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Zhao, Kun
Publications (7 of 7) Show all publications
Zhao, K., Zander, O., Bolin, T. & Ying, Z. (2018). EIRP of user equipment with beam forming capabilities at 28 GHz. In: IET Conference Publications: . Paper presented at 12th European Conference on Antennas and Propagation, EuCAP 2018, 9 April 2018 through 13 April 2018. Institution of Engineering and Technology (CP741)
Open this publication in new window or tab >>EIRP of user equipment with beam forming capabilities at 28 GHz
2018 (English)In: IET Conference Publications, Institution of Engineering and Technology , 2018, no CP741Conference paper, Published paper (Refereed)
Abstract [en]

The equivalent isotropic radiated power (EIRP) has been used for defining the user equipment (UE) power class in millimeter wave (mmWave) frequencies in 3rd generation partnership project (3GPP) discussion since high directional antenna array systems with beamforming capability will be used in UE for future cellular communications. In this paper, we first briefly review the progress of 3GPP standardization on mmWave UE. Then, the EIRP of UE at 28 GHz with possible array topologies, in possible use cases, with imperfect precoders and the measurement uncertainties are discussed.

Place, publisher, year, edition, pages
Institution of Engineering and Technology, 2018
Keywords
3GPP, Beamforming, EIRP, MmWave, UE, Directive antennas, Equivalence classes, Millimeter waves, Mobile telecommunication systems, Uncertainty analysis, 3rd generation partnership project (3GPP), Equivalent isotropic radiated power, High-directional, Measurement uncertainty, Millimeter waves (mmwave), mm-Wave, Beam forming networks
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-247469 (URN)2-s2.0-85057295842 (Scopus ID)
Conference
12th European Conference on Antennas and Propagation, EuCAP 2018, 9 April 2018 through 13 April 2018
Note

QC20190503

Available from: 2019-05-03 Created: 2019-05-03 Last updated: 2019-05-03Bibliographically approved
Zhao, K., Gustafson, C., Liao, Q., Zhang, S., Bolin, T., Ying, Z. & He, S. (2017). Channel Characteristics and User Body Effects in an Outdoor Urban Scenario at 15 and 28 GHz. IEEE Transactions on Antennas and Propagation, 65(12), 6534-6548
Open this publication in new window or tab >>Channel Characteristics and User Body Effects in an Outdoor Urban Scenario at 15 and 28 GHz
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2017 (English)In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 65, no 12, p. 6534-6548Article in journal (Refereed) Published
Abstract [en]

The effect of a user's body on channel characteristics for single user downlink transmission in an urban scenario for the fifth generation (5G) systems is investigated with ray-tracing at 15 and 28 GHz. Three different designs of user equipment (UE) antennas are fabricated and integrated into a mobile phone prototype, and their 3-D radiation patterns are measured both with and without a user. The user remains in Cellular Telephone Industries Association (CTIA) standard data mode and talk mode during measurements. The results show that the user's body will cause a strong shadowing loss and generate a large fluctuation on the received signal strength of the UE at both 15 and 28 GHz, which is crucial to channel modeling studies at frequencies above 6 GHz. In addition, the user's body effect on a linear array system in an UE is presented, and the main challenges for the future work are also addressed.

Place, publisher, year, edition, pages
IEEE, 2017
Keywords
5G, array, body effect, channel, millimeter wave (mmWave), mobile phone, user equipment (UE)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-215256 (URN)10.1109/TAP.2017.2740959 (DOI)000417885000031 ()2-s2.0-85028501647 (Scopus ID)
Funder
Swedish Research Council, 621-2011-4620
Note

QC 20171005

Available from: 2017-10-05 Created: 2017-10-05 Last updated: 2018-01-12Bibliographically approved
Zhao, K. (2017). Mobile Antenna Systems for 4G and 5G Applications with User Body Interaction. (Doctoral dissertation). Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Mobile Antenna Systems for 4G and 5G Applications with User Body Interaction
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the thesis, the user body effect on antennas in a mobile terminal is discussed. In order to overcome the degradation of Multiple-Input Multiple-Output (MIMO) performance due to the user body effect, a quad-elements MIMO antenna array which can mitigate the body effect through an adaptive antenna switching method is introduced for 4G mobile terminals. In addition, various bezel MIMO antennas that are robust to the impedance mismatching caused by the user effect have also been presented.

