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  • 1.
    Alayón Glazunov, Andrés
    et al.
    Division of Electromagnetic Engineering, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Prasad, Sathyaveer
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Signal Processing Lab, KTH Royal Institute of Technology, Stockholm, Sweden.
    Händel, Peter
    ACCESS Linnaeus Centre; Signal Processing Lab, KTH Royal Institute of Technology, Stockholm, Sweden.
    Experimental Characterization of the Propagation Channel along aVery Large Virtual Array in a Reverberation Chamber2014In: Progress in Electromagnetics Research B, ISSN 1937-6472, E-ISSN 1937-6472, Vol. 59, p. 205-217Article in journal (Refereed)
    Abstract [en]

    We show that the combined use of radio frequency absorbers and directive antennas can produce significant changes of the radio propagation channel properties along the positions of a virtual array inside a reverberation chamber. A multidimensional characterization of the channel was performed at 40 antenna positions with spacing of 0:233λ at 1 GHz. The average power, the Ricean K-factor, the coherence bandwidth, the r.m.s. delay spread, the mean delay, the beamforming power angle spectrum and array antenna correlation have been studied for different arrangements in the reverberation chamber. The analysis shows that the joint average over time and frequency channel behavior is, as expected, rather homogeneous along the very large array. However, individual realizations of the channel present a pronounced selective behavior in space, time and frequency with parameters varying along the positions of the virtual array suggesting that a heterogeneous behavior of the radio channels can be emulated in reverberation chambers. An important application of the presented study comprises testing of antenna array designs and algorithms in multipath environments. Further development may lead to Over The Air testing of Multiple Input Multiple Output antenna systems of various sizes, i.e., from small to very large arrays.

  • 2.
    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.

  • 3.
    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.

  • 4.
    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.

  • 5.
    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.

  • 6.
    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.

  • 7.
    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.

  • 8.
    Björsell, Niclas
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Händel, Peter
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    A Statistical Evaluation of ADC Histogram Tests with Arbitrary Stimuli Signal2005In: ADDA 2005, 2005, p. 259-264Conference paper (Refereed)
    Abstract [en]

    Histogram tests are a commonly used method for characterizing analogue to digital converters. However, different stimuli signals can be used in the histogram test. An overview of common input stimuli for the test is presented. Previous works have analysed the statistical properties of the resulting histograms for different stimuli signals, separately. In this paper, generally applicable results for asymptotically unbiased minimum variance estimator and Cramer-Rao lower bound are derived, irrespective of used input stimuli. Where available, the general expression is compared and found in accordance with signal-specific expressions.

  • 9.
    Björsell, Niclas
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Händel, Peter
    Signal Processing Lab., ACCESS Linnaeus Center, School of Electrical Engineering, Royal Institute of Technology, Stockholm, Sweden.
    Achievable ADC Performance by Postcorrection Utilizing Dynamic Modeling of the Integral Nonlinearity2008In: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, article id 497187Article in journal (Refereed)
    Abstract [en]

    There is a need for a universal dynamic model of analog to digital converters (ADC) aimed for post-correction. However, it is complicated to fully describe the properties of an ADC by a single model. An alternative is to split up the ADC model in different components, where each component has unique properties. In this paper, a model based on three components is used, and a performance analysis for each component is presented. Each component can be post-corrected individually and by the method that best suits the application. The purpose with post-correction of an ADC is to improve the performance. Hence, for each component, expressions for the potential improvement have been developed. The measures of performance are total harmonic distortion (THD) and signal to noise and distortion (SINAD) and to some extent spurious free dynamic range (SFDR).

  • 10.
    Björsell, Niclas
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Händel, Peter
    Royal Institute of Technology, Stockholm.
    Dynamic behavior models of analog to digital converters aimed for post-correction in wideband applications2006In: IMEKO Workshop on ADC and DAC Modelling and Testing, September 17-22, 2006, Rio de Janeiro, 2006, p. 5-Conference paper (Refereed)
    Abstract [en]

    In this paper a dynamic behavior model of analog to digital converters is proposed. The model is aimed for post correction in wideband applications. The suggested post correction method is a combination of look up tables and model based correction. The model consists of three components. The first is a component represented by a Hammerstein model; that is a static nonlinearity followed by a time invariant linear filter. The second component is a nonparametric model caused by significant deviation from the characterized integral nonlinearity and the output from the Hammerstein model. The third component contains of the remaining deviation and is considered as a random model error. Results from simulations verify that the examined ADC can be described by an ordinary Hammerstein model and a static look-up table.

