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  • 1.
    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.

  • 2.
    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.

  • 3.
    Fritzin, Jonas
    et al.
    Ericsson AB; Linköpings universitet.
    Alvandpour, Atila
    Linköpings universitet.
    Landin, Per
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Chalmers.
    Fager, Christian
    Chalmers.
    Linearity, intermodulation distortion and ACLR in outphasing amplifiers2013In: 2013 IEEE MTT-S International Microwave Symposium Digest, IEEE conference proceedings, 2013, article id 6697584Conference paper (Refereed)
    Abstract [en]

    The distortion from amplitude and phase imbalance in outphasing amplifiers is discussed. The relation between dynamic range (DR) and suppression of distortion is shown to approximately follow a simple linear relationship depending on the DR. Approximate relations between adjacent channel leakage power ratio (ACLR) for different kinds of commonly used communication signals and two-tone intermodulation distortion are given. Relations between loss in output power and reduction of DR as functions of duty cycle in switching-based outphasing amplifiers are also given. An approximate method to evaluate the possible performance of digital pre-distortion (DPD) is also given by considering a DPD capable of correcting all distortions except amplitude imbalance. The predicted performance is compared to the performance obtained using a DPD-model found in the literature. The results show that the method is in good agreement, demonstrating that the proposed method can be used for design and evaluation of predistorted outphasing amplifiers. 

  • 4.
    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.

  • 5.
    Landin, Per
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. KTH, Signalbehandling.
    Digital Baseband Modeling and Correction of Radio Frequency Power Amplifiers2012Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Aspects related to behavioral modeling and correction of distortions for radio frequency (RF) power amplifiers (PAs) are treated in the thesis.   

    When evaluating the performance of a behavioral model it is important to, first of all, use an evaluation criterion, and second, make sure that the criterion actually tells something about the behavior one wishes to describe. This is used in the weighted error spectral power ratio (WESPR) criterion by means of a frequency dependent weighting function. When the parameters of the models are estimated a suitable error criterion should likewise be used. The frequency weighting function in the WESPR is used in the extraction of the parameters. It is shown on two types of PAs that the model performance measured as WESPR can be improved while the model complexity is reduced compared to the standard frequency neutral criterion.   

    When building a model of a system it is advantageous to take account of the physical structure and incorporate this knowledge into the model. It can improve model performance and possibly reduce the number of parameters. By starting from a physically motivated nonlinear model of a RF PA, the commonly used memory polynomial (MP) models are derived. Additionally, three novel MP model structures are derived. Using data measured on a PA it is found that two of these model structures have lower model errors while using fewer parameters than models previously published in the literature.   

    Methods to increase the power efficiency and the linearity of RF PAs have been investigated. One of these methods is digital predistortion (DPD) which improves the linearity, thus facilitating operation at higher power levels which improves power efficiency. The other method is a signal shaping method that makes the signal more favorable to the PA by reducing the highest peaks to lower values. It is experimentally shown that the combination of DPD and signal shaping results in an increase of power efficiency in the order of 2-4 times. An instability in the feedback loop that updates the parameters of the DPD was also identified and two solutions were proposed. One solution changes the parameters of the DPD in such a way that the instability is avoided and the other changes the signal to avoid high amplitudes.   

    The nonlinear effects of class-D outphasing amplifiers are considered. Four model structures are proposed and evaluated on data measured from two amplifiers. In order to reduce the distortions in the output signal from the amplifiers an algorithm using constant envelope amplitude (purely phase-modulated) signals is proposed. The DPD is evaluated and found to reduce the distortions in a state-of-the-art 32 dBm class-D outphasing PA to make it fulfill the linearity requirements for downlink signals used in the universal mobile telecommunications system (UMTS).

  • 6.
    Landin, Per
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Barbé, Kurt
    Vrije Universiteit Brussel.
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    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.
    Proofs of Derivations in Memory Polynomial Baseband Modeling of RF Power Amplifiers2011Report (Other academic)
    Abstract [en]

    This paper contains supporting derivations for the paperMemory Polynomial Baseband Modeling of RF Power Am-plifiers. All references to numbered equations, propositionsand assumptions are to the corresponding number inMemoryPolynomial Baseband Modeling of RF Power Amplifiers.

  • 7.
    Landin, Per
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics. Chalmers University of Technology, Gothenburg, Sweden .
    Eriksson, Thomas
    Chalmers University of Technology, Gothenburg, Sweden.
    Fritzin, Jonas
    Ericsson AB; Linköping University.
    Alvandpour, Atila
    Linköping University.
    Behavioral modeling of outphasing amplifiers considering memory effects2013In: 2013 IEEE MTT-S International Microwave Symposium Digest, IEEE conference proceedings, 2013, article id 6697764Conference paper (Refereed)
    Abstract [en]

    This paper proposes a behavioral model structure for outphasing amplifiers. The model performance is evaluated on a class-D CMOS outphasing amplifier and compared with two models found in the literature. The proposed model structure also allows the use of memory in a parallel Hammerstein-like setting. The proposed models show improvements in adjacent channel error power ratio (ACEPR) of approximately 5 dB in addition to being linear in the parameters. The lower model errors enable the use and design of improved predistorters taking frequency dependency (memory effects) in outphasing amplifiers into account. 

