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  • 101.
    Wisell, David
    et al.
    Royal Institute of Technology, Stockholm, Sweden.
    Rönnow, Daniel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Händel, Peter
    Royal Institute of Technology, Stockholm, Sweden.
    A bandwidth extension technique for dynamic characterization of power amplifiers2006Inngår i: 2006 IEEE Instrumentation and Measurement Technology Conference Proceedings, 2006, s. 1972-1976Konferansepaper (Fagfellevurdert)
    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.

  • 102.
    Wisell, David
    et al.
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik. Ericsson AB, Stockholm, Sweden; Signal Processing Laboratory, Royal Institute of Technology, Stockholm, Sweden.
    Rönnow, Daniel
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik. Westerngeco AS, Asker, Norway..
    Händel, Peter
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik. Signal Processing Laboratory, Royal Institute of Technology, Stockholm, Sweden.
    A technique to extend the bandwidth of an RF power amplifier test bed2007Inngår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 56, nr 4, s. 1488-1494Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 103.
    Zenteno, Efrain
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. ACCESS Linnaeus Centre, Department of Signal Processing, KTH Royal Institute of Technology, Stockholm.
    Amin, Shoaib
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. ACCESS Linnaeus Centre, Department of Signal Processing, KTH Royal Institute of Technology, Stockholm.
    Isaksson, Magnus
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Rönnow, Daniel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    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 Pursuit2014Inngår i: Proceedings of the 44th European Microwave Conference, 2014, s. 833-836Konferansepaper (Fagfellevurdert)
    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.

  • 104.
    Zenteno, Efrain
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap. KTH, Signalbehandling.
    Piazza, Roberto
    Shankar, Bhavani
    Rönnow, Daniel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap. KTH, Signalbehandling.
    Ottersten, Björn
    KTH, Signalbehandling.
    A MIMO Sympol Rate Signal Digital Predistorter for Nonlinear Multicarrier Satellite ChannelsManuskript (preprint) (Annet vitenskapelig)
  • 105.
    Zenteno, Efrain
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Royal Institute of Technology (KTH), Stockholm, Sweden.
    Piazza, Roberto
    University of Luxembourg.
    Shankar, Bhavani
    University of Luxembourg.
    Rönnow, Daniel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Ottersten, Björn
    University of Luxembourg.
    Low complexity predistortion and equalization in nonlinear multicarrier satellite communications2015Inngår i: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, Vol. 2015, artikkel-id 30Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 106.
    Zenteno, Efrain
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. 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
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    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 channels2015Inngår i: IET Communications, ISSN 1751-8628, E-ISSN 1751-8636, Vol. 9, nr 16, s. 2053-2059Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 107.
    Zenteno, Efrain
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Department of Signal Processing, KTH Royal Institute of Technology, Stockholm, Sweden; Electron- ics and Telecommunication Department, Universidad Catolica San Pablo, Arequipa, Peru.
    Rönnow, Daniel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    MIMO Subband Volterra Digital Predistortion for Concurrent Aggregated Carrier Communications2017Inngår i: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 65, nr 3, s. 967-979Artikkel i tidsskrift (Fagfellevurdert)
    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.

123 101 - 107 of 107
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