  • 11.
    Björsell, Niclas
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Händel, Peter
    Signal Processing Laboratory, Royal Institute of Technology, Stockholm, Sweden.
    Histogram Tests for Wideband Applications2008In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 57, no 1, p. 70-75Article in journal (Refereed)
    Abstract [en]

    Characterization and testing of analog-to-digital converters (ADCs) are important in many different aspects. Histogram test is a common method to characterize the linearity features of an ADC. Two commonly used stimuli signals are sine waves and Gaussian noise. This paper presents a metrological comparison between Gaussian and sine wave histogram tests for wideband applications; that is we evaluate the performance in characterization of the ADC and the usability of post-correction. A post-correction procedure involves characterization of the ADC non-linearity and then use of this information by processing the ADC output samples to remove the distortion.

    The results show that the Gaussian histogram test gives reasonable accuracy to measure non-linearities. However, it does not result in a suitable model for post-correction in wideband applications. A single-tone sine wave histogram will be a better basis for post-correction. Best result can be obtained if the look-up table is trained with several single-tone sine waves in the frequency band.

  • 12.
    Björsell, Niclas
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Händel, Peter
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Post-Correction of Under-Sampled Analog to Digital Converters2007In: IEEE Instrumentation and Measurement Technology Conference, 2007Conference paper (Refereed)
    Abstract [en]

    Applications with wide bandwidth and high center frequencies force the analog to digital converter (ADC) to be active in a working range with less dynamic performance in relation to lower frequency bands. However using under-sampling techniques in combination with post-correction methods enable a combination of high sampling rate, wide bandwidth and low distortion. In this paper the employed dynamic post-correction is a combination of look-up tables and model based correction. The results are mainly based on measurements on a 12 bit 210 MSPS ADC. The improvement in total harmonic distortion and spurious free dynamic range are acceptable over a wide frequency range and it is robust to variations in amplitude.

  • 13.
    Björsell, Niclas
    et al.
    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, ACCESS Linnaeus Center.
    Jansson, Magnus
    Royal Institute of Technology,Signal Processing Lab, ACCESS Linnaeus Center.
    Medawar, Samer
    Royal Institute of Technology, Signal Processing Lab, ACCESS Linnaeus Center.
    Improved Estimate of Parametric Models for Analogue to Digital Converters by Using Weighted Integral Nonlinearity Data2010In: 17th Symposium IMEKO TC4 - Measurement of Electrical Quantities, 15th International Workshop on ADC Modelling and Testing, and 3rd Symposium IMEKO TC19: Environmental Measurements / [ed] Linus Michaeli, Jan Saliga, 2010, p. 597-600Conference paper (Refereed)
    Abstract [en]

    Error modelling has played a major role in generating post-corrections of analogue to digital converters (ADC). Benefits by using parametric models for post-correction are that they requires less memory and that they are easier to identify for arbitrary signals. However, the parameters are estimated in two steps; firstly, the integral nonlinearity (INL) is estimated and secondly, the model parameters. In this paper we propose a method to improve the performance in the second step, by utilizing information about the statistical properties of the first step.

  • 14.
    Björsell, Niclas
    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.
    Händel, Peter
    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.
    Kautz-Volterra modelling of an analogue-to-digital converter using a stepped three-tone excitation2007In: 12th IMEKO TC-4 International Workshop on ADC MODELLING AND TESTING, Iasi, Romania, September 2007, 2007, p. 107-112Conference paper (Refereed)
  • 15.
    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.

  • 16.
    Björsell, Niclas
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Nader, Charles
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Signal Processing Lab, Royal Institute of Technology, Stockholm, Sweden.
    Händel, Peter
    Signal Processing Lab, Royal Institute of Technology, Stockholm, Sweden.
    Multi-tone design for out-of-band characterization of nonlinear RF modules using harmonic sampling2010In: 2010 IEEE International Instrumentation and Measurement Technology Conference, I2MTC 2010: Proceedings, Piscataway, NJ: IEEE Service Center , 2010, p. 620-623, article id 5488231Conference paper (Refereed)
    Abstract [en]

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

  • 17.
    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.

  • 18.
    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.

