| 1. |
- Klionsky, Daniel J., et al.
(författare)
-
Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 2. |
- Avendal, Johan, et al.
(författare)
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Diversity performance of multiband antennas for compact mobile terminals
- 2007
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Spatial diversity is a popular multiple antenna system technique, due to simplicity in implementation. However, its application has thus far been limited to systems where the electrical separation between adjacent antennas typically exceeds half a wavelength. This is because a more compact design induces higher antenna correlation and impedance mismatch, which results in lower diversity gains. In this paper, the performance of a compact multiband diversity antenna is investigated in both simulations and measurements. The dual-antenna structure is designed for the future WCDMA bands of WCDMA850, WCDMA1800 and 3G EU (UMTS), where the antenna separation at the WCDMA850 band is 0.24*wavelength. The measured results indicate that an average effective diversity gain of 7.3 dB at the 1% probability level can be achieved for the three bands.
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| 3. |
- Avendal, Johan, et al.
(författare)
-
Multiband diversity antenna performance study for mobile phones
- 2007
-
Ingår i: International Workshop on Antenna Technology (iWAT), 2007. - 1424410886 ; , s. 193-196
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Konferensbidrag (refereegranskat)abstract
- Spatial diversity is a popular multiple antenna system technique, due to simplicity in implementation. However, its application has thus far been limited to systems where the electrical separation between adjacent antennas typically exceeds half a wavelength. This is because a more compact design induces higher antenna correlation and impedance mismatch, which results in lower diversity gains. In this paper, the performance of a compact multiband diversity antenna is investigated in both simulations and measurements. The dual-antenna structure is designed for the future WCDMA bands of WCDMA850, WCDMA1800 and 3G EU (UMTS), where the antenna separation at the WCDMA850 band is 0.24*wavelength. The measured results indicate that an average effective diversity gain of 7.3 dB at the 1% probability level can be achieved for the three bands
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| 4. |
- Bolin, Thomas, et al.
(författare)
-
Two-antenna receive diversity performance in indoor environment
- 2005
-
Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 41:22, s. 1205-1206
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Tidskriftsartikel (refereegranskat)abstract
- Receive diversity gain performance of a two-antenna setup in an office environment is reported. The terminal is handheld in front of the user simulating a data mode scenario while walking around. The dual polarised base station sector antenna is placed at the end of a corridor. The results indicate that experimentally achieved diversity performance is similar to previously predicted theoretical data.
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| 5. |
- Chung, Min Keun, et al.
(författare)
-
LuMaMi28 : Real-Time Millimeter-Wave Multi-User MIMO Systems with Antenna Selection
- 2023
-
Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276. ; 22:11, s. 7944-7960
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents LuMaMi28, a real-time 28GHz multi-user (MU) multiple-input multiple-output (MIMO) testbed. In this testbed, the base station has 16 transceiver chains with a fully-digital beamforming architecture (with different pre-coding algorithms) and simultaneously supports multiple user equipments (UEs) with spatial multiplexing. The UEs are equipped with a beam-switchable antenna array for real-time antenna selection where the one with the highest channel magnitude, out of four pre-defined beams, is selected. For the beam-switchable antenna array, we consider two kinds of UE antennas, with different beam-width and different peak-gain. Based on this testbed, we provide measurement results for millimeter-wave (mmWave) MU-MIMO performance in different real-life scenarios with static and mobile UEs. We explore the potential benefit of the mmWave MU-MIMO systems with antenna selection based on measured channel data, and discuss the performance results through real-time measurements.
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| 6. |
- Chung, Min Keun, et al.
(författare)
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Millimeter-Wave Massive MIMO Testbed with Hybrid Beamforming
- 2020
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Ingår i: Conference Record of the 54th Asilomar Conference on Signals, Systems and Computers, ACSSC 2020. - 1058-6393. - 9780738131269 ; 2020-November, s. 309-313
-
Konferensbidrag (refereegranskat)abstract
- Massive multiple-input multiple-out (MIMO) technology is vital in millimeter-wave (mmWave) bands to obtain large array gains. However, there are practical challenges, such as high hardware cost and power consumption in such systems. A promising solution to these problems is to adopt a hybrid beamforming architecture. This architecture has a much lower number of transceiver (TRx) chains than the total antenna number, resulting in cost- and energy-efficient systems. In this paper, we present a real-time mmWave (28GHz) massive MIMO testbed with hybrid beamforming. This testbed has a 64-antenna/16-TRx unit for beam-selection, which can be expanded to larger array sizes in a modular way. For testing everything from baseband processing algorithms to scheduling and beam-selection in real propagation environments, we extend the capability of an existing 100-antenna/100-TRx massive MIMO testbed (below 6GHz), built upon software-defined radio technology, to a flexible mmWave massive MIMO system.
