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  • 1.
    Alizadeh, Mahmoud
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Royal Institute of Technology, Stockholm, Sweden.
    Amin, Shoaib
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. 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.
    Measurement and analysis of frequency-domain Volterra kernels of nonlinear dynamic 3x3 MIMO systems2017In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 66, no 7, p. 1893-1905Article in journal (Refereed)
    Abstract [en]

    Multiple-input multiple-output (MIMO) frequency-domain Volterra kernels of nonlinear order 3 are experimentally determined in bandwidth-limited frequency regions. How the effect of higher nonlinear orders can be reduced and how this affects the estimated errors are discussed. The magnitude and phase of the kernels areKramers-Kronig consistent. The self- and cross-kernels have different symmetries and the kernels are therefore determined and analyzed in different regions in the 3D frequency space. By analyzing the properties along certain paths in the 3D frequency space, the block structures for the respective kernels are determined. These block structures contain the significant blocks of the general block structures for third-order kernels. The device under test is a MIMO transmitter for radio frequency signals.

  • 2.
    Alizadeh, Mahmoud
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH, Teknisk informationsvetenskap.
    Händel, Peter
    KTH, Teknisk informationsvetenskap.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Basis Function Decomposition Approach in Piece-Wise Modeling for RF Power Amplifiers2018In: 6th Telecommunications forum TELFOR 2018, Belgrade: Telecommunications society , 2018Conference paper (Refereed)
    Abstract [en]

    In this paper, a new approach is proposed to decompose the basis functions in a piece-wise modeling technique for nonlinear radio frequency (RF) power amplifiers. The proposed technique treats the discontinuity problem of the model output at the joint points between different operating points, whereas preserves the linear and nonlinear properties of the original model within each region. Experimental results show that the proposed technique outperforms the conventional piece-wise model in terms of model errors.

  • 3.
    Alizadeh, Mahmoud
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics. KTH, Teknisk informationsvetenskap.
    Händel, Peter
    KTH, Teknisk informationsvetenskap.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Behavioral modeling and digital pre-distortion techniques for RF PAs in a 3 × 3 MIMO system2019In: International journal of microwave and wireless technologies, ISSN 1759-0795, E-ISSN 1759-0787Article in journal (Refereed)
    Abstract [en]

    Modern telecommunications are moving towards (massive) multi-input multi-output systems in 5th generation (5G) technology, increasing the dimensionality of the system dramatically. In this paper, the impairments of radio frequency (RF)power amplifiers (PAs) in a 3x3 MIMO system are compensated in both time and frequency domains. A three-dimensional(3D) time-domain memory polynomial-type model is proposed as an extension of conventional 2D models. Furthermore, a 3D frequency-domain technique is formulated based on the proposed time-domain model to reduce the dimensionality of the model, while preserving the performance in terms of model errors. In the 3D frequency-domain technique, the bandwidth of a system is split into several narrow sub-bands, and the parameters of the system are estimated for each subband. This approach requires less computational complexity, and also the procedure of the parameters estimation for each sub-band can be implemented independently. The device-under-test (DUT) consists of three RF PAs including input and output cross-talk channels. The proposed techniques are evaluated in both behavioural modelling and digital pre-distortion(DPD) perspectives. The results show that the proposed DPD technique can compensate the errors of non-linearity and memory effects by about 23.5 dB and 7 dB in terms of the normalized mean square error and adjacent channel leakage ratio, respectively.

  • 4.
    Alizadeh, Mahmoud
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Department of Signal Processing, ACCESS Linnaeus Center, The Royal Institute of Technology (KTH), Stockholm, Sweden.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    A two-tone test for characterizing nonlinear dynamic effects of radio frequency amplifiers in different amplitude regions2016In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 89, p. 273-279Article in journal (Refereed)
    Abstract [en]

    A new two-tone test method for radio frequency power amplifiers is presented. The test signal is a two-tone probing-signal superimposed on large-signals of different amplitude. The amplifier is, thus, excited in different amplitude regions. The amplitude and phase of the 3rd order intermodulation (IM) products are measured vs. frequency spacing and probing-signal amplitude in each region. The IM magnitude is a measure of the nonlinearity, while the frequency dependence and asymmetry are measures of the memory effects in the different regions. A Doherty and a class-AB amplifier were tested. For both amplifiers the IM magnitude increased by ∼15 dB from the lowest to the highest amplitude region. For the Doherty amplifier the behavior of the IM products vs. frequency spacing was similar in all regions, indicating similar memory effects. For the class-AB amplifier the IM vs. frequency spacing was significantly different in the different regions, which indicates different memory effects.

  • 5.
    Alizadeh, Mahmoud
    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.
    Händel, Peter
    Department of information science and engineering Royal Institute of Technology (KTH), Stockholm, Sweden.
    Characterization of Volterra Kernels for RF Power Amplifiers Using a Two-Tone Signal and a Large-Signal2018In: 2018 International Conference on Communications, COMM 2018 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2018, Vol. 1, p. 351-356Conference paper (Refereed)
    Abstract [en]

    The 3rd-order Volterra kernels of a radio frequency (RF) power amplifier (PA) are characterized using a large-signal and a two-tone probing-signal. In this technique, the magnitude and phase asymmetries of the kernels of the PA excited by the probing-signal are analyzed in different amplitude regions of the large-signal. The device under test is a class-AB PA operating at 2.14 GHz. The maximum sweeping frequency space of the probing-signal is 20 MHz. The results indicate that the Volterra kernels of the PA show different behaviors (frequency dependency and asymmetry) in different regions.

  • 6.
    Alizadeh, Mahmoud
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    KTH.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    A new Block-Structure Modeling Technique for RF Power Amplifiers in a 2x2 MIMO System2017In: 13th International Conference on Advanced Technologies, Systems and Services in Telecommunications (TELSIKS) / [ed] Milovanovic, B. D.; Doncov, N. S.; Stankovic, Z. Z.; Dimitrijevic, T. Z., IEEE , 2017, p. 224-227Conference paper (Refereed)
    Abstract [en]

    A new block-structure behavioral model is proposed for radio frequency power amplifiers in a 2x2 multiple-input multiple-output system including input cross-talk. The proposed model forms kernels of blocks of different nonlinear order that correspond to the significant frequency response of measured frequency domain Volterra kernels. The model can therefore well describe the input-output relationships of the nonlinear dynamic behavior of PAs. The proposed model outperforms conventional models in terms of model errors.

