Niclas
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Nader, Charles
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Signal Processing Lab, Royal Institute of Technology, Stockholm, Sweden.
    Händel, Peter
    Signal Processing Lab, Royal Institute of Technology, Stockholm, Sweden.
    Multi-tone design for out-of-band characterization of nonlinear RF modules using harmonic sampling2010In: 2010 IEEE International Instrumentation and Measurement Technology Conference, I2MTC 2010: Proceedings, Piscataway, NJ: IEEE Service Center , 2010, p. 620-623, article id 5488231Conference paper (Refereed)
    Abstract [en]

    In this paper we evaluate the generation of a multi-tone set for characterizing the behavior of nonlinear radio frequency (RF) modules in its out-of-band when harmonic sampling is used as digitizer. The purpose is to provide the reader with a tool to select proper frequencies and record length for a given application and test-bed. The method is based on simulations and the use of Sidon sequences. The proposed method is applicable to sparse discrete frequency multi-tones.

  • 2.
    Fraile, F
    et al.
    Universidad Politécnica de Valencia.
    Nader, Charles
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Guerri, J. C.
    Universidad Politécnica de Valencia.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    On the reuse of DVB-T transmitter infrastructure for DVB-T22011Conference paper (Refereed)
    Abstract [en]

    The new DVB-T2 standard was specifically designed to allow the reuse of DVB-T infrastructure if required. This paper presents measurement results that verify the correct performance of a commercial DVB Power Amplifier with DVB-T2 waveforms. Furthermore, the paper includes configuration guidelines and performance evaluation of the Tone Reservation PAPR reduction algorithm included in the DVB-T2 standard. PAPR reduction is key technology when reusing DVB-T amplifiers for DVB-T2 transmissions without penalizing amplifier efficiency.

  • 3.
    Landin, Per
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Nader, Charles
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    Björsell, Niklas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    KTH Royal Institute of Technology.
    Overview of Synergetic OFDM Crest Factor Reduction and DigitalPre-Distortion for RF PAs2011In: RFMTC11, 2011Conference paper (Other academic)
    Abstract [en]

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

  • 4.
    Landin, Per Niklas
    et al.
    University of Gävle, Center for RF Measurement Technologies.
    Nader, Charles
    University of Gävle, Center for RF Measurement Technologies.
    Björsell, Niclas
    University of Gävle, Center for RF Measurement Technologies.
    Isaksson, Magnus
    University of Gävle, Center for RF Measurement Technologies.
    Wisell, David
    Ericsson AB.
    Händel, Peter
    University of Gävle, Center for RF Measurement Technologies.
    Andersen, Olav
    Ericsson AB.
    Keskitalo, Niclas
    University of Gävle, Center for RF Measurement Technologies.
    Wideband Characterization of Power Amplifiers Using Undersampling2009In: 2009 IEEE MTT-S International Microwave Symposium, Boston: IEEE MTT , 2009, p. 1365-1368Conference paper (Refereed)
    Abstract [en]

    In this paper a radio frequency power amplifier is measured and characterized by the use of undersampling based on the generalized Zhu-Frank sampling theorem. A test system has been designed allowing the bandwidth of the stimuli signal to be 100 MHz in the characterization process. That would not be possible with any vector signal analyzer on the market. One of the more challenging problem within the proposed concept is the model validation process. Here, two different techniques for model validation are proposed, the multitone and the spectrum scan validation methods.

  • 5.
    Nader, Charles
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Enhancing Radio Frequency System Performance by Digital Signal Processing2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis measurement systems for the purpose of characterization of radio frequency power amplifiers are studied. Methods to increase the speed, accuracy, bandwidth, as well as to reduce the sampling requirements and testing cost are presented. A method intended for signal shaping with respect to peak to-average ratio reduction and its effects-improvements on the radio frequency front-end performance is investigated.

    A time domain measurement system intended for fast and accurate measurements and characterization of radio frequency power amplifiers is discussed. An automated, fast and accurate technique for power and frequency sweep measurements is presented. Multidimensional representation of measured figure of merits is evaluated for its importance on the production-testing phase of power amplifiers.

    A technique to extend the digital bandwidth of a measurement system is discussed. It is based on the Zhu-Frank generalized sampling theorem which decreases the requirements on the sampling rate of the measurement system. Its application for power amplifiers behavioral modeling is discussed and evaluated experimentally.

    A general method for designing multitone for the purpose of out-of-band characterization of nonlinear radio frequency modules using harmonic sampling is presented. It has an application with the validation of power amplifiers behavioral models in their out-of-band frequency spectral support when extracted from undersampled data.

