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  • 1. Helander, Jakob
    et al.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Sony Mobile Commun AB, Sweden.
    Ying, Zhinong
    Sjöberg, Daniel
    Performance Analysis of Millimeter-Wave Phased Array Antennas in Cellular Handsets2016In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 15, p. 504-507Article in journal (Refereed)
    Abstract [en]

    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.

  • 2. Syrytsin, Igor
    et al.
    Zhang, Shuai
    Pedersen, Gert Frolund
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bolin, Thomas
    Ying, Zhinong
    Statistical Investigation of the User Effects on Mobile Terminal Antennas for 5G Applications2017In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 65, no 12, p. 6596-6605Article in journal (Refereed)
    Abstract [en]

    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.

  • 3.
    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.

  • 4.
    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.

  • 5.
    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.

  • 6.
    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. SONY Mobile Communications AB, Sweden.
    Ying, Z.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hu, J.
    Investigation of surface waves suppression on 5G handset devices at 15 GHz2016In: 2016 10th European Conference on Antennas and Propagation, EuCAP 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, article id 7481336Conference paper (Refereed)
    Abstract [en]

    The challenge of surface wave excitation and propagation to millimeter-wave (mm-wave) antennas of future fifth-generation (5G) cellular system is addressed in this paper. This paper presents three different schemes by simulation, including mushroom-like electromagnetic band-gap (EBG) structures, cross-shaped resonant structures and T-shaped wave trap structures, to suppress surface wave propagation in handset devices at 15 GHz. We also investigate the positional influence of EBG structures on the radiation patterns of two slot array antennas on a mock-up. The measurement results suggest that gain, sidelobe level and radiation efficiency are all increased when the EBG structures are placed close to the radiating element.

  • 7. Ying, Z.
    et al.
    Chiu, C. -Y
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Sony Mobile Communications AB, Sweden.
    Zhang, S.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Antenna design for diversity and MIMO application2016In: Handbook of Antenna Technologies, Springer, 2016, Vol. 2, p. 1479-1530Chapter in book (Refereed)
    Abstract [en]

    Recently, multiple-input multiple-output (MIMO) technology and diversity have attracted much attention both in industry and academia due to high data rate and high spectrum efficiency. By increasing the number of antennas at the transmitter and/or the receiver side of the wireless link, the diversity/MIMO techniques can increase wireless channel capacity without the need of additional power or spectrum in rich scattering environments. However, due to limited space of small mobile devices, the correlation coefficients between MIMO antenna elements are usually very high, and the total efficiencies of MIMO elements would be degraded severely due to mutual couplings. In addition, the human body causes high losses on electromagnetic waves. In real applications, the presence of users may result in significant reduction of total antenna efficiencies, and the correlations of MIMO antenna systems are also highly affected. In this chapter, the performance of some basic MIMO antennas as well as recent technologies to improve MIMO antenna performance of portable devices and mobile terminals are reviewed. The interactions between MIMO antennas and human body are also addressed particularly in mobile terminals application.

  • 8. Ying, Z.
    et al.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Network Technology, Sweden .
    Bolin, T.
    Helander, J.
    Sjöberg, D.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Scannavini, A.
    Foged, L. J.
    Nicolas, G.
    Study of phased array in UE for 5G mm wave communication system with consideration of user body effect2016In: 2016 10th European Conference on Antennas and Propagation, EuCAP 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, article id 7481215Conference paper (Refereed)
    Abstract [en]

    The latest study of the millimeter wave (mmWave) phased array in user device (UE) for 5G communication is presented in this paper. Particularly, the body effect on the phased array in a UE/mobile terminal at 15 GHz is investigated with the 3D measured data. Its impact on the recently introduced parameter for phased array in mobile terminal, the total scanning pattern, body loss and the coverage efficiency, is analyzed.

  • 9. Ying, Zhinong
    et al.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bolin, Thomas
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Scannavini, Alessandro
    Foged, Lars J.
    Nicolas, Gross
    Multiplexing Efficiency of High Order MIMO in Mobile Terminal for 5G communication at 15GHz2016In: 2016 INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION (ISAP), IEEE , 2016, p. 594-595Conference paper (Refereed)
    Abstract [en]

    The multiplexing efficiency of high order MIMO in mobile terminal at 15GHz for 5G communication is studied in this paper. The multiplexing efficiency of two MIMO topologies are compared is calculated with a narrow angular spread Gaussian distributed incoming wave model in order to illustrate the mm wave channel characterize.

