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  • 1.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    RF EMF Exposure of Beam-Steering Slot Array in 5G User Equipment at 15 GHz2017In: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 177-178Conference 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.

  • 2.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    Understandings of Maximum Spatially-Averaged Power Density in 5G RF EMF Exposure Study2017In: 2017 INTERNATIONAL WORKSHOP ON ANTENNA TECHNOLOGY: SMALL ANTENNAS, INNOVATIVE STRUCTURES, AND APPLICATIONS (IWAT), IEEE , 2017, p. 115-117Conference 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.

  • 3.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Thors, Björn
    Colombi, Davide
    Lundberg, Oscar
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Power Density Measurements at 15 GHz for RF EMF Compliance Assessments of 5G User Equipment2017In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 65, no 12, p. 6584-6595Article in journal (Refereed)
    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.

  • 4.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Mobile Antenna Systems for 4G and 5G Applications with User Body Interaction2017Doctoral 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. 

  • 5.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Gustafson, Carl
    Liao, Qinghi
    KTH, School of Education and Communication in Engineering Science (ECE).
    Zhang, Shuai
    Bolin, Thomas
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Channel Characteristics and User Body Effects in an Outdoor Urban Scenario at 15 and 28 GHz2017In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 65, no 12, p. 6534-6548Article in journal (Refereed)
    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.

  • 6.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Helander, Jakob
    Sjoberg, Daniel
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bolin, Thomas
    Ying, Zhinong
    User Body Effect on Phased Array in User Equipment for the 5G mmWave Communication System2017In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 16, p. 864-867Article in journal (Refereed)
    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.

  • 7.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Zander, O.
    Bolin, T.
    Ying, Z.
    EIRP of user equipment with beam forming capabilities at 28 GHz2018In: IET Conference Publications, Institution of Engineering and Technology , 2018, no CP741Conference 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.

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