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Gunnarsson, Sara, et al.
(författare)
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MmWave Massive MIMO in Real Propagation Environment : Performance Evaluation Using LuMaMi28GHz
- 2021
-
Ingår i: 55th Asilomar Conference on Signals, Systems and Computers, ACSSC 2021. - 9781665458283 ; , s. 80-84
-
Konferensbidrag (refereegranskat)abstract
- This paper presents measurement and analysis results for millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) performance in different real-life scenarios with moderate user equipment (UE) mobility. For the measurement campaign, the developed massive MIMO testbed operating at 28GHz called LuMaMi28GHz is employed. In this testbed, the base station has 16 transceiver chains with a fully digital beamforming architecture (with different pre-coding algorithms) and simultaneously supports multiple users with spatial multiplexing. The UEs are equipped with a beam-switchable antenna array for real-time antenna selection where the one with the highest channel magnitude, out of four pre-defined beams, is selected. We explore the potential benefit and features of mmWave massive MIMO systems with antenna selection based on both measured (and recorded) channel data and real-time system performance evaluation.
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| 11. |
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| 12. |
- He, Wang, et al.
(författare)
-
Fast Power Density Assessment of 5G Mobile Handset Using Equivalent Currents Method
- 2021
-
Ingår i: IEEE Transactions on Antennas and Propagation. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-926X .- 1558-2221. ; 69:10, s. 6857-6869
-
Tidskriftsartikel (refereegranskat)abstract
- As the fifth-generation (5G) mobile communication is utilizing millimeter-wave (mmWave) frequency bands, electromagnetic field (EMF) exposure emitted from a 5G mmWave mobile handset should be evaluated and compliant with the relevant EMF exposure limits in terms of peak spatial-average incident power density (PD). In this work, a fast PD assessment method for a 5G mmWave mobile handset using the equivalent current (EQC) method is proposed. The EQC method utilizes the intermediate-field (IF) data collected by a spherical measurement system to reconstruct the EQCs over a reconstruction surface and then computes the PD in close proximity of the mobile handset with acceptable accuracy. The performance of the proposed method is evaluated using a mmWave mobile handset mock-up equipped with four quasi-Yagi antennas. The assessed PD results are compared with those computed using full-wave simulations and also those measured with a planar near-field (NF) scanning system. In addition, three influencing factors related to the accuracy of the EQC method, namely, the angular resolution, the phase error, and the handset position in the IF measurements, are also analyzed. The proposed method is a good candidate for fast PD assessment of EMF exposure compliance testing in the mmWave frequency range.
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| 13. |
- He, Wang, et al.
(författare)
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Implications of Incident Power Density Limits on Power and EIRP Levels of 5G Millimeter-Wave User Equipment
- 2020
-
Ingår i: IEEE Access. - : Institute of Electrical and Electronics Engineers (IEEE). - 2169-3536. ; 8, s. 148214-148225
-
Tidskriftsartikel (refereegranskat)abstract
- User equipment (UE) is required to comply with the relevant radio frequency (RF) electromagnetic field (EMF) exposure limits, which are of relevance to establish the maximum permissible transmitted power and the maximum equivalent isotropically radiated power (EIRP). Recently, international RF EMF exposure guidelines, such as those published by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) as well as by the IEEE, have been updated. In this paper, the implications of the revised incident power density limits are investigated in terms of maximum permissible transmitted power and the maximum EIRP for devices operating in close proximity of the user. A similar analysis is conducted according to the US Federal Communications Commission (FCC) regulation on RF exposure. EMF compliance of UE is studied by means of numerical modelling of patch antenna arrays of different array sizes taking into consideration of possible beam-steering operations, at frequencies ranging from 10 GHz to 100 GHz. The results are compared with the 3rd Generation Partnership Project (3GPP) requirements on the total radiated power (TRP) and EIRP levels. The present implications of the incident power density limits for 5G millimeter-wave UE will give valuable insights to mobile equipment manufacturers, network operators, and standardization bodies.
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| 14. |
- He, Wang, et al.