  • 19.
    Fritzin, Jonas
    et al.
    Linköping University.
    Jung, Ylva
    Linköping University.
    Landin, Per Niklas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Enqvist, Martin
    Linköping University.
    Alvandpour, Atila
    Linköping University.
    Phase predistortion of a class-D outphasing RF amplifier in 90 nm CMOS2011In: IEEE Transactions on Circuits and Systems - II - Express Briefs, ISSN 1549-7747, E-ISSN 1558-3791, Vol. 58, no 10, p. 642-646Article in journal (Refereed)
    Abstract [en]

    This brief presents a behavioral model structure and5a model-based phase-only predistortion method that are suitable for outphasing RF amplifiers. The predistortion method is based on a model of the amplifier with a constant gain factor and phase rotation for each outphasing signal, and a predistorter with phase rotation only. The method has been used for EDGE and wide-band code-division multiple-access (WCDMA) signals applied to a Class-D outphasing RF amplifier with an on-chip transformer used for power combining in 90-nm CMOS. The measured peak power at 2 GHz was +10.3 dBm with a drain efficiency and power-added efficiency of 39% and 33%, respectively. For an EDGE 8 phase-shift-keying (8-PSK) signal with a phase error of 3 degrees between the two input outphasing signals, the measured power at 400 kHz offset was −65.9 dB with predistortion, compared with −53.5 dB without predistortion. For a WCDMA signal with the same phase error between the input signals, the measured adjacent channel leakage ratio at 5-MHz offset was -50.2 dBc with predistortion, compared with -38.0 without predistortion.

  • 20.
    Händel, Peter
    Signal Processing Lab, School of Electrical Engineering, Royal Institute of Technology, Stockholm, Sweden.
    Power Spectral Density Error Analysis of Spectral Subtraction Type of Speech Enhancement Methods2007In: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, no 96384Article in journal (Refereed)
    Abstract [en]

    A theoretical framework for analysis of speech enhancement algorithms is introduced for performance assessment of spectral subtraction type of methods. The quality of the enhanced speech is related to physical quantities of the speech and noise (such as stationarity time and spectral flatness), as well as to design variables of the noise suppressor. The derived theoretical results are compared with the outcome of subjective listening tests as well as successful design strategies, performed by independent research groups.

  • 21.
    Händel, Peter
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Björsell, Niclas
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Jansson, Magnus
    Medawar, Samer
    Modeling the dynamics of analog-digital-converters at radio frequency2007In: RF Measurement Technology Conference, Gävle 11-12 September 2007, 2007Conference paper (Other (popular science, discussion, etc.))
  • 22.
    Händel, Peter
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik. University of Gävle, Center for RF Measurement Technologies. Royal Institute of Technology, Signal Processing Lab, ACCESS Linnaeus Centre, Stockholm, Sweden.
    Prasad, Sathyaveer
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik. University of Gävle, Center for RF Measurement Technologies. Royal Institute of Technology, Signal Processing Lab, ACCESS Linnaeus Centre, Stockholm, Sweden.
    Beckman, Claes
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik. University of Gävle, Center for RF Measurement Technologies.
    Maximum likelihood estimation of reverberation chamber direct-to-scattered ratio2009In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 45, no 25, p. 1285-1286Article in journal (Refereed)
    Abstract [en]

    The exact maximum likelihood estimator of the direct-to-scattered ratio of the Rician channel in a reverberation chamber is derived and its performance analysed. It is shown that the estimator obeys a non-central F-distribution, the mean value and variance of which are derived. For well stirred chambers, it is shown that the systematic error in the estimated ratio may be significant.

  • 23.
    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 2×2 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

  • 24.
    Khan, Zain Ahmed
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH, Royal Institute of Technology.
    Händel, Peter
    KTH, Royal Institute of Technology, Stockholm, Sweden.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    A Comparative Analysis of the Complexity/Accuracy Tradeoff in the Mitigation of RF MIMO Transmitter Impairments2017In: 2017 89th ARFTG Microwave Measurement Conference (ARFTG), IEEE, 2017, article id 8000827Conference paper (Refereed)
    Abstract [en]

    This paper presents a comparative analysis of the complexity accuracy tradeoff in state-of-the-art RF MIMO transmitter mitigation models. The complexity and accuracy of the candidate models depends on the basis functions considered in these models. Therefore, a brief description of the mitigation models is presented accompanied by derivations of the model complexities in terms of the number of FLOPs. Consequently, the complexity accuracy tradeoff in the candidate models is evaluated for a 2 × 2 RF MIMO transmitter. Furthermore, the model complexities are analyzed for increasing nonlinear orders and number of antennas.