  • 7.
    Amin, Shoaib
    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.
    Händel, Peter
    Dept of Signal Processing, KTH 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.
    Characterization and modeling of RF amplifiers with multiple input signals2016Conference paper (Refereed)
    Abstract [en]

    A characterization technique for RF PAs excited with multiple signals is presented. The technique can be used for characterization of memory effects in IM/CM products. The extracted information can in return be of use for modifying behavioral models to better capture memory in IM/CM products.

  • 8.
    Amin, Shoaib
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Department of Signal Processing, School of Electrical Engineering, KTH.
    Händel, Peter
    Department of Signal Processing, School of Electrical Engineering, KTH.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Digital Predistortion of Single and Concurrent Dual Band Radio Frequency GaN Amplifiers with Strong Nonlinear Memory Effects2017In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 65, no 7, p. 2453-2464, article id 7855827Article in journal (Refereed)
    Abstract [en]

    Electrical anomalies due to trapping effects in Gallium Nitride (GaN) power amplifiers (PAs)give rise to long-term or strong memory effects. We propose novel models based on infinite impulse response (IIR) fixed pole expansion techniques for the behavioural modeling and digital pre-distortion of single-input-single-output (SISO) and concurrent dual-bandGaN PAs. Experimental results show that the proposed models outperform the corresponding finite impulse response (FIR) models by up to 17 dB for the same number of model parameters. For the linearization of a SISO GaN PA the proposed models give adjacent channel power ratios (ACPRs) that are 7 to 17 dBlower than the FIR models. For the concurrent dual-band case, the proposed models give ACPRs that are 9to 14 dB lower than the FIR models.

  • 9.
    Amin, Shoaib
    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.
    Khan, Zain Ahmed
    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.
    Händel, Peter
    ACCESS Linnaeus Centre, Department of Signal Processing, KTH Royal Institute of Technology, Stockholm.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Concurrent dual-band power amplifier model modification using dual two-tone test2016In: 46th Europena Microwave Conference (EUMC) 2016, 2016, p. 186-189Conference paper (Refereed)
    Abstract [en]

    A dual two-tone technique for the characterization of memory effects in concurrent dual-band transmitters is revisited to modify a 2D-DPD model for the linearization of concurrent dual-band transmitters. By taking into account the individual nonlinear memory effects of the self- and cross-kernels, a new2D modified digital pre-distortion (2D-MDPD) model is proposed,which not only supersedes the linearization performance but also reduces the computational complexity compared to the 2DDPDmodel in terms of a number of floating point operations(FLOPs). Experimental results show an improvement of 1.7 dBin normalized mean square error (NMSE) and a 58% reduction in the number of FLOPs.

  • 10.
    Amin, Shoaib
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH.
    Landin, Per
    Chalmers University of Technology.
    Händel, Peter
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. ACCESS Linnaeus Centre, Signal Processing Lab, KTH Royal Institute of Technology.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Behavioral Modeling and Linearization of Crosstalk and Memory Effects in RF MIMO Transmitters2014In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 62, no 4, p. 810-823Article in journal (Refereed)
    Abstract [en]

    This paper proposes three novel models for behavioral modeling and digital pre-distortion (DPD) of nonlinear 2$,times,$ 2 multiple-input multiple-output (MIMO) transmitters in the presence of crosstalk. The proposed models are extensions of the single-input single-output generalized memory polynomial model. Three types of crosstalk effects were studied and characterized as linear, nonlinear, and nonlinear & linear crosstalk. A comparative study was performed with previously published models for the linearization of crosstalk in a nonlinear 2 $,times,$2 MIMO transmitter. The experiments indicate that, depending on the type of crosstalk, the selection of the correct model in the transmitter is necessary for behavioral modeling and sufficient DPD performance. The effects of coherent and partially noncoherent signal generation on the performance of DPD were also studied. For crosstalk levels of ${-}{hbox{30}}$ dB, the difference in the normalized mean square error and adjacent channel power ratio was found to be 3–4 dB between coherent and partially noncoherent signal generation.

  • 11.
    Amin, Shoaib
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH, Signalbehandling.
    Landin, Per N.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    KTH, Signalbehandling.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    2D Extended envelope memory polynomial model for concurrent dual-band RF transmitters2017In: International journal of microwave and wireless technologies, ISSN 1759-0795, E-ISSN 1759-0787, Vol. 9, no 8, p. 1619-1627Article in journal (Refereed)
    Abstract [en]

    The paper presents a 2D extended envelope memory polynomial (2D-EEMP) model for concurrent dual-band radio frequency (RF) power amplifiers (PAs). The model is derived based on the physical knowledge of a dual-band RF PA. The derived model contains cross-modulation terms not included in previously published models; these terms are found to be of importance for both behavioral modeling and digital pre-distortion (DPD). The performance of the derived model is evaluated both as the behavioral model and DPD, and the performance is compared with state-of-the-art2D-DPD and dual-band generalized memory polynomial (DB-GMP) models. Experimental result shows that the proposed model resulted in normalized mean square error (NMSE) of -51.7/-51.6dB and adjacent channel error power ratio (ACEPR) of -63.1/-63.4 dB, for channel 1/2, whereas the 2D-DPD resulted in the largest model error and DB-GMP resulted in model parameters that are 3 times more than those resulted with the proposed model with the same performance. As pre-distorter, the proposed model resulted in adjacent channel power ratio (ACPR) of -55.8/ -54.6 dB for channel 1/2 and is 7-10 dB lower than those resulted with the 2D-DPD model and2-4 dB lower compared to the DB-GMP model.

  • 12.
    Amin, Shoaib
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH, Signalbehandling.
    Van Moer, Wendy
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    Department of Signal Processing, KTH 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.
    Characterization of concurrent dual-band power amplifiers using a dual two-tone excitation signal2015In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 64, no 10, p. 2781-2791, article id 7104121Article in journal (Refereed)
    Abstract [en]

    A method to characterize the memory effects in a nonlinear concurrent dual-band transmitter is presented. It is an extension of the conventional two tone test for power amplifiers to concurrent dual band transmitters. The output signal of a concurrent dual-band transmitter is affected not only by intermodulation products but also by cross-modulation products. In one frequency band, the transmitter is excited by a two tone signal which frequency separation is swept. In the second band the transmitter is concurrently excited by an other two tone signal with slightly wider frequency separation. The frequency difference of the two signals is fixed during the frequency sweep. The two tone test is made at different power levels. The upper and lower third-order inter- and cross-modulation products are measured. The asymmetry between the upper and lower third-order inter- and cross-modulation products are measures of the transmitter's memory effects. The measurement results show that the memory effects are more dominant in the third-order intermodulation products than in the cross modulation products. An error analysis and system calibration was performed and measurement results for two different devices are presented.

