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  • 51.
    Landin, Per Niklas
    et al.
    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.
    Odd and Odd-Even Memory Polynomial Representations2013Report (Other academic)
    Abstract [en]

    It is shown that the absolute value of a complex-valued function can be expressed as a polynomial in the square of the absolute value of the function. A series expansion is given and related to the Volterra-series. The results find application in explaining and improving the understanding of the “even” order memory polynomial models.

  • 52.
    Landin, Per
    et al.
    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.
    RF PA Modeling Considering Odd-Even and Odd Order Polynomials2016In: 2015 IEEE Symposium on Communications and Vehicular Technology in the Benelux (SCVT), New York: Institute of Electrical and Electronics Engineers (IEEE), 2016, article id 7374233Conference paper (Refereed)
    Abstract [en]

    The use of “even” order polynomial terms in radio frequency power amplifier behavioral modeling and digital pre-distortion linearization has long been discussed. This contribution mathematically shows that the purely odd polynomials and the odd-even polynomials are equivalent up to the truncation error inherent in the model itself. The choice of odd or odd-even polynomial is equivalent to a choice of basis functions wherein the odd-even representation does not provide a richer set of basis functions, as earlier has been claimed. Modeling using measured data from a power amplifier shows that the difference in performance between the odd and odd-even polynomials is negligible for models at high nonlinear order. These findings are important to explain the appearance and use of the odd and odd-even models in power amplifier modeling and digital pre-distortion.

  • 53.
    Lastras-Martínez, L. F.
    et al.
    Max-Planck-Institut Festkorperforschung, Stuttgart, Germany; Instituto de Investigación en Comunicación Optica, Universidad Autonóma de San Luis Potosí, San Luis Potosí, Mexico.
    Rönnow, Daniel
    Max-Planck-Institut Festkorperforschung, Stuttgart, Germany.
    Santos, P. V.
    Max-Planck-Institut Festkorperforschung, Stuttgart, Germany; Paul-Drude-Institut für Festkörperelektronik, Berlin, Germany.
    Cardona, M.
    Max-Planck-Institut Festkorperforschung, Stuttgart, Germany.
    Eberl, K.
    Max-Planck-Institut Festkorperforschung, Stuttgart, Germany.
    Optical anisotropy of (001)-GaAs surface quantum wells2001In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 64, no 24, p. 2453031-2453038, article id 245303Article in journal (Refereed)
    Abstract [en]

    We report a reflectance difference spectroscopy (RDS) study of the optical anisotropy of GaAs:(001) surface quantum wells consisting of a thin GaAs layer (3-30 nm thick) embedded between an arsenic reconstructed surface and an AlAs barrier. The RDS spectra display anisotropic contributions from the free surface and from the GaAs/AlAs interface. By comparing RDS spectra for the c(4×4) and (2×4) surface reconstructions, we separate these two contributions, and demonstrate that the anisotropy around the E1 and E11 transitions comprises a component originating from modifications of bulk states near the surface. The latter is attributed to anisotropic strains induced by the surface reconstruction. The experimental data are well described by a model for the RDS response of the multilayer structures, which also takes into account the blue energy shifts and the changes in oscillator strength of the E1 and E11 transitions induced by quantum-well confinement.

  • 54.
    Lastras-Martí­nez, L. F.
    et al.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Santos, P. V.
    Paul-Drude-Institut für Festkörperelektronik, Berlin, Germany.
    Rönnow, Daniel
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Cardona, M.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Specht, P.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Eberl, K.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Reflectance difference spectroscopy of GaAs asymmetric surface quantum wells above the fundamental gap1998In: Physica status solidi. A, Applied research, ISSN 0031-8965, E-ISSN 1521-396X, Vol. 170, no 2, p. 317-321Article in journal (Refereed)
    Abstract [en]

    We report Reflectance Difference (RD) measurement on (001) GaAs surface quantum wells (QW) under Ultra High Vacuum (UHV) conditions from 1.7 to 5.0eV. The QW is embedded between an arsenic-rich reconstructed GaAs surface and an AlAs barrier. The samples, grown by MBE with a protective arsenic cap layer, were heated to 320 and 430°C to desorb the As layer and form c(4 x 4) and (2 x 4) surface reconstructions, respectively. By modifying the surface reconstructure, we are able to separate the contributions to the optical anisotropy from the surface region (mainly associated with the As dimers) from those originating below the surface.

  • 55.
    Lefez, B.
    et al.
    Laboratoire D'analyse, Université de Rouen, Mont Saint Aignan, France.
    Kartouni, K.
    Laboratoire D'analyse, Université de Rouen, Mont Saint Aignan, France.
    Lenglet, M.
    Laboratoire D'analyse, Université de Rouen, Mont Saint Aignan, France.
    Rönnow, Daniel
    Institute of Technology, Uppsala University, Uppsala, Sweden.
    Ribbing, C. G.
    Institute of Technology, Uppsala University, Uppsala, Sweden.
    Application of reflectance spectrophotometry to the study of copper (I) oxides (Cu2O and Cu3O2) on metallic substrate1994In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 22, no 1-12, p. 451-455Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to characterize the compounds grown on copper during the oxidation at low temperature (T < 523 K) by optical methods: photoluminescence and UV‐Visible‐NIR diffuse reflectance spectroscopy. Two cuprous oxides Cu2O and Cu3O2 have been studied. The absorption of Cu2O films in the range 450–630 nm is mainly due to non‐stoichiometry bands associated with copper and oxygen vacancies. Cu3O2 is characterized by an optical band gap greater than that of Cu2O (respectively 2.25 and 1.95 eV) and by an intense luminescence emission at 760–780 nm. Cu3O2 may be considered as a gross defect structure of Cu2O (a Cu 2O = 0.427 nm, a Cu 3O 2 = 0.431 nm). The experimental approach of the oxidation mechanism reveals that at 423 K Cu2O is the primary product which later on is transformed into Cu3O2. Experimental and calculated optical absorption curves disclose the nucleation of CuO inside the cuprous oxides layer for oxidation in the range 473–523 K.