  • 25.
    Khan, Zain Ahmed
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Royal Institute of Technology, KTH.
    Zenteno, Efrain
    Universidad Católica San Pablo.
    Händel, Peter
    Royal Institute of Technology (KTH).
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Digital Predistortion for Joint Mitigation of I/Q Imbalance and MIMO Power Amplifier Distortion2017In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 65, no 1, p. 322-333, article id 7600411Article in journal (Refereed)
    Abstract [en]

    This paper analyzes the joint effects of in-phase and quadrature (I/Q) imbalance and power amplifier (PA) distortion for RF multiple input multiple output (MIMO) transmitters in the presence of crosstalk. This paper proposes candidate models for the digital predistortion of static I/Q imbalanced sources exciting a dynamic MIMO Volterra system. The proposed models are enhanced using a novel technique based on subsample resolution to account for dynamic I/Q imbalance distortions. Finally, the computational complexity of the proposed models is analyzed for implementation suitability in digital platforms. It is shown that the error spectrum for the proposed models in subsample resolution reaches the noise floor of the measurements. The proposed models achieve a normalized mean squared error of -50 dB and an adjacent channel power ratio of -57 dB for signal bandwidths upto 65 MHz and crosstalk levels ranging to -10 dB. These results demonstrate the effectiveness of the proposed techniques in the joint mitigation of I/Q imbalance and PA distortion with crosstalk for a typical 2x2 MIMO telecommunication setup.

  • 26.
    Khan, Zain Ahmed
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Department of Information Science and Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Zenteno, Efrain
    Universidad Católica San Pablo, Arequipa, Peru.
    Händel, Peter
    Department of Information Science and Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Extraction of the Third-Order 3x3 MIMO Volterra Kernel Outputs Using Multitone Signals2018In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 66, no 11, p. 4985-4999Article in journal (Refereed)
    Abstract [en]

    This paper uses multitone signals to simplify the analysis of 3×3 multiple-input multiple-output (MIMO) Volterra systems by isolating the third-order kernel outputs from each other. Multitone signals fed to an MIMO Volterra system yield a spectrum that is a permutation of the sums of the input signal tones. This a priori knowledge is used to design multitone signals such that the third-order kernel outputs are isolated in the frequency domain. The signals are designed by deriving the conditions for the offset and spacing of the input frequency grids. The proposed technique is then validated for the six possible configurations of a 3x3 RF MIMO transmitter impaired by crosstalk effects. The proposed multitone signal design is used to extract the third-order kernel outputs, and their relative contributions are analyzed to determine the dominant crosstalk effects for each configuration.

  • 27.
    Khan, Zain Ahmed
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH Royal Institute of Technology.
    Zenteno, Efrain
    Universidad Católica San Pablo.
    Händel, Peter
    KTH Royal Institute of Technology.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. University of Gävle.
    Identification of Third Order 3x3 MIMO Volterra Kernels using Multitone Excitation SignalsManuscript (preprint) (Other academic)
  • 28.
    Khan, Zain Ahmed
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH Royal Institute of Technology, Stockholm, Sweden.
    Zenteno, Efrain
    Deptartment of Electronics and Telecommunications, Universidad Catolica San Pablo, Arequipa, Peru.
    Händel, Peter
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Multitone design for third order MIMO volterra kernels2017In: 2017 IEEE MTT-S International Microwave Symposium (IMS), IEEE conference proceedings, 2017, p. 1553-1556Conference paper (Refereed)
    Abstract [en]

    This paper proposes a technique for designing multitone signals that can separate the third order multiple input multiple output (MIMO) Volterra kernels. Multitone signals fed to a MIMO Volterra system yield a spectrum that is a permutation of the sums of the input signal tones. This a priori knowledge is used to design multitone signals such that the output from the MIMO Volterra kernels does not overlap in the frequency domain, hence making it possible to separate these kernels from the output of the MIMO Volterra system. The proposed technique is applied to a 2×2 RF MIMO transmitter to determine its dominant hardware impairments. For input crosstalk, the proposed method reveals the dominant self and cross kernels whereas for output crosstalk, the proposed method reveals that only the self kernels are dominant.

  • 29.
    Khan, Zain Ahmed
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH.
    Zenteno, Efrain
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    KTH.
    Density estimation models for strong nonlinearities in RF power amplifiers2014In: Proceedings of the Asia-Pacific Microwave Conference 2014, 2014, p. 116-118Conference paper (Refereed)
    Abstract [en]

    The paper presents a method for modeling strongnonlinear effects in power amplifiers based on the principlesof density estimation. The static nonlinear transfer function isobtained by averaging measured data. The performance obtainedwith density estimation is similar to the one using high ordernonlinear static polynomial models. The benefit of consideredmethod over the ones using polynomial models is that the formerestimates blindly the structure of the transfer function and doesnot suffer from numerical instabilities.