  • 13.
    Amin, Shoaib
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Van Moer, Wendy
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    Department of Information Science and Engineering, KTH 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.
    Rebuttal to "On Dual-Band Amplifications Using Dual Two-Tones Clarifications and Discussions"2017In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 66, no 10, p. 2795-2797Article in journal (Refereed)
    Abstract [en]

    This rebuttal is to "€œOn dual-band amplifications using dual two-tone: Clarifications and discussion". In the following, we provide our reply.

  • 14.
    Amin, Shoaib
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Zenteno, Efrain
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Landin, Per
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    ACCESS Linnaeus Centre, Signal Processing Lab, KTH Royal Institute of Technology.
    Noise Impact on the Identification of DigitalPredistorter Parameters in the Indirect LearningArchitecture2012In: 2012 Swedish Communication Technologies Workshop (Swe-CTW), IEEE conference proceedings, 2012, p. 36-39Conference paper (Refereed)
    Abstract [en]

    The indirect learning architecture (ILA) is the mostused methodology for the identification of Digital Pre-distorter(DPD) functions for nonlinear systems, particularly for highpower amplifiers. The ILA principle works in black box modelingrelying on the inversion of input and output signals of thenonlinear system, such that the inverse is estimated. This paperpresents the impact of disturbances, such as noise in the DPDidentification. Experiments were performed with a state-of-artDoherty power amplifier intended for base station operationin current telecommunication wireless networks. As expected,a degradation in the performance of the DPD (measured innormalized mean square error (NMSE)) is found in our experiments.However, adjacent channel power ratio (ACPR) canbe a misleading figure of merit showing improvement in theperformance for wrongly estimated DPD functions.

  • 15.
    Andersson, Daniel
    et al.
    Radarbolaget.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Ottoson, Patrik
    Radarbolaget.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Radar Images of Leaks in Building Elements2015In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 78, p. 1726-1731Article in journal (Refereed)
    Abstract [en]

    Through leakage in the building envelope there is a penetration of air, water vapor and particles. The degree of leakage of air can be quantified by existing methods. However, the location of adventitious openings is often not known. In order to overcome the limitations in existing methods, a non-contact and non-destructive method based on ultra-wide bandwidth radar technology is suggested. A test-bed is designed that can measure with different polarization to be able to detect flaws in different directions. Initial measurements shows promising results for further development of the method of using radar images to find leaks in building elements.

  • 16.
    Bennett, J. M.
    et al.
    Physics Division, Michelson Laboratory, Naval Air Warfare Center, China Lake, CA, United States.
    Rönnow, Daniel
    Acreo AB, Kista, Sweden.
    Test of Opticlean strip coating material for removing surface contamination2000In: Applied Optics, ISSN 0003-6935, E-ISSN 1539-4522, Vol. 39, no 16, p. 2737-2739Article in journal (Refereed)
    Abstract [en]

    The strip coating material, Opticlean, which has been reformulated, has been shown to remove 1-5-mu m-diameter particles as well as contamination remaining from previous drag wipe cleaning on a used silicon wafer. In addition, no residue that produced scattering was found on a fresh silicon wafer when Opticlean was applied and then stripped off. The total integrated scattering technique used for the measurements could measure scattering levels of He-Ne laser light as low as a few ppm (parts in 106), corresponding to a surface roughness of <1 Angstrom rms.

  • 17.
    Björsell, Niclas
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Royal Inst Technol, ACCESS Linnaeus Ctr, Stockholm, Sweden.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Royal Inst Technol, ACCESS Linnaeus Ctr, Stockholm, Sweden.
    Händel, Peter
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Royal Inst Technol, ACCESS Linnaeus Ctr, Stockholm, Sweden.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Kautz-Volterra modelling of analogue-to-digital converters2010In: Computer Standards & Interfaces, ISSN 0920-5489, E-ISSN 1872-7018, Vol. 32, no 3, p. 126-129Article in journal (Refereed)
    Abstract [en]

    In many test and measurement applications, the analogue-to-digital converter (ADC) is the limiting component. Using post-correction methods can improve the performance of the component as well as the over all measurement system. In this paper an ADC is characterised by a Kautz-Volterra (KV) model, which utilises a model-based post-correction of the ADC with general properties and a reasonable number of parameters. It is also shown that the inverse model has the same dynamic properties as the direct KV model. Results that are based on measurements on a high-speed 12-bit ADC, shows good results for a third order model.

  • 18.
    Björsell, Niclas
    et al.
    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.
    Händel, Peter
    Measuring Volterra kernels of analog to digital converters using a stepped three-tone scan2006In: Proceedings of the IEEE Instrumentation and Measurement Technology Conference, 2006. IMTC 2006, 2006, p. 1047-1050Conference paper (Refereed)
    Abstract [en]

    Volterra theory can be used to mathematically model nonlinear dynamic components such as analog-to-digital converter (ADC). This paper describes how frequency domain Volterra kernels of an ADC are determined from measurements. The elements of Volterra theory are given and practical issues are considered, such as methods for signal conditioning, finding the appropriate test signals scenario and suitable sampling frequency. The results show that for the used pipeline ADC, the frequency dependence is significantly stronger for second order difference products than for sum products and the linear frequency dependence was not as pronounced as that of the second order Volterra kernel.

  • 19.
    Björsell, Niclas
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Sucháneck, Petr
    Department of Measurement, Czech Technical University, Prague, Czech Republic.
    Händel, Peter
    Signal Processing Laboratory, Royal Institute of Technology, Stockholm, Sweden.
    Rönnow, Daniel
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik. WesternGeco, Asker, Sweden.
    Measuring Volterra kernels of analog to digital converters using a stepped three-tone scan2008In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 57, no 4, p. 666-671Article in journal (Refereed)
    Abstract [en]

    Volterra theory can be used to mathematically model nonlinear dynamic components such as analog-to-digital converter (ADC). This paper describes how frequency domain Volterra kernels of an ADC are determined from measurements. The elements of Volterra theory are given and practical issues are considered, such as methods for signal conditioning, finding the appropriate test signals scenario and suitable sampling frequency. The results show that for the used pipeline ADC, the frequency dependence is significantly stronger for second order difference products than for sum products and the linear frequency dependence was not as pronounced as that of the second order Volterra kernel. It is suggested that the Volterra kernels have the symmetry properties of a specific box model, namely a parallel Hammerstein systems.