  • 56.
    Lindstrom, T
    et al.
    Department of Materials Science, Ångström Laboratory, Uppspla University, Uppsala, Sweden.
    Rönnow, Daniel
    ACREO AB, Kista, Sweden.
    Total integrated scattering from transparent substrates in the infrared region: validity of scalar theory2000In: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 39, no 2, p. 478-487Article in journal (Refereed)
    Abstract [en]

    Integrated light scattering, from thin, transparent silicon wafers with different front and backside surface roughness is investigated. The measurements are made at near normal incidence in the IR wavelength region 5 to 20 μm using an integrating sphere. A method to separate the scattering contribution from each interface for measurements on transparent samples is introduced. Scalar scattering theory is used to calculate the effective root mean square roughness from reflectance and transmittance measurements, and these values are compared to profilometer data, correcting for the different bandwidth limits. Scattering measurements are performed with both the rough and the smooth surface of the wafer oriented toward the light source, which results in additional knowledge. The maximum ratio between the root mean square roughness and the wavelength of the light, to be used in scalar theory, is found to be considerably higher for the transmittance case than for the reflectance case. In agreement with theory, the calculated root mean square roughness is found to be proportional to the refractive index of incident medium in reflectance, and to the difference in refractive indices of incident and refracting medium for the transmittance case.

  • 57.
    Lindström, T.
    et al.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Kullman, L.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Rönnow, Daniel
    Max-Planck-Institut für Festkörperforschung, Stuttgart ,Germany.
    Ribbing, C. G.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Granqvist, C. G.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Electrochromic control of thin film light scattering1997In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 81, no 3, p. 1464-69Article in journal (Refereed)
    Abstract [en]

    Total and diffuse reflectance spectra were measured on Al surfaces covered with electrochromic W oxide films in colored and bleached states. Vector perturbation theory was used for analyzing the spectra. The diffuse reflectance appeared to originate from correlated (uncorrelated) interface roughness when the W oxide film was fully colored (bleached). Assuming partially correlated interfaces led to agreement between experimental and calculated spectra. The use of an electrochromic film appears a promising method to control the relative contributions of the interfaces to the resulting scattering.

  • 58.
    n/a, Sarika
    et al.
    Department of Electronics and Communication Engineering, Amity School of Engineering and Technology, Amity University, Noida, Uttar Pradesh, India; Department of Electronics and Communication Engineering, BSAITM, Faridabad, Haryana, India.
    Tripathy, M. R.
    Department of Electronics and Communication Engineering, Amity School of Engineering and Technology, Amity University, Noida, Uttar Pradesh, India.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Dual band Frequency Selective Surface for X-band applications2016In: Progress in Electromagnetic Research Symposium (PIERS): Proceedings 2016, IEEE, 2016, p. 5039-5042, article id 7735828Conference paper (Refereed)
    Abstract [en]

    In this paper, a novel dual band pass Frequency Selective Surface (FSS) is presented. The FSS is a L9 shaped structure with dimensions 7 × 7mm2 and substrate thickness h = 0.762 mm. The proposed FSS aims to provide dual pass-bands in X-band. A stacked array FSS is also studied to broaden the transmission band of the structure. An equivalent circuit model is also given for analyzing the frequency characteristics of the proposed design. The simulation results and the results of equivalent circuit model are in synchronization with each other. HFSS software is used for simulation process and Agilent’s ADS software has been used to get the results of Equivalent Circuit model.

  • 59.
    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.

  • 60.
    Niklasson, Gunnar A.
    et al.
    Department of Materials Science, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Rönnow, Daniel
    Department of Materials Science, The Ångström Laboratory, Uppsala University, Uppsala, Sweden; Institute of Optical Research, Electrum, Kista, Sweden.
    Strömme, Maria
    Department of Materials Science, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Kullman, Lisen
    Department of Materials Science, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Nilsson, Hans
    Department of Materials Science, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Roos, Arne
    Department of Materials Science, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Surface roughness of pyrolytic tin dioxide films evaluated by different methods2000In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 359, no 2, p. 203-209Article in journal (Refereed)
    Abstract [en]

    The scaling of surface roughness in thin spray pyrolyzed fluorinated tin dioxide films of different thicknesses was obtained from atomic force microscopy. The data show that, within experimental uncertainties, the effective dimensionality of the surface is 2; hence no evidence of fractal surface roughness was found. Other methods – based upon light scattering and cyclic voltammetry – gave additional information on the surface topography. Cyclic voltammetry measurements show that the reaction sites on the surface are distributed in a fractal structure and may be identified with hillocks seen in surface reliefs.

  • 61.
    Nostell, P
    et al.
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Roos, A.
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Rönnow, Daniel
    Max Planck Institut für Festkörperforschung, Stuttgart, Germany.
    Single-beam integrating sphere spectrophotometer for reflectance and transmittance measurements versus angle of incidence in the solar wavelength range on diffuse and specular samples1999In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 70, no 5, p. 2481-2494Article in journal (Other academic)
    Abstract [en]

    A multipurpose instrument for the measurement of reflectance and transmittance versus angle of incidence for both specular and diffuse samples in the solar wavelength range has been constructed and evaluated. The instrument operates in the single-beam mode and uses a common light source for three experimental setups. Two integrating spheres, 20 cm in diameter, are used for diffuse transmittance and reflectance measurements. The transmittance sphere can be turned around an axis through the sample to vary the angle of incidence. The reflectance sphere uses a center mounted sample and a special feature is the position of the detector, which is mounted on the sample holder at the center of the sphere. This way the detector always sees the same part of the sphere wall and no light can reach the detector directly from the sample. The third setup is an absolute instrument for specular samples. It uses a small averaging sphere as a detector. The detector is mounted on an arm which rotates around the center of the sample, and it can thus pick up both the reflected and transmitted beams including all multiply reflected components. The averaging sphere detector is insensitive to small side shifts of the detected beams and no multiple reflections between detector and optical system occur. In this report a number of calibration procedures are presented for the three experimental setups and models for the calculation of correct transmittance and reflectance values from measured data are presented. It is shown that for integrating sphere measurements, the geometry of the sphere and the diffusivity of the sample as well as the sphere wall reflectance and port losses are important factors that influence the result. For the center mounted configuration these factors are particularly important and special emphasis is given to the evaluation of the reflectance sphere model. All three instrument setups are calibrated using certified reference materials and nonscattering mirrors and substrates. The results are also compared to the results of a double-beam Beckman integrating sphere for near normal angles of incidence and Fresnel calculations. The results in this article show that good agreement is obtained between results from the different instruments if, and only if, proper evaluation procedures are applied to the measured signals.

