| 1. |
- Magnusson, Håkan, et al.
(författare)
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A cross-coupled dual-loop feedback power amplifier driver
- 2005
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Ingår i: Proceedings of the 2005 European Conference on Circuit Theory and Design. - 0780390660 - 9780780390669 ; , s. 309-312
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Konferensbidrag (refereegranskat)abstract
- This paper presents a wide-band power amplifier (PA) driver with matched output. A dual-loop cross-coupled feedback is applied on a simple two stage core amplifier. The use of a dual-loop feedback provides a broad-band 50 Ω output match without the use of any area consuming matching networks. The PA driver exhibits a gain higher than 6.4 dB, more than +1.9dBm 1-dB compression point with S22 less than -22 dB at the output, while dissipating 42 mA from a 1.8V supply. The output IP3 is better than +13.9 dBm at 2.4 GHz.
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| 2. |
- Andrijevic, Goran, et al.
(författare)
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Multistandard receiver for home networking and digital media
- 2004
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Ingår i: 22ND NORCHIP CONFERENCE, PROCEEDINGS. - NEW YORK : IEEE. - 0780385101 ; , s. 131-134
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Konferensbidrag (refereegranskat)abstract
- We propose a fully integrated multistandard receiver architecture that fulfills coming media and networking needs of homes. The receiver uses a dual-IF architecture to cover receive bands from 170 MHz to 920 MHz and the Industrial, Scientific and Medical (ISM) band at 2.4GHz. Key performance values meet the DVB-T, Zigbee, Bluetooth and 802.11b requirements (Sensitivity -72.5dBm. available SNR=28dB. Noise Figure 6.7dB. Adjacent Channel Protection Ratio-ACPR=-44dB, IIP3 = -11 dBm).
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| 3. |
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| 4. |
- Magnusson, Håkan, et al.
(författare)
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Multiband multi-standard transmitter using a compact power amplifier driver
- 2005
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Ingår i: 2005 IEEE Radio Frequency Integrated Circuits (RFIC) Symposium, Digest of Papers. - NEW YORK, NY : IEEE. - 0780389832 ; , s. 491-494
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Konferensbidrag (refereegranskat)abstract
- This paper presents a multistandard transmitter solution using a new power amplifier (PA) driver [1] operating in the broadcast, mobile, and the 2&5 GHz ISM bands. The use of dual-loop feedback in the driver provides a matched output without area consuming matching networks. The circuit size is as small as 0.3 mm(2) for the used 0.18 mu m CMOS process, saving about 0.7 mm(2) silicon area. Measurement results show a gain higher than 7.8 dB with a maximum output power of +4 dBm for all bands and using a supply voltage of 1.8V.
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| 5. |
- Abdalmoaty, Mohamed, 1986-
(författare)
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Learning Stochastic Nonlinear Dynamical Systems Using Non-stationary Linear Predictors
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The estimation problem of stochastic nonlinear parametric models is recognized to be very challenging due to the intractability of the likelihood function. Recently, several methods have been developed to approximate the maximum likelihood estimator and the optimal mean-square error predictor using Monte Carlo methods. Albeit asymptotically optimal, these methods come with several computational challenges and fundamental limitations.The contributions of this thesis can be divided into two main parts. In the first part, approximate solutions to the maximum likelihood problem are explored. Both analytical and numerical approaches, based on the expectation-maximization algorithm and the quasi-Newton algorithm, are considered. While analytic approximations are difficult to analyze, asymptotic guarantees can be established for methods based on Monte Carlo approximations. Yet, Monte Carlo methods come with their own computational difficulties; sampling in high-dimensional spaces requires an efficient proposal distribution to reduce the number of required samples to a reasonable value.In the second part, relatively simple prediction error method estimators are proposed. They are based on non-stationary one-step ahead predictors which are linear in the observed outputs, but are nonlinear in the (assumed known) input. These predictors rely only on the first two moments of the model and the computation of the likelihood function is not required. Consequently, the resulting estimators are defined via analytically tractable objective functions in several relevant cases. It is shown that, under mild assumptions, the estimators are consistent and asymptotically normal. In cases where the first two moments are analytically intractable due to the complexity of the model, it is possible to resort to vanilla Monte Carlo approximations. Several numerical examples demonstrate a good performance of the suggested estimators in several cases that are usually considered challenging.