    A method for unfolding the frequency spectrum of undersampled wideband signals is presented. It is of high 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 method is presented in a compact form, it eliminates ambiguities caused by folded frequency spectra standing outside the Nyquist band, and is relevant for calibration matters.

    A convex optimization reduction-based method of peaks-to-average ratio of orthogonal frequency division multiplexing signals is presented and experimentally validated for a wireless local area network system. Improvements on the radio frequency power amplifier level are investigated with respect to power added efficiency, output power, in-band and out-of-band errors. The influence of the power distribution in the excitation signal on power amplifier performance was evaluated.

  • 6.
    Nader, Charles
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH, Signalbehandling.
    Signal Shaping and Sampling-based Measurement Techniques for Improved Radio Frequency Systems2012Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Wireless communication systems are omnipresent in our day-to-day life, with high expectations regarding capacity, reliability and power efficiency. In order to satisfy the capacity and reliability expectations, today's wireless systems are adopting sophisticated modulation schemes, such as orthogonal frequency division multiplexing (OFDM), which shape today's wireless signals with large bandwidths and high crest factors. On top of that, it is anticipated that different wireless systems/standards will co-exist and share the same radio frequency (RF) front-end in order to reduce the network implementation cost.

      Such signals characteristics and systems coexistence put high requirements on the amplification stage which in best scenarios is considered weakly nonlinear. As a result, the power amplifier needs to be backed-off for linear operation. However, such power back-off reduces the operation's efficiency. Reducing the crest factor of the wireless signal and the possibility to linearize by means of digital pre-distortion the operation behavior of the power amplifier when operated near its maximum allowed continuous wave (CW) operating power range would lead to the optimal linearity and efficiency of operation.

      In order to achieve a good linearization performance, accurate baseband behavioral models are needed which requires measuring time domain signals whose spectra spread largely due to the nonlinear operation of the power amplifier. Such spectrum spreading, denoted by spectral regrowth, puts high requirements on today's sampling-based measurement systems as a trade-of between the sampling rate and amplitude resolution exists in today's generation of analog-to-digital converters, in addition to a limitation in the available analog bandwidth. Overcoming such measurement challenges could lead to the design of expensive measurement systems which is not favorable.

      In this thesis, the performance of RF transmitters is improved by combining the use of a smart crest factor reduction technique with an enhanced digital pre-distortion technique which allows operating the power amplifier near its CW 1-dB compression point, offering a significant increase in the efficiency of operation while satisfying the standard constraints on information error and spectral emission. Furthermore, the performance of RF measurement receivers is improved by reducing the requirements on the digital bandwidth by means of an evolved harmonic sampling technique, and by reducing the requirements on the analog bandwidth and design cost by means of a digital bandwidth interleaving technique and a signal separation technique based on an advanced sparse reconstruction methodology.

  • 7.
    Nader, Charles
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    The True Value of a PhD in the Eyes of Industry2014In: IEEE Instrumentation & Measurement Magazine, ISSN 1094-6969, E-ISSN 1941-0123, Vol. 17, no 5, p. 24-25Article in journal (Other academic)
  • 8.
    Nader, Charles
    et al.
    University of Gävle, Center for RF Measurement Technologies.
    Altahir, Hibah
    University of Gävle, Center for RF Measurement Technologies.
    Andersen, Olav
    Ericsson AB.
    Björsell, Niclas
    University of Gävle, Center for RF Measurement Technologies.
    Condo, Edith
    University of Gävle, Center for RF Measurement Technologies.
    Keskitalo, Niclas
    University of Gävle, Center for RF Measurement Technologies.
    De La Rosa, Hector
    Freescale Semiconductor Nordic AB.
    Automated multidimensional characterization of power amplifier for design and production2009In: 2009 IEEE Instrumentation and Measurement Technology Conference Proceedings, Singapore: I&M Society , 2009, p. 144-148Conference paper (Refereed)
    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.

  • 9.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    Royal Insstitute of Technology, Signal Processing Lab.
    Unfolding the frequency spectrum of undersampled wideband data2011In: Signal Processing, ISSN 0165-1684, E-ISSN 1872-7557, Vol. 91, no 5, p. 1347-1350Article in journal (Refereed)
    Abstract [en]

    In this letter, we discuss the problem of unfolding the frequency spectrum for undersampled wideband data. The problem is of relevance to state-of-the-art radio frequency measurement systems, which capture repetitive waveform based on a sampling rate that violates the Nyquist constraint. The problem is presented in a compact form by the inclusion of a complex operator called the CN operator. The ease-of-use problem formulation eliminates the ambiguity caused by folded frequency spectra, in particular those with lines standing on multiples of the Nyquist frequency that are captured with erroneous amplitude and phase values. (C) 2010 Elsevier B.V. All rights reserved.

