1,123 research outputs found

    Scaling up MIMO: Opportunities and Challenges with Very Large Arrays

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    This paper surveys recent advances in the area of very large MIMO systems. With very large MIMO, we think of systems that use antenna arrays with an order of magnitude more elements than in systems being built today, say a hundred antennas or more. Very large MIMO entails an unprecedented number of antennas simultaneously serving a much smaller number of terminals. The disparity in number emerges as a desirable operating condition and a practical one as well. The number of terminals that can be simultaneously served is limited, not by the number of antennas, but rather by our inability to acquire channel-state information for an unlimited number of terminals. Larger numbers of terminals can always be accommodated by combining very large MIMO technology with conventional time- and frequency-division multiplexing via OFDM. Very large MIMO arrays is a new research field both in communication theory, propagation, and electronics and represents a paradigm shift in the way of thinking both with regards to theory, systems and implementation. The ultimate vision of very large MIMO systems is that the antenna array would consist of small active antenna units, plugged into an (optical) fieldbus.Comment: Accepted for publication in the IEEE Signal Processing Magazine, October 201

    Design of Multi-Antenna System for UMTS Clamshell Mobile Phones with Ground Plane Effects Considerations

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    In this paper, the influence of the ground plane dimensions on the port-to-port isolation of two closely-spaced Universal Mobile Telecommunications System (UMTS) Planar Inverted-F Antennas (PIFAs) with and without neutralization line is first presented. Parametric studies show the existence of an optimal size of the ground plane allowing optimizing the isolation and the efficiency of the considered antenna-system. The results obtained with this study are used in the second part to develop an efficient neutralized multi-antenna system for clamshell-type mobile phones. The obtained results, in terms of isolation, matching and diversity for the two possible configurations of the clamshell system in use namely the open and the closed states, show that good performance are obtained in the open state and preserved in the closed state. Prototypes of these two configurations are realized and measurement results are in good agreement with the simulations

    Minimization of Mutual Coupling Using Neutralization Line Technique for 2.4 GHz Wireless Applications

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    YesThis paper presented a planar printed multiple-input-multiple-output (MIMO) antenna with a dimension of 100 x 45 mm2. It composed of two crescent shaped radiators placed symmetrically with respect to the ground plane. Neutralization line applied to suppress mutual coupling. The proposed antenna examined both theoretically and experimentally, which achieves an impedance bandwidth of 18.67% (over 2.04-2.46 GHz) with a reflection coefficient < -10 dB and mutual coupling minimization of < -20 dB. An evaluation of MIMO antennas is presented, with analysis of correlation coefficient, total active reflection coefficient (TARC), capacity loss and channel capacity. These characteristics indicate that the proposed antenna suitable for some wireless applications

    Design and Measurement-Based Evaluation of Multi-Antenna Mobile Terminals for LTE 3500 MHz Band

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    Design of multi-element antennas for small mobile terminals operating at higher frequencies remains challenging despite smaller antenna dimension and possibility of achieving electrically large separation between them. In this paper, the importance of the type of radiating elements operating at 3400-3600 MHz and their locations on the terminal chassis are highlighted. An isotropic radiation pattern that receives incoming signals from arbitrary directions is obtained by combining the radiation patterns of multiple antennas with localized chassis current distribution. Four multiport antennas configurations with two- and eight-element antennas are designed and evaluated experimentally in indoor propagation environments. Our proposed designs of multi-element antennas provide the highest MIMO channel capacity compared to their counterparts using antennas with less localized chassis current distribution, even in the presence of user's hand

    Miniaturized DGS and EBG structures for decoupling multiple antennas on compact wireless terminals

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    MIMO (Multiple Input Multiple Output) technology has been presented to significantly increase the wireless channel capacity and reliability without requiring additional radio spectrum or power. In MIMO systems, multiple antennas are mounted at both the transmitter and the receiver. When this technology is employed for a compact wireless terminal, one of the most challenging tasks is to reduce the high mutual coupling between closely placed antenna array elements. The high mutual coupling produces high correlation between antenna elements and affects the channel capacity of MIMO system. The objectives of this thesis are to design practical miniaturized structures to reduce high mutual coupling for small wireless terminals. The research is conducted in the following areas. Initially, a PIFA design and two-element PIFA array are proposed and optimized to operate at 1.9GHz. A pair of two coupled quarter-wavelength linear slits is inserted in a compact ground plane, resulting in significant reduction of the mutual coupling across antenna operating frequency band. In order to take up less space on the ground plane, instead of the linear slits, miniaturized convoluted slits are implemented between the two closely placed PIFAs. Although the convoluted slits have small area and are positioned close to the edges of the ground plane, the miniaturized convoluted slit structures achieve a reduction of mutual coupling between antenna elements and succeed in reducing the effect of the human body (head and hand) to the antennas. In order to further reduce the size of the slits etched on the compact ground plane, a novel double-layer slit-patch EBG structure is proposed. It consists of a two-layer structure including conducting patches and aperture slits placed on either side of a very thin dielectric layer. They are placed in very close proximity to each other (55ÎĽm). A two-element printed CPW-fed monopole array operating around 2.46GHz and a two-element UWB planar monopole array operating from 3GHz to 6GHz have been employed to investigate the proposed slit-patch EBG structures. The optimized double-layer slit-patch EBG structure yields a significant reduction of the mutual coupling and produces the maximum miniaturization of antenna array. Another novel convoluted slit-patch EBG structure has been presented to reduce the mutual coupling between two PIFAs operating at 1.9GHz. These results demonstrate that the slit-patch EBG structure is a feasible technology to reduce the mutual coupling between multiple antennas for compact wireless terminals

    The study on used of tropical wood sawdust as a replacement fine aggregates in concrete mix

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    The amount of wastage produced in the construction industry is increases. The revolution making alterations to conventional concrete had been introduced. Industrial wastage such as fly ash, sawdust, and sludge are often used to replace material in the concrete mix, by that, the value of sustainability increase. Reusing waste materials can reduce renewable and non-renewable resources such as sand and water. This study emphasis the mechanical properties of the lightweight concrete regarding the replacement of material, sawdust into the concrete mix by 0% (control sample), 10%, 20% and 40% for grade 30 N/mm2. The objectives for this study are to determine the mechanical behavior of concrete mix with partial replacement of recycled fine aggregates, to determine the concrete properties consolidating recycled tropical wood sawdust, and to identify the optimum percentage partial replacement of recycled tropical wood sawdust in the concrete mix. For fresh concrete, slump test were performed to determine the workability of the concrete while for hardened concrete tests were compressive strength test, water absorption test and density test. The tests were carried out at the age of 7 days and 28 days. The result shown that 10% of sawdust replacement in the concrete mix recorded the highest amount of compressive strength, lowest water absorption and highest density compared to the control sample
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