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  • 1.
    Liu, Qi
    et al.
    Zhejiang University, China.
    Zhang, Shuai
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Compact printed two dipole array antenna with a high front-back ratio for ultra-high-frequency radio-frequency identification handheld reader applications2015In: IET Microwaves, Antennas & Propagation, ISSN 1751-8725, E-ISSN 1751-8733, Vol. 9, no 1, p. 73-78Article in journal (Refereed)
    Abstract [en]

    A printed two-dipole array antenna with a high front-back ratio is proposed for ultra-high-frequency (UHF) radio-frequency identification handheld readers. The proposed antenna is a parasitic dual-element array with the ends of both elements folded back towards each other for additional coupling. The antenna features a compact size of 89 mm x 87 mm and works properly with satisfactory gain and total efficiency in the wide UHF band of 860-960 MHz. Furthermore, the front-to-back ratio of 15-26.8 dB, the peak gain of 3.7-4.4 dBi and the total efficiency of more than 80% in the Federal Communication Commission (FCC) band make the proposed antenna attain high performance in the FCC band.

  • 2. Pan, T.
    et al.
    Zhang, Shuai
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Z.
    Liu, H.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. South China Normal University, China .
    Compact circularly polarized RFID tag antenna with an embedded U-shaped feedline for metallic surfaces2014In: Progress in Electromagnetics Research Symposium, 2014, p. 1567-1571Conference paper (Refereed)
    Abstract [en]

    A passive radio frequency identification (RFID) tag antenna with circular polarization (CP) radiation is proposed to operate at 902-928MHz and mount on metallic surfaces. A U-shaped terminal short-circuited feedline welded to a tag-chip is embedded in a rectangular slot to achieve a coupled feeding and a good impedance matching. By employing two truncated corners and two L-shaped slots with unequal length on the patch, a good left-hand circular polarization (LHCP) and compact size are obtained. The measured impedance bandwidth of the antenna is 85MHz (875-960 MHz), while the simulated 3-dB CP bandwidth is 6MHz (912-918 MHz). The proposed tag antenna shows reasonable read ranges when mounted on the metal plate in the following experiment.

  • 3.
    Sun, Fei
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhang, Shuai
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A General Method for Designing a Radome to Enhance the Scanning Angle of a Phased Array Antenna2014In: Progress In Electromagnetics Research, ISSN 1070-4698, E-ISSN 1559-8985, Vol. 145, p. 203-212Article in journal (Refereed)
    Abstract [en]

    We propose a general method to design an arbitrarily shaped radome which can extend the scanning angle of a phased array antenna through finite embedded transformation (FET). The main advantage of our method is that the relationship between the incident angle and steered output angle of the radome can be designed in advance (e.g., a linear relation can be achieved). Unlike a traditional FET, which is often applied onto a slab region, we first apply FET onto an arbitrarily shaped region to bestow the desired radome with an arbitrary shape. Two specific examples have been given to demonstrate our method. Numerical simulations show good performance of our radome.

  • 4.
    Zhang, Shuai
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Investigating and Enhancing Performance of Multiple Antenna Systems in Compact MIMO/Diversity Terminals2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Today, owners of small communicating device are interested in transmitting or receiving various multimedia data. By increasing the number of antennas at the transmitter and/or the receiver side of the wireless link, the diversity/Multiple-Input Multiple-Output (MIMO) techniques can increase wireless channel capacity without the need for additional power or spectrum in rich scattering environments. However, due to the limited space of small mobile devices, the correlation coefficients between MIMO antenna elements are very high and the total efficiencies of MIMO elements degrade severely. Furthermore, the human body causes high losses on electromagnetic wave. During the applications, the presence of users may result in the significant reduction of the antenna total efficiencies and highly affects the correlations of MIMO antenna systems. The aims of this thesis are to investigate and enhance the MIMO/diversity performance of multiple antenna systems in the free space and the presence of users.

    The background and theory of multiple antenna systems are introduced briefly first. Several figures of merits are provided and discussed to evaluate the multiple antenna systems. The decoupling techniques are investigated in the multiple antenna systems operating at the higher frequencies (above 1.7 GHz) and with high radiation efficiency. The single, dual and wide band isolation enhancements are realized through the half-wavelength decoupling slot, quarter-wavelength decoupling slot with T-shaped impedance transformer, tree-like parasitic element with multiple resonances, as well as the different polarizations and radiation patterns of multiple antennas.

