| 1. |
- Abbas, Taimoor, et al.
(författare)
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Line-of-Sight Obstruction Analysis for Vehicle-to-Vehicle Network Simulations in a Two Lane Highway Scenario
- 2013
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Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2013
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Tidskriftsartikel (refereegranskat)abstract
- In vehicular ad-hoc networks (VANETs) the impact of vehicles as obstacles has largely been neglected in the past. Recent studies have reported that the vehicles that obstruct the line-of-sight (LOS) path may introduce 10-20 dB additional loss, and as a result reduce the communication range. Most of the traffic mobility models (TMMs) today do not treat other vehicles as obstacles and thus can not model the impact of LOS obstruction in VANET simulations. In this paper the LOS obstruction caused by other vehicles is studied in a highway scenario. First a car-following model is used to characterize the motion of the vehicles driving in the same direction on a two-lane highway. Vehicles are allowed to change lanes when necessary. The position of each vehicle is updated by using the car-following rules together with the lane-changing rules for the forward motion. Based on the simulated traffic a simple TMM is proposed for VANET simulations, which is capable to identify the vehicles that are in the shadow region of other vehicles. The presented traffic mobility model together with the shadow fading path loss model can take in to account the impact of LOS obstruction on the total received power in the multiple-lane highway scenarios.
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| 2. |
- Gustafsson, Mats, et al.
(författare)
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Absorption Efficiency and Physical Bounds on Antennas
- 2010
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Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2010
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Tidskriftsartikel (refereegranskat)abstract
- Abstract—The all spectrum absorption efficiency appears in the physical bounds on antennas expressed in the polarizability dyadics. Here, it is shown that this generalized absorption efficiency is close to 1/2 for small idealized dipole antennas and for antennas with a dominant resonance in their absorption. Also, the usefulness of this parameter is analyzed for estimation of antenna performance. The results are illustrated with numerical data for several antennas.
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| 3. |
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| 4. |
- Hult, Tommy, et al.
(författare)
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The Effect of Mutual Coupling on a High Altitude Platform Diversity System Using Compact Antenna Arrays
- 2010
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Ingår i: International Journal of Antennas and Propagation. - : Hindawi Publishing Corporation. - 1687-5869 .- 1687-5877. ; 2010
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the destructive effects of mutual coupling and spatial correlation between the separate antenna elements on a combined diversity system consisting of multiple HAPs (High-Altitude Platforms) employing various compact MIMO (Multiple-Input Multiple-Output) antenna array configurations, in order to enhance the mutual information in HAP communication links. In addition, we assess the influence of the separation angle between HAPs on system performance, and determine the optimal separation angles that maximize the total mutual information of the system for various compact MIMO antennas. Simulation results show that although the mutual information is degraded by mutual coupling and spatial correlation, the proposed HAP diversity system still provides better performance compared to a nondiversity system for all tested scenarios.
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| 5. |
- Kanth, Rajeev Kumar, et al.
(författare)
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Study on Glass-Epoxy-Based Low-Cost and Compact Tip-Truncated Triangular Printed Antenna
- 2012
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Ingår i: International Journal of Antennas and Propagation. - : Hindawi Publishing Corporation. - 1687-5869 .- 1687-5877. ; , s. 184537-
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Tidskriftsartikel (refereegranskat)abstract
- Printed antennas based on glass epoxy substrate have been developed. On the basis of required specifications and assigned frequencies, tip-truncated triangular printed antennas have been designed, analyzed, and fabricated. The performances of the antennas have been measured in terms of return loss, frequency of operation, bandwidth, and radiation pattern. Triangular microstrip antenna (TMSA) configuration consisting of copper as active radiating patch and glass epoxy as dielectric substrate has been screened out to achieve the essential characteristics and satisfying recommended low-cost antenna. The Method of Moment (MOM) analyzing techniques have been employed to realize the required specific properties, whereas optimized tip truncation technique and varying feed point location give rise to suitable LHCP or RHCP configuration of the printed antenna. The coaxial probe signal feed arrangement have been considered for this work. The proposed printed antennas are suitable for communication links between ships or buoys and satellites specially for navigation purpose.
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| 6. |
- Lindgren, Tore, et al.
(författare)
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A measurement system for the position and phase errors of the elements in an antenna array subject to mutual coupling
- 2012
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Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2012
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Tidskriftsartikel (refereegranskat)abstract
- When deploying large antenna arrays in arctic environments, a local measurement system may be necessary in order to ensure control over the position and phase of the individual antenna elements. In this paper, a method of estimating the position and phase of each individual antenna element in the presence of mutual coupling is presented. It uses both measurements of the scattering matrix in the array and measurements of the electric field using a minimum of four probes located in the near field of the array. Simulations show that the method gives accurate results even in the presence of noise in the measurements. The geometry of the probe-array system affects the performance significantly.