  • 62.
    Ottosson, Patrik
    et al.
    Radarbolaget, Gävle, Sweden.
    Andersson, Daniel
    Radarbolaget, Gävle, Sweden.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    UWB Radio Measurement and Time-Domain Analysis of Anisotropy in Wood Chips2018In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 18, no 22, p. 9112-9119Article in journal (Refereed)
    Abstract [en]

    Ultra-wideband (UWB) radio transmission measurements have been used to determine the moisture content of wood chips using a time domain technique. Wood chips have been found to have birefringent dielectric properties acting as an anisotropic dielectric effective medium. Birefringence in wood chips occurs because of the orientation and the shape of wood chips, and microscopic structures of these objects, like wood fibers. The birefringence gives rise to two different wavefronts along the principal axes that have different dielectric properties. Each wavefront has a specific time-domain signal, that can be used to determine the moisture content. In industrial applications, for example in measurement on wood chips in trucks, the vertical polarization direction is the preferable polarization because this signal has higher signal-to-noise ratio (SNR), which makes the signal more identifiable at longer distance (2-3 m). Thus, UWB radio transmission measurement and time-domain analysis is a robust technology to investigate larger containers of wood chips and to determine the moisture content with high accuracy.

  • 63.
    Piazza, Roberto
    et al.
    University of Luxembourg.
    Shankar, Bhavani
    University of Luxembourg.
    Zenteno, Efrain
    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.
    Grotz, Joel
    Senior System engineer SES.
    Zimmer, Frank
    SES, Betzdorf, Luxemburg.
    Grässlin, Michael
    Steinbeis Transfer Centre for Space, Gäufelden, Germany.
    Heckman, Fredrik
    Cioni, Stefano
    ESA/ESTEC, Noordwijk, The Netherlands.
    Multicarrier digital pre-distortion/ equalization techniques for non-linear satellite channels2012In: 30th AIAA International Communications Satellite Systems Conference (ICSSC), 2012Conference paper (Refereed)
    Abstract [en]

    Two key advances are envisaged for future missions: (a) spectrally efficient transmission to meet the increasing demand and (b) sharing of satellite capacity among different links to meet power/massrequirements.Joint amplification of multiple-carrier DVB-S2 signals using a single High-Power Amplifier (HPA) is a particular application of satellite resource sharing. However, effects specific tosuch a scenariothat degrade power and spectral efficiencies include (a) an increased Adjacent Channel Interference caused by non-linear characteristic ofthe HPA and (b)increased peak to average power ratio. The paper studies signal processing techniques –digital pre-distortion (DPD) at the gateway and equalization (EQ) at the User Terminal–to mitigate the non-linear effects and improve power as well as spectral efficiencies.While the algorithms for DPD and EQ are described in literature, their use in multi-carrier scenario is novel and poses new challenges that are investigated in the paper.

  • 64.
    Piazza, Roberto
    et al.
    University of Luxembourg.
    Shankar, Bhavani
    University of Luxembourg.
    Zenteno, Efrain
    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.
    Liolis, Konstantinos
    SES, TechCom, Beltzdorf, Luxembourg.
    Zimmer, Frank
    SES, TechCom, Beltzdorf, Luxembourg.
    Grässlin, Michael
    Steinbeis Transfer Centre for Space, Gäufelden, Germany.
    Berheide, Tomas
    Steinbeis Transfer Centre for Space, Gäufelden, Germany.
    Cioni, Stefano
    ESA/ESTEC Noordwijk, Netherlands.
    Sensitivity Analysis of Multicarrier Digital Pre-distortion/ Equalization Techniques for Non-linear Satellite Channels2013In: 31st AIAA International Communications Satellite Systems Conference, 2013Conference paper (Refereed)
  • 65. Roos, A.
    et al.
    Rönnow, Daniel
    Diffuse reflectance and transmittance spectra of an interference layer: 1. Model formulation and properties1994In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 33, no 34, p. 7908-7917Article in journal (Refereed)
    Abstract [en]

    A model for the calculation of the diffuse reflectance and transmittance of a single interference layer with rough interfaces on a transparent substrate is presented. The model is based on electric field calculations and scalar scattering theory, and it assumes that the interfaces of the layer are totally uncorrelated. Examples are given of calculated spectra in which the parameters of the model are varied systematically to show the influence from different interface roughness and refractive index combinations as well as absorption in the film. A wavelength-dependent effective root-mean-square roughness is introduced. This depends on the nature of the roughness, and the bandwidth limits are given by the experimental conditions. Finally, total integrated scattering spectra are calculated and the importance of taking multiple reflections in the substrate into account is shown.

  • 66.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Characterizing multiple input multiple output radio frequency devices2013In: Proceedings of the International Conference on Recent Trends in Materials and Devices, ICRTMD-13, 2013, p. 4-7Conference paper (Refereed)
  • 67.
    Rönnow, Daniel
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Determination of interface roughness cross correlation of thin films from spectroscopic light scattering measurements1997In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 81, no 8, p. 3627-3636Article in journal (Refereed)
    Abstract [en]

    Diffuse reflectance and transmittance spectra collected in different scattering angle intervals have been analyzed in order to determine the interface roughness cross correlation of thin films. Different angle intervals correspond to different roughness length scales; the cross correlation as a function of length scale can hence be determined. Sputter deposited ZrO2 films were analyzed. The transition from correlated to uncorrelated film interfaces was found to occur at longer length scales, when the film thickness increased.