  • 8.
    Landin, Per
    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.
    Keskitalo, Niklas
    University of Gävle, Center for RF Measurement Technologies.
    Tornblad, Olof
    Infineon Technologies.
    Sideband asymmetries in RF Power LDMOS Before and After Digital Predistortion2009Conference paper (Other academic)
    Abstract [en]

     The merging of the fields of RF engineering and signal processing has introduced concepts such as behavioral modeling and enabled digital linearization schemes for wireless devices, such as power amplifiers (PAs). Despite that this process has been going on for a number of years much work remains to be done. The links between physical behavior and mathematical models are far from well-understood as are the optimum strategies for device design. This study focus on digital predistortion properties of a one-stage PA consisting of a power transistor mounted in a test fixture. The device under test (DUT) is an Infineon PTF210451E, a 45W transistor intended for usage in the frequency bands 2010-2025 MHz and 2110-2170 MHz. The test fixture is also designed by Infineon Technologies.  The signal types used in the measurements are single and double carrier wideband code division multiple access (WCDMA) signals. The double carrier WCDMA signals have tone-spacings of 5, 10 and 15 MHz. Normal two-tone measurements are also presented. 

  • 9.
    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.

  • 10.
    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.

  • 11.
    Landin, Per Niklas
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    On Radio Frequency Behavioral Modeling: Measurement Techniques, Devices and Validation Aspects2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Radio frequency (RF) power amplifiers (PA) are still the most troublesome part of a wireless system due to their inherent nonlinearity, low powerefficiency and high distortions. Better tools are needed to understand and correct the undesirable behavior. Some of these tools are behavioral models. A behavioral model is often thought of as a black box with some inputs and some outputs. In the case here these inputs are sampled signals which means that the modeling amounts to finding a mathematical relationship between the input signal(s) and the output signal(s).

    This thesis considers some requirements for behavioral modeling of said systems by presenting methods for general performance evaluation and improvement by considering a frequency weighted error criterion. A high performance measurement system is also needed. The performance of the available system is compared to the performance of a well recognized system, the large signal network analyzer (LSNA). The results show that the existing measurement system can extract behavioral models with the same performance as the LSNA and can give lower performance validation errors.

    Still the need for higher bandwidths drives the measurement systems to the limits, especially the digital parts. By utilizing the so called Zhu-Frank generalized sampling theorem, behavioral modeling of a PA is done by using data acquired at a sampling rate lower than the Nyquist rate. Models of a PA are extracted and the performance is evaluated using the normalized mean square error (NMSE) criterion. For prediction and correction of the output signals the stability of the models regarding changes must be investigated. One such study considering controlled variations on the output load of the PA is done and both the predictive and corrective capabilities of the models are evaluated. The predictive capability gets up to 7 dB worse measured as adjacent channel error power ratio (ACEPR) and the corrective, as digital predistortion, gets up to 13 dB worse measured as adjacent channel power ratio (ACPR).

  • 12.
    Landin, Per Niklas
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Barbé, Kurt
    Vrije Universiteit Brussel.
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    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.
    Memory Polynomial Baseband Modeling of RF Power Amplifiers2012In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662Article in journal (Refereed)
  • 13.
    Landin, Per Niklas
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Bengtsson, Olof
    Isaksson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Power Amplifier Behavioural Model Mismatch Sensitivity and the Impact on Digital Predistortion Performance2009In: Proc. 39th European Microwave Conference (EuMC), IEEE conference proceedings, 2009, p. 338-341Conference paper (Refereed)
    Abstract [en]

    This paper presents an investigation of poweramplifier behavioural model performance sensitivity to in-bandreflections. The measurement system and model extractionprocess is presented together with the results and an analysis ofthe effect of parameter variations in a digitally predistortedsystem. A load-pull system is used together with a digitalbaseband model extraction system to identify the impact onmodelling performance. The results show that the modelperformance varies greatly with in-band reflection magnitudeand phase on the amplifier output. It is also shown that a digitalpredistortion based on a model extracted at matched conditions,where it gives an excellent improvement of 20 dB in adjacentchannel leakage ratio (ACLR), gives a poor improvement of 7 dBfor miss-matched conditions with as low reflections as Γ=0.2(return loss 14 dB). This indicates that in-band reflections needto be considered and adaptive predistortion used also for lowVSWR system like base-stations for telecommunication.