(författare)
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RF Compliance Study of Temperature Elevation in Human Head Model Around 28 GHz for 5G User Equipment Application : Simulation Analysis
- 2018
-
Ingår i: IEEE Access. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2169-3536. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- The crowdedness of current cellular bands and the demand for higher transmission speed prompt the use of the millimeter-wave spectrum for the next-generation mobile communication. In the millimeter-wave frequencies, the dosimetric quantity for human exposure to electromagnetic fields changes from the specific absorption rate to incident power density. In this paper, we used 28-GHz beam-steering patch arrays, a dipole antenna, and plane waves to investigate the temperature elevation in a multi-layer model of human head and its correlation with power density metrics. The power density averaged over one square-centimeter in free space and the peak temperature elevation in tissue at 28 GHz have good correlation. The peak temperature elevation indicated by the power density averaged one square-centimeter also agrees well with the peak temperature elevation induced by the plane waves. The results show that the averaging area of a few square-centimeters may be a good candidate for the spatial-average power density. The findings provide valuable input to the ongoing revision and updating of relevant safety standards and guidelines.
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| 15. |
- Helander, Jakob, et al.
(författare)
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Characterization of Millimeter Wave Phased Array Antennas in Mobile Terminal for 5G Mobile System
- 2015
-
Ingår i: [Host publication title missing]. ; , s. 7-8
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a characterization method for millimeter wave (mmWave) phased array antennas in the mobile terminal for 5G communication. Arrays of different antenna designs, operating at 28 GHz, are evaluated according to novel characterization methods in this context - the total scan pattern of the phased array and its respective coverage efficiency. The results show the relevance of evaluating antenna array designs according to these characteristics, and illustrate, by introducing pattern diversity through sub-array schemes, that the coverage efficiency can be enhanced.
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| 16. |
- Helander, Jakob, et al.
(författare)
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Performance Analysis of Millimeter-Wave Phased Array Antennas in Cellular Handsets
- 2016
-
Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1536-1225 .- 1548-5757. ; 15, s. 504-507
-
Tidskriftsartikel (refereegranskat)abstract
- This letter discusses the usage of high-gain steerable antenna arrays operating at millimeter-wave (mmWave) frequencies for future cellular networks (5G). Based on the probable outline of the 5G networks, a method for characterizing phased array antennas in cellular handsets has been introduced. For analyzing the performance, the total scan pattern of the array configuration together with its respective coverage efficiency are essential to consider in order to compare different antenna designs and topology approaches with each other. Two design approaches and subarray schemes of these have been considered in order to illustrate the relevance of such a characterization method. The results show the importance of evaluating potential array antennas in such manners. The method can be applied to much more complex system models, where polarization diversity, hand and body effect, and statistical modeling of the channel may be included.
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| 17. |
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| 18. |
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| 19. |
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| 20. |
- Lau, Buon Kiong, et al.
(författare)
-
Antenna design challenges and solutions for compact MIMO terminals
- 2011
-
Ingår i: 2011 International Workshop on Antenna Technology (iWAT). - 9781424491339 - 9781424491346
-
Konferensbidrag (refereegranskat)abstract
- The design of antennas for compact multiple-input multiple-output (MIMO) terminals is a challenging feat, due to the space constraint and the physical structure of the terminal. The space constraint forces the antennas to be closely spaced, which degrades MIMO performance due to high signal correlation and low antenna efficiency. Moreover, the terminals are equipped with ground planes which further complicate the implementation of antennas for good MIMO performance. This paper elaborates on the two aforementioned challenges in MIMO antenna design and surveys recent techniques that are developed to address these challenges.
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| 21. |
- Li, Hui, et al.
(författare)
-
An efficient co-located MIMO antenna for compact terminals
- 2012
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The limited volume of mobile handset and the phenomenon of chassis excitation complicate the design of multiple antennas for MIMO applications. In this work, a compact co-located dual-antenna system implemented on one edge of a 100 mm by 40 mm chassis is proposed for operation below 1 GHz. The dual-antenna structure includes a folded monopole to excite the fundamental electric dipole mode of the chassis and a coupled loop working at its own fundamental magnetic dipole mode. In this way, angle and polarization diversities are achieved. In order to overcome the coupling induced by the close proximity between the feed lines of the two antennas, the phase of the feed current on the folded monopole can be optimized to achieve an isolation of above 20 dB. The phase optimization approach can also be applied to other multi-antenna systems that has similar coupling problem from the proximity of feeds. Moreover, to compensate for the narrowband property, the loop antenna can be made tunable to cover a large bandwidth. Good MIMO performance, in terms of capacity and multiplexing efficiency, is attained with the proposed antenna system. The co-located dual antenna prototype was fabricated and its performance was verified in measurements.
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| 22. |
- Li, Hui, et al.
