| 1. |
- Cismasu, Marius, et al.
(författare)
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Optimal Charges and Currents on Small Wire Antennas
- 2012
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Ingår i: IEEE Antennas and Propagation Society International Symposium (APSURSI), 2012. - 1522-3965 .- 1947-1491. - 9781467304610 ; , s. 1-2
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Konferensbidrag (refereegranskat)abstract
- The optimum surface charge on a thin wire antenna is computed using a variational formulation in the low-frequency limit. This charge and its corresponding current are compared with simulation results for self resonant structures. The comparison shows that the currents and charges on self resonant structures resemble those in the static limit to a great extent.
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| 2. |
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| 3. |
- Harrysson, Fredrik, et al.
(författare)
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Evaluation of user hand and body impact on multiple antenna handset
- 2010
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Ingår i: [Host publication title missing]. - 1522-3965 .- 1947-1491. - 9781424449675
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Konferensbidrag (refereegranskat)abstract
- From our experimental investigation of multiple-antenna performance and user impact of a realistic mobile terminal setup, we find that apart from the important loss of efficiency due to the user hand, the impact on the individual antennna elements and the directional impact of the user body shadowing have quite small influence on the diversity and capacity performance. It is found that the top and bottom placement of antennas within the handset case are the most efficient to be used with up to two antenna elements. There are, however, significant diversity and capacity gain that can be explored by using four distributed antennas even if only two radio chains are available through hybrid selection and combining schemes. It was also found that the practical method of choosing antennas based on signal power for 2 branch MIMO with 4 available handset antennas, performs well compared to the optimal solution.
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| 4. |
- Li, Hui, et al.
(författare)
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Generating multiple characteristic modes below 1 GHz in small terminals for MIMO antenna design
- 2013
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Ingår i: IEEE International Symposium on Antennas and Propagation, 2013. - 1947-1491 .- 1522-3965. - 9781467353175 ; , s. 180-181
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Konferensbidrag (refereegranskat)abstract
- Designing multiple antennas in small terminals at frequency bands below 1 GHz is challenging due to severe mutual coupling among antenna elements. The severe coupling is often the result of simultaneous excitation of the fundamental characteristic mode of the terminal chassis by more than one antenna element. In this work, we propose to solve the coupling problem by manipulating the chassis structure to allow more than one characteristic mode to resonate at frequencies below 1 GHz. To demonstrate our design concept and its practicality, we show the opportunistic use of the metallic bezel popular in smartphone design for obtaining two characteristic modes that can be efficiently excited by antenna elements at 0.81 GHz. Due to the inherent orthogonality of the modes, proper excitation of these modes by two antenna elements will result in orthogonal radiation patterns and high isolation between the antenna ports. Therefore, the proposed approach enables the effective use of the chassis to achieve MIMO antennas with good performance.
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| 5. |
- McPhedran, Ross, et al.
(författare)
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Resonances and Fields near Metamaterial Inclusions
- 2012
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Ingår i: Antennas and Propagation Society International Symposium (APSURSI), 2012 IEEE. - 1522-3965 .- 1947-1491. - 9781467304627
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Konferensbidrag (refereegranskat)abstract
- We consider systems of particles in two dimensions with negative dielectric permittivity and sharp corners. The field divergences near the corners of the inclusions are non-square-integrable for negative permittivities in a range depending on the corner angle, and the leading term for small distances is provided by the static term. We have developed a highly accurate numerical method which uses adaptive techniques to resolve field behaviour near the corners. We use this to elucidate the resonant spectrum associated with the effective permittivity of arrays of such particles, and in particular its behaviour as the particles approach touching.
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| 6. |
- Miers, Zachary, et al.
