| 1. |
- Björkqvist, Oskar, et al.
(författare)
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A Novel Efficient Multiple Input Single Output RF Energy Harvesting Rectification Scheme
- 2017
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Ingår i: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538632840 ; , s. 1605-1606
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Konferensbidrag (refereegranskat)abstract
- In this work an implementation of an ambient radio frequency harvesting system utilizing multiple input single output approach is demonstrated. Measurements of typical ambient radiation have been conducted with respect to power levels and frequency to determine which communication signals are suitable for harvesting. The measurement campaign showed that the WiFi frequency band at 2.45 GHz is a good candidate for indoors applications. A Greinacher voltage doubler is used for the rectification. A multiple input single output - MISO scalable scheme approach is implemented that is able to provide a DC differential output voltage. Simulated and experimental results proved the MISO rectenna to be an efficient scheme for RF harvesting.
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| 2. |
- Björkqvist, Oskar, et al.
(författare)
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Additive manufactured dielectric Gutman lens
- 2019
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology. - 0013-5194 .- 1350-911X. ; 55:25, s. 1318-1320
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Tidskriftsartikel (refereegranskat)abstract
- In this Letter, the design of a 3D printed fully dielectric Gutman lens is presented. The authors demonstrate the feasibility of using highly accessible and cheap additive manufacturing technology to produce a compact and high performing antenna lens. The lens is designed to operate at Ku band and utilises a flat feed surface that approximates the focal sphere. The flat feed surface allows for beam steering that requires only translational movement of the feed. The lens has a measured realised gain of 20 dBi with 3 dB scan loss at +45°. The lens finds applications in systems that require high gain antennas, such as the new generation of satellite and 5G communications and radar technology.
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| 3. |
- Björkqvist, Oskar, et al.
(författare)
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Additive Manufactured Three Dimensional Luneburg Lens for Satellite Communications
- 2019
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Ingår i: 13th European Conference on Antennas and Propagation, EuCAP 2019. - : Institute of Electrical and Electronics Engineers (IEEE). - 9788890701887
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Konferensbidrag (refereegranskat)abstract
- A method for designing gradient refractive index (GRIN) lenses with additive manufacturing or 3D-printing at K-u band is presented. To demonstrate the potential of the method, we designed a Luneburg lens using a single low-loss dielectric material available for 3D-printers. The gradient index is realized by varying the local material fill density of the lens. We demonstrate with full wave simulations that the structure is able to transform a spherical electromagnetic wave to a plane wave. When the lens is fed with a rectangular waveguide, the overall antenna has a gain of 23 dBi with side lobe levels of -12.5 dB in K-u band. This lens, when integrated with a circular polarized feeding system, could find application for ground satellite communications.
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| 4. |
- Björkqvist, Oskar, et al.
(författare)
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Wireless Sensor Network Utilizing Radio-Frequency Energy Harvesting for Smart Building Applications
- 2018
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Ingår i: IEEE Antennas & Propagation Magazine. - : Institute of Electrical and Electronics Engineers (IEEE). - 1045-9243 .- 1558-4143. ; 60:5, s. 124-136
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Tidskriftsartikel (refereegranskat)abstract
- The scope of this article is to develop a modular radio-frequency (RF) energy-harvesting system for smart buildings that can act as a power source for sensing devices. Electromagnetic field-strength measurements at the main campus of the KTH Royal Institute of Technology in Stockholm, Sweden, were carried out to define the strength of the available ambient signals. Mainly two spectra were available for possible RF harvesting, i.e., two cellular bands [GSM1800 and third generation (3G)] and the 2.45-GHz Wi-Fi band. Based on these measurements, a modular approach for the system was adopted. The system is composed from two modules: 1) a Wi-Fi rectenna system composed of eight dual-polarized patch antennas and 16 rectifiers to produce eight differential voltage sources connected in series and 2) a cellular rectenna system composed of eight linear tapered slot antennas and eight rectifiers to produce four differential voltage sources connected in series. We propose an innovative multiple-input, single-output (MISO) wave rectifier that yields an efficient differential output. Both rectenna modules offer full azimuthal coverage and can operate either together or independently.
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| 5. |
- Dahlberg, Oskar, et al.
(författare)
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A Novel 32 Port Cube MIMO Combining Broadside and Endfire Radiation Patterns for Full Azimuthal Coverage - A Modular Unit Approach for a Massive MIMO System
- 2017
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Ingår i: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538632840 ; , s. 1641-1642
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Konferensbidrag (refereegranskat)abstract
- In this paper we propose a novel 32 antenna port multiple-input-multiple-output (MIMO)-cube. The total volume of the cube is 320 x 320 x 120 mm(3) . On two faces, endfire radiating linear tapered slot antennas (LTSAs) are placed and on the remaining sides, a mix of both LTSAs and broadside patch antennas are placed. In total 16 LTSAs and 8 dual polarized patches are used. The LTSA is designed to operate at the GSM and 3G bands, from 1.7 to 2.3 GHz. A corrugation pattern is introduced along the edges of the LTSAs covering one face to increase directivity and decrease sidelobes. The LTSAs are placed in two different orientations in order to receive two polarisations. The patch antenna is dual band and dual polarized. It operates in the frequency bands 2.4-2.5 and 5.45-5.6 GHz where Wi-Fi communication is made. The spatial placement, with antennas on all sides of the cuboid, ensures full azimuthal coverage despite the high directivity of the antennas. Using different antennas on different faces of the cube further optimizes the volume efficiency of the cube for azimuthal coverage.
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| 6. |
- Mattsson, Martin, et al.