  • 68.
    Rönnow, Daniel
    Uppsala university, Uppsala, Sweden.
    Elastic light scattering by thin films: spectroscopic measurements and analysis1996Doctoral thesis, comprehensive summary (Other academic)
  • 69.
    Rönnow, Daniel
    Department of Technology, Uppsala University, Uppsala, Sweden; Max-Planck-Institut für , Stuttgart, Germany.
    Interface roughness statistics of thin films from angle-resolved light scattering at three wavelengths1998In: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 37, no 2, p. 696-704Article in journal (Refereed)
    Abstract [en]

    The possibility of determining interface roughness and cross-correlation statistics of the two interfaces of a thin film from angle-resolved light scattering data at three wavelengths is investigated. It is shown that angle-resolved light scattering measurements at three wavelengths are not sufficient to determine the three power spectral density functions describing the thin film roughness. An attempt to combine reflectance and transmittance scattering to determine the roughness of a thin film on a transparent substrate appears to work and provides encouraging results.

  • 70.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    pth-order inverse of the Volterra series for multiple-input multiple-output non-linear dynamic systems2018In: IET Circuits, Devices & Systems, ISSN 1751-858X, E-ISSN 1751-8598, Vol. 12, no 4, p. 403-412Article in journal (Refereed)
    Abstract [en]

    A method to determine the pth-order inverse of the Volterra series of multiple-input multiple-output non-linear dynamic systems is presented; it combines time- and frequency-domain techniques to determine the Volterra series of the inverse as a function of the forward system's Volterra series. The method can be used for continuous and discrete time systems. Each operator of non-linear order n of the inverse is a function of the forward system's operators of non-linear order n and lower. It is shown that the pth-order post-inverse is equal to the pth-order preinverse. For the special case that there are no linear cross terms and that the linear memory effects are negligible the kernels of the forward and inverse models are approximately the same. In an example, an approximate inverse model of a model of a concurrent dual band radio frequency amplifier is derived. © The Institution of Engineering and Technology 2018.

  • 71.
    Rönnow, Daniel
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Software for determining the third order Volterra kernels of radio frequency power amplifiers2005Report (Other academic)
    Abstract [en]

    Software for determining the third order Volterra kernels of radio frequency power amplifiers is presented. The background theory is included, the source code in Matlab is appended and some examples are given as illustrations and for verification of the code.

  • 72.
    Rönnow, Daniel
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Amin, Shoaib
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Department of Signal Processing, ACCESS Linnaeus Centre, KTH Royal Institute of Technology, Stockholm, Sweden.
    Alizadeh, Mahmoud
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Department of Signal Processing, ACCESS Linnaeus Centre, KTH Royal Institute of Technology, Stockholm, Sweden.
    Zenteno, Efrain
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Phase noise coherence of two continuous wave radio frequency signals of different frequency2017In: IET Science, Measurement & Technology, ISSN 1751-8822, E-ISSN 1751-8830, Vol. 11, no 1, p. 77-85Article in journal (Refereed)
    Abstract [en]

    A method is proposed for determining the correlated and uncorrelated parts of phase noise spectra (PNS) of two continuous wave radio signals of different frequencies, ω1 and ω2. The PNS of the two signals and of mixed signals are measured. The PNS are modelled as having a correlated part that is the same for both signals, except for a multiplicative factor, and uncorrelated parts, that are different for the two signals. A property of the model that the PNS of some mixing products are linear combinations of the PNS of the signals at ω1, ω2, and ω1 − ω2 is experimentally verified. The difference of the PNS at ω1 + ω2 and ω1 − ω2 is proportional to the correlated part of the PNS and is a part of auxiliary functions that are used for finding the multiplicative factor and the correlated, partly correlated, and uncorrelated phase noise at different offset frequencies. A conventional spectrum analyser was used to characterise two signal generators, a phase-coherent and a non-phase-coherent one. For the phase-coherent generator the phase noise of two signals was found to be correlated for offset frequencies below 10 Hz, partly correlated for 10 Hz–1 kHz and uncorrelated above 1 kHz.

  • 73.
    Rönnow, Daniel
    et al.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Andersson, S. K.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Niklasson, G. A.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Surface Roughness Effects in Ellipsometry: Comparison of Truncated Sphere and Effective Medium Models1995In: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 4, no 6, p. 815-821Article in journal (Refereed)
    Abstract [en]

    We investigate the applicability of effective medium models for describing the effects of surface roughness on ellipsometric data. The ellipsometric parameters of a model surface composed of truncated spherical bumps on a substrate were calculated and compared to the Bruggeman effective medium theory. It is possible to fit the model calculations with the Bruggeman theory. However, the thickness and volume fraction of the effective medium layer describing the surface roughness do not correspond to the physical height and volume fraction of the bumps on the model surface.

  • 74.
    Rönnow, Daniel
    et al.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Bergkvist, M.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Roos, A.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Ribbing, C.-G.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Determination of interface roughness by using a spectroscopic total-integrated-scatter instrument1993In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 32, no 19, p. 3448-3451Article in journal (Refereed)
    Abstract [en]

    A spectroscopic total-integrated-scatter instrument has been constructed. It uses a Coblentz sphere for the collection of the scattered light and a lamp with a monochromator as a light source. It can be used to measure diffuse reflectance as well as transmittance. The instrument has been used to measure diffuse reflectance of thermally and chemical-vapor-deposition oxidized silicon wafers. Comparisons are made with measurements by using a spectrophotometer with an integrating sphere. The data have been interpreted with a parameterized model for light scattering from a double layer, to obtain rms surface roughness values for the two interfaces of the oxide film.