  • 30.
    Landin, Per N.
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Chalmers University of Technology, Göteborg, Sweden; KTH Royal Institute of Technology, Stockholm, Sweden; Vrije Universiteit Brussel, Belgium.
    Barbé, Kurt
    Vrije Universiteit Brussel, Belgium.
    Van Moer, Wendy
    Vrije Universiteit Brussel, Belgium.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Two novel memory polynomial models for modeling of RF power amplifiers2015In: International journal of microwave and wireless technologies, ISSN 1759-0795, E-ISSN 1759-0787, Vol. 7, no 1, p. 19-29Article in journal (Refereed)
    Abstract [en]

    Two novel memory polynomial models are derived based on physical knowledge of a general power amplifier (PA). The derivations are given in detail to facilitate derivations of other model structures. The model error in terms of normalized mean square error (NMSE) and adjacent channel error power ratio (ACEPR) of the novel model structures are compared to that of established models based on the number of parameters using data measured on two different amplifiers, one high-power base-station PA and one low-power general purpose amplifier. The novel models show both lower NMSE and ACEPR for any chosen number of parameters compared to the established models. The low model errors make the novel models suitable candidates for both modeling and digital predistortion.

  • 31.
    Landin, Per
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Nader, Charles
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    Björsell, Niklas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    KTH Royal Institute of Technology.
    Overview of Synergetic OFDM Crest Factor Reduction and DigitalPre-Distortion for RF PAs2011In: RFMTC11, 2011Conference paper (Other academic)
    Abstract [en]

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

  • 32.
    Landin, Per Niklas
    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.
    Händel, Peter
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Comparison of Evaluation Criteria for Power Amplifier Behavioral Modeling2008In: IEEE MTT-S International Microwave Symposium Digest; 2008, Atlanta, GA, USA, 2008, p. 1441-1444Conference paper (Refereed)
  • 33.
    Landin, Per Niklas
    et al.
    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
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Parameter Extraction and Performance Evaluation Method for Increased Performance in RF Power Amplifier Behavioral Modeling2010In: International Journal of RF and Microwave Computer-Aided Engineering, ISSN 1096-4290, E-ISSN 1099-047X, Vol. 20, no 2, p. 200-208Article in journal (Refereed)
  • 34.
    Landin, Per Niklas
    et al.
    University of Gävle, Center for RF Measurement Technologies.
    Nader, Charles
    University of Gävle, Center for RF Measurement Technologies.
    Björsell, Niclas
    University of Gävle, Center for RF Measurement Technologies.
    Isaksson, Magnus
    University of Gävle, Center for RF Measurement Technologies.
    Wisell, David
    Ericsson AB.
    Händel, Peter
    University of Gävle, Center for RF Measurement Technologies.
    Andersen, Olav
    Ericsson AB.
    Keskitalo, Niclas
    University of Gävle, Center for RF Measurement Technologies.
    Wideband Characterization of Power Amplifiers Using Undersampling2009In: 2009 IEEE MTT-S International Microwave Symposium, Boston: IEEE MTT , 2009, p. 1365-1368Conference paper (Refereed)
    Abstract [en]

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

  • 35.
    Lundin, Henrik
    et al.
    Global IP Sound Europe AB, Stockholm, Sweden.
    Skoglund, Mikael
    chool of Electrical Engineering, Royal Institute of Technology, Stockholm, Sweden.
    Händel, Peter
    chool of Electrical Engineering, Royal Institute of Technology, Stockholm, Sweden.
    On the Estimation of Quantizer Reconstruction Levels2006In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 55, no 6, p. 2176-2182Article in journal (Refereed)
    Abstract [en]

    We consider the problem of estimating the optimal reconstruction levels of a fixed quantizer, such as the amplitude quantization part of an analog-to-digital converter. A probabilistic transfer function model is applied for the quantizer. Two different assumptions are made for the transfer function, and an estimator based on order statistics is applied. The estimator turns out to give better results in terms of mean square error than the commonly applied sample mean.

  • 36. Medawar, Samer
    et al.
    Björsell, Niclas
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Händel, Peter
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Jansson, Magnus
    Dynamic characterization of analog-digital-converters2007In: Mosharaka International Conference on Wireless Communications and Mobile Computing, 2007Conference paper (Refereed)
  • 37. Medawar, Samer
    et al.
    Händel, Peter
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Björsell, Niclas
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Jansson, Magnus
    ADC characterization by dynamic integral nonlinearity2008In: Proceedings of the 13th Workshop on ADC Modelling and Testing, 2008, p. 1037-1042Conference paper (Refereed)
    Abstract [en]

    Wide band characterization of analog-digital converter integral nonlinearity (INL) based on parametric modeling and least-squares parameter t is performed. In particular, the variations in the INL due to the frequency of the ADC stimuli are modeled. The INL is divided into two main entities describing the static and dynamic behavior of the ADC, respectively. The static component is modeled by a high code component (HCF) of piecewise linear segments centered around zero. A static low code (LCF) polynomial inherent to the INL data is added to the segments to complete the static part of the model. The INL dynamic part is modeled by an LCF polynomial. Method implementation is considered and is applied to 12-bit ADC data at 210 MSPS.