  • 20.
    Cardona, M.
    et al.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Rönnow, Daniel
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Santos, P. V.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Ellipsometric investigations of piezo-optical effects1998In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 313-314, p. 10-17Article in journal (Refereed)
    Abstract [en]

    An introduction to the stress-induced birefringence of solids, with emphasis on cubic and amorphous materials, is given. Most available experimental data have been obtained in the frequency region below the electronic absorption edge: the corresponding coefficients of the stress-optical tensor are then real. Above the edge (and also in the IR region of the Reststrahlen) they become complex. Ellipsometry is an excellent tool for the investigation of complex stress-optical functions. It also yields the hydrostatic pressure induced changes in the dielectric functions. Data obtained recently for diamond and zincblende-type crystals and their theoretical interpretation are discussed.

  • 21.
    Choudhary, Vipin
    et al.
    Department of Electronics and Communication, ASET, Amity University Uttar Pradesh, Noida, India .
    Gupta, Aastha
    Department of Electronics and Communication, ASET, Amity University Uttar Pradesh, Noida, India .
    Tripathy, Malay Ranjan
    Department of Electronics and Communication, 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.
    A compact multi-band slotted circular patch MIMO antenna with defective ground surface for wireless application2017In: 2017 4th International Conference on Signal Processing and Integrated Networks (SPIN), IEEE conference proceedings, 2017, p. 33-37, article id 8049911Conference paper (Refereed)
    Abstract [en]

    A compact multi band slotted two elements MIMO antenna is designed on FR4 substrate with the dimensions 60×60×1.5 mm3 and an εr of 4.4. To achieve high isolation between the radiation elements, a Defected Ground Surface (DGS) technique is applied. The isolation between the elements and gain both increased considerably. In the simulated and measured return loss vs frequency results, multi bands are obtained. The maximum isolation is obtained as -36.32 dB at 8.8 GHz in the measured results.

  • 22.
    Eroglu, Abdullah
    et al.
    Department of Electrical and Computer Engineering, Purdue University Fort Wayne, Fort Wayne, IN, USA..
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Design of multilayer and multiline microstrip directional coupler with closed form relations2018In: Progress In Electromagnetics Research C, ISSN 1937-8718, E-ISSN 1937-8718, Vol. 83, p. 1-14Article in journal (Refereed)
    Abstract [en]

    Design, simulation, implementation and measurement results of multiline and multilayer microstrip directional couplers are given with closed form relations. Step-by-step design procedure reflecting the design practice of directional couplers, which requires only information on coupling level, port impedances and operational frequency, is presented. The method based on the synthesis technique applied in the design of conventional two-line microstrip symmetrical directional couplers is adapted to design multilayer directional couplers with the aid of electromagnetic simulators using parametric analysis with curve fitting method. The proposed design method is compared with the measurement results and accuracy is verified. It has been also shown that the directivity of the couplers designed using the multilayer structure is improved significantly. A method such as the one presented in this paper can be used to design multilayer two-line and three-line directional couplers which can be integrated to the front end of an RFID systems to provide the required isolation between transmitter and receiver and prevent signal leakage due to use of conventional circulators.

  • 23.
    Feng, Xin Mei
    et al.
    Department of Microbiology, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden.
    Olsson, J.
    Centre for Human Studies of Foodstuffs, Uppsala University, Uppsala, Sweden.
    Swanberg, M.
    Department of Microbiology, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden.
    Schnürer, J.
    Department of Microbiology, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden.
    Rönnow, Daniel
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Image analysis for monitoring the barley tempeh fermentation process2007In: Journal of Applied Microbiology, ISSN 1364-5072, E-ISSN 1365-2672, Vol. 103, no 4, p. 1113-1121Article in journal (Refereed)
    Abstract [en]

    Aims: To develop a fast, accurate, objective and nondestructive method for monitoring barley tempeh fermentation. Methods and Results: Barley tempeh is a food made from pearled barley grains fermented with Rhizopus oligosporus. Rhizopus oligosporus growth is important for tempeh quality, but quantifying its growth is difficult and laborious. A system was developed for analysing digital images of fermentation stages using two image processing methods. The first employed statistical measures sensitive to image colour and surface structure, and these statistical measures were highly correlated (r = 0.92, n = 75, P < 0.001) with ergosterol content of tempeh fermented with R. oligosporus and lactic acid bacteria (LAB). In the second method, an image-processing algorithm optimized to changes in images of final tempeh products was developed to measure number of visible barley grains. A threshold of 5 visible grains per Petri dish indicated complete tempeh fermentation. When images of tempeh cakes fermented with different inoculation levels of R. oligosporus were analysed the results from the two image processing methods were in good agreement. Conclusion: Image processing proved suitable for monitoring barley tempeh fermentation. The method avoids sampling, is nonintrusive, and only requires a digital camera with good resolution and image analysis software. Significance and Impact of the Study: The system provides a rapid visualization of tempeh product maturation and qualities during fermentation. Automated online monitoring of tempeh fermentation by coupling automated image acquisition with image processing software could be further developed for process control.

  • 24.
    Flattery, Kyle
    et al.
    Indiana University - Purdue University Fort Wayne, Fort Wayne, USA.
    Amin, Shoaib
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. ACCESS Linnaeus Centre, Signal Processing Dept, KTH Royal Institute of Technology, Stockholm, Sweden.
    Mahamat, Yaya
    Indiana University - Purdue University Fort Wayne, Fort Wayne, USA..
    Eroglu, Abdullah
    Indiana University - Purdue University Fort Wayne, Fort Wayne, USA..
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    High Power Combiner/Divider Design for Dual Band RF Power Amplifiers2015In: Proceedings of the 2015 International Conference on Electromagnetics in Advanced Applications: ICEAA 2015, IEEE Press, 2015, p. 1036-1039Conference paper (Refereed)
    Abstract [en]

    Design of low loss with an enhanced thermal profile power divider/combiner for high power dual-band Radio Frequency (RF) power amplifier applications is given. The practical implementation, low loss and substrate characteristics make this type of combiner ideal for high power microwave applications. The combiner operational frequencies are chosen to operate at 900 MHz and 2.14 GHz, which are common frequencies for concurrent dual band RF power amplifiers. The analytical results are verified with simulation results for various cases and agreement has been observed on all of them.