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| 7. |
- Lui, H., et al.
(författare)
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Mutual Coupling in Antenna Arrays 2013
- 2014
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Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2014
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The invention of antenna arrays opened up the door for microwave sensing and communications. Most applications of antenna arrays are in the defense and wireless communications areas. The introduction of multiple-input-multiple-output (MIMO) concept in recent years has opened up further opportunities in that the system performance can be maintained with a smaller number of antennas. The existence of mutual coupling effect, that is, the electromagnetic interaction between antenna elements, appears as an undesirable effect in most of these cases. The transmitted and received signals can be significantly distorted such that the signals no longer depend solely on the antenna elements, but also on the array structure and the surrounding environment. Such distortions result in the reduction of channel capacities in communications applications, as well as poor accuracies in ranging and direction finding. In most applications, the mutual coupling effect is unknown. A major challenge is then to characterize this undesirable effect and to accurately estimate the unknown parameters (range, direction) without a priori knowledge of the signal environment.This special issue, which is the third one in its series, provides an international forum for researchers to disseminate their results and ideas to tackle some of these challenging research problems. Five dedicated papers have contributed to this special issue. These papers concern the mutual coupling and its impacts on MIMO communications, direction finding, and MIMO radar. To help interested readers with a quick reference to the main themes of these papers, we briefly introduce them as follows.The first paper entitled “Self-interference cancellation-based mutual-coupling model for full-duplex single-channel MIMO systems,” concerns the mutual coupling problem in MIMO communications. The paper addresses the self-interference and mutual-interference of a full-duplex single-channel MIMO communications system.In the presence of mutual coupling, the array manifold is perturbed, which results in poor accuracies in direction finding. The paper “Accurate DOA estimations using microstrip adaptive arrays in the presence of mutual coupling effect” proposes a method to calibrate the undesirable mutual coupling effect for arrays with non-omni-directional radiating elements. The third paper, entitled “2-D direction of arrival estimation for cross array in the presence of mutual coupling,” introduces a noniterative algorithm based on the Propagation Method for accurate two-dimensional direction finding problems using a cross array in the presence of mutual coupling. The paper “AR model-based direction-of-arrival estimation of coherent signals in the presence of unknown mutual coupling” provides a novel signal processing solution based on a spatial autoregression (AR) model for coherent direction finding of uniform linear arrays.The fifth paper of this special issue, entitled “Root-MUSIC based angle estimation for MIMO radar with unknown mutual coupling,” explores the direction finding solutions in MIMO radar. A Root-MUSIC based solution is proposed to estimate the incoming signal direction with unknown mutual coupling.All papers appearing in this special issue have been subject to a strict peer-reviewing process. They are of high quality and address the mutual coupling problem from different perspectives. Through this special issue, we have provided a medium of dissemination for valuable ideas and conclusions on mutual coupling research. At the same time, we hope that more research innovations can be stimulated for future advances on this subject.
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| 8. |
- Lui, Hoi-Shun, 1980, et al.
(författare)
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Direction-of-Arrival Estimation of Closely Spaced Emitters Using Compact Arrays
- 2013
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Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2013, s. Art. no. 104848-
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Tidskriftsartikel (refereegranskat)abstract
- Performance evaluation of direction-of-arrival (DOA) estimation algorithms has continuously drawn significant attention in the past years. Most previous studies were conducted under the situation that antenna element separation is about half wavelength in order to avoid the appearance of grating lobes. On the other hand, recent developments in wireless communications have favoured the use of portable devices that utilize compact arrays with antenna element separations of less than half wavelength. Performance evaluation of DOA estimation algorithms employing compact arrays is an important and fundamental issue, but it has not been fully studied. In this paper, the performance of the matrix pencil method (MPM) that applies to DOA estimations is investigated through Monte Carlo simulations. The results show that closely spaced emitters can be accurately resolved using linear compact array with an array aperture as small as around half wavelength.
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| 9. |
- Lui, Hoi-Shun, 1980, et al.
(författare)
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Mutual Coupling Compensation for Direction-of-Arrival Estimations Using the Receiving-Mutual-Impedance Method
- 2010
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Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2010
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Tidskriftsartikel (refereegranskat)abstract
- A short review of the receiving-mutual-impedance method (RMIM) for mutual coupling compensation in direction finding applications using linear array is conducted. The differences between the conventional-mutual-impedance method (CMIM) and RMIM, as well as the three different determination methods for receiving mutual impedance (RMI), will be discussed in details. As an example, direction finding with better accuracies is used for demonstrating the superiority of mutual coupling compensation using RMIM.
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| 10. |
- Lui, Hoi-Shun, 1980, et al.
(författare)
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Mutual Coupling in Antenna Arrays 2011
- 2012
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Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2012, s. Art. no. 715138-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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