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  • 101.
    Siri, M. S.
    et al.
    Purdue University, Department of Electronics & Computer Engineering, USA.
    Schafer, B. W.
    Purdue University, Department of Electronics & Computer Engineering, USA.
    Steffen, A. M.
    Purdue University, Department of Electronics & Computer Engineering, USA.
    Eroglu, A.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Purdue University, Department of Electronics & Computer Engineering, USA.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Tunable Tapped Combline Bandpass Filters for RFID Systems2017In: 2017 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (APWC), IEEE , 2017, p. 240-243Conference paper (Refereed)
    Abstract [en]

    Design, simulation and measurement results of a tunable planar bandpass filter with a tapped combline topology using diodes as active devices for varactor effect is given. Tunable planar bandpass filter that can operate from 900MHz to 1.6GHz with an enhanced attenuation characteristics are obtained. Diodes are used with an applied bias voltage to have capacitance variation from 0.84 [pF] to 5.08 [pF]. The proposed method eliminates the need for using different active devices and bias voltages and simplifies the geometry that eases implementation. The simulation and measurement results are compared and found in agreement. The method presented in this paper can be integrated in RFID systems to improve the common leakage problem in TX-RX due to poor isolation in circulators.

  • 102.
    Tripathy, Malay Ranjan
    et al.
    Amity University Uttar Pradesh, Noida, Uttar Pradesh, India.
    Choudhary, Vipin
    Amity University Uttar Pradesh, Noida, Uttar Pradesh, India.
    Gupta, Aastha
    Amity University Uttar Pradesh, Noida, Uttar Pradesh, India.
    Ranjan, Priya
    Amity University Uttar Pradesh, Noida, Uttar Pradesh, India.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    A diamond-shaped fractal bow-tie antenna for THz applications2019In: Advances in Communication, Cloud, and Big Data / [ed] Sarma H., Borah S., Dutta N., Springer , 2019, p. 97-104Chapter in book (Refereed)
    Abstract [en]

    A compact multiband diamond-shaped fractal bow-tie terahertz antenna is designed on FR4_epoxy substrate with permittivity 4.4. The dimension of substrate is 4 × 6 × 1.5 mm 3 . Multi-bands are obtained in S 11 versus frequency plots. The effects of creating defects in the ground plane of the antenna were studied and analyzed to get the optimized performance of antenna in the frequency bands at 0.500, 0.560, and 0.594 THz, respectively. © Springer Nature Singapore Pte Ltd. 2019.

  • 103.
    Tripathy, Malay Ranjan
    et al.
    Department of Electronics and Communication Engineering, ASET, Amity University, Noida, India.
    Kumar, Rajesh
    Department of Electronics and Communication Engineering, BSAITM, Faridabad, Haryana, India.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Design and Analysis of Metafractal Antenna for Wireless Applications2015In: PIERS 2015 Prague: Progress in Electromagnetics Research Symposium : Proceedings, Cambridge, MA: The Electromagnetics Academy , 2015, p. 2376-2380Conference paper (Refereed)
    Abstract [en]

    In this paper, a new design of metafractal antenna is proposed. The dimensionof the patch is 44 £ 44mm2 and the FR4 substrate is used for this. The fractal antenna withmetamaterial ground plane is used for di®erent iterations. The results show that with the increaseof the number of iterations the bandwidth is increased. In the case of higher iterations for somefrequency bands return loss results are improved but for other frequency bands these are degraded.