(författare)
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Design of multi-antenna feeding for MIMO terminals based on characteristic modes
- 2013
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Ingår i: IEEE International Symposium on Antennas and Propagation, 2013. - 1522-3965 .- 1947-1491. - 9781467353175 ; , s. 182-183
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Konferensbidrag (refereegranskat)abstract
- Conventional antennas in single-antenna terminals that resonate at frequencies lower than 1 GHz usually rely on the chassis as the main radiator. To effectively exploit chassis excitation for MIMO terminals, each of the multiple antennas is required to excite one distinct chassis mode. However, in today's terminals, there is typically only one chassis mode that can radiate efficiently at frequencies below 1 GHz. Fortunately, it has been shown that minor modifications in the chassis structure can cause more than one mode to resonate at these frequencies. Nevertheless, proper antenna feeding methods are needed to practically tap into these modes. In this paper, we propose a general technique to feed orthogonal chassis modes of a given conducting structure using the theory of characteristic modes. By separating a radiating structure into individual modal currents, the near field radiating properties are exploited for capacitive or inductive feeding without significant coupling to other orthogonal modes of radiation. As a proof of concept, we apply the technique to feed a modified terminal chassis that has two significant characteristic modes at 0.89 GHz.
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| 7. |
- Miers, Zachary, et al.
(författare)
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Design of multimode multiband antennas for MIMO terminals using characteristic mode analysis
- 2014
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Ingår i: IEEE International Symposium on Antennas and Propagation, 2014. - 1947-1491 .- 1522-3965. - 9781479935383 ; , s. 1429-1430
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Konferensbidrag (refereegranskat)abstract
- Characteristic mode analysis provides unparalleled insights into designing high performance multiple-input multiple-output (MIMO) terminal antennas at frequencies where the antenna elements are constrained to be electrically small. Conventionally, an electrically small single-antenna utilizes the fundamental characteristic mode of the terminal chassis to obtain sufficient bandwidth while maintaining high radiation efficiency. However, modern MIMO terminals require two or more antennas per frequency band, and they tend to excite the same fundamental chassis mode, resulting in severe coupling and correlation, and poor overall system performance. Recently, characteristic mode analysis of the chassis is proposed to design highly efficient multimode multiband MIMO antennas with significant bandwidth using electrically small feed elements. Two distinct and excitable characteristic modes were created at frequencies above and below 1 GHz, for a typical smartphone’s form factor. This paper provides an overview of the method and highlights its versatility for practical implementation in standard plastic cased smartphones as well as in the popular metal-bezeled smartphones, with only minor modifications to the chassis.
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| 8. |
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| 9. |
- Vasilev, Ivaylo, et al.
(författare)
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On user effect compensation of MIMO terminals with adaptive impedance matching
- 2013
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Ingår i: IEEE International Symposium on Antennas and Propagation, 2013. - 1947-1491 .- 1522-3965. ; , s. 174-175
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Konferensbidrag (refereegranskat)abstract
- Proximity of user has been established as a major cause of performance degradation in multiple-input multiple-output (MIMO) terminals. Here, we investigate the potential of adaptive impedance matching (AIM) to improve the performance of two MIMO terminals in a free space (FS) and a two-hand (TH) user scenario, assuming uniform 3D angular power spectrum for the incoming signal. The results show that lossless uncoupled AIM circuits can enhance the MIMO capacity of the terminals by up to 43% relative to standard 50 ohm terminations. In particular, the largest capacity gain is obtained in the terminal with good matching but narrower antenna bandwidth and worse isolation performance, for the TH scenario. On the other hand, the terminal with poorer matching but higher isolation and significantly larger bandwidth has lower average capacity in FS. However, it is more robust to user proximity, and hence it achieves only 8% capacity gain with AIM in the TH scenario. Therefore, antenna design parameters can significantly influence potential benefits of AIM in practice.
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| 10. |
- Ying, Zhinong, et al.
(författare)
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Diversity antenna terminal evaluation
- 2005
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Ingår i: IEEE Antennas and Propagation Society, AP-S International Symposium (Digest). - 1947-1491 .- 1522-3965. - 0780388836 ; 2 A, s. 375-378
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Konferensbidrag (refereegranskat)abstract
- Simulated and measured correlation and diversity performance for a couple of two-antenna concepts are presented. The results indicate that the three-dimensional isotropic incident field is a good reference case to evaluate diversity performance in a multi-antenna application.
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