  • 10. Zhang, S.
    et al.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Z.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Body loss study of beamforming mode in LTE MIMO mobile terminals2015In: 2015 9th European Conference on Antennas and Propagation, EuCAP 2015, IEEE conference proceedings, 2015Conference paper (Refereed)
    Abstract [en]

    This paper mainly focuses on the investigation of the body loss of beamforming mode in LTE MIMO mobile terminals with CTIA user effects. The research of the body loss and radiation efficiency is carried out over different phase differences between two ports of each MIMO antenna. During studies, four kinds of typical LTE MIMO antennas are used, namely, collocated ground free (GF), parallel GF, parallel on ground (OG) and orthogonal OG MIMO antennas, under four mobile terminal lengths at low and high frequencies. Two kinds of CTIA user effects are included in the research. From the studies, the parallel GF MIMO antenna type exhibits the best beamforming performance in the four MIMO antenna types. In order to verify the simulations, envelope correlation coefficients of two MIMO antenna prototypes are measured. All the measured results agree well with the simulated.

  • 11.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Diagonal Antenna-Chassis Mode and Its Application for Wideband LTE MIMO Antennas in Mobile HandsetsArticle in journal (Other academic)
  • 12.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Z.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Body-effect-adaptive compact wideband LTE MIMO antenna array with quad elements for mobile terminals2013In: PIERS Proceedings, Stockholm, Sweden, Aug. 12{15, 2013, Electromagnetics Academy , 2013, p. 1858-1861Conference paper (Refereed)
    Abstract [en]

    A body-effect-adaptive compact wideband LTE MIMO antenna array with quad elements for mobile terminals is proposed in this paper. It can cover the bands of 750-960 and 1700-2700MHz with a low envelope correlation coefficient. Through different combinations two of the four elements can be utilized as dual element LTE MIMO antenna array to reduce three kinds of body effects (head and hand; single hand; dual hands) with the other two ports open. Some common rules about the body effects are introduced. The conclusions about the optimal chassis locations of LTE MIMO antenna elements to improve MIMO performance are also presented.

  • 13.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Aalborg University, Denmark.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Z.
    He, Sailing
    Investigation of Diagonal Antenna-Chassis Mode in Mobile Terminal LTE MIMO Antennas for Bandwidth Enhancement2015In: IEEE Antennas & Propagation Magazine, ISSN 1045-9243, E-ISSN 1558-4143, Vol. 57, no 2, p. 217-228, article id 7087389Article in journal (Refereed)
    Abstract [en]

    A diagonal antenna-chassis mode is investigated in long-term evolution multiple-input-multiple-output (LTE MIMO) antennas. The MIMO bandwidth is defined in this paper as the overlap range of the low-envelope correlation coefficient, high total efficiency, and -6-dB impedance matching bandwidths. Utilizing the diagonal mode analysis, the MIMO bandwidth of the collocated MIMO antennas is improved efficiently at the frequencies of lower than 960 MHz. This is realized through moving the three bandwidths to the same range without the degradation of impedance bandwidth and total efficiency. The physical mechanism of the mismatch of these three bandwidth ranges is also explained. Furthermore, the diagonal antenna-chassis mode is also studied for MIMO elements in the adjacent and diagonal corner locations. As a practical example, a wideband collocated LTE MIMO antenna is proposed and measured. It covers the bands of 740-960 and 1700-2700 MHz, where the total efficiencies are better than -3.4 and -1.8 dB, with <inf>ρe</inf> lower than 0.5 and 0.1, respectively. The measurements agree well with the simulations. Since the proposed method only needs to modify the excitation locations of the MIMO elements on the chassis, this method is valid for different types of symmetrical or asymmetrical MIMO antennas to improve the MIMO bandwidth.