    In the lower bands (lower than 960 MHz), due to the low radiation efficiency and strong chassis mode, the work mainly focused on how to directly reduce the correlations and enlarge the total efficiency. A new mode of mutual scattering mode is introduced. By increasing the Q factors, the radiation patterns of multiple antennas are separated automatically to reduce the correlations. With the inter-element distance larger than a certain distance, a higher Q factor also improved the total efficiency apart from the low correlation. A wideband LTE MIMO antenna with multiple resonances is proposed in mobile terminals. The high Q factors required for the low correlation and high efficiencies in mutual scattering mode is reduced with another mode of diagonal antenna-chassis mode. Hence, the bandwidth of wideband LTE MIMO antenna with multiple resonances mentioned above can be further enlarged while maintaining the good MIMO/diversity performance.

    The user effects are studied in different MIMO antenna types, chassis lengths, frequencies, port phases and operating modes. Utilizing these usefully information, an adaptive quad-element MAS has been proposed to reduce the user effects and the some geranial rules not limited to the designed MAS have also been given.

  • 5.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Alayón Glazunov, Andrés
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Reduction of the envelope correlation coefficient with improved total efficiency for mobile LTE MIMO antenna arrays: Mutual scattering mode2013In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 61, no 6, p. 3280-3291Article in journal (Refereed)
    Abstract [en]

    A mutual scattering mode is introduced in this paper. Utilizing this mode, the correlation of a lossy long-term evolution (LTE) multiple-input and multiple-output (MIMO) antenna array can be reduced efficiently, even down to zero, by increasing the Q factors of the MIMO antenna elements. In practice, the Q factors can be straight forwardly tuned through different input impedance matching. The zero correlation occurs at a Q factor higher than that resulting from the conjugate input impedance matching. On one hand, if the inter-element distance is larger than a certain distance (what we denominate as the Critical Distance), the total efficiency can also be improved in addition to reducing the correlation. On the other hand, when the inter-element distance is less than the critical distance, a reference MIMO antenna with high correlation and high total efficiency is obtained. This antenna can well be proposed for over-the-air (OTA) measurement applications. The introduced scattering mode is investigated for dual monopoles on a large lossy ground plane and for various mobile terminal MIMO antenna designs. A wideband MIMO antenna, with multiple resonances, covering the band 746-870 MHz is proposed with the envelope correlation coefficient and total efficiency less than 0.5 and higher than 50% (-3 dB), respectively. Measurements and simulations agree well for all the fabricated prototypes. The envelope correlations and the multiplexing efficiencies of the prototypes are also investigated in propagation channels with Gaussian distributed angle of arrivals.

  • 6.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Glazunov, Andrés Alayon
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Reduction of the Envelope Correlation Chofficient with Improved Total Efficiency for Mobile LTE MIMO Antennas Arroys: Mutual Scattering ModeArticle in journal (Other academic)
  • 7.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Khan, Salman Naeem
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Reducing Mutual Coupling for an Extremely Closely-Packed Tunable Dual-Element PIFA Array Through a Resonant Slot Antenna Formed In-Between2010In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 58, no 8, p. 2771-2776Article in journal (Refereed)
    Abstract [en]

    An efficient mutual coupling reduction method is introduced for an extremely closely packed tunable dual-element planar inverted-F antenna (PIFA) array. High isolation can be achieved through a lambda(0)/2 folded slot antenna formed by a slot on the ground plane and the neighboring edges of the two PIFAs. Direct coupling is blocked by the slot antenna through radiating the coupling power into free space. A measured isolation of more than 36.5 dB can be achieved between the two parallel individual-element PIFAs operating at 2.4 GHz WLAN band with an inter-PIFA spacing of less than 0.063 lambda(0) (center to center) or 0.0147 lambda(0) (edge to edge). Since there is only a narrow slot antenna formed between the PIFAs in the present method, the distance can be further reduced to less than 0.0016 lambda(0) (edge to edge) with the maximal isolation of better than 40 dB. Both measured and simulation results show the effectiveness of the present mutual coupling reduction method.