  • 25.
    Granqvist, C. G.
    et al.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Azens, A.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Kullman, L.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Rönnow, Daniel
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Progress in Smart Windows Research: Improved Electrochromic W Oxide Films and Transparent Ti-Ce Oxide Counter Electrodes1996In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 8, no 1-4, p. 97-106Article in journal (Refereed)
    Abstract [en]

    We review recent work on sputter deposited W-oxide-based films. Improved electrochemical durability was obtained by electron bombardment during deposition, and enhanced coloration/bleaching dynamics was obtained by fluorination. Spectrally resolved scattering measurements indicated that haze levels ≪ 1 % could be reached. Oblique angle deposition could yield angular selectivity. New results are given for sputtered Ti-Ce oxide films, showing their capacity as counter electrodes in transparent electrochromic devices.

  • 26.
    Granqvist, C.-G.
    et al.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Azens, A.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Hjelm, A.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Kullman, L.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Niklasson, G. A.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Rönnow, Daniel
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Strömme, M.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Veszelei, M.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Vaivars, G.
    Institute of Solid State Physics, University of Latvia, Riga, Latvia.
    Recent advances in electrochromics for smart windows applications1998Conference paper (Other academic)
  • 27.
    Granqvist, C.-G.
    et al.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Azens, A.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Hjelm, A.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Kullman, Lisen
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Niklasson, Gunnar A.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Rönnow, Daniel
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Strömme, Maria
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Veszelei, M.
    The Ångström Laboratory, Deptartment of Material Science, Uppsala University, Uppsala, Sweden.
    Vaivars, G.
    Institute of Solid State Physics, University of Latvia, Riga, Latvia.
    Recent advances in electrochromics for smart windows applications1998In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 63, no 4, p. 199-216Article in journal (Other academic)
    Abstract [en]

    Electrochromic smart windows are able to vary their throughput of radiant energy by low-voltage electrical pulses. This function is caused by reversible shuttling of electrons and charge balancing ions between an electrochromic thin film and a transparent counter electrode. The ion transport takes place via a solid electrolyte. Charge transport is evoked by a voltage applied between transparent electrical conductors surrounding the electrochromic film/electrolyte/counter electrode stack. This review summarizes recent progress concerning: (i) calculated optical properties of crystalline WO3, (ii) electrochromic properties of heavily disordered W oxide and oxyfluoride films produced by reactive magnetron bias sputtering, (iii) novel transparent reactively sputter-deposited Zr-Ce oxide counter electrodes and (iv) a new proton-conducting antimonic-acid-based polymer electrolyte. Special in depth presentations are given on elastic light scattering from W-oxide-based films and of electronic band structure effects affecting opto-chronopotentiometry data in Zr-Ce oxide. The review also contains some new device data for an electrochromic smart window capable of very high optical transmittance.

    Electrochromic smart windows are able to vary their throughput of radiant energy by low-voltage electrical pulses. This function is caused by reversible shuttling of electrons and charge balancing ions between an electrochromic thin film and a transparent counter electrode. The ion transport takes place via a solid electrolyte. Charge transport is evoked by a voltage applied between transparent electrical conductors surrounding the electrochromic film/electrolyte/counter electrode stack. This review summarizes recent progress concerning: (i) calculated optical properties of crystalline WO3, (ii) electrochromic properties of heavily disordered W oxide and oxyfluoride films produced by reactive magnetron bias sputtering, (iii) novel transparent reactively sputter-deposited Zr-Ce oxide counter electrodes and (iv) a new proton-conducting antimonic-acid-based polymer electrolyte. Special in depth presentations are given on elastic light scattering from W-oxide-based films and of electronic band structure effects affecting opto-chronopotentiometry data in Zr-Ce oxide. The review also contains some new device data for an electrochromic smart window capable of very high optical transmittance.

  • 28.
    Granqvist, Claes-Göran
    et al.
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Azens, A.
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Isidorsson, Jan
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Kharrazi, M.
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Kullman, Lisen
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Lindström, T.
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Niklasson, Gunnar A.
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Ribbing, Carl-Gustaf
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Rönnow, Daniel
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Strömme, Maria
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Veszelei, M.
    Department of Materials Science, Uppsala University, Uppsala, Sweden.
    Towards the smart window: progress in electrochromics1997In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 218, p. 273-279Article in journal (Refereed)
    Abstract [en]

    Electrochromic devices have the ability to produce reversible and persistent changes of their optical properties. The phenomenon is associated with joint ion and electron transport into/out of an electrochromic thin film, in most cases being a transition metal oxide. This paper outlines the various applications of such devices in smart windows suitable for energy-conscious architecture, in variable-reflectance mirrors, and in display devices. Critical materials issues and design concepts are discussed. The paper also covers two specific research topics: computed electronic structure of crystalline WO3 incorporating ionic species, showing how reflectance modulation emerges from a first-principles calculation; and Li+ dynamics in heavily disordered Ti oxide, illustrating how diffusion constants derived from impedance spectroscopy can be reconciled with the Anderson—Stuart model.

  • 29.
    Gupta, Ashta
    et al.
    Department of Electronics and Communication, ASET, Amity University Uttar Pradesh Noida, India.
    Tripathy, Malay Ranjan
    Department of Electronics and Communication, ASET, Amity University Uttar Pradesh Noida, India.
    Choudhary, Vipin
    Department of Electronics and Communication, 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.
    A compact four-element MIMO antenna for WLAN/WiMAX and HiperLAN applications2016In: 2016 IEEE Annual India Conference (INDICON), 2016Conference paper (Refereed)
    Abstract [en]

    A compact four-element multi-input-multi-output (MIMO) antenna useful for wireless ultra-wide band (UWB) applications and systems is introduced in this paper. The frequency bandwidth obtained with the proposed UWB antennas is 1.5 to 12.5 GHz. The substrate material used is FR4 with dielectric coefficient of 4.4. The dimension of the substrate is 30×60×1.5 mm3 and the dielectric loss tangent is 0.02. The Envelope Correlation Coefficient (ECC) and Diversity gain are calculated in this paper with values within their acceptable limits.