  • 14.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    Bolin, Thomas
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Body Loss and MIMO Performance Investigation of Different Mobil Terminal LTE MIMO Antenna Typer with User EffectsArticle in journal (Other academic)
  • 15.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Adaptive Quad-Element Multi-Wideband Antenna Array for User-Effective LTE MIMO Mobile Terminals2013In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 61, no 8, p. 4275-4283Article in journal (Refereed)
    Abstract [en]

    An LTE MIMO antenna array, which is adaptive to the effects of the user's body, is presented for mobile terminals. The bands of 750-960 MHz and 1700-2700 MHz are covered with a good efficiency in free space. Three kinds of user effects are studied, namely, "SAM head and PDA hand," "PDA hand," and "dual hands." The array is formed by selecting the best two elements out of four, with the two ports and grounding points of the other two elements open. The user effects on MIMO channel capacity are reduced through the adaptive selection of two optimal antenna elements. The total efficiency, envelope correlation coefficient, and multiplexing efficiency are presented for the three kinds of user effects. In the lower band, the decreased correlation due to the optimal selection improves the multiplexing efficiency. The underlying physical mechanisms and some general rules are discussed. The specific absorption rate (SAR) in the "SAM head and PDA hand" case is studied. Experiments for the three kinds of user effects are also carried out.

  • 16.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Diagonal Antenna-Chassis Mode for Wideband LTE MIMO Antenna Arrays in Mobile Handsets (Invited)2013In: 2013 International Workshop on Antenna Technology, iWAT 2013, IEEE , 2013, p. 407-410Conference paper (Refereed)
    Abstract [en]

    In this paper, the diagonal antenna-chassis mode is introduced to reduce the correlation between MTMO antenna elements. With this mode a wideband LTE MIMO antenna array is proposed, which can cover an impedance bandwidth of 747-960 MHz with an envelope correlation coefficient (ECC) less than 0.5 and an total efficiency better than -3 dB.

  • 17.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    MIMO Reference Antennas for OTA Applications2013In: 2013 IEEE Antennas and Propagation Society International Symposium (APSURSI), IEEE , 2013, p. 2243-2244Conference paper (Refereed)
    Abstract [en]

    In this paper, MIMO reference antennas with different correlation coefficients are proposed for Over-The-Air (OTA) applications. The correlation can be simply controlled through a slot etched on a dual-feed PIFA with the similar total efficiency. Three kinds of situations are investigated with the proposed method: high correlation (HC), mid correlation (MC), and low correlation (LC). In order to verify the introduced idea, the measurements of correlations and efficiencies are carried out in a reverberation chamber. The simulation and measurement agree well with each other.

  • 18.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhu, Bangguo
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    MIMO reference antennas for OTA applications2013In: 2013 7th European Conference on Antennas and Propagation, EuCAP 2013, New York: IEEE , 2013, p. 2556-2557Conference paper (Refereed)
    Abstract [en]

    In this paper, MIMO reference antennas with different correlation coefficients are proposed for Over-The-Air (OTA) applications. The correlation can be simply controlled through a slot etched on a dual-feed PIFA with the similar total efficiency. Three kinds of situations are investigated with the proposed method: high correlation (HC), mid correlation (MC), and low correlation (LC). In order to verify the introduced idea, the measurements of correlations and efficiencies are carried out in a reverberation chamber. The simulation and measurement agree well with each other.

  • 19.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhu, Bangguo
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    MIMO Reference Antennas with Controllable Correlations and Total Efficiencies2014In: Progress In Electromagnetics Research, ISSN 1070-4698, E-ISSN 1559-8985, Vol. 145, p. 115-121Article in journal (Refereed)
    Abstract [en]

    MIMO reference antennas are proposed for over the air (OTA) measurement applications. The reference antennas could get rid of feeding cable interference and control envelope correlation coefficients (ECC) continuously by only changing the length of an etched slot on a dual-feed PIFA. If only the ECC is investigated, the MIMO reference antenna is optimized to have a small variation of total efficiency from 70% to 50% when the ECC increases from 0.1 to 0.88. The prototypes are fabricated and measured in a scattered field chamber (SFC). Measurements agree well with the simulations. If the MIMO performance is studied, the MIMO reference antenna is proposed to own a large variation of total efficiencies from 90% to 47% while the ECC increases from 0 to 0.98. The bandwidth of the proposed reference antennas depend on the size of the antennas. This method is valid for all the frequencies.

  • 20.
    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. 