  • 8.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Lau, B. K.
    Sunesson, A.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Compact UWB MIMO antenna for USB dongles with angle and polarization diversity2012In: IEEE Antennas and Propagation Society, AP-S International Symposium (Digest), 2012, p. 778-781Conference paper (Refereed)
    Abstract [en]

    A compact dual-element antenna suitable for ultrawideband (UWB) MIMO operation is proposed in this work. The size of the antenna is 25 mm by 40 mm and it covers the lower UWB band of 3.15-5.15 GHz. Apart from the inherent wideband isolation obtained through the different angle and polarization characteristics in the radiation patterns of the individual elements, the gap between the two antenna elements is also utilized to enhance both the isolation and impedance bandwidths. Simulation and experimental results reveal that, within the band of interest, the achieved isolation is over 20 dB and the envelope correlation of the radiation patterns is below 0.1.

  • 9.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Lau, Buon Kiong
    Lund University.
    Sunesson, Anders
    Lund University.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Closely Located Dual PIFAs with T-Slot Induced High Isolation for MIMO Terminals2011In: 2011 IEEE INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION (APSURSI), 2011, p. 2205-2207Conference paper (Refereed)
    Abstract [en]

    This paper presents an efficient technique to enhance the isolation between two closely spaced PIFAs for MIMO mobile terminals. The proposed decoupling method is based on a T-shape slot impedance transformer and it enables an inter-PIFA spacing of 1 mm to be achieved. The 10 dB impedance bandwidth and 20 dB isolation bandwidth cover the 2.4 GHz WLAN band (2.4-2.48 GHz), with a maximum isolation of 44 dB. The efficiency, gain, radiation patterns of the two-PIFA prototype are also verified in measurements.

  • 10.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Lau, Buon Kiong
    Sunesson, Anders
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Closely-Packed UWB MIMO/Diversity Antenna With Different Patterns and Polarizations for USB Dongle Applications2012In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 60, no 9, p. 4372-4380Article in journal (Refereed)
    Abstract [en]

    A closely-packed ultrawideband (UWB) multiple-input multiple-output (MIMO)/diversity antenna (of two elements) with a size of 25 mm by 40 mm is proposed for USB dongle applications. Wideband isolation can be achieved through the different patterns and polarizations of the two antenna elements. Moreover, the slot that is formed between the monopole and the ground plane of the half slot antenna is conveniently used to further enhance the isolation at the lower frequencies and to provide an additional resonance at one antenna element in order to increase its bandwidth. The underlying mechanisms of the antenna's wide impedance bandwidth and low mutual coupling are analyzed in detail. Based on the measurement results, the proposed antenna can cover the lower UWB band of 3.1-5.15 GHz, and within the required band, the isolation exceeds 26 dB. The gains and total efficiencies of the two antenna elements are also measured. Furthermore, a chassis mode can be excited when a physical connection is required between the ground planes of the two antenna elements. Without affecting the performance of the half slot element, the monopole can now cover the band of 1.78-3 GHz, apart from the UWB band. The proposed antenna structure is found to provide good MIMO/diversity performance, with very low envelope correlation of less than 0.1 across the UWB band.

  • 11.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Lau, Buon Kiong
    Tan, Yi
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Mutual Coupling Reduction of Two PIFAs With a T-Shape Slot Impedance Transformer for MIMO Mobile Terminals2012In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 60, no 3, p. 1521-1531Article in journal (Refereed)
    Abstract [en]

    An efficient technique is introduced to reduce mutual coupling between two closely spaced PIFAs for MIMO mobile terminals. The proposed mutual coupling reduction method is based on a T-shape slot impedance transformer and can be applied to both single-band and dual-band PIFAs. For the proposed single-band dual PIFAs, the 10 dB impedance bandwidth covers the 2.4 GHz WLAN band (2.4-2.48 GHz), and within the WLAN band an isolation of over 20 dB is achieved. Moreover, the dual-band version covers both the WLAN band and the WiMAX band of 3.4-3.6 GHz, with isolations of over 19.2 dB and 22.8 dB, respectively. The efficiency, gain and radiation patterns of the two-PIFA prototypes are verified in measurements. Due to very low pattern correlation and very good matching and isolation characteristics, the capacity performances are mainly limited by radiation efficiency. The single-band and dual-band PIFAs are also studied with respect to their locations on the ground plane. An eight-fold increase in the bandwidth of one PIFA is achieved, when the single-band PIFAs are positioned at one corner of the ground plane, with the bandwidth of the other PIFA and the good isolation unchanged.