(författare)
-
Antenna design tradeoff of multiple antenna terminals with ground plane excitation
- 2010
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- It is known that the compactness of mobile terminals complicates the design of multiple antennas, since coupling between the antennas increases when they are placed in proximity of one another. While it is possible to mitigate coupling between closely spaced antennas, a tradeoff in bandwidth is required. In this paper, we highlight ground plane excitation as an additional dimension to consider in the design of multiple antenna terminals. This is because small ground plane can interact with the antenna elements and contribute significantly to their radiation characteristics. In particular, the ground plane effect is important for mobile frequency bands lower than 1 GHz, due to the physical dimensions of today’s mobile terminals. Our results show that several design parameters, namely element locations, spacing between elements, and radiation characteristics of individual elements, must be jointly considered in order to achieve the optimum performance tradeoff for multiple antenna terminals. For example, for a two-antenna setup, even though coupling between the elements can be reduced by decreasing the element spacing to avoid ground plane excitation for one of the antennas, the bandwidth is reduced.
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| 23. |
- Li, Hui, et al.
(författare)
-
Characteristic Mode Based Tradeoff Analysis of Antenna-Chassis Interactions for Multiple Antenna Terminals
- 2012
-
Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 60:2, s. 490-502
-
Tidskriftsartikel (refereegranskat)abstract
- The design of multiple antennas in compact mobile terminals is a significant challenge, due to both practical and fundamental design tradeoffs. In this paper, fundamental antenna design tradeoffs of multiple antenna terminals are presented in the framework of characteristic mode analysis. In particular, interactions between the antenna elements and the characteristic modes and their impact on design tradeoffs are investigated in both theory and simulations. The results reveal that the characteristic modes play an important role in determining the optimal placement of antennas for low mutual coupling. Moreover, the ability of antenna elements to localize the excitation currents on the chassis can significantly influence the final performance. To demonstrate the effectiveness of the proposed approach, a dual-band, dual-antenna terminal is designed to provide an isolation of over 10 dB for the 900 MHz band without additional matching or decoupling structures. A tradeoff analysis of bandwidth, efficiency, effective diversity gain and capacity is performed over different antenna locations. Finally, three fabricated prototypes verify the simulation results for representative cases.
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| 24. |
- Li, Hui, et al.
(författare)
-
Decoupling of Multiple Antennas in Terminals With Chassis Excitation Using Polarization Diversity, Angle Diversity and Current Control
- 2012
-
Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 60:12, s. 5947-5957
-
Tidskriftsartikel (refereegranskat)abstract
- Excitation of the chassis enables single-antenna terminals to achieve good bandwidth and radiation performance, due to the entire chassis being utilized as the main radiator. In contrast, the same chassis excitation phenomenon complicates the design of multiple antennas for MIMO applications, since the same characteristic mode of the chassis may be effectively excited by more than one antenna, leading to strong mutual coupling and severe MIMO performance degradation. In this paper, we introduce a design concept for MIMO antennas to mitigate the chassis-induced mutual coupling, which is especially relevant for frequency bands below 1 GHz. We illustrate the design concept on a dual-antenna terminal at 0.93 GHz, where a folded monopole at one chassis edge excites the chassis' fundamental electric dipolemode and a coupled loop at the other chassis edge excites its own fundamental magnetic dipole mode. Since the two radiationmodes are nearly orthogonal to each other, an isolation of over 30 dB is achieved. Moreover, we show that the antenna system can be conveniently modified for multiband operation, such as in the 900/1800/2600MHz bands. Furthermore, by controlling the phase of the feed current on the folded monopole, the two antennas can be co-located on the same chassis edge with an isolation of over 20 dB. The co-located dual-antenna prototype was fabricated and verified in the measurements.
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| 25. |
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| 26. |
- Li, Hui, et al.
(författare)
-
Isolation enhancement of compact MIMO antennas with current localization
- 2010
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, we study the influence of current localization on the isolation between two antennas in a compact terminal setting. The two antennas are chosen to be a monopole and a PIFA, respectively. The degree of current localization is controlled by the permittivity value of the PIFA’s dielectric loading. Both lossless and lossy cases are simulated in order to ascertain the underlying performance impact from current localization and its potential use in real implementation. Our results show that significant isolation enhancement is achieved with more localized currents. Moreover, the technique improves diversity and capacity performance both at the center frequency and over a given bandwidth. In addition, PIFAs with dielectric loading of higher permittivity and more localized currents are physically smaller.
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| 27. |
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| 28. |
- Liao, Qingbi, et al.
