| 1. |
- Afsar Doost, Sepideh, 1983, et al.
(författare)
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Digital Predistortion Using a Vector Switched Model
- 2012
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 60:4, s. 1166-1174
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Tidskriftsartikel (refereegranskat)abstract
- Abstract—A switched behavioral model considering memory effects with special focus on ”difficult” amplifier architectures is proposed in this paper. The proposed model is shown to be very simple and linearly identifiable. A digital predistorter based on the proposed model is implemented for a 100–W, 2.6 GHz Doherty power amplifier that has been considered difficult in other reports, and it is shown that the proposed model can succesfully linearize the amplifier. In particular, the proposed model and the digital predistorter is shown to outperform other state-of-the-art models and digital predistorers in terms of computational complexity for a given desired accuracy.
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| 2. |
- Andersson, Christer, 1982, et al.
(författare)
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A 1-3-GHz Digitally Controlled Dual-RF Input Power-Amplifier Design Based on a Doherty-Outphasing Continuum Analysis
- 2013
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 61:10, s. 3743-3752
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a linear multi-harmonic analysis method to evaluate the performance of digitally controlled dual RF-input power amplifiers (PAs). The method enables, due to its low computational cost, optimization of PA efficiency and bandwidth in a complex design space involving two independent inputs. Under the idealized assumption of short-circuited higher harmonics, the analysis is used to prove the existence of a Doherty-outphasing continuum, featuring high average efficiency over 100% fractional bandwidth. With this result as a foundation, a combiner incorporating microwave transistor parasitics is analyzed without assuming short-circuited higher harmonics, showing that high average efficiencies are also achievable under more realistic conditions. A PA is straightforwardly designed from these calculation results using two 15-W GaN HEMTs. The simulated layout-ready (large-signal transistor model) PA average drain efficiency exceeds 50% over 1.1-3.7 GHz for a 6.7-dB peak-to-average power-ratio WCDMA signal. The measured PA has a maximum output power of 44 +/- 0.9 dBm and a 6-dB output power back-off (OPBO) power-added efficiency (PAE) of 45% over 1-3 GHz. After applying digital pre-distortion, excellent linearity is demonstrated when transmitting the WCDMA signal, resulting in an adjacent channel leakage power ratio lower than -57 dBc with corresponding average PAE of 50% and 40% at 1.2 and 2.3 GHz, respectively. This is, to the authors' knowledge, the most wideband OPBO efficiency enhanced PA reported to date, proving the effectiveness of employing linear multi-harmonic analysis in dual-input PA design.
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| 3. |
- Andersson, Christer, 1982, et al.
(författare)
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A packaged 86 W GaN transmitter with SiC varactor-based dynamic load modulation
- 2013
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Ingår i: 43rd European Microwave Conference, EuMC 2013 - Held as Part of the 16th European Microwave Week, EuMW 2013, Nuremberg, Germany, 7-10 October 2013. - 9782874870316 ; , s. 283-286
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Konferensbidrag (refereegranskat)abstract
- Output power scaling based on class-J dynamic load modulation (DLM) theory is used to design an unprecedentedly high power microwave transmitter with varactor-based DLM functionality. Matching networks are realized on high dielectric constant substrates in order to reduce the form factor. The fully matched DLM PA incorporates a 24-mm GaN HEMT powerbar and a stack of four SiC varactors, all fit into a CuW package (40 mm × 20 mm). Peak output power is reconfigurable by changing the drain voltage, while retaining the DLMeffect. Under pulsed conditions at 40 V the PA delivers a peak power of 86 W at 2.14 GHz. Efficiency enhancement by DLM is 10-15 percentage-units at 6 dB output power back-off (OPBO). Employing digital predistortion (DPD) with a vector switched generalized memory polynomial (VS-GMP) the ACLR is -46 dBc at an average output power of 17 W and a drain efficiency of 34%. These results prove the potential for high output power levels in varactor-based DLM transmitters.
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| 4. |
- Andersson, Christer, 1982, et al.