  • 75.
    Rönnow, Daniel
    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.
    Laporte-Fauret, Baptiste
    Bordeaux INP, Enseirb-Matmeca Bordeaux, France.
    Determination of elongation of electrically smallobjects in building structures by polarimetric synthetic aperture radar2017In: I2MTC 2017 - 2017 IEEE International Instrumentation and Measurement Technology Conference: Proceedings, Torino: IEEE, 2017, p. 1520-1524, article id 7969898Conference paper (Refereed)
    Abstract [en]

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

  • 76.
    Rönnow, Daniel
    et al.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Cardona, M.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Lastras-Martínez, L. F.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Piezo-optical coefficients of ZnSe and ZnTe above the fundamental gap1999In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 59, no 8, p. 5581-5590Article in journal (Refereed)
    Abstract [en]

    The piezo-optical coefficients P11-P12 and P44 have been measured for ZnSe and ZnTe above the fundamental gap (in the energy ranges 2.6-5.5 eV and 2.0-5.5 eV, respectively) by using reflectance difference spectroscopy. The measured spectra of P11-P12 and P44 show good Kramers-Kronig consistency between their real and imaginary parts. Values for the deformation potentials D1 5, D3 3, and D3 5 for the E1 and E1 + Δ1 transitions were estimated by fitting the spectral dependence of P11-P12 and P44 to analytical line shapes based on a one-electron approximation.

  • 77.
    Rönnow, Daniel
    et al.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Christensen, N. E.
    Institute of Physics and Astronomy, Århus University, Århus, Denmar.
    Cardona, M.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Deformation potentials of the E1 transition in Ge, GaAs, InP, ZnSe, and ZnTe from ab initio calculations1999In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 59, no 8, p. 5575-5580Article in journal (Refereed)
    Abstract [en]

    The deformation potentials D1 1, D3 3, D1 5, and D3 5, which represent the effects of strain on the E1 electronic interband transitions, have been calculated for Ge, GaAs, InP, ZnSe, and ZnTe using the full-potential linear muffin-tin orbital method within the local-density approximation. These deformation potentials exhibit no strong variations between L and Γ throughout the Brillouin zone. It is therefore legitimate to use an average to interpret strain-optical experiments. The values of these deformation potentials are approximately the same for all calculated materials. The agreement with experimental data is good for Ge, GaAs, and InP. For ZnSe and ZnTe the agreement with the few extant experimental data is poorer: The magnitude of the calculated deformation potentials is smaller than found experimentally. This may reflect a breakdown of the conventional theory of strain optical constants based on one-electron interband transitions. The corresponding deformation potentials, D1,0 5 and D3,0 5, representing the effects of optical phonons at the center of the Brillouin zone on the E1 transitions are also presented.

  • 78.
    Rönnow, Daniel
    et al.
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Eisenhammer, T.
    TiNOX GmbH, München, Germany.
    Roos, A.
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Surface roughness characterisation of a thin transparent dielectric-silver tandem by spectroscopic light scattering1998In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 52, no 1-2, p. 37-43Article in journal (Refereed)
    Abstract [en]

    Spectroscopic light scattering was measured on a system of a dielectric layer on top of a thin (13 nm) silver film on a glass substrate. The analysis included both forward and backward scattering and excellent agreement between measured and modelled results was achieved. The theoretical analysis showed that the film interfaces were correlated, i.e. the substrate roughness was replicated, and that the interface roughness (root mean square) was in the nanometer range.

  • 79.
    Rönnow, Daniel
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Händel, Peter
    Signal Processing, Royal Institute of Technology, Stockholm, Sweden.
    Nonlinear distortion noise and linear attenuation in MIMO systems - theory and application to multiband transmitters2019In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 67, no 20, p. 5203-5212Article in journal (Refereed)
    Abstract [en]

    Nonlinear static multiple-input multiple-output (MIMO) systems are analyzed. The matrix formulation of Bussgang's theorem for complex Gaussian signals is rederived and put in the context of the multivariate cumulant series expansion. The attenuation matrix is a function of the input signals' covariance and the covariance of the input and output signals. The covariance of the distortion noise is in addition a function of the output signal's covariance. The effect of the observation bandwidth is discussed. Models of concurrent multiband transmitters are analyzed. For a transmitter with dual non-contiguous bands expressions for the normalized mean square error (NMSE) vs input signal power are derived for uncorrelated, partially correlated, and correlated input signals. A transmitter with arbitrary number of non-contiguous bands is analysed for correlated and uncorrelated signals. In an example, the NMSE is higher when the input signals are correlated than when they are uncorrelated for the same input signal power and it increases with the number of frequency bands. A concurrent dual band amplifier with contiguous bands is analyzed; in this case the NMSE depends on the bandwidth of the aggregated signal.

  • 80.
    Rönnow, Daniel
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Isaksson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Digital predistortion of radio frequency power amplifiers using a Kautz-Volterra model2006In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 42, no 13, p. 780-782, article id 20060460Article in journal (Refereed)
    Abstract [en]

    A digital predistortion algorithm for radio frequency power amplifiers based on orthonormal basis functions is presented. It has the same general properties as a Volterra model, but fewer parameters. Experimentally, using a 3.84 MHz wide signal at 2.14 GHz, the adjacent channel power was suppressed 12 to 15 dB, which was 5 to 7 dB more than a polynomial predistorter.

  • 81.
    Rönnow, Daniel
    et al.
    Department of technology, Uppsala university, Uppsala, Sweden.
    Isidorsson, J.
    Department of technology, Uppsala university, Uppsala, Sweden.
    Niklasson, G. A.
    Department of technology, Uppsala university, Uppsala, Sweden.
    Surface Roughness of Sputtered ZrO2 Films Studied by Atomic Force Microscopy and Spectroscopic Light Scattering1996In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 54, no 4 Suppl. B, p. 4021-4026Article in journal (Refereed)
    Abstract [en]

    ZrO2 films were prepared by reactive sputtering. Elastic light scattering was used to determine the cross correlation of the substrate and film interface roughness. Surface profiles were measured with atomic-force microscopy. The power spectral density functions could be fitted by the K-correlation model, suggesting self-affine fractal surfaces. The roughness of the film front surfaces was of the same order of magnitude as the substrate roughness. We have derived a replication factor from experimental data that gives information on the evolution of the contribution of the substrate roughness.