  • 30.
    Händel, Peter
    et al.
    Department of Information Science and Engineering, KTH 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.
    Dirty MIMO Transmitters: Does It Matter?2018In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, no 8, p. 5425-5436Article in journal (Refereed)
    Abstract [en]

    The radio frequency transmitter is a key component in contemporary MIMO OFDM systems. A detailed study of a 2&#x00D7;2 MIMO transmitter subjected to correlated input data streams, nonlinear distortion, thermal noise, and crosstalk is provided by stochastic modeling. The effects of correlated input streams, crosstalk and nonlinearities are studied in detail, and exemplified both by approximate expressions and numerical simulations. Key results include exact and approximate expressions for the normalized mean-squared error (NMSE) for systems with or without digital predistortion, the relationship between NMSE and the signal-to-noise-and-distortion ratio, the properties of the distortion noise, and a novel design for power amplifier back-off for MIMO-transmitters subject to crosstalk. The theoretical derivations are illustrated by numerical examples and simulation results, and their relationship to state-of-the-art research are discussed. OAPA

  • 31.
    Händel, Peter
    et al.
    Department of Information Science and Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Modeling Mixer and Power Amplifier Impairments2019In: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 29, no 7, p. 441-443, article id 8733818Article in journal (Refereed)
    Abstract [en]

    Combating the effects of mixer and power amplifier (PA) imperfections on transmitter performance is crucial for the design of wireless systems. PA compression and in-phase/quadrature imbalance are analyzed for a single-input-single-output transmitter model. The influence of the imperfection on the normalized mean squared error (NMSE) of the transmitter is studied using an analytical framework that relies on the classic Bussgang theory. The study concludes with a closed-form expression for the NMSE that provides insights into the behavior of the transmitter. © 2019 IEEE.

  • 32.
    Isaksson, Magnus
    et al.
    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.
    A Kautz-Volterra Behavioral Model for RF Power Amplifiers2006In: IEEE MTT-S International Microwave Symposium Digest, 2006, 2006, p. 485-488Conference paper (Refereed)
    Abstract [en]

    A new type of behavioral power amplifier (PA) model, a discrete-time Kautz-Volterra (KV) model, is presented. In the model a priori knowledge of the system properties in terms of different poles for different nonlinear orders is used, which is needed for modeling nonlinear and linear memory effects in PAs. An accurate model can thus be achieved with a small number of parameters. Simulated results of parallel Hammerstein and Wiener structures and from modeling the behavior of a PA are presented

  • 33.
    Isaksson, Magnus
    et al.
    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.
    A Parameter-Reduced Volterra Model for Dynamic RF Power Amplifier Modeling based on Orthonormal Basis Functions2007In: International Journal of RF and Microwave Computer-Aided Engineering, ISSN 1096-4290, E-ISSN 1099-047X, Vol. 17, no 6, p. 542-551Article in journal (Refereed)
    Abstract [en]

    A nonlinear dynamic behavioral model for radio frequency power amplifiers is presented. It uses orthonormal basis functions, Kautz functions, with complex poles that are different for each nonlinear order. It has the same general properties as Volterra models, but the number of parameters is significantly smaller. Using frequency weighting the out-of-band model error can be reduced. Using experimental data it was found that the optimal poles were the same for different input powers and for the different nonlinear orders. The optimal poles were also the same for direct and inverse models, which could be explained theoretically to be a general property of nonlinear systems with negligible linear memory effects. The model can be used as either a direct or inverse model with the same model error for power amplifiers with negligible linear memory effects.

  • 34.
    Isaksson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik. Royal Institute of Technology, Signal Processing Lab, Stockholm, Sweden.
    Wisell, David
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik. Royal Institute of Technology, Signal Processing Lab, Stockholm, Sweden; Ericsson AB, Gävle, Sweden.
    Eng, Anders
    Syntronic AB, Gävle, Sweden.
    Rönnow, Daniel
    WestemGeco AS, Asker, Norway.
    A Study of a Variable-Capacitance Drain Network's Influence on Dynamic Behavioral Modeling of an RF PA2007In: 69th ARFTG Microwave measurement conference, Honolulu, HI, USA, 2007, p. 112-116Conference paper (Refereed)
    Abstract [en]

    An investigation of the complex-valued parameters of two different dynamic behavioral models due to changes in the drain decoupling network of a PA has been performed. The study is based on complex-envelope measurements on a real PA. The complex coefficients of the parallel Hammerstein (PH) and the optimal pole placements of the Kautz-Volterra (KV) models are analyzed. It is concluded that the parameters follow smooth, predictable functions and that the KV poles give a robust description of the PA's memory effects compared with the PH model.

  • 35.
    Isaksson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Wisell, David
    Rönnow, Daniel
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    A Comparative Analysis of Behavioral Models for RF Power Amplifiers2006In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 54, no 1, p. 348-359Article in journal (Refereed)
    Abstract [en]

    A comparative study of nonlinear behavioral models with memory for radio-frequency power amplifier (PAs) is presented. The models are static polynomial, parallel Hammerstein (PH), Volterra, and radial basis-function neural network (RBFNN). Two PAs were investigated: one was designed for the third-generation (3G) mobile telecommunication systems and one was designed for the second-generation (2G). The RBFNN reduced the total model error slightly more than the PH, but the error out of band was significantly lower for the PH. The Volterra was found to give a lower model error than did a PH of the same nonlinear order and memory depth. The PH could give a lower model error than the best Volterra, since the former could be identified with a higher nonlinear order and memory depth. The qualitative conclusions are the same for the 2G and 3G PAs, but the model errors are smaller for the latter. For the 3G PA, a static polynomial gave a low model error as low as the best PH and lower than the RBFNN for the hardest cross validation. The models with memory, PH, and RBFNN, showed better cross-validation performance, in terms of lower model errors, than a static polynomial for the hardest cross validation of the 2G PA.

  • 36.
    Isaksson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Wisell, David
    Rönnow, Daniel
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Behavioural Amplifier Modelling Using Sampled Complex Envelope Measurement Data2005In: Proc. Gigahertz 2005, 2005, p. 213-216Conference paper (Refereed)
  • 37.
    Isaksson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Wisell, David
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik. Ericsson AB, Gävle, Sweden.
    Rönnow, Daniel
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Nonlinear Behavioral Modeling of Power Amplifiers Using Radial-Basis Function Neural Networks2005In: 2005 IEEE MTT-S International Microwave Symposium Digest, 2005, p. 1967-1970Conference paper (Refereed)
    Abstract [en]

    A radial-basis function neural network (RBFNN) is proposed for modeling the dynamic nonlinear behavior of RF power amplifiers. In the model the signal's envelope is used. The model requires less training than a model using both IQ-data. Sampled input and output signals from a power amplifier for 3G were used in the identification and validation. The RBFNN is compared with a parallel Hammerstein model. For a memory depth of one sample the RBFNN gives a better model, in- and out-of-band; for three samples the RBFNN reduces the in-band error more while the Hammerstein model reduces the error out-of-band more.