(författare)
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Channel Capacity Analysis of Different Mobile Antenna Array Topologies in the Outdoor Urban Environment for 5G mm Wave System
- 2017
-
Ingår i: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538632840 ; , s. 1473-1474
-
Konferensbidrag (refereegranskat)abstract
- The 15 and 28 GHz frequency bands have been identified as interesting candidates for future 5G cellular communication systems. In this paper, based on ray-tracing simulations, we investigate the channel capacities at 15 and 28 GHz for a number of different array processing techniques, including beamforming, spatial multiplexing, and two types of hybrid beamforming. This is done for an 8 x 32 multiple input multiple output system, for the single user case. The hybrid beamforming techniques combines the beamforming and spatial multiplexing techniques, in order to reduce the number of analog-to-digital converters and thereby reducing the system complexity, while still maintaining multiplexing capabilities for improved system capacities. The achieved channel capacities the hybrid beamforming techniques with up to four parallel streams outperforms pure beamforming, but does not reach capacities close to that of full spatial multiplexing. This indicates that the outdoor channel can support multiplexing of more than four parallel data streams to a single user.
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| 29. |
- Liao, Qingbi, et al.
(författare)
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Simulations and Measurements of 15 and 28 GHz Indoor Channels with Different Array Configurations
- 2017
-
Ingår i: 2017 INTERNATIONAL WORKSHOP ON ANTENNA TECHNOLOGY. - : IEEE. - 9781509051779 ; , s. 256-259
-
Konferensbidrag (refereegranskat)abstract
- There are many different frequency bands above 6 GHz and into the mm-wave range above 30 GHz that are possible candidates for use in future 5G cellular systems. In this paper, we present some results for wireless channels at 15 and 28 GHz in an indoor scenario. The results are based on both measurements and ray tracing simulations. Basic comparisons of measured and simulated power-delay profiles, angle of departure and received power are presented to give an insight to the possibilities and limitations of utilizing ray tracing to characterize the indoor wireless channel at 15 and 28 GHz. We show that it is important to consider human body shadowing as well as finer structures and details in the ray tracing environment model in order to achieve reasonable results. Lastly, we also perform ray tracing simulations to assess the performance of a number of different array signal processing techniques, including beamforming, hybrid beamforming and spatial multiplexing.
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| 30. |
- Mahmood, Faraz, et al.
(författare)
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Decoupling techniques of compact and broadband MIMO antennas for handheld devices
- 2012
-
Ingår i: IEEE 6th European Conference on Antennas and propagation (EuCAP 2012). ; , s. 1-5
-
Konferensbidrag (refereegranskat)abstract
- This paper presents an innovative MIMO antenna system consisting of two broadband antennas combined with a 90° or 180° hybrid coupler. The antenna system is suitable for future MIMO systems due to its wide decoupled bandwidth (from 698 to 2700 MHz) covering 23 frequency bands of LTE. Enhanced antenna performance is achieved by radiator slitting and ground plane modification. Moreover, supplemental meandered line ground structures are utilized to miniaturize the antenna size. The low profile antenna with its wide impedance bandwidth, high efficiency, low correlation and quasi-omni directional radiation pattern is attractive for the existing and future 4G mobile communication devices. Simulated and measured results including input reflection, mutual coupling, correlation, and antenna efficiency is presented and analyzed.
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| 31. |
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| 32. |
- Olano, N., et al.
(författare)
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WLAN MIMO throughput test in reverberation chamber
- 2008
-
Ingår i: 2008 IEEE International Symposium on Antennas and Propagation and USNC/URSI National Radio Science Meeting, APSURSI; San Diego, CA; United States; 5 July 2008 through 12 July 2008. - 9781424420421 ; , s. Art. no. 4619377-
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Konferensbidrag (refereegranskat)abstract
- The present paper describes the first repeatable full system measurement setting for WLAN link throughput at the transport layer payload. This is the effective rate of the link to be offered to the applications and determines the quality of the user experience. The measurement is done in a reverberation chamber.
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| 33. |
- Owais, Owais, et al.
(författare)
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Wideband planar antenna with modified ground plane
- 2010
-
Ingår i: Microwave and optical technology letters (Print). - : Wiley. - 0895-2477 .- 1098-2760. ; 52:11, s. 2581-2585
-
Tidskriftsartikel (refereegranskat)abstract
- In this article a miniaturized planar antenna is presented for broadband applications. Antenna miniaturization is achieved by modifying the ground plane that creates a different current path thus increasing the effective dimension of the antenna. In addition, dual chopping, slitting, and radiator position offsetting provide wideband behavior and relatively good impedance matching. The low profile antenna with its wide bandwidth, linear phase response and quasi-omnidirectional radiation pattern is attractive for the existing and future communication devices of small size. Simulated and measured results for the proposed antenna are presented and analyzed.
