| 1. |
- Azremi, Abdullah Al-Hadi, et al.
(author)
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Design and Measurement-Based Evaluation of Multi-Antenna Mobile Terminals for LTE 3500 MHz Band
- 2013
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In: Progress in Electromagnetics Research B. - 1937-6472. ; 53:53, s. 241-266
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Journal article (peer-reviewed)abstract
- 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.
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| 2. |
- Azremi, A.A.H., et al.
(author)
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On diversity performance of two-element coupling element based antenna structure for mobile terminal
- 2010
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In: EuCAP 2010 Fourth European Conference on Antennas and Propagation, Barcelona, 12-16 April 2010.
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Conference paper (peer-reviewed)abstract
- In wireless communication systems, multipath interference has a significant impact on system design and performance. Fast fading is caused by the coherent summation of one or more echoes from many reflection points reaching the receive antenna. Antenna diversity can be used to mitigate multipath fading. The main challenge of antenna diversity in practical application is the integration of multiple antennas on a small ground plane. Two-element antenna structure based on coupling element antenna concept for diversity application has been studied in previous work and it has shown to be feasible for low frequency diversity application with stable and low envelope correlation across wide frequency range. The studied structure has been tuned to be operating at 1600 MHz for measurement evaluation purpose. This paper presents an analysis of diversity performance of the structure in terms of efficiencies, envelope correlation, and apparent and effective diversity gains in isotropic (i.e. statistically uniform) propagation channel, using spherical near-field technique in an ideal line-of-sight environment (anechoic chamber) and inside reverberation chamber. The envelope correlation is less than 0.1 and the diversity gain is equal to 10.2 dB at 99% reliability level using selection combining technique across simulation and both measurement methods. The measurement techniques are compared to show how accurately the diversity performance of a mobile terminal antenna can be estimated.
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| 3. |
- Gomez-Calero, C., et al.
(author)
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Comparison of different MIMO antenna arrays and user's effect on their performances
- 2013
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In: Microwave and Optical Technology Letters. - : Wiley. - 1098-2760 .- 0895-2477. ; 55:9, s. 2039-2043
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Journal article (peer-reviewed)abstract
- Multiple-input multiple-output (MIMO) systems have entailed a great enhancement in wireless communications performances. The use of multiple antennas at each side of the radio link has been included in recent drafts and standards such as WLAN, WIMAX, or DVB-T2. The MIMO performances depend on the antenna array characteristics and thus several aspects have to be taken into account to design MIMO antennas. In the literature, many articles can be found in terms of capacity or antenna design, but in this article, different types of antenna arrays for MIMO systems are measured in a reverberation chamber with and without a phantom as a users head. As a result, the MIMO performances are degraded by the user in terms of efficiency, diversity gain, and capacity. Omnidirectional antennas such as monopoles with high radiation efficiency offer the highest performance for a rich scattering nonline of sight indoor environment.
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| 4. |
- Gómez Calero, Carlos, 1981, et al.
(author)
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Effect of Mutual Coupling and Human Body on MIMO Performances
- 2009
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In: 2009 Proceedings of the Third European Conference on Antenna and Propagation, EuCAP. - 9783000245732 ; , s. 1042-1046
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Conference paper (peer-reviewed)abstract
- In the last recent years, MIMO (Multiple Input and Multiple Output) system have been studied and developed by many researchers. These systems allow an increase in the binary data rate and the improvement of the quality of received signals, due to spatial multiplexing and space-time diversity. The performances of MIMO systems depend on the antenna design. In this paper, we focused on the importance of mutual coupling and human effect on the MIMO performances. Three different types of antennas have been designed: monopoles, cross-polarized dipoles and a Planar Inverted-F Antennas (PIFAs). The antennas work at 2.45 GHz for WLAN applications and also PIFAs work at GSM 1800 and 5.4 GHz for the other WLAN band. The results show the importance of spacing among radiating elements due to the mutual coupling and measurements in a reverberation chamber comparing the effect of the user's head.
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| 5. |
- Jamaly, Nima, 1979, et al.
