| 1. |
- Aliakbari Abar, Hanieh, et al.
(författare)
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Characteristic mode analysis of planar dipole antennas
- 2019
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Ingår i: 2019 13th European Conference on Antennas and Propagation (EuCAP). - 9788890701887 - 9781538681275
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Konferensbidrag (refereegranskat)abstract
- Planar monopole antennas are popular due to their attractive properties, but their operating mechanisms are still not well understood. Based on image theory, planar monopoles can be analyzed using their dipole counterparts. Here, the bandwidth and radiation pattern of planar dipoles is studied in detail using characteristic mode analysis for different design parameters. The results show that insignificant modes can help to improve the bandwidth without contributing to the radiation property. Moreover, a tradeoff is observed between pattern stability and impedance bandwidth as the dipole width varies. Furthermore, it is found that an offset in the feed point leads to a degradation in both the modal and impedance bandwidths.
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| 2. |
- Aliakbari Abar, Hanieh, et al.
(författare)
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Impact of capacitive coupling element design on antenna bandwidth
- 2018
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Ingår i: European Conference on Antennas and Propagation (EuCAP), 2018.. ; :CP741
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Konferensbidrag (refereegranskat)abstract
- A coupling element is typically used to excite one of more characteristic modes of a structure to form some desired radiation properties. In particular, non-resonant coupling elements (CEs) are attractive, since it is electrically small and can be more conveniently integrated into the structure, such as the chassis of a mobile terminal. In this case, the chassis is the primary radiator of the mobile terminal. However, there is still limited knowledge on how to design andoptimize coupling elements. In this paper, we examine how the dimensions of a single capacitive coupling element (CCE) influence the potential bandwidth of exciting the fundamental dipole mode of a rectangular terminal chassis. The parametric study shows that the CCE must not be too small electrically, for the sake of bandwidth. However, the bandwidth saturates when the size of the CCE is increased beyond a certain threshold. Therefore, this study provides some useful insights and guidelines for CCE design.
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| 3. |
- Aliakbari Abar, Hanieh, et al.
(författare)
-
On modal excitation using capacitive coupling elements and matching network
- 2019
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Ingår i: 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting. - 9781728106922
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Konferensbidrag (refereegranskat)abstract
- A resonant characteristic mode (CM) is useful for antenna design if it is properly excited and well matched to the source. In this paper, we consider the feed design for the excitation of the fundamental CM of a rectangular chassis. The tradeoff between the required number of capacitive coupling elements (CCE) and matching elements used for achieving a given antenna bandwidth is studied. The results reveal that in order to attain the modal bandwidth of the fundamental mode, the use of multiple CCEs with optimal placement and phase simplifies the required matching network.
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| 4. |
- Aliakbari Abar, Hanieh, et al.
(författare)
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Wideband SIW-based Low-cost Multi-layer Slot Antenna Array for E-Band Applications
- 2019
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Ingår i: IEEE Transactions on Components, Packaging and Manufacturing Technology. - 2156-3950. ; , s. 1-1
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a substrate integrated waveguide (SIW) slot antenna array for wideband gigabyte mobile radio application in E-band. The wideband unit cell design is based on simultaneous feeding of 4-element radiation slots with a higher order cavity mode directly excited by a simple slot aperture fed by a microstrip fork-like tuning stub. Employing the higher order mode along with the slot aperture facilitate low loss, simple feeding network and lower sensitivity to fabrication errors. To cancel the beam tilt versus frequency, the higher order mode unit cell is used in a 2 × 2 array along with a differential feeding structure. The array was designed and taped out using a new high-resolution multi-layer PCB technology and characterized by using the constructed millimeter wave measurement setup at KU Leuven /IMEC. This technology provides the possibility to stack micro-vias in PCB boards and reduce fabrication cost compared to other multi-layer technologies in mm-wave bands. The proposed array in 2 × 2 array configuration has a measured bandwidth of 11.4 GHz (16%), a total efficiency of 69%, a realized gain of 12 dBi at 72 GHz and a 3-dB gain bandwidth that covers the entire impedance bandwidth. In comparison to existing E-band SIW slot arrays (compensating for array sizes), the proposed design achieves similar or better performance in bandwidth but with lower cost, lower sensitivity to fabrication tolerances and higher total efficiency.
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| 5. |
- Chen, Yikai, et al.