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| 34. |
- Plicanic, Vanja, et al.
(författare)
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Actual diversity performance of a multiband diversity antenna with hand and head effects
- 2009
-
Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 57:5, s. 1547-1556
-
Tidskriftsartikel (refereegranskat)abstract
- Using the metric actual diversity gain (ADG), diversity performance is investigated for a compact mobile terminal prototype with two internal, triple frequency band antennas in four different cases of user interaction. ADG is presented as a preferred alternative to apparent diversity gain and effective diversity gain. Absorption due to user proximity causes degradation and imbalance in mean effective gain of the antennas over the frequency bands, contributing to a degradation in diversity performance. However, user-induced changes in the antenna patterns cause a decrease in correlation in the low frequency band, which facilitates increased diversity gain. The study reveals that a significant net diversity gain, i.e., ADG of 5-8 dB compared to a single antenna prototype, can be achieved using multiband antennas in the proximity of a user, even at low frequencies for antennas with high mutual coupling.
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| 35. |
- Plicanic, Vanja, et al.
(författare)
-
Antenna diversity evaluation for mobile terminals
- 2006
-
Ingår i: European Space Agency, (Special Publication) ESA SP. - 0379-6566 .- 1609-042X. ; 626 SP
-
Konferensbidrag (refereegranskat)abstract
- In this paper we are focusing on the practical, engineering way of evaluating and characterizing the multi-channel antenna solutions on the mobile terminal. Two methods of calculating the parameters, describing the diversity performance, are described and the practical use of the methods in simulations and measurements are presented and evaluated. The time saving aspect of using the scattering parameters is lifted forward but also its limitations. For comparison, a statistical method for calculating Diversity Gain is also presented. This evaluation is performed for two multi-channel antenna solutions with different characteristics for the purpose of characterizing different diversity performances.
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| 36. |
- Plicanic, Vanja, et al.
(författare)
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Channel capacity performance of multi-band dual antenna in proximity of a user
- 2009
-
Ingår i: 2009 IEEE International Workshop on Antenna Technology: Small Antennas and Novel Metamaterials (IWAT). - 9781424443956 ; , s. 41402-41402
-
Konferensbidrag (refereegranskat)abstract
- This paper presents an evaluation of single input single output (SISO), single input multiple output (SIMO) and multiple input multiple output (MIMO) channel capacities for a dual antenna prototype in proximity of a user. The dual antenna prototype mimics today’s small mobile phone design in size and in comprising internal, compact, multi-band antennas. Four different user cases are evaluated by measuring the antenna radiation performance for each of the different interactions between a phantom user and the antenna. Measurements of a single antenna prototype with user are also performed for comparisons between the SISO case and the SIMO/MIMO cases. Depending on the user interaction case, the MIMO capacity of the prototype is between 40-90% at 850 MHz and 60-80% at 2100 MHz higher than the SISO performance of the single antenna prototype or the best antenna on the dual antenna prototype.
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| 37. |
- Plicanic, Vanja, et al.
(författare)
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Influence of user hand on the performance of a multiband diversity antenna
- 2008
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The increasing demand on improved reception and high data throughput brings into focus the design of compact multiband antenna terminals with diversity reception capability. In particular, the influence of user on diversity performance is of current interest. In this paper, the diversity performance of compact tri-band antennas (WCDMA850, WCDMA1800 and UMTS 2100) for mobile handsets is evaluated in the data mode position. The results indicate that the user hand has a significant negative effect on the mean effective gains of the diversity antennas. On the other hand, the signal correlation is relatively unaffected by the hand, and it even improved for the WCDMA850 band. However, the decrease in correlation between the branches in the WCDMA850 band is inadequate to offset the degradation in diversity system gain resulting from the reduced mean effective gains. Moreover, the loss of efficiency due to mutual coupling is particularly severe at the WCDMA850 band. Consequently, only a small diversity system gain of less than 1 dB is obtained for the lowest band, whereas a 5 dB gain is achieved for the higher bands.
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| 38. |
- Plicanic, Vanja, et al.
(författare)
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On MIMO capacity of a dual multiband antenna prototype with user interactions
- 2008
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents an evaluation of single input single output (SISO), single input multiple output (SIMO) and multiple input multiple output (MIMO) channel capacities for a dual antenna prototype in proximity of a user. The dual antenna prototype mimics today’s small mobile phone design in size and in comprising internal, compact, multi-band antennas. Four different user cases are evaluated by measuring the antenna radiation performance for each of the different interactions between a phantom user and the antenna. Measurements of a single antenna prototype with user are also performed for comparisons between the SISO case and the SIMO/MIMO cases. Depending on the user interaction case, the MIMO capacity of the prototype is between 40-90% at 850 MHz and 60-80% at 2100 MHz higher than the SISO performance of the single antenna prototype or the best antenna on the dual antenna prototype.