  • 104.
    Wisell, David H.
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik. Ericsson Telecom AB, Stockholm, Sweden; Signal Processing Lab, Royal Institute of Technology, Stockholm, Sweden.
    Rudlund, Björn
    Racomna AB, Uppsala, Sweden; Omicron AB, Stockholm, Sweden.
    Rönnow, Daniel
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik. WesternGeco AS, Asker, Norway.
    Characterization of memory effects in power amplifiers using digital two-tone measurements2007In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 56, no 6, p. 2757-2766Article in journal (Refereed)
    Abstract [en]

    In this paper, a novel method to measure the amplitude and phase of two-tone third-order intermodulation products generated in a high-power amplifier is presented. The method is based on the sampled input and output signals of the amplifier. The presented measurement setup and the associated algorithms for the calculation of the amplitudes and phases are considerably faster and simpler than the current methods. By making use of the sampled input and output signals of the amplifier and the signal processing techniques, the need for a nonlinear reference, a tunable attenuator, and a phase shifter in the existing measurement setups is eliminated, which makes it simple and easy to use. Hence, this is a substantial simplification of the measurement setup compared to what has been reported earlier. The proposed measurement setup is also suitable for fast automated measurements, which is of interest for many applications that are both laboratory and production oriented. In addition, a method to increase the bandwidth of the measured signal is used to overcome the bandwidth limitation set by the Nyquist criteria for sampled systems. Measurements are done on two base-station high-power amplifiers and are found to be in agreement with theory and reference measurements.

  • 105. Wisell, David
    et al.
    Isaksson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Keskitalo, Niclas
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Rönnow, Daniel
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Wideband characterization of a Doherty amplifier using behavioral modeling2006In: 67th ARFTG Conference 2006, 2006, p. 190-199Conference paper (Refereed)
    Abstract [en]

    A Doherty amplifier was investigated using behavioral amplifier modeling techniques. A measurement system for simultaneous wide bandwidth (>100 MHz) and large dynamic range (similar to 70 dBc ACLR) sampled measurements that are needed for the behavioral modeling is presented. Both the measurement system and the performance of the Doherty amplifier are described. The findings are that the well known and widely used parallel Hammerstein model, also denoted the memory polynomial model, is well suitable also for modeling and predistortion of Doherty amplifiers, and that a Doherty amplifier can be designed with only minor memory effects. This is seen in the modeling error, which is reduced by 13 dB, compared with a constant gain, using a memoryless polynomial model and only 6 dB further by adding memory to the model.

  • 106.
    Wisell, David
    et al.
    Royal Institute of Technology, Stockholm, Sweden.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    Royal Institute of Technology, Stockholm, Sweden.
    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.

  • 107.
    Wisell, David
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik. Ericsson AB, Stockholm, Sweden; Signal Processing Laboratory, Royal Institute of Technology, Stockholm, Sweden.
    Rönnow, Daniel
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik. Westerngeco AS, Asker, Norway..
    Händel, Peter
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik. Signal Processing Laboratory, Royal Institute of Technology, Stockholm, Sweden.
    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.

  • 108.
    Zenteno, Efrain
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. ACCESS Linnaeus Centre, Department of Signal Processing, KTH Royal Institute of Technology, Stockholm.
    Amin, Shoaib
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. ACCESS Linnaeus Centre, Department of Signal Processing, KTH Royal Institute of Technology, Stockholm.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    ACCESS Linnaeus Centre, Department of Signal Processing, KTH Royal Institute of Technology, Stockholm.
    Combating the Dimensionality of Nonlinear MIMO Amplifier 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 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.

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  • 109.
    Zenteno, Efrain
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences. KTH, Signalbehandling.
    Piazza, Roberto
    Shankar, Bhavani
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences. KTH, Signalbehandling.
    Ottersten, Björn
    KTH, Signalbehandling.
    A MIMO Sympol Rate Signal Digital Predistorter for Nonlinear Multicarrier Satellite ChannelsManuscript (preprint) (Other academic)
  • 110.
    Zenteno, Efrain
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Royal Institute of Technology (KTH), Stockholm, Sweden.
    Piazza, Roberto
    University of Luxembourg.
    Shankar, Bhavani
    University of Luxembourg.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Ottersten, Björn
    University of Luxembourg.
    Low complexity predistortion and equalization in nonlinear multicarrier satellite communications2015In: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, Vol. 2015, article id 30Article in journal (Refereed)
    Abstract [en]