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| 6. |
- Karimi Neghlani, Paria, 1986-, et al.
(författare)
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Tailored grain morphology via a unique melting strategy in electron beam-powder bed fusion
- 2021
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Ingår i: Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 824
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Tidskriftsartikel (refereegranskat)abstract
- This study presents a unique melting strategy in electron beam-powder bed fusion of Alloy 718 to tailor the grain morphology from the typical columnar to equiaxed morphology. For this transition, a specific combination of certain process parameters, including low scanning speeds (400–800 mm/s), wide line offsets (300–500 μm) and a high number of line order (#10) was selected to control local solidification conditions in each melt pool during the process. In addition, secondary melting of each layer with a 90° rotation with respect to primary melting induced more vigorous motions within the melt pools and extensive changes in thermal gradient direction, facilitating grain morphology tailoring. Four different types of microstructures were classified according to the produced grain morphology depending on the overlap zone between two adjacent melt pools, i.e., fully-columnar (overlap above 40 %), fully-equiaxed (overlap below 15 %), mixed columnar-equiaxed grains, and hemispherical melt pools containing mixed columnar-equiaxed grains (overlap ~20–25 %). The typical texture was <001>; however, the texture was reduced significantly through the transition from the columnar to equiaxed grain morphology. Along with all four different microstructures, shrinkage defects and cracks were also identified which amount of them reduced by a reduction in areal energy input. The hardness was increased through the transition, which was linked to the growth of the γʺ precipitates and high grain boundary density in the fully-equiaxed grain morphology.
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| 7. |
- Fransson, Johan E.S., et al.
(författare)
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Estimation of Forest Stem Volume using ALOS-2 PALSAR-2 Satellite Images
- 2016
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Ingår i: Proceedings of 36th IEEE International Geoscience and Remote Sensing Symposium, IGARSS 2016; Beijing; China; 10-15 July 2016. - 9781509033324 ; 2016-November, s. Art no 7730388, Pages 5327-5330
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Konferensbidrag (refereegranskat)abstract
- © 2016 IEEE. A first evaluation of ALOS-2 PALSAR-2 data for forest stem volume estimation has been performed at a coniferous dominated test site in southern Sweden. Both the Fine Beam Dual (FBD) polarization and the Quad-polarimetric mode were investigated. Forest plots with stem volume reaching up to a maximum of about 620 m 3 ha -1 (corresponding to 370 tons ha -1 ) were analyzed by relating backscatter intensity to field data using an exponential model derived from the Water Cloud Model. The estimation accuracy of stem volume at plot level (0.5 ha) was calculated in terms of Root Mean Square Error (RMSE). For the best case investigated an RMSE of 39.8% was obtained using one of the FBD HV-polarized images. The corresponding RMSE for the FBD HH-polarized images was 43.9%. In the Quad-polarimetric mode the lowest RMSE at HV- and HH-polarization was found to be 43.1% and 66.1%, respectively.
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| 8. |
- Hallberg, Håkan, et al.
(författare)
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Investigation of microstructure evolution during self-annealing in thin Cu films by combining mesoscale level set and ab initio modeling
- 2016
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Ingår i: Journal of the Mechanics and Physics of Solids. - : Elsevier BV. - 1873-4782 .- 0022-5096. ; 90, s. 160-178
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Tidskriftsartikel (refereegranskat)abstract
- Microstructure evolution in thin Cu films during room temperature self-annealing is investigated by means of a mesoscale level set model. The model is formulated such that the relative, or collective, influence of anisotropic grain boundary energy, mobility and heterogeneously distributed stored energy can be investigated. Density functional theory (DFT) calculations are performed in the present work to provide the variation of grain boundary energy for different grain boundary configurations. The stability of the predominant (111) fiber texture in the as-deposited state is studied as well as the stability of some special low-Σ grain boundaries. Further, the numerical model allows tracing of the grain size distribution and occurrence of abnormal grain growth during self-annealing. It is found that abnormal grain growth depends mainly on the presence of stored energy variations, whereas anisotropic grain boundary energy or mobility is insufficient to trigger any abnormal growth in the model. However, texture dependent grain boundary properties, mobility in particular, contribute to an increased content of low-Σ boundaries in the annealed microstructure. The increased presence of such boundaries is also promoted by stored energy variations. In addition, if the stored energy variations are sufficient the coexisting (111) and (001) texture components in the as-deposited state will evolve into a (001) dominated texture during annealing. Further, it is found that whereas stored energy variations promote the stability of the (001) texture component, anisotropic grain boundary energy and mobility tend to work the other way and stabilize the (111) component at the expense of (001) grains.