  • 10.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    OFDM PAPR Reduction by Convex Optimization: A Power Amplifier Point-of-View2010In: 2010 IEEE International Microwave Workshop Series on "RF Front-ends for Software Defined and Cognitive Radio Solutions": IMWS 2010 - Proceedings, 2010Conference paper (Refereed)
    Abstract [en]

    In this paper we evaluate the application of convex optimization for PAPR reduction on OFDM 802.11a signal type. A radio frequency power amplifier is measured and characterized while excited by both original and optimized OFDM signals. A state-of-art test setup was used for the purpose. 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.

  • 11.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    Kungliga Tekniska högskolan.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Peak-to-average power reduction of OFDM signals by convex optimization: experimental validation and performance optimization2011In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 60, no 2, p. 473-479Article in journal (Refereed)
    Abstract [en]

    We evaluated the application of 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.

  • 12.
    Nader, Charles
    et al.
    University of Gävle, Center for RF Measurement Technologies. University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Landin, Per Niklas
    University of Gävle, Center for RF Measurement Technologies. University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Björsell, Niclas
    University of Gävle, Center for RF Measurement Technologies. University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Isaksson, Magnus
    University of Gävle, Center for RF Measurement Technologies. University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Wisell, David
    Ericsson AB.
    Händel, Peter
    KTH, EES, Signal processing lab.
    Andersen, Olav
    Ericsson AB.
    Keskitalo, Niclas
    University of Gävle, Center for RF Measurement Technologies.
    Wideband Power Amplifiers Characterization by Undersampling: Zhu-Frank Sampling Theorem2009Conference paper (Other academic)
  • 13.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Landin, Per Niklas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Van Moer, Wendy
    Vrije Universiteit Brussel .
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    Royal Institute of Technology, Signal Processing Lab.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Peak-power Controlling Technique for Enhancing Digital Pre-distortion of RF Power Amplifiers2012In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 60, no 11, p. 3571-3581Article in journal (Refereed)
    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.

  • 14.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Landin, Per
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Van Moer, Wendy
    Vrije Universiteit Brussel .
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Peak-to-average power ratio reduction versus digital pre-distortion in OFDM based systems2011In: 2011 IEEE MTT-s International Microwave Symposium, Institute of Electrical and Electronics Engineers Inc , 2011, p. 5972830-Conference paper (Refereed)
    Abstract [en]

    In this paper we evaluate the effect of applying peak-to-average power ratio (PAPR) reduction and digital pre-distortion (DPD) on 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.

  • 15.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Landin, Per
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    Björsell, Niklas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    KTH Royal Institute of Technology.
    Performance Evaluation of Peak-to-Average Power Ratio Reduction and Digital Pre-Distortion for OFDM Based Systems2011In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 59, no 2, p. 3504-3511Article in journal (Refereed)
    Abstract [en]

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

  • 16.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Van Moer, Wendy
    Vrije Universiteit Brussel .
    Barbé, Kurt
    Vrije Universiteit Brussel .
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    Characterizing the out-of-band nonlinear behaviour of RF devices: the key to success2011In: 2011 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), New York: IEEE conference proceedings, 2011, p. 790-794Conference paper (Refereed)
    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.

  • 17.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    Barbé, Kurt
    Vrije Universiteit Brussel.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Evolved Harmonic Sampling: a Tool to Reduce the Digital Bandwidth Requirement of RF Receivers2011In: RFMTC11, Gävle, 2011Conference paper (Other academic)
  • 18.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Van Moer, Wendy
    Vrije Universiteit Brussel .
    Barbé, Kurt
    Vrije Universiteit Brussel .
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Harmonic Sampling and Reconstruction of Wide-band Undersampled Waveforms: Breaking the Code2011In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 59, no 11, p. 2961-2969Article in journal (Refereed)
  • 19.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Van Moer, Wendy
    Vrije Universiteit Brussel .
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    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 Waveforms2012In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 61, no 11, p. 2960-2971Article in journal (Refereed)
  • 20.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Van Moer, Wendy
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Wideband Radio Frequency Measurements: From Instrumentation to Sampling Theory2013In: IEEE Microwave Magazine, ISSN 1527-3342, E-ISSN 1557-9581, Vol. 14, no 2, p. 85-98Article in journal (Refereed)
    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.

  • 21.
    Van Moer, Wendy
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Hamid, Mohamed
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Barbe, Kurt
    Vrije Universiteit Brussel, ELEC.
    Nader, Charles
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Saving lives by integrating cognitive radios into ambulances2012In: Medical Measurements and Applications Proceedings (MeMeA), 2012 IEEE International Symposium on, Budapest, 2012, p. 1-4Conference paper (Refereed)
    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.

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