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| 39. |
- Plicanic, Vanja, et al.
(författare)
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Performance of a multiband diversity antenna with hand effects
- 2008
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Ingår i: International Workshop on Antenna Technology (iWAT 2008). ; , s. 478-481
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Konferensbidrag (refereegranskat)abstract
- The implementation of multiband diversity antennas in compact mobile handsets, for the purpose of increasing transmission quality, is a topic of current interest in the mobile phone industry. In order to achieve the expected performance improvement in typical operating conditions, we not only have to contend with the challenges of designing multiple multiband antennas, which are closely spaced within the compact handset and thus strongly interacting with one another electromagnetically [1], we also need to keep in check the electromagnetic interaction between the whole antenna system (i.e., the handset) and the user. Previous studies have concluded that the presence of a user degrades the mean effective gain (MEG) of the diversity antennas significantly [1]-[3]. Different results have been presented on the effect of the user on the correlation coefficient, no effect [1] and a significant increase of the correlation [2], [3], have been pointed out. However, these studies have been performed on simple single band antennas in talk position. In this paper a more realistic approach is presented by choosing the diversity antenna system to comprise compact versions of PIFA and monopole antennas which cover three WCDMA bands: WCDMA850, WCDMA1800 and UMTS [4]. Such compact antennas are easily conformable for small mobile phone products [4]. The choice of the bands, as well as the evaluation of the diversity performance for the data mode position, is derived from the increasing demand on HSDPA applications in the mobile phone market. The investigation of user interaction presented in this paper focuses on the comparison between the free space and data mode diversity performance of a tri-band “stick” phone size prototype in the uniform 3D propagation environment. A state-of-the-art phantom hand from IndexSAR [5] is used to hold the diversity prototype in the data mode position.
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| 40. |
- Syrytsin, Igor, et al.
(författare)
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Statistical Investigation of the User Effects on Mobile Terminal Antennas for 5G Applications
- 2017
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Ingår i: IEEE Transactions on Antennas and Propagation. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-926X .- 1558-2221. ; 65:12, s. 6596-6605
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the user effects on mobile terminal antennas at 28 GHz are statistically investigated with the parameters of body loss, coverage efficiency, and power in the shadow. The data are obtained from the measurements of 12 users in data and talk modes, with the antenna placed on the top and bottom of the chassis. In the measurements, the users hold the phone naturally. The radiation patterns and shadowing regions are also studied. It is found that a significant amount of power can propagate into the shadow of the user by creeping waves and diffractions. A new metric is defined to characterize this phenomenon. A mean body loss of 3.2-4 dB is expected in talk mode, which is also similar to the data mode with the bottom antenna. A body loss of 1 dB is expected in data mode with the top antenna location. The variation of the body loss between the users at 28 GHz is less than 2 dB, which is much smaller than that of the conventional cellular bands below 3 GHz. The coverage efficiency is significantly reduced in talk mode, but only slightly affected in data mode.
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| 41. |
- Tian, Ruiyuan, et al.
(författare)
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A compact six-port dielectric resonator antenna array: MIMO channel measurements and performance analysis
- 2010
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X. ; 58:4, s. 1369-1379
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Tidskriftsartikel (refereegranskat)abstract
- MIMO systems ideally achieve linear capacity gain proportional to the number of antennas. However, the compactness of terminal devices limits the number of spatial degrees of freedom (DOFs) in such systems, which motivates efficientantenna design techniques to exploit all available DOFs. In this contribution, we present a compact six-port dielectric resonator antenna (DRA) array which utilizes spatial, polarization and angle diversities. To evaluate the proposed DRA array, a measurement campaign was conducted at 2.65GHz in indoor officescenarios for four 6 × 6 multiple antenna systems. Compared to the reference system of monopole arrays which only exploit spatial diversity, the use of dual-polarized patch antennas at the transmitter enriches the channel’s DOF in the non-line-of-sight scenario. Replacing the monopole array at the receiver withthe DRA array that has a 95% smaller ground plane, the 10% outage capacity evaluated at 10 dB reference signal-to-noise ratio becomes equivalent to that of the reference system, due to the DRA’s rich diversity characteristics. In the line-of-sight scenario, the DRA array gives a higher DOF than the monopole array asthe receive counterpart to the transmit patch array. However, the outage capacity is 1.5 bits/s/Hz lower, due to the DRA array’s lower channel gain.