  • 12.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Z.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Mutual scattering mode for LTE MIMO antennas and its application to correlation reduction (invited)2012In: Antennas and Propagation (APCAP), 2012 IEEE Asia-Pacific Conference on, IEEE , 2012, p. 13-14Conference paper (Refereed)
    Abstract [en]

    A - mutual scattering mode -is introduced in this paper as a novel method to reduce the correlation for the LTE MIMO antenna arrays. This mode is mainly based on the increase of the Q factor for the closely-positioned MIMO antenna elements. With the increased Q factor, each element becomes a scatter for the other elements. Consequently, without adding any structure in the MIMO system, the radiation patterns will be separated to achieve a low correlation (even close to zero) in LTE 700 MHz bands. In practice, this high Q factor is realized through better impedance matching, which makes this mode quite easy to excite. When the effective MIMO element distance is larger than a certain value, better matching (higher Q factor) can not only reduce the correlation but also improve the efficiency (even though the mutual coupling becomes stronger).

  • 13.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Diagonal Chassis Mode for Mobile Handset LTE MIMO Antennas and Its Application to Correlation Reduction2012In: 2012 IEEE International Workshop On Electromagnetics: Applications And Student Innovation Competition (IWEM) / [ed] Tang, X; Xiao, S, IEEE , 2012, p. 3022-Conference paper (Refereed)
    Abstract [en]

    A new kind of chassis mode, namely, Diagonal Chassis Mode, is introduced in this paper. It can be easily excited for PIFAs by selecting a proper shorting point on the ground plane. Through this mode the correlation coefficient between MIMO PIFAs operating at LTE 700 MHz bands can be reduced effectively with the improvement of total efficiency and impedance bandwidth.

  • 14.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    Xiong, Jiang
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ultrawideband MIMO/Diversity Antennas With a Tree-Like Structure to Enhance Wideband Isolation2009In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 8, p. 1279-1282Article in journal (Refereed)
    Abstract [en]

    A compact printed ultrawideband (UWB) multiple-input-multiple- output (MIMO)/diversity antenna system (of two elements) with a size of 35 40 mm operating at a frequency range of 3.1-10.6 GHz is proposed. The wideband isolation can be achieved through a tree-like structure on the ground plane. The effectiveness of the tree-like structure is analyzed. Measured S-parameters show that the isolation is better than 16 dB (20 dB in most of the band) across the UWB of 3.1-10.6 GHz. The radiation patterns, gain, and envelope correlation coefficient are also measured. The proposed antenna is suitable for some portable MIMO/diversity applications.

  • 15.
    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)
  • 16.
    Zhang, Shuai
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Printed MIMO antenna system of four closely-spaced elements with large bandwidth and high isolation2010In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 46, no 15, p. 1052-1053Article in journal (Refereed)
    Abstract [en]

    A compact wideband printed MIMO antenna system (of four elements) with high isolation is presented. The proposed MIMO antenna system with an overall lateral size of only 0.43 lambda x 0.43 lambda can offer 22.8% bandwidth (1.63-2.05 GHz) and isolation of better than 24 dB. The measured gain is larger than 2.72 dBi over the whole band, and the calculated envelope correlation coefficient is better than 0.01. The radiation patterns and MIMO channel capacity are also measured.

  • 17.
    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.

  • 18.
    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.

  • 19.
    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)
  • 20.
    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.

  • 21.
    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.

  • 22.
    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.

  • 23.
    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.

  • 24.
    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.

  • 25. Zhao, K.
    et al.
    Zhang, Shuai
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    ENHANCE THE BANDWIDTH OF A ROTATED RHOMBUS SLOT ANTENNA WITH MULIPLE PARASITIC ELEMENTS2010In: Journal Electromagnetic Waves and Applications, ISSN 0920-5071, E-ISSN 1569-3937, Vol. 24, no 14-15, p. 2087-2094Article in journal (Refereed)
    Abstract [en]

    The bandwidth of a printed antenna with a rotated rhombus slot is enhanced further by introducing 7 parasitic stripes, one of which is embedded on an edge of the rhombus slot downside while the others are on the upside. The mechanism of the wideband antenna is explained. The measured results indicate a large impedance bandwidth of 122.6% (1.59GHz-6.63 GHz) for VSWR < 2. The radiation patterns are also measured and relatively stable throughout the whole operating band.

  • 26.
    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.

  • 27.
    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.

  • 28.
    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.

  • 29.
    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.

  • 30.
    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.

  • 31.
    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.

  • 32.
    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.

1 - 32 of 32
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