  • 38.
    Medawar, Samer
    et al.
    Signal Processing Laboratory, ACCESS Linnaeus Center, Royal Institute of Technology, Stockholm, Sweden.
    Händel, Peter
    Signal Processing Laboratory, ACCESS Linnaeus Center, Royal Institute of Technology, Stockholm, Sweden.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Jansson, Magnus
    Signal Processing Laboratory, ACCESS Linnaeus Center, Royal Institute of Technology, Stockholm, Sweden.
    Input Dependent Integral Nonlinearity Modeling for Pipelined Analog-Digital Converters2010In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 59, no 10, p. 2609-2620Article in journal (Refereed)
    Abstract [en]

    Integral nonlinearity (INL) for pipelined analog–digital converters (ADCs) operating at RF is measured and characterized. A parametric model for the INL of pipelined ADCs is proposed, and the corresponding least-squares problem is formulated and solved. The INL is modeled both with respect to the converter output code and the frequency stimuli, which is dynamic modeling. The INL model contains a static and a dynamic part. The former comprises two 1-D terms in ADC code that are a sequence of zero-centered linear segments and a polynomial term. The 2-D dynamic part consists of a set of polynomials whose parameters are dependent on the ADC input stimuli. The INL modeling methodology is applied to simulated and experimental data from a 12-bit commercial ADC running at 210 mega samples per second. It is demonstrated that the developed methodology is an efficient way to capture the INL of nowadays ADCs running at RF, and it is believed that the methodology is powerful for INL-based ADC postcorrection in wideband applications.

  • 39.
    Medawar, Samer
    et al.
    Signal Processing Lab, ACCESS Linnaeus Center, Stockholm, Sweden.
    Händel, Peter
    Signal Processing Lab, ACCESS Linnaeus Center, Stockholm, Sweden.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Jansson, Magnus
    Signal Processing Lab, ACCESS Linnaeus Center, Stockholm, Sweden.
    Model order determination and segmentation of analog-digital converters integral non linearity2010In: 2010 IEEE International Instrumentation and Measurement Technology Conference, I2MTC 2010: Proceedings, 2010, p. 36-41, article id 5488188Conference paper (Refereed)
    Abstract [en]

    Analog-digital converter (ADC) integral nonlinearity (INL) modeling is investigated. The model is comprised of two entities: a low code frequency (LCF) component modeled by an L-order polynomial, and a static high code frequency component (HCF), modeled by P linear disjoint segments centered around zero. Both model components are functions of the ADC output code k. A methodical way of estimating the LCF polynomial order L and the set of segments (number of and their borders), is suggested. The method computes the polynomial order L and the set of segments (number and borders) that minimizes the root mean square (RMS) distance between the INL data and its model. The method is applied to measured INL sequences of a 12-bit Analog Devices pipeline ADC (AD9430).

  • 40.
    Medawar, Samer
    et al.
    Signal Processing Lab, ACCESS Linnaeus Center, Royal Institute of Technology.
    Händel, Peter
    Signal Processing Lab, ACCESS Linnaeus Center, Royal Institute of Technology.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Jansson, Magnus
    Signal Processing Lab, ACCESS Linnaeus Center, Royal Institute of Technology.
    Pipelined Analog-Digital Converters Integral Nonlinearity Modeling for Post-Correction2010In: 17th Symposium IMEKO TC4 - Measurement of Electrical Quantities, 15th International Workshop on ADC Modelling and Testing, and 3rd Symposium IMEKO TC19: Environmental Measurements / [ed] Linus Michaeli, Jan Saliga, 2010, p. 585-590Conference paper (Refereed)
    Abstract [en]

    Input-dependent integral nonlinearity (INL) model is developed for pipeline ADC post-correction. The INL model consists of a static and dynamic part. The INL model is subtracted out of the ADC digital output for compensation. Static compensation is performed by adjacent sets of gains and offsets. Each set compensates an output code k range. The frequency content of the INL dynamic component is used to design a set of filters blocks that performs ADC compensation in the time domain. The compensation scheme is applied to measured data of two 12-bit ADCs of the same type (Analog Devices AD9430). Performance improvements in terms of spurious free dynamic range (SFDR), signal-to-noise and Distortion ratio (SINAD), intermodulation istortion (IMD) are obtained.