(författare)
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Decade bandwidth high efficiency GaN HEMT power amplifier designed with resistive harmonic loading
- 2012
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Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781467310871
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Konferensbidrag (refereegranskat)abstract
- The use of resistive loading at higher harmonics in wideband power amplifier design is proposed. Although the theoretical efficiency of such operation is lower than other classes the significantly simplified load network design potentially allows for multi-octave realizations. A decade bandwidth (0.4-4.1 GHz) GaN HEMT power amplifier was thereby designed, delivering more than 40 dBm output power with 10-15 dB gain and 40-62% drain efficiency. Linearized modulated signal amplification was then successfully demonstrated at multiple frequencies (0.9 to 3.5 GHz), using various downlink signals (LTE, WCDMA, WiMAX), with resulting ACLR lower than 46 dBc.
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| 5. |
- Andersson, Christer, 1982, et al.
(författare)
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Theory and Design of Class-J Power Amplifiers With Dynamic Load Modulation
- 2012
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 60:12, s. 3778-3786
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Tidskriftsartikel (refereegranskat)abstract
- A theory for class-J microwave amplifier operation as a function of drive level and fundamental load impedance is derived. Calculations show that, under appropriate operating conditions, it is sufficient to modulate the transistor load reactance to enable high-efficiency operation (>70%) over a large output power dynamic range (>10 dB) with high transistor power utilization. Such dynamic load modulation (DLM) networks are an ideal application of continuously tunable varactor technologies. Multiharmonic load–pull measurements are performed on a GaN HEMT and experimentally verify the theory of operation. A demonstrator amplifier using an SiC varactor technology is then designed and characterized by static measurements. The amplifier has a peak power of 38 dBm at 2.08 GHz and maintains efficiencies above 45% over 8 dB of power dynamic range. An analysis of the load network losses is performed to show the potential of the class-J DLM transmitter concept.
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| 6. |
- Andersson, Kristoffer, 1976, et al.
(författare)
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Oscilloscope based two-port measurement system using error-corrected modulated signals
- 2012
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Ingår i: 2012 Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits, INMMIC 2012. - 9781467329491
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Konferensbidrag (refereegranskat)abstract
- A technique to accurately measure modulated wideband signals in a two-port context is presented. The technique uses a four channel high frequency digital sampling oscilloscope to perform in-situ correction of both amplitude and phase of the modulated stimulus signal. An advantage of the proposed technique is that no assumption about the group delay has to be made. The technique is demonstrated in a source-pull system. The results clearly demonstrate the necessity of using error-correction in tuner based setups due to the large variations in group-delay over the measurement bandwidth. © 2012 IEEE.
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| 7. |
- Brynzér, Henrik, et al.
(författare)
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Sustainability and cost efficiency in Supply Chains
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The project was formed from three basic observations, which together considerably alter the requirements when designing the supply chains. First, the lean production deployment is now ruling the design of the work cells, e.g. the assembly stations. Second, the focus on sustainability and environmental consideration is calling for new models when designing the supply chains, and third, great cost and time reduction potentials are revealed in the supply chains when applying value stream mapping. The purpose of the project was to contribute to the understanding and to the methods of how to design and evaluate sustainable and cost efficient supply chains that supports lean production processes. The project involved all industrial actors of the FFI programme and relied to a large extent on case studies performed in the companies. These cases often combined the development of models and methods with testing and pilot implementations at the companies. Results were disseminated among the actors through workshops and seminars, which further strengthened the results and understanding of applicability. Among the theoretical contributions is the development of the concept of material exposure, as an interface between materials supply and assembly. This interface realizes the product of the material supply system in the form of an available component for the assembly system to assemble, given the requirements of the customer in form of the assembly system. These requirements govern how material exposure is realized and provides a framework for how materials supply systems can be designed. In this way, the principles of lean production in the assembly is supported by the material supply, while allowing the development of a material supply system that itself is lean.One case study investigated systems for repacking of material between packaging types, that may be necessary to meet the requirements of the assembly system at the same time as the transport costs are kept down. From the case study, a classification of compo¬nents that can be handled manually in this type of repacking were derived, and five different types of components were identified. The case study conclusions include the time to pick these components between different packaging types. These results have been put into further work in the case study company, regarding designing systems for repacking of material.A theoretical model was developed to compare how the choice of packaging affect cost and CO_2 emissions for the supply of materials. A case study chose to compare two different packages with fundamentally different characteristics, one of which was a conventional returnable packaging based on plastics and the other a disposable one-way packaging. In this case the disposable packaging turned out to be clearly advantageous from both a cost and an environmental perspective.A new methodology to describe and evaluate the fulfilment of requirements of material flows was developed within the sub-project ‘Materials Flow Mapping’. This methodol¬ogy provides the ability to better, and in more detail, study material flows and its activi¬ties. Such a level of detail in the analysis proved valuable as a basis for improvement work in the materials supply system, where there is a need to be able to describe the often non-value-added activities that occur.One sub-project was carried out with the aim of developing a cost model for estimating the cost of packaging, transport and in-plant logistics in a supply chain from suppliers to assembly, and to implement this in a software. This is an important contribution to the development of a decision tool for the selection of materials supply set up. The model represents a comparatively fast tool for obtaining cost estimates of various configura¬tions of the materials supply system.Finally, one sub-project has treated materials control, to support the research being done on the physical flows. The focus has been on pull-based materials planning with consid-eration to man, technology and organization (MTO), a need that was identified during the project. The result is two-fold, the first part being a model consisting of MTO factors that are important to take into account in the design and implementation phase of a pull-based system. Secondly, research has provided a better understanding of the potential problems during a process of implementing an external pull system and classified these problems based on the MTO dimensions.