  • 82.
    Rönnow, Daniel
    et al.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Kullman, L.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Granqvist, C. G.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Spectroscopic Light Scattering from Electrochromic Tungsten-oxide-based Films1996In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 80, no 1, p. 423-430Article in journal (Refereed)
    Abstract [en]

    Films of W oxide and oxyfluoride were made by reactive sputtering, and electrochromic absorption modulation was obtained by subsequent electrochemical Li intercalation. Total and diffuse transmittance and reflectance were measured in the 0.4-1 μm wavelength range using a newly developed instrument. The ratio between diffuse and total optical response was <0.2% for the transmittance and <1% for the reflectance irrespective of the electrochromic absorption level. These magnitudes of the scattering are acceptable for practical smart windows applications and lend credence to a description of electrochromism in terms of localized absorption centers. Vector perturbation theory for light scattering by a film with rough interfaces could be reconciled with the data, assuming uncorrelated roughness.

  • 83.
    Rönnow, Daniel
    et al.
    Max Planck Institut für Festkörperforschung, Stuttgart, Germany.
    Lastras-Martí­nez, L. F.
    Max Planck Institut für Festkörperforschung, Stuttgart, Germany.
    Cardona, M.
    Max Planck Institut für Festkörperforschung, Stuttgart, Germany.
    Isotope effects on the electronic critical points of germanium: Ellipsometric investigation of the E1 and E1+ Delta(1) transitions1998In: European Physical Journal B: Condensed Matter Physics, ISSN 1434-6028, E-ISSN 1434-6036, Vol. 5, no 1, p. 29-35Article in journal (Refereed)
    Abstract [en]

    Within the past years the optical excitations of electrons have been measured for semiconductor samples of different isotope compositions. The isotope shift observed have been compared with calculations of the effects of electron-phonon interaction on the electronic band structure. While qualitative agreement has been obtained, some discrepancies remain especially concerning the E1 and E1 + Delta(1) transitions. We have remeasured the effect of isotope mass on the E1 and E1 + Delta(1) transitions of germanium with several isotopic compositions. The results, obtained by means of spectroscopic ellipsometry, confirm that the real part of the gap self-energies induced by electron-phonon interaction is larger than found from band structure calculations, while the imaginary part agrees with those calculations, which are based on a pseudopotential band structure and a bond charge model for the lattice dynamics. Our results agree with predictions based on the measured temperature dependence of the gaps. We compare our data for E1 and E1 + Delta(1) with results for the lowest direct (E0) and indirect (E9) gaps. The measured values of Δ0 and Δ1 increase noticeably with increasing isotope mass. Similar effects have been observed in the temperature dependence of Delta(1) in alpha-Sn and GaSb. A microscopic explanation for this effect is not available.

  • 84.
    Rönnow, Daniel
    et al.
    Max Planck Institut für Festkörperforschung, Stuttgart, Germany.
    Lindström, T.
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Isidorsson, J.
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Ribbing, C.-G.
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Surface roughness of oxidised copper films studied by atomic force microscopy and spectroscopic light scattering1998In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 325, no 1-2, p. 92-98Article in journal (Refereed)
    Abstract [en]

    The interface roughness of Cu2O films produced by thermal oxidation of Cu was studied by spectroscopic elastic light scattering and atomic force microscopy. No correlation could be found between the roughness of the two interfaces, although the amplitude and the length scale of the roughness changed in the same way with film thickness for both interfaces. Both interfaces were found to have a fractal dimension of two. A first order perturbation theory was used to analyse the light scattering data; theory and experiment are in good agreement within the limits of the theory.

  • 85.
    Rönnow, Daniel
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Uppsala University, Department of Technology, Uppsala, Sweden.
    Roos, A.
    Uppsala University, Department of Technology, Uppsala, Sweden.
    Correction Factors for Reflectance and Transmittance Measurements of Scattering Samples in Focussing Coblentz Spheres and Integrating Spheres1995In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 66, no 3, p. 2411-2422Article in journal (Refereed)
    Abstract [en]

    The detector signals from a total integrated scatter (TIS) instrument, which uses a focusing Coblentz sphere, have been evaluated. Models for the calculation of correct reflectance and transmittance values for both scattering and nonscattering samples are presented. In particular, the correction for multiple reflections between sample and detector, the detector efficiency versus angle of incidence, and the symmetry properties of the Coblentz sphere have been investigated. Experimental results are compared with results obtained with an integrating sphere using a model for the correction of sphere asymmetry. The results show that the transmittance and reflectance values obtained with the TIS instrument and the integrating sphere agree only when the presented correction factors are properly taken into account.

  • 86.
    Rönnow, Daniel
    et al.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Roos, A.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Diffuse reflectance and transmittance spectra of an interference layer. 2. Evaluation of tin oxide-coated glass1994In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 33, no 34, p. 7918-7927Article in journal (Refereed)
    Abstract [en]

    A model for the calculation of diffuse reflectance and transmittance of a single interference layer on a transparent substrate is applied to pyrolytically deposited tin oxide films on glass. Total as well as diffuse reflectance and transmittance spectra were measured in an integrating sphere, and scattering levels between 0.002 and 0.1 were recorded. The optical constants and the thickness of the films were determined from the total reflectance and transmittance spectra. The wavelength-dependent effectiveroot-mean-square roughness of aluminum-coated tin oxide front surfaces was determined by the application of the scalar scattering theory. Surface roughness values between 5 and 25 nm were obtained. The obtained effective rms roughness values of the air-film interface were used together with the other film parameters to calculate the diffuse reflectance and transmittance spectra of the tinoxide-coated glass substrates. A comparison between calculated and experimental spectra showed good agreement for diffuse reflectance, diffuse transmittance, and total integrated scattering spectra.