  • 21.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Mobile Communications AB, Sweden.
    Bengtsson, E.
    Ying, Z.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Multiplexing efficiency of high order MIMO in mobile terminal in different propagation scenarios2016In: 2016 10th European Conference on Antennas and Propagation, EuCAP 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, article id 7481345Conference paper (Refereed)
    Abstract [en]

    The multiplexing efficiency of 4×4 higher order MIMO with different MIMO topologies under different propagation scenarios in a mobile terminal is presented in this study. The mean effective gain, correlation coefficient and multiplexing efficiency of different MIMO topologies are compared and the impact from the angular spread of the incoming wave is also studied. The results are instructive for the high order MIMO antenna design in mobile terminal.

  • 22.
    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.

  • 23.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. SONY Mobile Communications AB, Sweden.
    Helander, J.
    Ying, Z.
    Sjoberg, D.
    Gustafsson, M.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    MmWave phased array in mobile terminal for 5G mobile system with consideration of hand effect2015In: IEEE Vehicular Technology Conference, IEEE , 2015Conference paper (Refereed)
    Abstract [en]

    In this paper, the latest study of the millimeter wave (mmWave) phased array in mobile terminals for the 5G communication is presented. New parameters for evaluating the mmWave phased array in mobile terminals are introduced. Furthermore, the hand effect on the phased array in mobile terminal at 15 GHz is also investigated.

  • 24.
    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.

  • 25.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Z.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Antenna designs of smart watch for cellular communications by using metal belt2015In: 2015 9th European Conference on Antennas and Propagation, EuCAP 2015, IEEE conference proceedings, 2015Conference paper (Refereed)
    Abstract [en]

    In this paper, we present three cellular antenna designs for the smart watch application by using the metal watch belt. Our proposed antennas can cover cellular bands down to 700 MHz and up to 2.7GHz. Their performance in the free space and user cases are measured and discussed. The SAR evaluation guideline from FCC is also introduced and SAR measurement results are shown.

  • 26.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. SONY Mobile Communications AB, Sweden.
    Ying, Z.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Evaluation of combined TIS for high order MIMO system in mobile terminal2017In: 2017 11th European Conference on Antennas and Propagation, EUCAP 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 3684-3687, article id 7928570Conference paper (Refereed)
    Abstract [en]

    The maximum ratio combined total isotropic sensitivity (TIS) of high order MIMO system in a real phone prototype is presented in this paper. The value of combined TIS is estimated through antenna pattern combination and verified by experiments. The impact from the order of MIMO system, the propagation model and the user body effect are investigated.

  • 27.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Z.
    SONY Mobile Communications AB, Sweden.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Human exposure to mmWave phased array antennas in mobile terminal for 5G mobile system2015In: IEEE Vehicular Technology Conference, IEEE , 2015Conference paper (Refereed)
    Abstract [en]

    In this paper, results of the latest study regarding human exposure to the mmWave phase array in mobile terminal for 5G mobile communication are presented. FCC guideline has been reviewed and power density is used to evaluate the human exposure in the mmWave band. The purpose of the paper is to present the basic power density property of the mmWave phased array for terminal applications and the defect of the current standards of human exposure in the mmWave band. An IFA antenna phased array at 15GHz is simulated and the result shows the challenges of power density evaluation for this application.

  • 28.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    EMF Exposure Study Concerning mmWave Phased Array in Mobile Devices for 5G Communication2016In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 15, p. 1132-1135Article in journal (Refereed)
    Abstract [en]

    The electromagnetic field (EMF) exposure to millimeter-wave (mmWave) phased arrays in mobile devices for 5G communication is analyzed in this letter. Unlike the current cellular band, the EMF exposure in the mmWave band (10-200 GHz) is evaluated by the free-space power density instead of the specific absorption rate. However, current regulations have not been well defined for the mobile device application. In this letter, we present the power density property of phased arrays in mobile devices at 15 and 28 GHz. Uniform linear patch arrays are used, and different array configurations are compared. Suggestions for the power density evaluation are also provided.

  • 29.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES).
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES).
    Intrabody Communications Between Mobile Device and Wearable Device at 26 MHz2017In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 16, p. 549-552Article in journal (Refereed)
    Abstract [en]

    The application of using the capacitively coupled body area network (BAN) to build up the communication between a mobile phone and a wearable device is presented in this letter. The proposed system operates at 26 MHz, the capacitively coupled BAN channel is discussed, and electrode designs for wearable devices and smartphones are proposed. The transmission coefficient of the BAN channel is increased by 6.5 dB in the wearable device and 15 dB in the mobile phone with our optimized design of electrodes. Another 10 dB increment is also achieved by adding a parallel resonant circuit.