  • 38.
    Isaksson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Wisell, David
    Rönnow, Daniel
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Wide-Band Dynamic Modeling of Power Amplifiers Using Radial-Basis Function Neural Networks2005In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 53, no 11, p. 3422-3428Article in journal (Refereed)
  • 39.
    Ivanchenko, I.
    et al.
    O. Ya. Usikov Institute for Radiophysics and Electronics of the NAS of Ukraine, Kharkiv, Ukraine.
    Khruslov, M.
    O. Ya. Usikov Institute for Radiophysics and Electronics of the NAS of Ukraine, Kharkiv, Ukraine.
    Popenko, N.
    O. Ya. Usikov Institute for Radiophysics and Electronics of the NAS of Ukraine, Kharkiv, Ukraine.
    Shestopalov, Yury
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Mathematics.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Combined system of the microstrip antennas with different frequencies2016In: 2016 22nd International Conference on Applied Electromagnetics and Communications (ICECOM), 2016Conference paper (Refereed)
    Abstract [en]

    The combined system with microstrip antennas (f1=1.85GHz; f2=3.7GHz, f3=1.75GHz, f4= 3.5GHz) is presented. The measurements of the prototype characteristics have shown that elevation angle of peak directivity of the antennas is oriented to zenith. Simulated S11 at stated frequencies with the following minimum values of S11 = -34dB, f=1.85GHz; S11=-21dB, f=3.7GHz; S11 = -22dB, f=1.75GHz; S11=-19dB, f=3.5GHz are observed.

  • 40.
    Ivanchenko, Igor
    et al.
    O. Ya. Usikov Institute for Radiophysics and Electronics of the NAS of Ukraine, Ukraine.
    Khruslov, Maksym
    O. Ya. Usikov Institute for Radiophysics and Electronics of the NAS of Ukraine, Ukraine.
    Plakhtiy, Vadim
    O. Ya. Usikov Institute for Radiophysics and Electronics of the NAS of Ukraine, Ukraine.
    Popenko, Nina
    O. Ya. Usikov Institute for Radiophysics and Electronics of the NAS of Ukraine, Ukraine.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    X-band aperture antenna with hybrid dielectric inserts2016In: Progress In Electromagnetics Research C, ISSN 1937-8718, E-ISSN 1937-8718, Vol. 61, p. 27-35Article in journal (Refereed)
    Abstract [en]

    An X-band radiator as an open-ended waveguide with a hybrid dielectric insert is proposed. The insert is in the form of a parallelepiped, which fills the entire cross section of the waveguide and constitutes a Teflon matrix with local inhomogeneities in the form of dielectric cylinders with a different permittivity. The design allows for forming various near-field distributions and, hence, the radiator performance by means of definite combinations of the local inhomogeneities can be modified. A number of configurations in the location of air and quartz cylinders are investigated. The calculated and experimental results are in good agreement. The proposed approach to the near-field formation of the aperture antenna is promising, because the variety of possible configurations in the location of local inhomogeneities with different permittivity provides new opportunities in terms of designing both single radiators and antenna arrays.

  • 41.
    Ivanchenko, Igor
    et al.
    O.Ya. Usikov Institute for Radiophysics and Electronics of the National Academy of Sciences of Ukraine, Ukraine.
    Khruslov, Maksym
    O.Ya. Usikov Institute for Radiophysics and Electronics of the National Academy of Sciences of Ukraine, Ukraine.
    Popenko, Nina
    O.Ya. Usikov Institute for Radiophysics and Electronics of the National Academy of Sciences of Ukraine, Ukraine.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Electronics.
    Combined L–S-bands antenna module2019In: IET Microwaves, Antennas & Propagation, ISSN 1751-8725, E-ISSN 1751-8733, Vol. 13, no 5, p. 541-545Article in journal (Refereed)
    Abstract [en]

    A combined L-S-band antenna module consists of four rectangular patch antennas, two of which operate at the frequencies of the first harmonics (L-band), and two others at the frequencies of the second harmonics (S-band). The module is intended for use in super heterodyne signal reception circuits, for example in studying the various non-linear phenomena. The results of this study are presented in terms of improving the performance of each antenna and minimising their mutual influence. The resonance frequencies of the L-band antenna differ by 50MHz. All the antennas radiate close to the zenith and their beamwidths in two principal planes are virtually the same. At the resonance frequencies, the reflection coefficient is S-11<-30dB for the transmitting antenna, and S-11<-20dB for the receiving antenna. The minimum allowable distance between the antennas is determined, at which their mutual influence can be neglected (S-12<-50dB).

  • 42.
    Johansson, Anders
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Mathematics.
    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.
    An analysis of Kautz-Volterra models for modeling block structure nonlinear systems2010Report (Other academic)
    Abstract [en]

    Kautz-Volterra (KV) models of some nonlinear systems were analyzed. The relationsbetween the true pole of the analyzed systems and the optimal pole of the KV modelswere analyzed. The properties of nonlinear systems depend on the order of thesubsystems, since nonlinear operators do not commute. Wiener (H-N) andHammerstein (N-H) systems were analyzed.

  • 43.
    Kullman, L.
    et al.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Rönnow, Daniel
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Granqvist, C. G.
    Department of Technology, Uppsala University, Uppsala, Sweden.
    Elastic Light Scattering and Electrochemical Durability of Electrochromic Tungsten-oxide-based Films1996In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 288, no 1-2, p. 330-333Article in journal (Refereed)
    Abstract [en]

    Electrochromic W-oxide-based films were produced by reactive d.c. magnetron sputtering. Fluorination and substrate bias were used to modify the film properties. Spectral measurements of the total and diffuse light scattering showed that the diffuse component remained at much less than 1% in the visible, irrespective of electrochemical degradation, which is low enough for smart windows applications.

  • 44.
    Kumar, Devesh
    et al.
    Department of ECE, ASET, Amity University Uttar Pradesh, Noida, India.
    Tripathy, M. R.
    Department of ECE, 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.
    Geethu, P. S.
    Department of ECE, ASET, Amity University Uttar Pradesh, Noida, India.
    Saurabh, Lucky
    Department of ECE, ASET, Amity University Uttar Pradesh, Noida, India.
    Performance analysis of meta-material based bow-tie shaped fractal antenna for THz application2017In: Proceedings of the 7th International Conference Confluence 2017 on Cloud Computing, Data Science and Engineering, IEEE, 2017, p. 764-769, article id 7943253Conference paper (Refereed)
    Abstract [en]

    This paper presents design and analysis of meta-material based bowtie-shaped fractal antenna for the frequency range of l.l-l.8 THz for futuristic Terahertz applications. A meta-material-inspired structure isinserted on ground plane to enhance overall performance of the proposed design. A comparative analysis of various iterated designs has been carried out in detail. Performance parameters e.g. return loss, antenna gain, radiation efficiency, radiation pattern are presented and discussed. Simulated resultsshow the multiband nature of designed antennas. Maximum gain of 6.59 dB and return loss of −21.00 dB are obtained at 1.5455 THz and 1.1787 THz respectively. HFSS simulation software is used for simulation of the designs.

