| 1. |
- A. Mouris, Boules, et al.
(författare)
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A Dual-Polarized Multi-Antenna Structure for Simultaneous Transmission of Wireless Information and Power
- 2019
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Ingår i: 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, APSURSI 2019 - Proceedings. - : IEEE. ; , s. 1805-1806
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Konferensbidrag (refereegranskat)abstract
- In this paper, a dual-polarized multi-antenna structure is designed at 2.45 GHz with the goal of allowing simultaneous transmission of wireless information and power. Differential feeding was used to minimize the mutual coupling due to radiation leakage in addition to a mushroom-type EBG structure for suppressing the surface waves. Simulation results for the proposed structure show a mutual coupling level lower than -40 dB between the information transmitting antenna and the power transmitting antennas for both polarizations. The isolation level between the antennas is improved by at least 22 dB and 14 dB for the E-plane and H-plane coupling, respectively.
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| 2. |
- Bantavis, P. I., et al.
(författare)
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A Cost-Effective Wideband Switched Beam Antenna System for a Small Cell Base Station
- 2018
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Ingår i: IEEE Transactions on Antennas and Propagation. - : Institute of Electrical and Electronics Engineers Inc.. - 0018-926X .- 1558-2221. ; 66:12, s. 6851-6861
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Tidskriftsartikel (refereegranskat)abstract
- A wideband switched beam antenna array system operating from 2 to 5 GHz is presented. It is comprised of a 4 × 1 Vivaldi antenna elements and a 4 × 4 Butler matrix beamformer driven by a digitally controlled double-pole four-throw RF switch. The Butler matrix is implemented on a multilayer structure, using 90° hybrid couplers and 45° phase shifters. For the design of the coupler and phase shifter, we propose a unified methodology applied, but not limited, to elliptically shaped geometries. The multilayer realization enables us to avoid microstrip crossing and supports wideband operation of the beamforming network. To realize the Butler matrix, we introduce a step-by-step and stage-by-stage design methodology that enables accurate balance of the output weights at the antenna ports to achieve a stable beamforming performance. In this paper, we use a Vivaldi antenna element in a linear four-element array, since such element supports wideband and wide-scan angle operation. A soft condition in the form of corrugations is implemented around the periphery of the array, in order to reduce the edge effects. This technique improved the gain, the sidelobes, and helped to obtain back radiation suppression. Finally, impedance loading was also utilized in the two edge elements of the array to improve the active impedance. The proposed system of the Butler matrix in conjunction with the constructed array can be utilized as a common RF front end in a wideband air interface for a small cell 5G application and beyond as it is capable to simultaneously cover all the commercial bands from 2 to 5 GHz.
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| 3. |
- Bantavis, P. I., et al.
(författare)
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A Wideband Switched Beam Antenna System for 5G Femtocell Applications
- 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. 929-930
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Konferensbidrag (refereegranskat)abstract
- This work introduces a wideband switched beam system for femtocell 5G base stations. The system consists of a 4 x 1 Vivaldi linear array and a 4 x 4 Butler matrix able to operate from 1.9-5.1 GHz. A soft surface is introduced along the outer edges of the vivaldi elements of the array for side lobes and back radiation suppression.
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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
- Fakoukakis, F. E., et al.
(författare)
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Ultra-Wideband butler matrix Fed MIMO antennas
- 2015
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Konferensbidrag (refereegranskat)abstract
- This work elaborates on the design of an Ultra-Wideband (UWB) Butler matrix fed antenna array, implementing a Multiple Input-Multiple Output (MIMO) configuration. The system aims at applications in future Long Term Evolution (LTE) and multifunctional Radar systems. Specifically, based on the results of our previous works, the research is extended towards the implementation of a MIMO beamforming scheme. Different beamforming scenarios are applied, in order to maximize system performance and minimize noise and interference. A comprehensive analysis and design procedure is presented, along with system simulation results.
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| 8. |
- Jonsson, B. Lars G., et al.
(författare)
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Array Antenna Limitations
- 2013
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1536-1225 .- 1548-5757. ; 12, s. 1539-1542
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Tidskriftsartikel (refereegranskat)abstract
- This letter defines a physical-bound-based array figure of merit for both single and multiband array antennas. It provides a measure to compare their performance with respect to return loss, bandwidth(s), thickness of the array over the ground plane, and scan range. The result is based on a sum-rule result of Rozanov-type for linear polarization. For single-band antennas, it extends an existing limit for a given fixed scan-angle to include the whole scan range of the array, as well as the unit-cell structure in the bound. The letter ends with an investigation of the array figure of merit for some wideband and/or wide-scan antennas with linear polarization. We find arrays with a figure of merit >0.6 that empirically defines high-performance antennas with respect to this measure.