  • 30.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Sony Mobile Communication AB, Sweden.
    Zhang, S.
    Ying, Z.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Double ring antenna design for MIMO application in mobile terminals2015In: 2015 9th European Conference on Antennas and Propagation, EuCAP 2015, IEEE conference proceedings, 2015Conference paper (Refereed)
    Abstract [en]

    In this paper, We present a MIMO bezel antenna design composed by a seamless double metal ring structure. The MIMO antenna mainly operates in the loop mode and can cover the majority of globe cellular bands. Good efficiencies (>-4dB) and a low envelope correlation coefficient (<0.5) are achieved, which ensure a good MIMO performance of our proposed antenna. Moreover, our antenna also performance well in user cases as the loop mode and the seamless structure.

  • 31.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Sony Mobile Communications AB, Sweden .
    Zhang, Shuai
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Sony Mobile Communications AB, Sweden .
    Chiu, C. -Y
    Ying, Z.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Impact of size and decoupling element on some fundamental compact MIMO antennas2014In: 2014 International Workshop on Antenna Technology: Small Antennas, Novel EM Structures and Materials, and Applications, iWAT 2014, 2014, p. 136-139Conference paper (Refereed)
    Abstract [en]

    The effective bandwidth of fundamental MIMO antennas (ideal MIMO Dipole and ideal MIMO monopole) are studied in this paper. The S11 bandwidth, total efficiency bandwidth and envelope correlation coefficient bandwidth are shown, and effects from antenna sizes, matching and decoupling networks are analyzed. Furthermore, the effective bandwidth of MIMO antennas is defined in this paper as the overlap part of above three bandwidths; it can show a comprehensive performance of the MIMO system.

  • 32.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Sony Mobile Communications, Sweden .
    Zhang, Shuai
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Chiu, C. -Y
    Ying, Z.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    SAR study for smart watch applications2014In: IEEE Antennas and Propagation Society, AP-S International Symposium (Digest), IEEE conference proceedings, 2014, p. 1198-1199Conference paper (Refereed)
    Abstract [en]

    In this paper, we investigate the SAR performance of an IFA antenna for the smart watch application. The SAR performance is evaluated by both body shape phantoms and FCC standard flat phantoms. Differences of the SAR performance in different phantoms are compared and discussed.

  • 33.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhang, Shuai
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ishimiya, Katsunori
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Body-Insensitive Multimode MIMO Terminal Antenna of Double-Ring Structure2015In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 63, no 5, p. 1925-1936Article in journal (Refereed)
    Abstract [en]

    In this paper, we propose a novel multimode multi-input multi-output (MIMO) antenna system composed of a dual-element MIMO cellular antenna and dual-element MIMO Wi-Fi antenna for mobile terminal applications. The antenna system has a double-ring structure and can be integrated with the metal frame of mobile terminals. With the multimode excitation, the MIMO cellular antenna can operate at 830-900 MHz, 1700-2200 MHz, and 2400-2700 MHz, for 2G, 3G, and LTE bands, respectively. The MIMO Wi-Fi antenna can cover two Wi-Fi bands from 2.4 to 2.5 GHz and from 5.2 to 5.8 GHz. The effect of a user's body on the MIMO cellular antenna is investigated on CTIA standard phantoms and a real user. Since our antenna mainly operates in the loop mode, it has a much lower efficiency loss than conventional mobile antennas in both talking and data modes. Our theoretical analysis and experiments have shown that our design has low body loss and an attractive industrial design.

  • 34.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhang, Shuai
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Z.
    Bolin, T.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    SAR study of different MIMO antenna designs for LTE application in smart mobile handsets2013In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 61, no 6, p. 3270-3279Article in journal (Refereed)
    Abstract [en]

    This paper mainly focuses on the specific absorption rate (SAR) of the dual-element LTE MIMO antenna in mobile phones. Four designs of dual-element MIMO antenna (namely, dual semi-ground-free planar inverted-F antenna (PIFA), co-located antenna, dual OG PIFA in parallel position, and dual OG PIFA in orthogonal position) are studied under four typical LTE frequency points (0.75, 0.85, 1.9, and 2.1/2.6 GHz) when the ground plane length varies from 90 to 150 mm. The SAR, when dual elements operate simultaneously, is also studied through the SAR to PEAK location spacing ratio (SPLSR) according to the FCC standard. The simulations are carried out on both an SAM head phantom and a flat phantom by CST 2011, and measurements on the flat phantom are made with iSAR and DASY4 to verify the accuracy of our simulations.