  • 87.
    Rönnow, Daniel
    et al.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Roos, A.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Stray-light corrections in integrating-sphere measurements on low-scattering samples1994In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 33, no 25, p. 6092-6097Article in journal (Refereed)
    Abstract [en]

    A method for correcting integrating-sphere signals that considers differences in the angular distribution of scattered light is extended to sources of errors that are due to stray light from imperfect optical components. We show that it is possible to measure low levels of scattering, below 1%, by using a standard integrating sphere, provided that the various contributions to stray light are taken into account properly. For low-scattering samples these corrections are more important than those from the angular distribution of the scattering. A procedure for the experimental determination of stray-light components is suggested. Simple, easy to use, compact equations for the diffuse and specular reflectance and transmittance values of the sample as functions of the recorded signals are presented.

  • 88.
    Rönnow, Daniel
    et al.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Santos, P.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Cardona, M.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Anastassakis, E.
    Department of Physics, National Technical University, Athens, Greece.
    Kuball, M.
    Department of Physics, Brown University, Providence, United States.
    Piezo-optics of InP in the visible-ultraviolet range1998In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 57, no 8, p. 4432-4442Article in journal (Refereed)
    Abstract [en]

    The piezo-optical properties of InP above the fundamental gap have been investigated. Uniaxial stress was applied along the [001] and [111] crystal directions and spectroscopic ellipsometry was used to determine the piezo-optical coefficients P11 , P12, and P44 in the energy range 1.6-5.5 eV at room temperature. Deformation potentials were determined for the E1 and E1 + Delta(1) transitions. Semiempirical tight-binding calculations of the piezo-optical coefficients and deformation potentials are in reasonable agreement with experiment.

  • 89.
    Rönnow, Daniel
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Shahbazali, M.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    Baki, W.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    Tripathy, Malay Ranjan
    Department of Electronics and Communication Engineering Amity School of Engineering and Technology, Amity University, Noida, India.
    Effect on Lefthandedness from SRR Rotational Disorder2015In: PIERS 2015 Prague: Progress in Electromagnetics Research Symposium : Proceedings, Cambridge, MA: The Electromagnetics Academy , 2015, p. 2372-2375Conference paper (Refereed)
    Abstract [en]

    The split ring resonator (SRR) is the key element to obtain left handedness at microwave frequencies. The orientation of the SRR relative to the electromagnetic field is decisive for achieving lefthandedness. We investigate by simulations how the lefthandedness is affected by rotational disorder of the SRRs in an array of 2 x 11 SRRs. Rotational disorder of the inner ring has a minor effect on the lefthandedness. Combined rotational disorder of inner and outer ring has a similar effect as rotational disorder of the outer ring only. Rotational disorder causes a shift in the frequency range of lefthandedness.

  • 90.
    Rönnow, Daniel
    et al.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Veszelei, E.
    Swedish Institute of Space Physics, Uppsala Division, Uppsala, Sweden.
    Design review of an instrument for spectroscopic total integrated light scattering measurements in the visible wavelength region1994In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 65, no 2, p. 327-334Article in journal (Refereed)
    Abstract [en]

    A spectroscopic total integrated scattering instrument, which uses a focusing sphere and a broadband light source, has been constructed. It records total reflectance and transmittance spectroscopically, in the wavelength region 400-1000 nm. Diffuse reflectance and transmittance values below 10-4 can be registered. These measurements require low scattering optical components and low noise electronics. Design details are given about the detection system, particularly the low noise preamplifier. The purpose of the instrument is to measure diffuse reflectance and transmittance spectra of interference coatings. Such spectra can give information about the amplitude of the roughness of the interfaces and reveal if the interfaces are topographically correlated or uncorrelated. Examples of spectra in both reflectance and transmittance mode are given.

  • 91.
    Rönnow, Daniel
    et al.
    Racomna AB, Uppsala, Sweden.
    Veszelei, E.
    Racomna AB, Uppsala, Sweden.
    Bruce, S.
    Racomna AB, Uppsala, Sweden.
    Isidorsson, J.
    Faculty of Sciences, Division of Physics and Astronomy, Vrije Universiteit, Amsterdam, The Netherlands.
    Yttrium hydride layer with switchable microwave properties2004In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 467, no 1-2, p. 186-189Article in journal (Refereed)
    Abstract [en]

    We report on switching properties in the microwave region of yttrium hydride. A microstrip line of gold on a quartz substrate was used. A gap in the gold had an yttrium hydride layer of 1.0 ÎŒm thickness with a cap layer of 5 nm palladium and 2 nm aluminium oxide. The yttrium hydride was switched between a metallic and a semiconducting state with the exchange of hydrogen. The transmission (S21) and reflection (S11) coefficients were measured in the range 10 MHz-20 GHz. In the metallic state, the sample works like a microwave transmission line and in its semiconducting state, like a microwave resistor. The transmission coefficient was also measured at 5.0 GHz during hydrogenation and de-hydrogenation.

  • 92.
    Rönnow, Daniel
    et al.
    WesternGeco AS, Oslo, Norway.
    Wisell, David
    Ericsson AB, Gävle, Sweden.
    Isaksson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Three-Tone Characterization of Nonlinear Memory Effects in Radio Frequency Power Amplifiers2007In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 56, no 6, p. 2646-2657Article in journal (Refereed)
    Abstract [en]

    A stepped three-tone measurement technique based on digitally modulated baseband signals is used in characterizing radio-frequency power amplifiers (PAs). The bandwidths of the stepped measurement were 8.8 MHz for the input signal and 26.4 MHz for the output signal. A PA designed for third-generation mobile telecommunication system was analyzed. The amplitude and phase of the third-order Volterra kernel were determined from the identified intermodulation products. The properties of the Volterra kernel along certain paths in the 3-D frequency space were analyzed and compared to some box models for nonlinear systems. The main symmetry of the third-order Volterra kernel of this PA was found to be of the type given by the cascaded quadratic nonlinearities with a linear filter in between (a Hammerstein-Wiener system), and frequency dependence, i.e., memory effects, was found to be due to the effects at the baseband.