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| 9. |
- Jonsson, B. Lars G., et al.
(författare)
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On methods to estimate bandwidth performance for array antennas with ground plane
- 2014
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Ingår i: 2014 31th URSI General Assembly and Scientific Symposium, URSI GASS 2014. - 9781467352253
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Konferensbidrag (refereegranskat)abstract
- Array antenna impedance bandwidth performance is a critical factor for antenna design, in particular for arrays in radar application and more recently for array antennas in communication systems. A priori methods to quantify bandwidth include stored energy-based estimates through the quality factor antenna Q, and sum-rule based estimates based on the antenna as a scattering object. A recently introduced, array figure of merit, uses a square window or walltype estimate on the return-loss to obtain bounds in terms of return-loss level, bandwidth, scan-range and unit-cell specific geometrical and material information, it is based on a fundamental physics result, linking bandwidth to essentially the thickness of the array. An alternative approach is based on the Bode-Fano theory, resulting in bandwidth measures in terms of one or several quality factors. Both methods apply both to single and multi-band array antennas. Here we present these methods and make a comparison between the two approaches.
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| 10. |
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| 11. |
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| 12. |
- Kolitsidas, Christos I., et al.
(författare)
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A study of partial resonance control for edge elements in a finite array
- 2013
-
Ingår i: Progress In Electromagnetics Research Symposium Proceedings, Stockholm, Sweden, Aug. 12-15, 2013. - : Electromagnetics Academy. - 9781934142264 ; , s. 253-256
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Konferensbidrag (refereegranskat)abstract
- This work is focused on developing a method for compensating the edge effects in a mid-sized antenna array. Initially the resonance shift for the E-plane with respect to element position and scan angle was studied in finite × infinite array of strongly coupled dipoles. We show that geometrical tuning on the outermost elements of the array results in a 40% bandwidth improvement at the edge elements for a 40± scan angle. This improvement is compared with the original edge element behavior and it is achieved with a VSWR < 3 for the worst element. These modifications were based into two observations. Primarily, it was shown that by electrically connecting the edge elements we obtain an improvement in the interelement coupling. By adding stripes to the arms of the edge dipoles we obtained an additional degree of freedom that was used to improve the impedance of the edge elements. This procedure resulted in almost uniform VSWR behavior for all elements up to the edge for the finite × infinite approach.
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| 13. |
- Kolitsidas, Christos I., et al.
(författare)
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Edge effects in a strongly coupled dipole element array in triangular lattice
- 2014
-
Ingår i: Progress in Electromagnetics Research Symposium. - 9781934142288 ; , s. 487-490
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Konferensbidrag (refereegranskat)abstract
- In this work the focus is on the impact of edge effects in the equilateral triangular lattice of a strongly coupled dipole antenna array. A novel wideband strongly coupled, single polarized, dipole element is designed and studied in a triangular grid. The antenna element operates in 6: 1 bandwidth ratio. Our analysis for the edge effects is based the finite × infinite approach with multiple rows taken into account in order to capture the effects on the different edges that appear in triangular grids. The effects at the E-edge are studied as it is the plane where the currents are truncated. At the E-edge the variation on the behavior is mainly due to lack of closely coupling fields. Using the finite × infinite approach the variations along the E- edge of the array are studied for both rectangular and triangular grid. Finally, periodic resistive loading was used on the dipoles to dissipate the waves produced from the edges and smooth the impedance behavior along the array row.
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| 14. |
- Kolitsidas, Christos I., et al.
(författare)
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Exploiting asymmetry in a capacitively loaded strongly coupled dipole array
- 2014
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Ingår i: 2014 Loughborough Antennas and Propagation Conference, LAPC 2014. - 9781479936625 ; , s. 723-726
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Konferensbidrag (refereegranskat)abstract
- The scope of this work is to investigate asymmetry in a strongly coupled dipole array and exploit its effect for bandwidth and scanning improvement. Typically, antenna array elements are symmetrical in E-and H-plane. Introducing non-symmetric elements offers additional freedom to improve the array characteristics. The effect of non-symmetric elements is studied and a reference case is created with a symmetric element in unit cell design. The obtained bandwidth for the reference case is a 6:1 at the broadside. Using this element as a base for this work, we pixelate parts of the element and optimize this parts with a genetic algorithm. Having an initial design (solution) reduces significant the number of iterations needed for the genetic algorithm to converge. The element was studied in a rectangular and in triangular lattice. The results indicate that in both cases the performance is improved. Finally, the performance of the developed array element was investigated in terms of the array figure of merit, a general measure of array element performance. This resulted in the best known array figure of merit; 0.84.