  • 45.
    Kumar, Rajesh
    et al.
    Amity University, ASET, Department of Electronics & Communication Engineering, Noida, India; BSAITM, Faridabad, Haryana, India.
    Sarika,
    Amity University, ASET, Department of Electronics & Communication Engineering, Noida, India; BSAITM, Faridabad, Haryana, India.
    Tripathy, Malay Ranjan
    Amity University, ASET, Department of Electronics & Communication Engineering, Noida, India.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Orientation and Gap Independent Meta-surface Bowtie Antenna for WLAN Applications2017In: 2017 8TH INTERNATIONAL CONFERENCE ON COMPUTING, COMMUNICATION AND NETWORKING TECHNOLOGIES (ICCCNT), IEEE , 2017, article id 8203973Conference paper (Refereed)
    Abstract [en]

    A meta-surface loaded bowtie antenna with orientation and gap analysis depicting multi-band features from 1.5 GHz to 7.2 GHz is proposed. The orientation and the gap between the meta-surface unit cells are altered to investigate the effect on parameters like gain, bandwidth and directivity. The bowtie antenna uses FR4 material with relativity of 4.6, loss tangent of 0.02 and thickness h = 1.5 mm as substrate. The measured results of the fabricated antenna show a positive agreement with the simulation results. The proposed antenna shows the application in the range of WLAN. ANSYS High Frequency Structural Simulator (IIFSS) software is used to simulate the antenna.

  • 46.
    Kumar, Rajesh
    et al.
    Department of Electronics and Communication Engineering, ASET Amity University Uttar Pradesh, Noida, India.
    Sarika,
    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.
    Performance analysis of 2 × 2 MIMO antenna with meta-material for ultra-wideband applications2017In: 2017 Progress In Electromagnetics Research Symposium - Fall (PIERS - FALL), Electromagnetics Academy , 2017, p. 593-597Conference paper (Refereed)
    Abstract [en]

    A 2 × 2 MIMO antenna based on meta-material is designed and analyzed for ultra-wideband (UWB) applications. The antenna is designed on 1.6 mm thick FR4 substrate having small dimensions of 40 mm × 40 mm. The leaf shape antenna structure with Full Ground (FG) is chosen which provides three wide bands from 0.1 GHz to 1.2 GHz, 1.2 GHz to 6.3 GHz and 6.5 GHz to 15.3 GHz. The composition of ground is varied from FG to Partial Ground (PG) to eventually PG with meta-material (PG with MM). The effect of PG with MM layer on the leaf structure shows that the return losses become smoother in nature with merging of first two bands into one, i.e., 0.1 GHz to 6.2 GHz. The structure designed provides good amount of isolation between four antenna elements. The compact size of antenna provides applications in portable UWB, X-band and Ku-band. © 2018 Electromagnetics Academy. All rights reserved.

  • 47.
    Kumar, Rajesh
    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 .
    Sarika, n/a
    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.
    Multi-band slotted bowtie antenna for L, S and C band applications2017In: 2nd International Conference on Telecommunication and Networks (TEL-NET), 2017, p. 104-107Conference paper (Refereed)
    Abstract [en]

    A multi-band slotted bowtie antenna for L, S and C band applications is presented. The proposed antenna has the configuration of 40 mm58 mm1.5 mm. The slots are etched on the bowtie antenna to obtain multi-band features. The number of slots and spacing between them is varied for parametric study. The designed is fabricated on FR4 material and the measured and simulated results are in good agreement with each other thus confirming the proposed antenna design. High Frequency Structural Simulator (HFSS) is used for simulating the antenna design.

  • 48.
    Kumar, Rajesh
    et al.
    Amity University, Noida, India; BSAITM, Faridabad, Haryana, India.
    Tripathy, Malay Ranjan
    Amity University, Noida, India.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Multi Band Metamaterial Based Bowtie Antenna for Wireless Applications2015In: PIERS 2015 Prague: Progress in Electromagnetics Research Symposium : Proceedings, Cambridge, MA: Electromagnetics Academy , 2015, p. 2368-2371Conference paper (Refereed)
    Abstract [en]

    A new meta-material based bowtie antenna is proposed in this paper. Multi band response is observed in the simulated result of return loss for different frequencies (i.e., 1-12GHz). Apart from this it is seen that the return loss is improved in the case of metamaterial antenna in comparison to the conventional antenna. Simulated results of ζ and μ versus frequency are shown and it is observed that negative ζ and negative μ are obtained in different frequency bands respectively.

  • 49.
    Kumar, Rajesh
    et al.
    Department of Electronics and Communication Engineering, ASET, Amity University, Noida, Uttar Pradesh, India.
    Tripathy, Malay Ranjan
    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.
    Multi-resonant Bowtie Antenna with Modified Symmetric SRR for Wireless Applications2018In: IETE Journal of Research , E-ISSN 0974-780XArticle in journal (Refereed)
    Abstract [en]

    A modified symmetric split ring resonator (MSSRR) loaded bowtie antenna with multi-band features over a range of 1.6–7.1 GHz is proposed in this paper. The antenna is designed on FR4 substrate with relative permittivity εr = 4.1 and thickness 1.5 mm. The fabricated antenna size is 40 mm × 58 mm. The Modified Symmetric SRR used beneath the substrate is novel and consists of two circles that are broken into four quarter circles by four rods. The effect of MSSRR location and its geometry is investigated and analysed thoroughly. The measurement results of the fabricated antenna are in good agreement with the simulation results, which confirms the proposed antenna design’s properties. ANSYS High Frequency Structural Simulator (HFSS) software is used for simulating the antenna.

  • 50.
    Kumar, Umesh
    et al.
    Amity University Uttar Pradesh, ASET, Dept Elect & Commun Engn, Noida, India.
    Kumar, Devesh
    Amity University Uttar Pradesh, ASET, Dept Elect & Commun Engn, Noida, India.
    Tripathy, Malay Ranjan
    Amity University Uttar Pradesh, ASET, Dept Elect & Commun Engn, Noida, India.
    Ranjan, Priya
    Amity University Uttar Pradesh, ASET, Dept Elect & Commun Engn, Noida, India.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Metamaterial Based Fractal Antenna for THz Application2016In: 2016 PROGRESS IN ELECTROMAGNETICS RESEARCH SYMPOSIUM (PIERS), IEEE , 2016, p. 3814-3814Conference paper (Refereed)
123 1 - 50 of 108
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