  • 93.
    Sarika,
    et al.
    Department of Electronics and Communication Engineering, ASET Amity University Uttar Pradesh, Noida, India.
    Kumar, Rajesh
    Department of Electronics and Communication Engineering, ASET Amity University Uttar Pradesh, Noida, India.
    Tripathy, Malay Ranjan
    Department of Electronics and Communication Engineering, ASET Amity University Uttar Pradesh, Noida, India.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    3-D band-stop FSS for X-band and Ku-band2017In: 2017 Progress In Electromagnetics Research Symposium - Fall (PIERS - FALL), Electromagnetics Academy , 2017, p. 671-675Conference paper (Refereed)
    Abstract [en]

    A 3-D Frequency Selective Surface (FSS) with band-stop characteristics for X-band and Ku-band is proposed. A 3-D FSS unit cell is constructed by analyzing two 2-D FSS's. The size of the 3-D FSS unit cell is 5 mm × 5 mm wherein two layers of FR4 substrate with respective widths of 0.762 mm and 0.5 mm are used. Dual stop bands are obtained with this FSS unit cell around 10 GHz and 17.4 GHz; where a wide stop-band of 5.2 GHz is obtained. The parametric study carried out on the proposed design in terms change in nature of substrate, alternate use of different substrates and variation in angle of incidence. The 3-D FSS shows its band rejection property X-band and Ku-band respectively. Ansoft HFSS commercial EM solver software is used to carry out the simulation work.

  • 94.
    Sarika,
    et al.
    Department of Electronics and Communication Engineering, ASET, Amity University.
    Tripathy, Malay Ranjan
    Department of Electronics and Communication Engineering, ASET, Amity University.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    A wideband frequency selective surface reflector for 4G/X-Band/Ku-Band2018In: Progress In Electromagnetics Research C, ISSN 1937-8718, E-ISSN 1937-8718, Vol. 81, p. 151-159Article in journal (Refereed)
    Abstract [en]

    A Frequency Selective Surface (FSS) reflector with wideband response for 4G/X-band/Ku-band is proposed. The wideband FSS reflector consists of cascaded dual-layer patch FSS which is etched on separate layers of FR4 substrate. The targeted frequency range is 5–16 GHz. A wide stopband of 10.4 GHz (100% percent bandwidth) is obtained with two layers in cascade. The Equivalent Circuit (EC) method is used to approximate the simulated results. An extensive parametric study is also carried out to understand the effect of various combinations of FSS layers and their disposition. A panel of final FSS is fabricated where measured and simulated results agree well.

  • 95.
    Sarika, n/a
    et al.
    Department of Electronics and Communication Engineering, ASET, Amity University, Noida, Uttar Pradesh, India.
    Kumar, R.
    Department of Electronics and Communication Engineering, ASET, Amity University, Noida, Uttar Pradesh, India.
    Tripathy, Malay Tripathy
    Department of Electronics and Communication Engineering, ASET, Amity University, Noida, Uttar Pradesh, India.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    An approach to improve gain and bandwidth in bowtie antenna using frequency selective surface2019In: Smart Innovations in Communication and Computational Sciences: Proceedings of ICSICCS 2017, Volume 1 / [ed] Bijaya Ketan Panigrahi, Munesh C. Trivedi, Krishn K. Mishra, Shailesh Tiwari, Pradeep Kumar Singh, Springer, 2019, p. 219-227Conference paper (Refereed)
    Abstract [en]

    A novel approach of improving gain and bandwidth of bowtie antenna using Frequency Selective Surface (FSS) is presented. A 42 × 66 mm2 bowtie antenna is used. The 5 mm × 5 mm FSS unit cell consists of metallic square loop and grid wires on FR4 substrate with permittivity of 4.4 and loss tangent = 0.02. The effect of FSS layer on bowtie antenna is investigated in terms of parameters like gain and bandwidth. Simulation results show that gain and bandwidth of the bowtie antenna gets increased by a factor of two when the FSS layer is kept on it. Further, the effect of change of height of the substrate on gain and bandwidth is also studied. The proposed structure shows applications in X-band and Ku-band range. High-Frequency Structural Simulator (HFSS) software is used for the simulation. © Springer Nature Singapore Pte Ltd. 2019.

  • 96.
    Sarika, n/a
    et al.
    Department of Electronics and Communication Engineering, ASET, Amity University, Uttar Pradesh, Noida, India; Department of Electronics and Communication Engineering, BSAITM, Faridabad, Haryana, India .
    Kumar, Rajesh
    Department of Electronics and Communication Engineering, ASET, Amity University, Uttar Pradesh, Noida, India; Department of Electronics and Communication Engineering, BSAITM, Faridabad, Haryana, India .
    Tripathy, Malay Ranjan
    Department of Electronics and Communication Engineering, ASET, Amity University, Uttar Pradesh, Noida, India.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Fractal frequency selective surface based band stop filters for X-band and Ku-band applications2018In: Proceedings - 2017 3rd International Conference on Advances in Computing, Communication and Automation (Fall), ICACCA 2017, 2018Conference paper (Refereed)
    Abstract [en]

    In this paper, band stop filters using Fractal Frequency Selective Surface (FSS) approach for X-band and Ku-band applications are presented. A 10 mm χ 10 mm FSS unit cell is used and is evolved into four stages to get the fractal approach. Numerical results are calculated using Finite element method solver for electromagnetic structures from Ansys ie. HFSS. The transmission coefficients for each stage confirm the band stop filter property of FSS for X-band and Ku-band. Variation in arm length 'd' is studied both in horizontal and vertical direction respectively to calculate the change in narrow bands and bandwidth.

  • 97.
    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.

  • 98.
    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.

  • 99.
    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.

  • 100. 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.

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