The study of user body effect is later extended to frequency bands at 15 GHz and 28 GHz for future 5G communication systems. The results reveal that a human body will cause a significant shadowing loss, which will be a critical loss in 5G cellular networks.

The electromagnetic field (EMF) exposure of a mobile terminal is also studied in this thesis. Below 6 GHz, the simultaneous transmission specific absorption rate (SAR) for MIMO antennas is the primary concern due to its complicated assessment procedures. Above 6 GHz, the free space power density is adopted as the basic parameter of exposure limits globally, and preliminary studies have been presented to address major challenges in EMF exposure assessment for 5G mobile terminals. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. p. 65
Series
TRITA-EE, ISSN 1653-5146 ; 2017:137
Keywords
Antenna, MIMO, mmWave, Mobile communication, SAR, Power density, User body effect, Channel modeling, Multiplex efficiency
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-215266 (URN)978-91-7729-550-1 (ISBN)
Public defence
2017-10-27, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20171005

Available from: 2017-10-05 Created: 2017-10-05 Last updated: 2017-11-08Bibliographically approved
Xu, B., Zhao, K., Thors, B., Colombi, D., Lundberg, O., Ying, Z. & He, S. (2017). Power Density Measurements at 15 GHz for RF EMF Compliance Assessments of 5G User Equipment. IEEE Transactions on Antennas and Propagation, 65(12), 6584-6595
Open this publication in new window or tab >>Power Density Measurements at 15 GHz for RF EMF Compliance Assessments of 5G User Equipment
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2017 (English)In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 65, no 12, p. 6584-6595Article in journal (Refereed) Published
Abstract [en]

In this paper, different measurement schemes are studied in order to investigate the possibilities and limitations of scalar-and vector-based measurement systems for radio frequency electromagnetic fields compliance assessments of fifth generation mobile communication user equipment (UE). Two UE antenna array designs, transmitting at 15 GHz and employing patch and notch antenna elements, are considered for different phase excitations. Using free space power density as the exposure metric, the maximum permissible transmitted power of UE, compliant with the maximum permissible exposure limits specified by the U.S. Federal Communications Commission (FCC) and the basic restrictions of the International Commission on Non-Ionizing Radiation Protection, is determined. The accuracy of different measurement schemes is assessed using numerical simulation. Verifying measurements is carried out in a semiane-choic chamber. The results indicate that, for UE employing array antennas and intended to be used in immediate vicinity of the human body, scalar measurement systems used in combination with straightforward field combination techniques will lead to overly conservative results. A more accurate and less conservative approach for these products is to conduct separate measurements for different excitations in order to span the space of possible excitations. This will result in a more complicated measurement setup and increase the measurement time, which points to a need for very fast measurement systems.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2017
Keywords
Antenna array, assessment method, fifth generation (5G) mobile communication systems, maximum permissible transmitted power (MPTP), power density, radio frequency (RF) electromagnetic field (EMF) exposure, user equipment (UE)
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-221024 (URN)10.1109/TAP.2017.2712792 (DOI)000417885000035 ()2-s2.0-85038858525 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20180112

Available from: 2018-01-12 Created: 2018-01-12 Last updated: 2018-01-12Bibliographically approved
Xu, B., Zhao, K., He, S. & Ying, Z. (2017). RF EMF Exposure of Beam-Steering Slot Array in 5G User Equipment at 15 GHz. In: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings: . Paper presented at International Symposium of IEEE-Antennas-and-Propagation-Society / USNC/URSI National Radio Science Meeting, JUL 09-14, 2017, San Diego, CA (pp. 177-178). Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>RF EMF Exposure of Beam-Steering Slot Array in 5G User Equipment at 15 GHz
2017 (English)In: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 177-178Conference paper, Published paper (Refereed)
Abstract [en]

Above 6 GHz or 10 GHz, the radio frequency (RF) electro-magnetic field (EMF) exposure of user equipment (UE) is evaluated in terms of free space power density. The RF EMF exposure compliance of the fifth-generation (5G) UE with an 8 x 1 beam-steering slot array is analyzed in this paper. The maximum exposure (ME) and corresponding maximum permissible radiated power (MPRP) are calculated for different regulatory guidelines. The results give a good estimation on the range of compliance distance and MPRP of 5G UE, and provide the insight for the future RF EMF exposure compliance for the 5G communication. More results and comparisons of different sorts of arrays will be presented in the conference.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2017
Series
IEEE Antennas and Propagation Society International Symposium, ISSN 1522-3965
Keywords
15 GHz, 5G, beam steering, RF EMF exposure, slot array, user equipment
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-224106 (URN)10.1109/APUSNCURSINRSM.2017.8072131 (DOI)000424765300087 ()2-s2.0-85042288365 (Scopus ID)978-1-5386-3284-0 (ISBN)
Conference
International Symposium of IEEE-Antennas-and-Propagation-Society / USNC/URSI National Radio Science Meeting, JUL 09-14, 2017, San Diego, CA
Note