  • 41.
    Medawar, Samer
    et al.
    Signal Processing Laboratory, ACCESS Linnaeus Center, Royal Institute of Technology, Stockholm, Sweden.
    Händel, Peter
    Signal Processing Laboratory, ACCESS Linnaeus Center, Royal Institute of Technology, Stockholm, Sweden.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Jansson, Magnus
    Signal Processing Laboratory, ACCESS Linnaeus Center, Royal Institute of Technology, Stockholm, Sweden.
    Postcorrection of Pipelined Analog–Digital Converters Based on Input-Dependent Integral Nonlinearity Modeling2011In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 60, no 10, p. 3342-3350Article in journal (Refereed)
    Abstract [en]

    The integral nonlinearity (INL) is used for the postcorrection of analog-digital converters (ADCs). An input-frequency-dependent INL model is developed for the postcorrection. The model consists of a static term that is dependent on the ADC output code and a dynamic term that has an additional dependence on the input frequency. The concept of ADC digital output postcorrection by INL is first introduced. The INL model is subtracted from the digital output for postcorrection. The static compensation part is made by adjacent sets of gains and offsets, where each set corrects a range of output codes. The dynamic information, i.e., the frequency dependence of the INL dynamic component is used to construct a set of filter blocks that performs ADC compensation in the time domain. The compensation scheme is applied to the measured data of two ADCs of the same type (Analog Devices AD9430). Performance improvements in terms of spurious-free dynamic range, signal-to-noise and distortion ratio, intermodulation distortion, and noise are obtained. The dynamic compensation part, due to its frequency dependence, can be generalized; hence, a postcorrection block model can be used for compensating multiple ADCs of the same type.

  • 42.
    Medawar, Samer
    et al.
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Händel, Peter
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Royal Institute of Technology (KTH), Stockholm, Sweden.
    Murmann, Boris
    Stanford University.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Jansson, Magnus
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Dynamic Calibration of Undersampled Pipelined ADCs by Frequency Domain Filtering2013In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 62, no 7, p. 1882-1891Article in journal (Refereed)
    Abstract [en]

    Integral nonlinearity (INL) is used for the postcorrection of pipeline analog-digital converters (ADCs). An input-frequency-dependent INL model is developed for the compensation. The model consists of a static term that is dependent on the ADC output code, and a dynamic term that has an additional dependence on the input signal frequency. The INL model is subtracted from the digital output for postcorrection. The static compensation is implemented with a look-up-table. The dynamic calibration is performed by a bank of frequency domain filters using an overlap-add structure. Two ADCs of the same type (Analog Devices AD9430) are compensated for in the first three Nyquist bands. The performance improvements in terms of spurious-free dynamic range and intermodulation distortion are investigated. Using the proposed method, improvements up to 17 dB are reported in favorable scenarios.

  • 43.
    Medawar, Samer
    et al.
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Murmann, Boris
    Stanford University.
    Händel, Peter
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Jansson, Magnus
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Static Integral Nonlinearity Modeling and Calibration of Measured and Synthetic Pipeline Analog-to-Digital Converters2014In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 63, no 3, p. 502-511Article in journal (Refereed)
    Abstract [en]

    The integral nonlinearity (INL) modeling of pipeline analog-digital converters (ADCs) is investigated in this paper. The INL is divided into two distinct entities: a low code frequency component (LCF) and a high code frequency (HCF) component. Two static models are developed to represent the INL data. In both models, the LCF component is represented by a low-order polynomial. The HCF modeling is performed using two different basis functions: sinc and Gaussian. The structure of both HCF models is motivated by the pipeline architecture of the ADC under investigation. The model coefficients are estimated by applying the least-squares method to the measured INL data from two samples of a commercial pipeline ADC. The estimated HCF models are compared to each other and to previous models presented in the existing literature. In addition, the modeling methods are applied to synthetic HCF data generated by a pipeline ADC simulation model constructed in Matlab. The INL models are then used to calibrate the synthetic ADCs, and the improvements in spurious free dynamic range (SFDR) are compared to those obtained when the ADCs are compensated by the INL data. Furthermore, the capability of the HCF modeling to calibrate a given ADC is tested by using the HCF model to compensate a synthetically generated ADC output in which only the measured HCF sequence and noise are added to the quantization process. The resultsshow that the developed HCF models can achieve virtually complete calibration of the considered ADC.