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| 8. |
- Cao, Haiying, 1982, et al.
(författare)
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Comparison of bandwidth reduction schemes in dynamic load modulation power amplifier architectures
- 2011
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Ingår i: IEEE Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMIC), 2011. - 9781457706509 ; , s. 1-4
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Konferensbidrag (refereegranskat)abstract
- This paper compares bandwidth reduction schemes for baseband control signals used in high efficiency power amplifier (PA) architectures, such as envelope tracking and dynamic load modulation (DLM). The baseband control signal used in such architectures usually has 3–4 times wider bandwidth than the modulated radio frequency (RF) signal. Such a wideband signal brings challenges for practical hardware design. In this paper, two bandwidth reduction schemes originally used in envelope tracking are applied on a DLM PA. The performance of both schemes are investigated by simulation. The results show that the bandwidth of the baseband control signal can be effectively reduced from 12.5 MHz to 4 MHz, while at the same time, maintaining a 49% average power-added and acceptable linearity.
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| 9. |
- Cao, Haiying, 1982, et al.
(författare)
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Digital Predistortion for Dual-Input Doherty Amplifiers
- 2012
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Ingår i: RWW 2012 - Proceedings. 2012 IEEE Topical Conference on Power Amplifiers for Wireless and Radio Applications, PAWR 2012. Santa Clara, CA, 15-18 January 2012. - 9781457711541 ; , s. 45-48
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Konferensbidrag (refereegranskat)abstract
- This paper presents a digital predistortion techniquefor dual-input Doherty power amplifiers. The proposedtechnique utilizes both RF inputs of the main and peakamplifiers in the digital predistorter. The effectiveness ofthe resulting dual-input predistorter is evaluated on a twowayDoherty amplifier operating at 2.14 GHz with 53.5 dBmpeak output power. The experimental results demonstratethat the dual-input approach outperforms the conventionalsingle-input predistortion technique by ∼3 dB in terms ofadjacent channel leakage ratio.
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| 10. |
- Cao, Haiying, 1982, et al.
(författare)
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Digital Predistortion for High Efficiency Power Amplifier Architectures Using a Dual-input Modeling Approach
- 2012
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 60:2, s. 361-369
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a novel model is proposed for dual-input highefficiency power amplifier (PA) architectures, such as envelope tracking (ET) and varactor-based dynamic load modulation (DLM). Compared to the traditional single-input modeling approach, the proposed model incorporates the baseband supply voltage/load control as an input. This advantage makes the new approach capable to achieve maximized average power-added efficiency (PAE) and minimizedoutput distortion simultaneously. Furthermore, the new approach has shown to be robust towards time misalignment between the RF input and baseband supply voltage/load control signals, and it can be applied with a reduced-bandwidth baseband supply voltage/load control.Experiments have been performed in a varactor-based DLM PAarchitecture to evaluate the new modeling approach. The results show that it can achieve 9 dB and 7 dB better performance than the traditional approaches in terms of adjacent channel leakage ratio and normalized mean square error, respectively. At the same time, the average PAE is maximized. Similar results have been achieved with the proposed model even when reduced-bandwidth baseband loadcontrol signal is used or time misalignment between the RF and baseband load control input signals exists. Although the new approach is only tested with DLM architecture in this paper, it is very general and can be applied to ET architectures as well.
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