(author)
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A Revisit to Spatial Correlation in Terms of Input Network Parameters
- 2012
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In: IEEE Antennas and Wireless Propagation Letters. - 1548-5757 .- 1536-1225. ; 11, s. 1342-1345
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Journal article (peer-reviewed)abstract
- An alternative compact formula in terms of input network parameters for calculation of envelope correlations is provided. The main advantage of this formula is that it can be simply modified to include cases of lossy structures and general cases of correlated nonuniform multipath environments. This formula is based on the open-circuit covariance matrix of the multiport antennas. The latter can be either estimated or quickly measured in a reverberation chamber, which removes the need for costly measurements of the embedded far field patterns.
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| 6. |
- Jamaly, Nima, 1979, et al.
(author)
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Analysis and Measurement of Multiple Antenna Systems for Fading Channel Prediction in Moving Relays
- 2014
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In: 2014 8TH EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION (EUCAP). - 2164-3342. - 9788890701849 ; , s. 2015-2019
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Conference paper (other academic/artistic)abstract
- The performance of wireless data transmission to mobile vehicles is improved if channel state information is available at the transmitter but movement of vehicles causes outdating of channel estimates. The concept of a predictor antenna has recently been proposed, where an antenna is placed in front of other antennas on the roof of the vehicle to sense the radio environment in advance. This can comparatively provide an order-of-magnitude improvement in channel prediction performance. A potential problem with this idea is that closely placed antennas will experience mutual electromagnetic couplings. These may reduce the efficiency of the predictor antenna concept if they are not taken into account. In this paper, we discuss about how to treat the forgoing issue and eventually evaluate a promising candidate on measured channels. We argue that only open-circuit voltage method would be realistic for the present application. The usefulness of the proposed decoupling method is demonstrated on field measurements obtained in downtown Dresden, Germany. We also partly address the sensitivity of the open-circuit decoupling method to the accuracy of the utilized network parameters.
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| 7. |
- Jamaly, Nima, 1979, et al.
(author)
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Analysis of Antenna Pattern Overlap Matrix in Correlated Nonuniform Multipath Environments
- 2013
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In: Proceedings of the 7th European Conference on Antennas and Propagation. - 2164-3342. - 9788890701832 ; , s. 2113-2117
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Conference paper (peer-reviewed)abstract
- In this paper the covariance matrix of received voltage signals across ports of a multiport antenna in correlated multipath environments is formulated. This eventually leads to some expressions for mean effective gain and directivity in these environments, which to our best knowledge has not been addressed before. The notion of pattern overlap matrix is utilized to coin correlated pattern overlap matrix. We show the crucial role of the latter parameter in general correlated multipath environments.
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| 8. |
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| 9. |
- Jamaly, Nima, 1979, et al.
(author)
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Compact Formulas for Diversity Gain of Two-Port Antennas
- 2010
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In: IEEE Antennas and Wireless Propagation Letters. - 1548-5757 .- 1536-1225. ; 9, s. 970-973
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Journal article (other academic/artistic)abstract
- Accuracy limitation in evaluation of diversity gains based on cumulative distribution function curves is highlighted. New devised closed-form formulas are provided for Selection Combining and Maximum Ratio Combining diversity schemes rendering diversity gain as a function of correlation and radiation efficiencies. Accuracy of these formulas is studied and verified by numerical simulations. These formulas take a central role for the cases when engineers are limited to a finite number of measured voltage samples at different ports to provide them with accurate calculation of ergodic diversity gain. This letter also reveals dependency of different diversity gains upon total embedded efficiencies of branches and underscores the significance of identical efficiencies of two-element terminals for their optimum performance in multipath environments. © 2010 IEEE.
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| 10. |
- Jamaly, Nima, 1979, et al.
(author)
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Coupling effects on richness threshold of multi-port antennas in multipath environments
- 2012
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In: 15th International Symposium on Antenna Technology and Applied Electromagnetics, ANTEM 2012, Toulouse, 25-28 June 2012. - 9781467302906
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Conference paper (peer-reviewed)abstract
- This paper investigates convergence in diversity gain of multi-port antennas in non-rich multipath environments. It is shown that diversity gain convergence is faster in the presence of strong coupling. In this situation, richness threshold is also smaller. Furthermore, by linking convergence in diversity gain to convergence in antenna ports' correlations, the role of pattern diversity caused by coupling is highlighted. A range of variation for correlations is defined whose upper bound is used to quantify pattern diversity. The lower bound for this range is the corresponding spatial correlation in a rich multipath environment.
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