QC 20180314

Available from: 2018-03-14 Created: 2018-03-14 Last updated: 2018-03-14Bibliographically approved
Xu, B., Zhao, K., He, S. & Ying, Z. (2017). Understandings of Maximum Spatially-Averaged Power Density in 5G RF EMF Exposure Study. In: 2017 INTERNATIONAL WORKSHOP ON ANTENNA TECHNOLOGY: SMALL ANTENNAS, INNOVATIVE STRUCTURES, AND APPLICATIONS (IWAT). Paper presented at International Workshop on Antenna Technology - Small Antennas, Innovative Structures, and Applications (iWAT), MAR 01-03, 2017, Athens, GREECE (pp. 115-117). IEEE
Open this publication in new window or tab >>Understandings of Maximum Spatially-Averaged Power Density in 5G RF EMF Exposure Study
2017 (English)In: 2017 INTERNATIONAL WORKSHOP ON ANTENNA TECHNOLOGY: SMALL ANTENNAS, INNOVATIVE STRUCTURES, AND APPLICATIONS (IWAT), IEEE , 2017, p. 115-117Conference paper, Published paper (Refereed)
Abstract [en]

In the millimeter-wave (mmW) frequency band, radio frequency electromagnetic field (RF EMF) exposure is evaluated in terms of free space power density rather than the localized specific absorption rate (SAR) used in current cellular communications. In this study, we investigated RF EMF exposure of user equipment (UE) mock-ups employing a patch array operating at 15 GHz. Different understandings of maximum spatially-averaged power density to comply with different regulatory requirements are studied. Based on free space power density, the maximum permissible transmitted power (MPTP) of UE is calculated to compare the influence of different understandings. The analysis and results suggest that there is 1-2.6 dB MPTP difference for the ICNIRP limits and 0.1-1 dB MPTP difference for the proposed FCC limits depending on the varying compliance distance.

Place, publisher, year, edition, pages
IEEE, 2017
Keywords
RF EMF exposure, near field, power density, transmitted power
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-210969 (URN)10.1109/IWAT.2017.7915332 (DOI)000403326200033 ()2-s2.0-85019630044 (Scopus ID)978-1-5090-5177-9 (ISBN)
Conference
International Workshop on Antenna Technology - Small Antennas, Innovative Structures, and Applications (iWAT), MAR 01-03, 2017, Athens, GREECE
Note

QC 20170712

Available from: 2017-07-12 Created: 2017-07-12 Last updated: 2017-07-12Bibliographically approved
Zhao, K., Helander, J., Sjoberg, D., He, S., Bolin, T. & Ying, Z. (2017). User Body Effect on Phased Array in User Equipment for the 5G mmWave Communication System. IEEE Antennas and Wireless Propagation Letters, 16, 864-867
Open this publication in new window or tab >>User Body Effect on Phased Array in User Equipment for the 5G mmWave Communication System
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2017 (English)In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 16, p. 864-867Article in journal (Refereed) Published
Abstract [en]

The millimeter-wave phased array in the user equipment (UE) for 5G communication is studied in this letter. In particular, the body effect on the phased array in the UE at 15 GHz is investigated with the 3-D measurement data, and its impact on some key parameters for phased array in the UE, such as the total scan pattern, the coverage efficiency, and the probability of detection, are analyzed.

Place, publisher, year, edition, pages
IEEE, 2017
Keywords
Coverage efficiency, fifth-generation mobile system, human body effects, millimeter wave (mmWave), phased array, user equipment (UE) antenna
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-208282 (URN)10.1109/LAWP.2016.2611674 (DOI)000399319100039 ()2-s2.0-85018949860 (Scopus ID)
Note

QC 20170609

Available from: 2017-06-09 Created: 2017-06-09 Last updated: 2017-10-05Bibliographically approved
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