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| 15. |
- Kolitsidas, Christos I., et al.
(författare)
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Polarization aspects on a wideband antenna array based on asymmetrical elements
- 2016
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Ingår i: 2016 10th European Conference on Antennas and Propagation, EuCAP 2016. - : Institute of Electrical and Electronics Engineers (IEEE). - 9788890701863
-
Konferensbidrag (refereegranskat)abstract
- A significant challenge in future wireless networks is the design of a wideband wide-scan angle antenna arrays capable to accommodate multiple RF air interfaces. In this paper the effect on polarization is discussed for an array based on an asymmetric element. Employing asymmetric elements in an array it has been shown to be beneficial for extending the impedance bandwidth of the array. The introduced asymmetries will give rise to currents that contribute to cross-polarization. Two methods for assessing the cross polarization levels are implemented in this work: the infinite array approximation and the embedded element pattern method. The unit cell is modeled as a three port network by separating into two ports the fundamental array TE/TM Floquet modes and the feeding port.
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| 16. |
- Kolitsidas, Christos I., et al.
(författare)
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Rectangular vs. equilateral triangular lattice comparison in a T-slot loaded strongly coupled dipole array
- 2014
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Ingår i: 2014 31th URSI General Assembly and Scientific Symposium, URSI GASS 2014. - 9781467352253
-
Konferensbidrag (refereegranskat)abstract
- This work is focused on the impact of the array lattice in a strongly coupled dipole array. In order to study this, a wideband (6.2:1 BW ratio) dipole based array element was designed and used to compare lattice impact in our analysis. The element was designed using the unit cell analysis. In order to improve the bandwidth at the lower end of the frequency band the dipole was loaded with a T-slot increasing the electrical length. Based on this design a comparative analysis was conducted between rectangular and isosceles triangular lattices with respect to return loss, embedded element pattern and inter-element coupling. Emphasis was given to the analysis of the lattice comparison in the E-plane of the array as it is the most prone to variations with the array scanning.
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| 17. |
- Kolitsidas, Christos, et al.
(författare)
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Investigation of compensating the ground plane effect through array's inter-element coupling
- 2013
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Ingår i: 2013 7th European Conference on Antennas and Propagation (EuCAP). - New York : IEEE. - 9788890701832 ; , s. 1264-1267
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Konferensbidrag (refereegranskat)abstract
- Bandwidth and directivity are coupled and an increase in directivity provided by a ground plane tends to reduce bandwidth. Over the last decade it has been indicated that highly coupled antenna elements have the ability to provide wide band properties. Such structures often suffer from a bandwidth reduction when they are placed over a ground plane. This study focuses on the interaction between the ground plane and the inter-element coupling. The coupling can partially be modified and hence it can be seen as an extra degree of freedom, a mean to widen bandwidth for strongly coupled arrays in the presence of a ground plane.
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| 18. |
- Kolitsidas, Christos, 1984-
(författare)
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Literature review : Wideband/Multiband Antenna Arrays for Base Station Applications
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The scope of this literature study is to describe the current trends in multiband/wideband antenna arrays with wide scan angle that are applicable to the Chase project: Next Generation Antenna Arrays. The goal of this project is to develop a broadband/multiband antenna array that is able to operate at all commercial wireless protocols and provide wide scan angle capabilities. In the literature two different approaches have been developed for the array design procedure. The first approach, which is the classic design procedure, is based on the element and the array lattice selection. It is then expected that the array inherits the element behavior thus the characteristics of the array would be similar to element characteristics. Using this procedure the interelement coupling is treated as an undesired phenomenon which causes unwanted resonances inside the operating frequency range. Over the last decade a new technique was developed that utilize strongly coupled elements and they showed that these elements can provide wideband array characteristics. The first indicator for this behavior was the Vivaldi array. Here, it was shown that electrically connected Vivaldi elements can provide large bandwidth and wide scan angle range. This breakthrough opened a new research area were strongly coupled elements and coupling mechanisms are investigated, it has also generated a new design approach. This literature survey is organized on these two different approaches. In the first chapter we examine the elements that can provide wideband or multiband characteristics. In the second chapter the most promising strongly coupled arrays are examined and we compare their properties to the project requirements. We end this literature survey with conclusions selecting the most promising technologies.