  • 35.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhang, Shuai
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Z.
    Bolin, T.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    SAR study of different MIMO antenna designs for LTE application in smart mobile phones2012In: Antennas and Propagation Society International Symposium (APSURSI), 2012 IEEE, IEEE , 2012, p. 6348485-Conference paper (Refereed)
    Abstract [en]

    This paper reports a study of specific absorption rate (SAR) for LTE MIMO antennas in mobile phones, with special consideration to the effects of different chassis lengths and different types of MIMO antennas. Two designs of dual elements MIMO antenna are studied under two typical LTE and mobile phone frequency points. The simulations are carried out both for a specific anthropomorphic mannequin (SAM) head phantom and a flat phantom. The measurements on the flat phantom are carried out as well to verify our simulation results.

  • 36.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhang, Shuai
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    Bolin, Thomas
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Reduce The Hand-Effect Body Loss For Lte Mobile Antenna In Ctia Talking And Data Modes2013In: Progress In Electromagnetics Research, ISSN 1070-4698, E-ISSN 1559-8985, Vol. 137, p. 73-85Article in journal (Refereed)
    Abstract [en]

    The reduction in the radiation efficiency of an antenna in a mobile handset due to user's hand effects in the talking and data modes is studied. A parameter called "body loss" is defined to evaluate the degradation of the radiation efficiency. A C-fed on-ground (OG) PIFA antenna, which can cover two typical LTE bands of 0.75 GHz-0.96 GHz and 1.7 GHz-2.1 GHz, is used to study the property of the hand-effect body loss in two CITA test positions: the talking and data modes. Three different positions of the proposed antenna in the talking mode are compared, and the position with the antenna located on the bottom of the mobile handset and facing the head is recommended for minimal body loss. A modified design with a smaller antenna width is proposed to reduce further the hand-effect body loss in the talking and data modes.

  • 37.
    Zhao, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhang, Shuai
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    MIMO performance study of different antennas for LTE mobile phones in CTIA test mode2013In: 2013 7th European Conference on Antennas and Propagation (EuCAP), New York: IEEE , 2013, p. 727-731Conference paper (Refereed)
    Abstract [en]

    This paper reports a study of body loss for LTE MIMO antennas in mobile phones with the effects of different mobile phone lengths. Two designs of dual elements MIMO antenna (dual Semi PIFA and co-located antenna) are studied under two typical LTE and mobile phone frequency points (0.85GHz and 1.9 GHz) with three mobile phone lengths (110mm, 130mm and 150mm). And the performance of correlation and multiplex efficiency are also evaluated. The simulations are carried out on talking position in CTIA standard. In order to verify the simulation results, the measurements for the dual semi PIFA are carried out as well. The analysis for the results provides novel and useful information for the design of LTE MIMO antennas in mobile phones for body loss optimization.

  • 38. Zhou, F.
    et al.
    Liu, Q.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A dual-band loop MIMO antenna for smart watch applications2016In: 2016 Progress In Electromagnetics Research Symposium, PIERS 2016 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 1262-1266Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose a dualband loop MIMO antenna with Wi-Fi 2.4/5.2/5.8 GHz bands for smart watch applications. The antenna is constituted of a 25-mm long folded loop strip and an L-shape coupling strip. Two antenna elements are put at the adjacent side of the ground and are vertical to the system ground. With the coupling strip, the loop antenna can generate a quarter-wavelength resonant mode at about 2.45 GHz and a higher order mode cover 5.2 GHz and 5.8 GHz. The dimension of the system ground is 38mm × 38mm × 0.3mm and a 2mm gap between the antenna and the ground is set to alleviate the strong coupling between the antenna and the ground. The simulation results show the MIMO antenna system have good S11 and S12 performance across 2.4 GHz to 2.5 GHz and 5.2 GHz to 5.8 GHz. Further, as the antenna system is dedicated to be embedded in a smart watch, the body effect and the SAR are also investigated in the research.

1 - 38 of 38
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