  • 14.
    Landin, Per Niklas
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Fager, Christian
    Chalmers.
    Isaksson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik.
    Andersson, Kristoffer
    Chalmers.
    Power Amplifier Behavioral Modeling Performance Comparison of the LSNA and the Modulation-Domain System2008In: 72nd ARFTG Microwave Measurement Symposium, 2008, Portland, OR., 2008, p. 73-78Conference paper (Refereed)
  • 15.
    Landin, Per Niklas
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Fritzin, Jonas
    Linköping University.
    Jung, Ylva
    Linköping University.
    Enqvist, Martin
    Linköping University.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Alvandpour, Atila
    Linköping University.
    Digital baseband pre-distortion of class-D outphasing amplifiers2012In: Proceedings Gigahertz Symposium 2012, 2012Conference paper (Other academic)
    Abstract [en]

    This paper presents a novel structure and method for modeling and digitally pre-distorting outphasing amplifiers. The models and pre-distortion are evaluated on a CMOS low-power class-D outphasing amplifier using uplink WCDMA signals. Using the proposed pre-distorter improves the ACLR by no less than 12 dB making the amplifier fulfill the 3GPP requirements on ACLR.

  • 16.
    Landin, Per Niklas
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Fritzin, Jonas
    Linköping University.
    Van Moer, Wendy
    Vrije Universiteit Brussel.
    Isaksson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Alvandpour, Atila
    Linköping University.
    Modeling and digital predistortion of class-D outphasing RF power amplifiers2012In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 60, no 6, p. 1907-1915Article in journal (Refereed)
    Abstract [en]

    This paper presents a direct model structure for describing class-D outphasing power amplifiers (PAs) and a method for digitally predistorting these amplifiers. The direct model structure is based on modeling differences in gain and delay, nonlinear interactions between the two paths, and differences in the amplifier behavior. The digital predistortion method is designed to operate only on the input signals' phases, to correct for both amplitude and phase mismatches. This eliminates the need for additional voltage supplies to compensate for gain mismatch. Model and predistortion performance are evaluated on a 32-dBm peak-output-power class-D outphasing PA in CMOS with on-chip transformers. The excitation signal is a 5-MHz downlink WCDMA signal with peak-to-average power ratio of 9.5 dB. Using the proposed digital predistorter, the 5-MHz adjacent channel leakage power ratio (ACLR) was improved by 13.5 dB, from -32.1 to -45.6 dBc. The 10-MHz ACLR was improved by 6.4 dB, from -44.3 to -50.7 dBc, making the amplifier pass the 3GPP ACLR requirements.

  • 17.
    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.
    A review of validation criteria for behavioral power amplifier models2008Conference paper (Other academic)
  • 18.
    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)
  • 19.
    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)
  • 20.
    Landin, Per Niklas
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik. University of Gävle, Center for RF Measurement Technologies.
    Isaksson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för elektronik. University of Gävle, Center for RF Measurement Technologies.
    Keskitalo, Niclas
    University of Gävle, Center for RF Measurement Technologies.
    Tornblad, Olof
    A Study of memory effects of RF power LDMOS before and after digital predistortion2009In: Wireless and Microwave Technology Conference, 2009. WAMICON '09. IEEE 10th Annual, 2009, p. 1-5Conference paper (Refereed)
    Abstract [en]

    Sideband asymmetries in distortion products are created due to electrical and thermal memory effects and this can be difficult to correct for in a digital predistortion algorithm. In this study, sideband asymmetries in third-order intermodulation distortion products before and after digital predistortion were investigated using 2-tone and 2-carrier WCDMA signals. The parallel Hammerstein (PH) model was used in the digital predistortion algorithm. The sign of the asymmetries before correction were found to depend on power level. Memoryless correction lead to an increase in asymmetries for some power ranges whereas using a PH model of order 13 with only one order of memory length lead to good correction over a large power range.

  • 21.
    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.

  • 22.
    Landin, Per Niklas
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Odd and Odd-Even Memory Polynomial Representations2013Report (Other academic)
    Abstract [en]

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

  • 23.
    Landin, Per Niklas
    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.
    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.
    Peak-Power Controlled Digital Predistorters for RF Power Amplifiers2012In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 60, no 11, p. 3582-3590Article in journal (Refereed)
    Abstract [en]

    This paper investigates the issue of “predistorter blow-up,” i.e., uncontrolled peak expansion caused by the predistorter. To control the peak expansion, an extension of the multistep indirect learning architecture (MS-ILA) is proposed by adding a constraint that describes the allowed peak power of the predistortion signal. The resulting optimization problem is shown to be convex and an optimization method is formulated to solve it. Measurements on a class-AB power amplifier (PA) using orthogonal frequency-division multiplex signals show that the peak control works as intended and prevents the MS-ILA from generating high peaks when the PA is operated in compression. The restriction on the peak power also prevents the performance degradation occurring due to the “blow-up” problem. This makes the proposed controlled MS-ILA a safer option than the standard MS-ILA. In addition to controlling the peak input power to the PA, using the proposed method it was possible to increase the output power by 1.3 dB while fulfilling requirements of less than 40-dB adjacent channel leakage power ratio, compared to the standard five-step MS-ILA. Reduced peak power also reduces the requirements on linearity in signal generation, resolution in computations, and analog-to-digital and digital-to-analog conversion.