    Aiming to reduce the power/mass requirements in satellite transponders and toreduce mission costs, joint amplification of multiple-carriers using a singleHigh-Power Amplifier (HPA) is being considered. In this scenario, a carefulinvestigation of the resulting power efficiency is essential as amplification isnonlinear, and multicarrier signals exhibit enlarged peak-to-average power ratio.Thus, operating the amplifier close to saturation vastly increases signal distortionresulting in a severe degradation of performance, especially for higher ordermodulations. This paper proposes a reduced-complexity digital pre-distortion(DPD) scheme at the transmitter and a corresponding equalizer (EQ) at thereceiver to mitigate these nonlinear effects. Scenarios include both the forward aswell as the return links. In particular, the paper exploits the MIMO Volterrarepresentation and builds on a basis pursuit approach using a LASSO (leastabsolute shrinkage and selection operator) algorithm to achieve an effienct basisrepresentation, avoiding large computational complexity, to describe the selectionof pre-distorter/ equalizer model. The work further compares and contrasts thetwo mitigation techniques taking various system aspects into consideration. Thegains, in performance and amplification efficiency, demonstrated by the use ofDPD/ EQ motivate their inclusion in next generation satellite systems.

  • 111.
    Zenteno, Efrain
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Dept. of Signal Processing, KTH Royal Institute of Technology, Stockholm, Sweden .
    Piazza, Roberto
    Interdisciplinary Centre for Security, Reliability and Trust (SnT), University of Luxembourg, Luxembourg.
    Shankar, M.R. Bhavani
    Interdisciplinary Centre for Security, Reliability and Trust (SnT), University of Luxembourg, Luxembourg.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Ottersten, Björn
    Interdisciplinary Centre for Security, Reliability and Trust (SnT), University of Luxembourg, Luxembourg.
    Multiple-input multiple-output symbol rate signal digital predistorter for non-linear multi-carrier satellite channels2015In: IET Communications, ISSN 1751-8628, E-ISSN 1751-8636, Vol. 9, no 16, p. 2053-2059Article in journal (Refereed)
    Abstract [en]

    A digital predistortion (DPD) scheme is presented for non-linear distortion mitigation in multi-carrier satellite communication channels. The proposed DPD has a multiple-input multiple-output architecture similar to data DPD schemes. However, it enhances the mitigation performance of data DPDs using a multi-rate processing algorithm to achieve spectrum broadening of non-linear operators. Compared to single carrier (single-input single-output) signal (waveform) DPD schemes, the proposed DPD has lower digital processing rate reducing the required hardware cost of the predistorter. The proposed DPD outperforms, in total degradation, both data and signal DPD schemes. Further, it performs closest to a channel bound described by an ideally mitigated channel with limited maximum output power.

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  • 112.
    Zenteno, Efrain
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Department of Signal Processing, KTH Royal Institute of Technology, Stockholm, Sweden; Electron- ics and Telecommunication Department, Universidad Catolica San Pablo, Arequipa, Peru.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    MIMO Subband Volterra Digital Predistortion for Concurrent Aggregated Carrier Communications2017In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 65, no 3, p. 967-979Article in journal (Refereed)
    Abstract [en]

    This paper presents a multiple-input multiple-output (MIMO) nonlinear mitigation technique for closely spaced concurrent aggregated carrier systems. The transmitter architecture considers band-limited sources, where the predistorter and signal bandwidth are the same, thus reducing transmitter hardware cost and power consumption. The technique relies on multirate processing and linear filtering and uses the carrier frequencies to isolate the contribution of linear and nonlinear basis functions to the desired bands. This approach can be used with any MIMO model structure. In particular, models are linear in the parameters of low computational complexity. The technique was evaluated using three concurrent carriers of 50 MHz each fed to a Doherty amplifier. The results show significant reduction in the error vector magnitude and improvements for the transmitter efficiency using the proposed compensation technique.

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