| 1. |
- Mowlér, Marc, et al.
(författare)
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Capacity and Gain Analysis of a Reconfigurable MEMS Antenna
- 2008
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Ingår i: Nordic Conference on Radio Science and Communications (RVK).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents the investigation results on therecon¯gurable properties of an antenna array compris-ing of four feed elements and four parasitic elementsplaced on a ¯nite ground plane. This antenna is in-tended to improve the diversity gain for a Multiple In-put Multiple Output (MIMO) communication system.We intend to use a recon¯gurable antenna to com-bat the problem of signal deterioration in a handhelddevice so that it can get optimum signal strength inany orientation. With our presented antenna, we canachieve up to sixteen di®erent con¯gurations depend-ing on the requirement. The di®erent con¯gurationsare controlled with the help of RF switches which areimplemented using micro-electromechanical systems(MEMS). The recon¯gurable antenna was fabricatedand tested for its impedance and radiation character-istics and the results were found to be in reasonable agreement with the simulations. Channel measure-ments were made with the help of a MIMO test setup.
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| 2. |
- Mowlér, Marc, et al.
(författare)
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Joint estimation of mutual coupling, element factor, and phase center in antenna arrays
- 2007
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Ingår i: EURASIP Journal on Wireless Communications and Networking. - : Springer Science and Business Media LLC. - 1687-1472 .- 1687-1499. ; 2007:1, s. 030684-
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Tidskriftsartikel (refereegranskat)abstract
- A novel method is proposed for estimation of the mutual coupling matrix of an antenna array. The method extends previous work by incorporating an unknown phase center and the element factor (antenna radiation pattern) in the model, and treating them as nuisance parameters during the estimation of coupling. To facilitate this, a parametrization of the element factor based on a truncated Fourier series is proposed. The performance of the proposed estimator is illustrated and compared to other methods using data from simulations and measurements, respectively. The Cramer-Rao bound (CRB) for the estimation problem is derived and used to analyze how the required amount of measurement data increases when introducing additional degrees of freedom in the element factor model. We find that the penalty in SNR is 2.5 dB when introducing a model with two degrees of freedom relative to having zero degrees of freedom. Finally, the tradeoff between the number of degrees of freedom and the accuracy of the estimate is studied. A linear array is treated in more detail and the analysis provides a specific design tradeoff.
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| 3. |
- Mowlér, Marc, et al.
(författare)
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Methods and bounds for antenna array coupling matrix estimation
- 2007
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Ingår i: 2007 IEEE International Conference on Acoustics, Speech, and Signal Processing. - : IEEE. - 1424407273 - 1424407281 ; , s. 881-884
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Konferensbidrag (refereegranskat)abstract
- A novel method is proposed for estimation of the mutual coupling matrix of an antenna array. The method extends previous work by incorporating an unknown phase center and the element factor (antenna radiation pattern) in the model, and treating these as nuisance parameters during the estimation of coupling. To facilitate this, a parametrization of the element factor based on a truncated Fourier series is proposed. The Cramer-Rao bound (CRB) for the estimation problem is derived and used to analyze how the required amount of measurement data increases when introducing a more and more flexible model for the element factor. Finally, the performance of the proposed estimator is illustrated using data from measurements on an 8-element antenna array.
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| 4. |
- Mowlér, Marc, et al.
(författare)
-
Switched MEMS Antenna for Handheld Devices
- 2008
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Ingår i: ICT-MobileSummit 2008.
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Konferensbidrag (refereegranskat)abstract
- This paper presents the investigation results on the reconfigurableproperties of a monopole antenna array. The antenna array comprises of four feedelements and four parasitic elements on a finite ground plane. This antenna isintended to improve the diversity gain for a Multiple Input Multiple Output (MIMO)communication system. We intend to combat the problem of signal deterioration inhandheld devices by the use of reconfigurable antenna. A common communicationproblem seen in the handheld devices is the change in strength of radio signal whenthe orientation of the device is changed. Reconfigurable antennas can be used get ridof this nuisance so that what ever be the orientation, the handheld device still gets thebest possible signal level. With our presented antenna, we can achieve up to sixteendifferent configurations depending upon the requirement. The differentconfigurations are controlled with the help of RF switches which are implementedusing micro-electromechanical systems (MEMS). The reconfigurable antenna wasfabricated and tested for its impedance and radiation characteristics and the resultswere found to be in reasonable agreement with the simulations.