(författare)
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Benchmark problem definition and cross-validation for characteristic mode solvers
- 2018
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Ingår i: European Conference on Antennas and Propagation (EuCAP), 2018.. - : Institution of Engineering and Technology. - 9781785618161
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Konferensbidrag (refereegranskat)abstract
- In October 2016, the Special Interest Group on Theory of Characteristic Modes (TCM) initiated a coordinated effort to perform benchmarking work for characteristic mode (CM) analysis. The primary purpose is to help improve the reliability and capability of existing CM solvers and to provide the means for validating future tools. Significant progress has already been made in this joint activity. In particular, this paper describes several benchmark problems that were defined and analyzes some results from the cross-validations of different CM solvers using these problems. The results show that despite differences in the implementation details, good agreement is observed in the calculated eigenvalues and eigencurrents across the solvers. Finally, it is concluded that future work should focus on understanding the impact of common parameters and output settings to further reduce variability in the results.
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| 6. |
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| 7. |
- Lau, Buon Kiong, et al.
(författare)
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Innovations in antenna systems for communications
- 2016
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Ingår i: Cooperative Radio Communications for Green Smart Environments. - 9788793379145 - 9788793379152 ; , s. 383-422
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Lau, Buon Kiong
(författare)
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Systematic design of MIMO terminal antennas using Theory of Characteristic Modes
- 2015
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Ingår i: European Microwave Conference (EuMC), 2015. - 9782874870392 ; , s. 17-19
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Konferensbidrag (refereegranskat)abstract
- The Theory of Characteristic Modes (TCM) offers a natural and systematic way to design Multiple-Input Multiple-Output (MIMO) antennas with high total efficiency and uncorrelated antenna patterns. In this paper, recent advances in the growing field of TCM-aided MIMO antenna design are reviewed. In particular, the focus is on the challenging problem of designing MIMO antennas for compact mobile terminals below 1 GHz. It was found that low correlation can be achieved by allowing only one antenna to excite the single-mode terminal chassis. However, this led to small bandwidths for other antennas. To improve the bandwidth performance, the chassis could be slightly modified to support multiple excitable modes, which can give larger bandwidths for the multi-antennas designed to couple into these modes.
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| 9. |
- Li, Hui, et al.
(författare)
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Analysis and estimation of MIMO-SAR for multi-antenna mobile handsets
- 2017
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; , s. 1522-1527
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Tidskriftsartikel (refereegranskat)abstract
- Measuring MIMO-SAR is an important part of mobile handset evaluation, following the introduction of uplink MIMO transmission schemes in LTE-Advanced. However, the measurement of MIMO-SAR is complex and time-consuming. In this paper, 6 unique dual-antenna mobile handsets, including both typical and novel designs, are analyzed to determine the dependence of MIMO-SAR on antenna configuration and correlation. It is found that, for certain antenna configurations, the location of the maximum MIMO-SAR and the corresponding relative phase between the ports can be predicted. This can be applied to drastically reduce measurement time. In addition, dual-antennas with low envelope correlation coefficients in the radiation patterns also offer near-orthogonal electric near-fields. This leads to smaller MIMO-SAR than stand-alone SAR (S-SAR) over all relative phases, making MIMO-SAR measurement unnecessary. The results also provide guidelines for designing multi-antenna handsets with low SARs. For verification, the S- SAR and MIMO-SAR at relative phase of 0° were measured for several handsets. The measured SAR distributions showed good agreement with the simulated ones.
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| 10. |
- Li, Hui, et al.
(författare)
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Characteristic mode based pattern reconfigurable antenna for mobile handset
- 2015
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Ingår i: European Conference on Antennas and Propagation (EuCAP), 2015. - 9788890701856
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Konferensbidrag (refereegranskat)abstract
- Pattern reconfigurability is a desirable feature of mobile handset antennas, as it enables the antennas to adapt to non-stationary propagation environments. However, it is difficult to vary the radiation pattern of a handset antenna at frequencies below 1 GHz because the entire chassis commonly acts as the main radiator. Hence, designing pattern reconfigurability based on the antenna element (secondary radiator) alone can severely limit the achievable pattern diversity. In this work, a dual-band (0.85-0.90 GHz and 1.93-2.11 GHz) handset antenna with pattern reconfigurability at the low band is designed by loading the periphery of the chassis with a metal bezel. The bezel loading adds a new resonant characteristic mode to the chassis, on top of the fundamental resonant mode. These two modes are selectively excited for pattern reconfigurability using a suitable feed and two PIN diodes, which yield an envelope correlation of below 0.2 in the low band (0.07 at 0.87 GHz). Moreover, since the proposed antenna is fully integrated into the bezel structure, it does not occupy any extra space on the chassis, which also allows more antennas to be implemented, e.g., for MIMO applications.
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