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| 9. |
- Larsson, Stefan, et al.
(författare)
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On horizontal variability in lime-cement columns in deep mixing
- 2005
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Ingår i: Geotechnique. - : Thomas Telford Ltd.. - 0016-8505 .- 1751-7656. ; 55:1, s. 33-44
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Tidskriftsartikel (refereegranskat)abstract
- The variability with respect to results from hand-operated penetrometer tests on lime-cement column cross-sections is investigated by means of spatial correlation structures. Experimental directional semi-variograms are evaluated for a large number of column cross-sections from two field tests. Analyses of variance (ANOVA) are performed in order to investigate the influence of various factors in the installation process on the inherent variability. The paper also briefly discusses the concept of sufficient mixing: the link between the mixing process and the mechanical system. The results have been interpreted within the framework of variance reduction based on an averaging model for axially loaded columns. The results from the two field tests show that the radius is the dominating variable in the variability, and different types of correlation structure can be obtained in spite of the fact that they have been equally installed. The mechanical mixing work does not significantly influence the type of spatial correlation structure. Furthermore, a simple design consideration shows that the variance reduction has a major influence on the determination of the partial factor of safety.
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| 10. |
- Marklund, Ture Jesper, 1970, et al.
(författare)
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Performance of an Automotive Under-Body Diffuser Applied to a Sedan and a Wagon Vehicle
- 2013
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Ingår i: SAE International Journal of Passenger Cars - Mechanical Systems. - : SAE International. - 1946-3995 .- 1946-4002. ; 6:1, s. 293-307
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Tidskriftsartikel (refereegranskat)abstract
- Reducing resistance forces all over the vehicle is the most sustainable way to reduce fuel consumption. Aerodynamicdrag is the dominating resistance force at highway speeds, and the power required to overcome this force increases by the power three of speed. The exterior body and especially the under-body and rear-end geometry of a passenger car aresignificant contributors to the overall aerodynamic drag. To reduce the aerodynamic drag it is of great importance to have a good pressure recovery at the rear. Since pressure drag is the dominating aerodynamic drag force for a passenger vehicle,the drag force will be a measure of the difference between the pressure in front and at the rear. There is high stagnationpressure at the front which requires a base pressure as high as possible. The pressure will recover from the sides by a taperangle, from the top by the rear wind screen, and from the bottom, by a diffuser. It is not necessarily the case that anoptimized lower part of the rear end for a wagon-type car has the same performance as for a sedan or hatch-back car. Thisstudy focused on the function of an under-body diffuser applied to a sedan and wagon car. The diffuser geometry waschosen from a feasibility stand-point of a production vehicle such as a passenger car. The fluid dynamic function andtheory of the automotive under-body diffuser working as a drag reduction device is discussed. The flow physics of theunder-body and the wake was analyzed to understand the diffuser behaviour in its application to lift and drag forces on avehicle in ground proximity. This work is mainly a numerical analysis that uses the traditional CFD approach from theautomotive industry. Results from this study show a potential to reduce aerodynamic drag of the sedan car approximately10%, and the wagon car by 2-3 %. The possible gain was much bigger for the sedan vehicle and the optimum occurs at ahigher diffuser angle. This was most likely due to the fact that the sedan car in its original shape produced more lift force than the wagon, a wagon usually produces very little lift or even down-force. Lift forces were also reduced with the use of under-body covers with diffuser. The down-force increased, or lift force decreased, linearly with increased diffuser angle, and the trend was the same for both sedan and wagon rear ends. Flow analysis of the wake showed the importance of how the wake is balanced.
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