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- Plicanic, Vanja, et al.
(författare)
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Capacity maximisation of a handheld MIMO terminal with adaptive matching in an indoor environment
- 2011
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 47:16, s. 900-901
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Tidskriftsartikel (refereegranskat)abstract
- This letter reports the capacity performance of a handheld dual-band dual-antenna compact MIMO terminal, which utilizes uncoupled adaptive impedance matching for capacity maximisation. The capacity is evaluated at 0.825 GHz and 2.35 GHz in an indoor office environment. The results show that adaptive matching enhances capacity by up to 44% and 22% at the low and high frequency bands, respectively, relative to no matching. At the low band, the capacity gain is attributed to both increased received power and decreased channel eigenvalue dispersion, whereas at the high band, the capacity gain is only due to increased power.
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- Vasilev, Ivaylo, et al.
(författare)
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Adaptive impedance matching performance of MIMO terminals with different bandwidth and isolation properties in realistic user scenarios
- 2013
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Ingår i: European Conference on Antennas and Propagation (EuCAP), 2013. - 2164-3342. - 9788890701832 - 9781467321877 ; , s. 2590-2594
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Konferensbidrag (refereegranskat)abstract
- Using the metric of channel capacity, three dual-antenna multiple-input multiple-output (MIMO) terminals with adaptive impedance matching were evaluated at LTE Band 13 in four different user scenarios using simulation. Each of the three terminals is equipped with a slot-monopole antenna and a planar inverted-F antenna (PIFA). The slot monopole is fixed at one edge of the chassis, whereas the location of the PIFA differs among the terminals to provide different bandwidth and isolation characteristics in free space (FS). The results show that adaptive matching leads to an average capacity gain of up to 24% at the center frequency, favoring the terminal with the smallest antenna bandwidth and the largest isolation. However, the maximum capacity gain from adaptive matching decreases to 15.7% when averaged over the entire system bandwidth. Moreover, the terminal with moderate antenna bandwidth and isolation offers the best overall absolute capacity performance under different user scenarios, indicating a design tradeoff. These results highlight important design considerations for MIMO terminals with adaptive impedance matching.
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| 7. |
- Vasilev, Ivaylo, et al.
(författare)
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Experimental investigation of adaptive impedance matching for a MIMO terminal with CMOS SOI tuners
- 2016
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480. ; 64:5, s. 1622-1633
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that user proximity introduces absorption and impedance mismatch losses that severely degrade multiple-input multiple-output (MIMO) performance of handset antennas. In this work, we experimentally verified the potential of adaptive impedance matching (AIM) to mitigate user interaction effects and identified the main AIM gain mechanism in realistic systems. A practical setup including custom-designed CMOS silicon-on-insulator (SOI) impedance tuners implemented on a MIMO handset was measured in three propagation environments and 10 real user scenarios. The results indicate that AIM can improve MIMO capacity by up to 42% equivalent to 3.5 dB of multiplexing efficiency (ME) gain. Taking into account the measured losses of 1 dB in the integrated tuners, the maximum net ME gain is 2.5 dB suggesting applicability in practical systems. Variations in ME gains of up to 1.5 dB for different hand-grip styles were mainly due to differences in impedance mismatch and tuner loss distribution. The study also confirmed earlier results on the significant differences in mismatch and absorption between phantoms and real users, in which the phantoms underestimated user effects and therefore AIM gains. Finally, propagation environments of different angular spreads were found to give only minor ME gain variations.
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| 10. |
- Vasilev, Ivaylo, et al.
(författare)
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Impact of antenna design on MIMO performance for compact terminals with adaptive impedance matching
- 2016
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 64:4, s. 1454-1465
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Tidskriftsartikel (refereegranskat)abstract
- Using the metrics of channel capacity and multiplexing efficiency, the adaptive impedance matching (AIM) performances of two multiple-input multiple-output (MIMO) terminals with different antenna designs were evaluated and compared. The evaluation was performed in LTE Band 18 Downlink (860-875 MHz) under realistic usage conditions of two measured user handgrips and simulated propagation channels with different angular spreads (ASs). The results provide potential performance gains from AIM based on realistic MIMO terminal prototypes, and the underlying mechanisms by which the gains were achieved, which can serve as antenna and AIM circuit design guidelines. In particular, the evaluation revealed that ideal uncoupled AIM networks can increase the capacity by up to 52% relative to 50 ohm terminations. However, the observed gains depend heavily on the antenna design, the user scenario and the channel’s angular spread. For example, the wideband design in different user cases experienced capacity gain of 4-9% from AIM in uniform 3D channels, in contrast to the 1.3-44% gain seen in a conventional narrowband design. In non-uniform channels with small ASs, the AIM gain for different mean incident angles depends on the absolute mean effective gain (MEG) and the change in correlation due to AIM; In cases where AIM has little impact on correlation, the mean incident angles with high AIM gains were close to those with high MEGs.
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