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| 19. |
- Kolitsidas, Christos
(författare)
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Next Generation Wideband Antenna Arrays for Communications and Radio Astrophysics
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wideband, wide-scan antenna arrays are a promising candidate for the future wireless networks and as well as an essential part of experimental radio astrophysics. Understanding the underline physics of the element performance in the array environment is paramount to develop and improve the performance of array systems. The focus of this thesis is to develop novel wideband antenna array technologies and develop new theoretical insights of the fundamental limits of antenna arrays. The developed methodologies have also been extended to include a radio astrophysics application for the global 21cm experiment. Investigating the fundamental antenna array limits and extracting general performance measures can provide a priori estimates for any application of arrays. In this thesis, a general measure for antenna arrays, the array figure of merit is proposed. This measure couples bandwidth, height from the ground plane and reflection coefficient in a bounded quantity. An extension of the array figure of merit that is able to provide matching, bandwidth and directivity/gain limits is also introduced.The soft Vivaldi array is introduced as a novel wideband, wide-scan angle array technology. Periodic structure loading has been utilized to improve the array's performance and mold the electromagnetic wave behavior to our benefit. The soft condition has been utilized in the same manner as the conventional soft-horn antenna at the Vivaldi element. An integrated matching layer in the form of periodic strip loading is introduced. A single polarized soft Vivaldi array prototype has been developed fabricated and measured. The developed finite array has been loaded with a soft condition in the periphery to mitigate edge effects. The results indicated improved cross-polarization and side-lobe levels.A new class of wideband antenna arrays, the Strongly Coupled Asymmetric Dipole Array (SCADA) was also proposed in this thesis. Exploiting asymmetry in the array element introduces an additional degree of freedom that improves bandwidth and scanning performance. A novel methodology for terminating finite arrays is also proposed. The theory and an experimental antenna array is presented with good agreement between measured and simulated results. An effort to integrate a vertical wide angle matching layer was also addressed and a prototype array with this concept is presented.In the last part of this thesis, a methodology for the detection of the global cosmological 21cm signal from the Epoch of Reionization (EoR) is developed. The main sources of errors in this experiment, the foregrounds and the antenna chromaticity are evaluated. A new algorithmic methodology for extracting the global EoR signal is proposed. The method is based on piecewise polynomial fitting and has successfully been applied and evaluated. An antenna array that is based on the methodologies described in this thesis has been developed and evaluated with the proposed algorithm.
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| 20. |
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| 21. |
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| 22. |
- 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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| 23. |
- Mattsson, Martin, 1991-, et al.
(författare)
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Dual-Band Dual-Polarized Full-Wave Rectenna Based on Differential Field Sampling
- 2018
-
Ingår i: IEEE Antennas and Wireless Propagation Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1536-1225 .- 1548-5757. ; 17:6, s. 956-959
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Tidskriftsartikel (refereegranskat)abstract
- A dual-band rectenna for radio frequency (RF) energy harvesting is presented in this letter. The proposed antenna has two concentric square patches electrically connected with a small microstrip line connection. Four ports are located in the inner patch. The configuration of the ports enables a differential field sampling scheme and dual polarization. The antenna operates for the WiFi frequency bands of 2.4 and 5.5 GHz with 7.52 and 7.26 dBi gain, respectively, for each frequency. A full-wave Greinacher voltage doubler rectifier for each polarization has been employed for RF-to-dc conversion. The proposed novel topology utilizes the differential field sampling for each polarization and quadruples the overall output voltage by the rectification process. The differential output voltage source from the rectenna can directly act as a power source as typically electronics require differential source for their operation.
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| 24. |
- 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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| 25. |
- Zetterström, Oskar, et al.
(författare)
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A 28-port MIMO Cube for Micro Base Station Applications
- 2020
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Ingår i: IEEE Transactions on Antennas and Propagation. - : Institute of Electrical and Electronics Engineers Inc.. - 0018-926X .- 1558-2221. ; 68:5, s. 3443-3452
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Tidskriftsartikel (refereegranskat)abstract
- A novel multi-band, dual-polarized, 28-port multiple-input multiple-output (MIMO) cube is presented. The cube structure enables dense placement of the antennas, whilst still allowing for low correlation between the individual antenna ports. The total size of the cube is roughly 2×2×7 λ30, where λ0 is the wavelength at the lowest used frequency. The novelty of the design lies in the use of a combination of orthogonally polarized endfire and broadside radiating antenna elements. Full use of all facets of the cube is achieved without the need to sacrifice bottom or top facets for mounting. Therefore, full azimuthal coverage for communication in two orthogonal polarizations is readily achieved. The system operates in both cellular and Wi-Fi 2:4, 5:5 GHz bands, with a targeted |S11| below –10 dB. The MIMO performance of the system is evaluated in two environments: the Rich Isotropic Multipath environment and the Random Line-of-Sight environment. These two scenarios represent the edge environments of any real-life propagation scenario in terms of the directional distribution of outgoing or incoming waves at a MIMO transceiver. The intended application of the system is micro base stations and repeaters, with possible extension to massive MIMO.
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