(författare)
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A high gain Dual-Polarised Differential Rectenna for RF Energy Harvesting
- 2017
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Ingår i: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538632840 ; , s. 1609-1610
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Konferensbidrag (refereegranskat)abstract
- A rectenna for radio frequency (RF) energy harvesting is presented in this paper. We introduce a novel technique for RF rectification that is based on differential field sampling and a Greinacher voltage doubler rectifier. The proposed rectification antenna is a dual polarized patch with 4 ports that operates for the WiFi frequency band of 2.4-2.5 GHz and has a gain of 6.75 dB at each port. The proposed novel topology doubles the amount of input power accepted for each polarization and then quadruples the overall output power. In addition we have a differential output voltage source that is typically required for the electronics connected to the harvesting system.
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| 7. |
- Silver, Gustaf, et al.
(författare)
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Exploiting Antenna Array Configurations for Efficient Simultaneous Wireless Information and Power Transfer
- 2017
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Ingår i: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538632840 ; , s. 1083-1084
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Konferensbidrag (refereegranskat)abstract
- Different patch antenna array configurations for Simultaneous Wireless Information and Wireless Power Transfer - SWIPT - were simulated and evaluated. The scope of the work is to provide configurations that can be used to minimise the interference between information and power transfer as well as provide some beamforming capabilities. Our assumption for all the evaluated structures are that two receive antennas are used for RF energy harvesting and one antenna is used for information exchange. The choice for two antennas for energy harvesting is based on that a differential DC output full-wave rectifier is used. Our analysis is based on patch antennas.
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| 8. |
- Björkqvist, Maria, et al.
(författare)
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Evaluation of a previously suggested plasma biomarker panel to identify Alzheimer's disease.
- 2012
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- There is an urgent need for biomarkers in plasma to identify Alzheimer's disease (AD). It has previously been shown that a signature of 18 plasma proteins can identify AD during pre-dementia and dementia stages (Ray et al, Nature Medicine, 2007). We quantified the same 18 proteins in plasma from 174 controls, 142 patients with AD, and 88 patients with other dementias. Only three of these proteins (EGF, PDG-BB and MIP-1δ) differed significantly in plasma between controls and AD. The 18 proteins could classify patients with AD from controls with low diagnostic precision (area under the ROC curve was 63%). Moreover, they could not distinguish AD from other dementias. In conclusion, independent validation of results is important in explorative biomarker studies.
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| 9. |
- Lee, Sangwook, et al.
(författare)
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A porous silicon immunoassay platform for fluorometric determination of alpha-synuclein in human cerebrospinal fluid
- 2014
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Ingår i: Microchimica Acta. - : Springer Science and Business Media LLC. - 1436-5073 .- 0026-3672. ; 181:9-10, s. 1143-1149
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Tidskriftsartikel (refereegranskat)abstract
- Levels of total and/or oligomeric alpha-synuclein may be used as a biomarker tool to aid in the diagnosis and development of new disease-modifying therapies. We report here on a porous silicon antibody microarray for the fluorimetric determination of cerebrospinal fluid levels of total alpha-synuclein, a protein involved the pathology of Parkinson's disease. The surface of porous silicon has a 3-dimensional macro- and nanoporous structure, and this offers a large binding capacity for capturing probe molecules. Porous silicon also warrants efficient immobilization of antibodies by surface adsorption, and does not require chemical immobilization. The platform requires 10 mu L of cerebrospinal fluid, and each test requires 4 h for assay only (including immobilization of capturing antibody). The limit of detection is 35 pg mL(-1) of alpha-synuclein in cerebrospinal fluid, and the dynamic analytical range extends from 0.01 to 100 ng center dot mL(-1).
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| 10. |
- Lindqvist, Daniel, et al.
(författare)
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Interleukin-6 Is Elevated in the Cerebrospinal Fluid of Suicide Attempters and Related to Symptom Severity
- 2009
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Ingår i: BIOLOGICAL PSYCHIATRY. - : Elsevier BV. - 0006-3223 .- 1873-2402. ; 66:3, s. 287-292
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Tidskriftsartikel (refereegranskat)abstract
- Background: Depressive disorders are associated with immune system alterations that can be detected in the blood. Cytokine concentrations in cerebrospinal fluid (CSF) and their relationship to aspects of suicidality have previously not been investigated. Methods: We measured interleukin-1 beta interleukin-6 (IL-6), interleukin-8, and tumor necrosis factor-a (TNF-alpha) in CSF and plasma of suicide attempters (n = 63) and healthy control subjects (n = 47). Patients were classified according to diagnosis and violent or nonviolent suicide attempt. We evaluated suicidal ideation and depressive symptoms using the Suicide Assessment Scale and the Montgomery-Asberg Depression Rating Scale (MADRS). We also analyzed the relation between cytokines and monoamine metabolites 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) in CSF, as well as the integrity of the blood-brain barrier as reflected by the CSF:serum albumin ratio. Results: IL-6 in CSF was significantly higher in suicide attempters than in healthy control subjects. Patients who performed violent suicide attempts displayed the highest IL-6. Furthermore, there was a significant positive correlation between MANS scores and CSF IL-6 levels in all patients. IL-6 and TNF-a correlated significantly with 5-HIAA and HVA in CSF, but not with MHPG. Cytokine levels in plasma and CSF were not associated, and patients with increased blood-brain barrier permeability did not exhibit elevated cytokine levels. Conclusions: We propose a role for CSF IL-6 in the symptomatology of suicidal behavior, possibly through mechanisms involving alterations of dopamine and serotonin metabolism.
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