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| 42. |
- Tian, Ruiyuan, et al.
(författare)
-
Characterization of MIMO antennas with multiplexing efficiency
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A simple and intuitive metric of multiplexing efficiency is proposed for evaluating the performance of MIMO antennas in the spatial multiplexing mode of operation. The metric is particularly useful for antenna engineers whose goal is to achieve the optimum antenna system design. Experimental results involving prototype mobile terminals highlight the effectiveness of our proposal.
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| 43. |
- Tian, Ruiyuan, et al.
(författare)
-
Impact of user on the multiplexing efficiency of a MIMO terminal antenna
- 2012
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Abstract in UndeterminedThis study investigates the impact of user on the multiplexing efficiency of a pentaband two-element MIMO terminal antenna. At the 750MHz band, the results show that the antenna total efficiency decreases by 4 dB in the presence of the user hand. However, this negative effect is partly compensated by the de-correlation effect of the hand. As a result, the multiplexing efficiency of the antenna degrades by only 2.4 dB in the hand scenario, as compared to the free space scenario. Throughout the study, we show that the impact of user hand and head on the efficiency and correlation performance can be conveniently quantified using the multiplexing efficiency metric.
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| 44. |
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| 45. |
- Tian, Ruiyuan, et al.
(författare)
-
Multiplexing efficiency of MIMO antennas
- 2011
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1548-5757. ; 10, s. 183-186
-
Tidskriftsartikel (refereegranskat)abstract
- A simple and intuitive metric of multiplexing efficiency is proposed for evaluating the performance of MIMO antennas in the spatial multiplexing mode of operation. Apart from gaining valuable insights into the impact of antenna efficiency, efficiency imbalance and correlation on multiplexing performance, the metric is particularly useful for antenna engineers whose goal is to achieve the optimum antenna system design. Experimental results involving prototype mobile terminals highlight the effectiveness of our proposal.
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| 46. |
- Tian, Ruiyuan, et al.
(författare)
-
Multiplexing efficiency of MIMO antennas in arbitrary propagation scenarios
- 2012
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Ingår i: 6th European Conference on Antennas and Propagation (EUCAP), 2012. - 9781457709180 ; , s. 373-377
-
Konferensbidrag (refereegranskat)abstract
- Multiplexing efficiency has recently been proposed as a performance metric for characterizing the absolute efficiency of MIMO antennas in a reference channel. In this work, we generalize this metric to account for arbitrary propagation channels, so the impact of the channel can also be studied. Using the extended definition of multiplexing efficiency, the respective roles of effective antenna gain and signal correlation due to nonisotropic incident fields can be clearly identified. A numerical evaluation based on two MIMO terminal prototypes and four different propagation scenarios is performed to demonstrate the effectiveness of the generalized metric. We find that the MIMO antenna with high total antenna efficiency and good pattern diversity offers a robust multiplexing efficiency performance in all the considered propagation scenarios.
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| 47. |
- Tian, Ruiyuan, et al.
(författare)
-
Multiplexing efficiency of MIMO antennas with user effects
- 2012
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Ingår i: IEEE International Symposium on Antennas and Propagation, 2012.
-
Konferensbidrag (refereegranskat)abstract
- Recently, the multiplexing efficiency metric is proposed for characterizing the MIMO performance of terminal antennas. Here, we show that it can also provide useful insights into the impact of user on MIMO terminal performance. In particular, the impact of user hand and head on the efficiency and correlation of a MIMO antenna can be conveniently quantified using the multiplexing efficiency metric. For example, we find that the hand introduces a 4 dB loss in total efficiency relative to the free space case, for a penta-band two-element MIMO terminal antenna operating at 750MHz. However, the multiplexing efficiency drops by only 2.4 dB, due to the de-correlation effect of the hand partly compensating the loss in total efficiency.
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| 48. |
- Tian, Ruiyuan, et al.
(författare)
-
Multiplexing efficiency of multiple antenna systems
- 2011
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Multiplexing efficiency is proposed as a simple and intuitive metric for characterizing multiple antenna systems in the spatial multiplexing mode of operation. Instead of comparing channel capacities of MIMO systems with different antennas, the metric offers valuable insights into the impact of antenna efficiency, efficiency imbalance and correlation on multiplexing performance. It is particularly useful in antenna design with the goal to achieve the optimum MIMO system performance. Experimental results involving mobile terminal prototypes highlight the effectiveness of the proposal.
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| 49. |
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| 50. |
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