  • 24.
    Landin, Per
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Rönnow, Daniel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    RF PA Modeling Considering Odd-Even and Odd Order Polynomials2016In: 2015 IEEE Symposium on Communications and Vehicular Technology in the Benelux (SCVT), New York: Institute of Electrical and Electronics Engineers (IEEE), 2016, article id 7374233Conference paper (Refereed)
    Abstract [en]

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

  • 25.
    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)
  • 26.
    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.

  • 27.
    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.

  • 28.
    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, Niklas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Händel, Peter
    KTH Royal Institute of Technology.
    Performance Evaluation of Peak-to-Average Power Ratio Reduction and Digital Pre-Distortion for OFDM Based Systems2011In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 59, no 2, p. 3504-3511Article in journal (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 two types of radio frequency power amplifiers when an orthogonal frequency division multiplexing (OFDM) signal is used. The power amplifiers under test are a standard class-AB amplifier and a Doherty amplifier. The PAPR reduction methods are based on a state-of-the art convex optimization formulation and on the standard clipping and filtering technique. The DPD method consists of modeling the behavior of the power amplifier using a parallel Hammerstein model, and then extracting the inverse parameters based on the indirect learning architecture. To achieve better DPD performance, extracting the DPD parameters based on multiple-step iterations is investigated. The cases where PAPR reduction and DPD are applied separately and combined are studied and investigated. Power amplifier figures of merit are evaluated. Good performance is shown when combining both pre-processing techniques up to a certain operating point where DPD performance deteriorates due to generation of strong peaks in the signal. In addition, a difference in the power amplifier behavior is reported and analyzed.

  • 29. Perea-Tamayo, R.
    et al.
    Bengtsson, O.
    Landin, Per
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Heinrich, W.
    A modular hybrid switching amplifier for wide-bandwidth supply-modulated RF power amplifiers2012In: 7th German Microwave Conference, GeMiC 2012, 2012, p. 6185190-Conference paper (Refereed)
    Abstract [en]

    A modular hybrid switching amplifier (HSA) for wide-bandwidth supply modulation of RF power amplifiers is presented. The HSA is designed for maximum 15 V supply voltage, 1 A supply current and 10 MHz bandwidth. The purpose is to compare alternative switch technologies. A case study is conducted on GaN-HEMT and Si-MOSFET, which are compared with regards to efficiency and linearity under different load conditions, based on simulations and on measurements of the fabricated designs. Design modifications to accommodate the alternative switch technologies are presented together with analysis of non-linearities including slew-rate induced amplitude distortion.

  • 30.
    Perea-Tamoya, Robert
    et al.
    Ferdinand-Braun-Institut (FBH), Leibniz-Institut für Höchstfrequenztechnik.
    Krellmann, Martin
    Ferdinand-Braun-Institut (FBH), Leibniz-Institut für Höchstfrequenztechnik.
    Bengtsson, Olof
    Ferdinand-Braun-Institut (FBH), Leibniz-Institut für Höchstfrequenztechnik.
    Landin, Per Niklas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences, Electronics.
    Heinrich, Wolfgang
    Ferdinand-Braun-Institut (FBH), Leibniz-Institut für Höchstfrequenztechnik.
    Investigation of GaN-HEMT Based Switches for Hybrid Switching Amplifier Supply-Modulators2012In: Frequenz, ISSN 0016-1136, E-ISSN 2191-6349, Vol. 66, no 11-12, p. 339-345Article in journal (Refereed)
    Abstract [en]

    An investigation of GaN-HEMT based switching stages in hybrid switching amplifiers (HSA) for wide-bandwidth supply modulation of RF power amplifiers is presented. The HSA is designed for maximum 15 V supply voltage, 1 A supply current and 10 MHz bandwidth. GaN-HEMT switch designs with alternative gate drive circuitry are investigated with regard to power, efficiency and linearity under different load conditions using simulations and measurements of the fabricated circuits. The full HSA showed an efficiency of 49.7% for a WCDMA envelope. A modified switching stage with improved gate-drive circuitry shows 85% efficiency in a 15 V buck-converter test-circuit for a 10 V conversion at 1 MHz over a 15 Ω load.

1 - 30 of 30
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