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| 5. |
- Nilsson, Martin, et al.
(författare)
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A Cluster Approach to Spatio-Temporal Channel Estimation
- 2000
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Ingår i: <em>IEEE International Conference on Acoustics, Speech, and Signal Processing</em>. - : IEEE. ; , s. 2757-2760
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Konferensbidrag (refereegranskat)abstract
- In a severe multipath environment the antenna receives multiple copies of the same transmitted signal. To solve for all waves is difficult if possible at all. In this paper we use the approach of grouping the spatio-temporalreflections into clusters. We study how the aperture and bandwidth affects the cluster resolution using experimental data. The measurements were obtained by transmitting linear FM (chirp) signals of 150 MHz bandwidth, in the 1800 MHz band. An antenna array of 16 elements was used as a receiver.
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| 6. |
- Viberg, Mats, 1961, et al.
(författare)
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Maximum Likelihood Array Processing in Spatially Correlated Noise Fields Using Parameterized Signals
- 1997
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Ingår i: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1941-0476 .- 1053-587X. ; 45, s. 996-1004
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with the problem of estimating signal parameters using an array of sensors. This problem is of interest in a variety of applications, such as radar and sonar source localization. A vast number of estimation techniques have been proposed in the literature during the past two decades. Most of these can deliver consistent estimates only if the covariance matrix of the background noise is known. In many applications, the aforementioned assumption is unrealistic. Recently, a number of contributions have addressed the problem of signal parameter estimation in unknown noise environments based on various assumptions on the noise. Herein, a different approach is taken. We assume instead that the signals are partially known. The received signals are modeled as linear combinations of certain known basis functions. The exact maximum likelihood (ML) estimator for the problem at hand is derived, as well as a computationally more attractive approximation. The Cramer Rao lower bound (CRB) on the estimation error variance is also derived and found to coincide with the CRB, assuming an arbitrary deterministic model and known noise covariance.
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| 7. |
- Völcker, Björn, et al.
(författare)
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Chirp Parameter Estimation Using Rank Reduction
- 1998
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Ingår i: Proceedings of the 32nd Asilomar Conference on Signals, Systems and Computers. - : IEEE. ; , s. 1443-1446
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Konferensbidrag (refereegranskat)abstract
- This paper considers the problem of estimating the bandwidth and the center frequency of a linear chirp signal from discrete-time noisy observations. The non-stationarity property of chirp signals implies that the signal has high rank and reduces the applicability of subspace based algorithms significantly. However, the special structure of the sample covariance matrix invites to use regular frequency estimation algorithms. We show how subspace type algorithms may be modified to provide accurate signal parameter estimates for linear chirp signals. The root-MUSIC algorithm is used as an example. Simulations compare the algorithm with a rank reduction method proposed by DiMonte and Arun (1990).
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| 8. |
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| 9. |
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| 10. |
- Abdu, Tedros Salih, et al.
(författare)
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Demand and Interference Aware Adaptive Resource Management for High Throughput GEO Satellite Systems
- 2022
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Ingår i: IEEE Open Journal of the Communications Society. - : Institute of Electrical and Electronics Engineers (IEEE). - 2644-125X. ; 3, s. 759-775
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Tidskriftsartikel (refereegranskat)abstract
- The scarce spectrum and power resources, the inter-beam interference, together with the high traffic demand, pose new major challenges for the next generation of Very High Throughput Satellite (VHTS) systems. Accordingly, future satellites are expected to employ advanced resource/interference management techniques to achieve high system spectrum efficiency and low power consumption while ensuring user demand satisfaction. This paper proposes a novel demand and interference aware adaptive resource management for geostationary (GEO) VHTS systems. For this, we formulate a multi-objective optimization problem to minimize the total transmit power consumption and system bandwidth usage while matching the offered capacity with the demand per beam. In this context, we consider resource management for a system with full-precoding, i.e., all beams are precoded; without precoding, i.e., no precoding is applied to any beam; and with partial precoding, i.e., only some beams are precoded. The nature of the problem is non-convex and we solve it by jointly using the Dinkelbach and Successive Convex Approximation (SCA) methods. The simulation results show that the proposed method outperforms the benchmark schemes. Specifically, we show that the proposed method requires low resource consumption, low computational time, and simultaneously achieves a high demand satisfaction.
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