  • 44.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    OFDM PAPR Reduction by Convex Optimization: A Power Amplifier Point-of-View2010In: 2010 IEEE International Microwave Workshop Series on "RF Front-ends for Software Defined and Cognitive Radio Solutions": IMWS 2010 - Proceedings, 2010Conference paper (Refereed)
    Abstract [en]

    In this paper we evaluate the application of convex optimization for PAPR reduction on OFDM 802.11a signal type. A radio frequency power amplifier is measured and characterized while excited by both original and optimized OFDM signals. A state-of-art test setup was used for the purpose. Improvements in power added efficiency, in-band errors, out-of-band spectral emissions are investigated for their relevance and a study of the power distribution in the excitation signal is evaluated.

  • 45.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    Kungliga Tekniska högskolan.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Peak-to-average power reduction of OFDM signals by convex optimization: experimental validation and performance optimization2011In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 60, no 2, p. 473-479Article in journal (Refereed)
    Abstract [en]

    We evaluated the application of convex optimization to peak-to-average power reduction on an orthogonal frequency division multiplexing (OFDM) 802.11a signal. A radio frequency power amplifier was excited with an OFDM-signal, and the peak-to-average reduced counterpart and its performance figure of merits were measured and compared. A state-of-art radio frequency test system with high accuracy was used for this purpose. Improvements due to optimization in output power and power added efficiency and the influence of the power distribution in the excitation signal on power amplifier performance were investigated. Improvements of 6dB in output power and 6.5% in power added efficiency were achieved on average near the operating region. The effect of preserving power-free guard subcarriers was introduced in the optimization algorithm and investigated regarding adjacent channel interference. An improvement of 9dB from that aspect was observed using half of the power-free subcarriers, which reveals the importance of a guard interval.

  • 46.
    Nader, Charles
    et al.
    University of Gävle, Center for RF Measurement Technologies. University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Landin, Per Niklas
    University of Gävle, Center for RF Measurement Technologies. University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Björsell, Niclas
    University of Gävle, Center for RF Measurement Technologies. University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Isaksson, Magnus
    University of Gävle, Center for RF Measurement Technologies. University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Wisell, David
    Ericsson AB.
    Händel, Peter
    KTH, EES, Signal processing lab.
    Andersen, Olav
    Ericsson AB.
    Keskitalo, Niclas
    University of Gävle, Center for RF Measurement Technologies.
    Wideband Power Amplifiers Characterization by Undersampling: Zhu-Frank Sampling Theorem2009Conference paper (Other academic)
  • 47.
    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.

  • 48.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Landin, Per
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Van Moer, Wendy
    Vrije Universiteit Brussel .
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Peak-to-average power ratio reduction versus digital pre-distortion in OFDM based systems2011In: 2011 IEEE MTT-s International Microwave Symposium, Institute of Electrical and Electronics Engineers Inc , 2011, p. 5972830-Conference paper (Refereed)
    Abstract [en]

    In this paper we evaluate the effect of applying peak-to-average power ratio (PAPR) reduction and digital pre-distortion (DPD) on RF power amplifiers when an OFDM signal is used. The cases where PAPR and DPD are applied separately and combined, are studied and investigated. Good performance is shown when combining both pre-processing techniques up to a certain operating point where DPD performance deteriorates. Solutions to improve the DPD performance at strong compression are suggested.

  • 49.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Van Moer, Wendy
    Vrije Universiteit Brussel .
    Barbé, Kurt
    Vrije Universiteit Brussel .
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    Characterizing the out-of-band nonlinear behaviour of RF devices: the key to success2011In: 2011 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), New York: IEEE conference proceedings, 2011, p. 790-794Conference paper (Refereed)
    Abstract [en]

    This paper presents a measurement recipe to characterize the out-of-band nonlinear behavior of RF devices when harmonic sampling is used as a digitizing technique. A major challenge to consider when using harmonic sampling is the overlapping of the aliased spectral bins of the digitized waveform. This challenge is more pronounced when using modulated excitation signals. In addition, the excitation signal used should mimic the real behavior of signals used in today's wireless systems. Hence, this paper provides the reader with a tool to select the proper excitation signal, sampling frequency and record length in order to achieve an accurate characterization of the nonlinear behavior of RF devices.

  • 50.
    Nader, Charles
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    Barbé, Kurt
    Vrije Universiteit Brussel.
    Björsell, Niclas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Evolved Harmonic Sampling: a Tool to Reduce the Digital Bandwidth Requirement of RF Receivers2011In: RFMTC11, Gävle, 2011Conference paper (Other academic)
12 1 - 50 of 61
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