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  • 1.
    Alayon Glazunov, Andres
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Expansion of the Kronecker and Keyhole Channels Into Spherical Vector Wave Modes2011In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 10, p. 1112-1115Article in journal (Refereed)
    Abstract [en]

    In this letter, we provide additional results on the expansion of wireless channels into spherical vector wave multipole modes. We specialize our results to multiple-input-multiple-output (MIMO) channels with Kronecker-product structure of the correlation matrix: 1) the Kronecker channel, and 2) the Keyhole channel. We show that the Kronecker or Keyhole structure of the multimode channel matrix implies the corresponding structure in the MIMO channel matrix. Moreover, we show that the separability of the joint probability distribution functions of the angle of arrival (AoA) and the angle of departure (AoD), i.e., the independence between the AoAs and the AoDs for co- and cross-polarized components results in a Kronecker-product structure of the full-correlation matrix of the multimode matrix for both the Kronecker and the Keyhole channels.

  • 2.
    Ebrahimpouri, Mahsa
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Ultrawideband Anisotropic Glide-Symmetric Metasurfaces2019In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 18, no 8, p. 1547-1551Article in journal (Refereed)
    Abstract [en]

    This letter presents a method to realize anisotropic two-dimensional designs with wideband operation. Glide symmetry has been proven to increase the bandwidth and equivalent refractive index of periodic structures. Here, two anisotropic glide-symmetric unit cells are proposed and characterized. Our simulated results prove that these unit cells follow the general behavior of periodic structures possessing glide symmetry. Moreover, we demonstrate that higher level of anisotropy can also be achieved by glide symmetry. Combining our proposed anisotropic glide-symmetric unit cell and transformation optics, a 30% compressed Luneburg lens is designed. The lens operates from 1 to 13 GHz.

  • 3.
    Frid, Henrik
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Closed-Form Relation between the Scan Angle and Feed Position for Extended Hemispherical Lenses based on Ray-Tracing2016In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 15, p. 1963-1966Article in journal (Refereed)
    Abstract [en]

    This letter presents a closed-form relation between the scan angle and feed position for extended hemispherical lenses. This relation is derived using ray tracing, and it is valid for both large and small scan angles, in excellent agreement with full-wave simulations. It is demonstrated that the relation is linear in the small-angle limit, and the effective focal length determining the scan angle is presented. It is also demonstrated that the scan angle only depends on the geometrical configuration, and that it is independent of the lens material. To demonstrate the applicability of this scan angle relation to the design of focal plane arrays (FPAs), we demonstrate that it can be used to determine the FPA spacing that results in -3-dB overlap between switched beams. A comparison with full-wave simulations of lenses with varying materials and FPA elements demonstrates a root-mean-square (rms) accuracy of 0.27 degrees for the scan angle estimation, and rms accuracy of 0.26 dB for the -3-dB overlap criterion between the central and adjacent beams. Finally, we present scaling rules, which show that the scan resolution is inversely proportional to the lens diameter, whereas the FPA spacing is independent of the total lens size.

  • 4. 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.

  • 5.
    Jonsson, B. Lars G.
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Kolitsidas, Christos I.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hussain, N.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Array Antenna Limitations2013In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 12, p. 1539-1542Article in journal (Refereed)
    Abstract [en]

    This letter defines a physical-bound-based array figure of merit for both single and multiband array antennas. It provides a measure to compare their performance with respect to return loss, bandwidth(s), thickness of the array over the ground plane, and scan range. The result is based on a sum-rule result of Rozanov-type for linear polarization. For single-band antennas, it extends an existing limit for a given fixed scan-angle to include the whole scan range of the array, as well as the unit-cell structure in the bound. The letter ends with an investigation of the array figure of merit for some wideband and/or wide-scan antennas with linear polarization. We find arrays with a figure of merit >0.6 that empirically defines high-performance antennas with respect to this measure.

  • 6. Li, Hui
    et al.
    Xiong, Jiang
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A Compact Planar MIMO Antenna System of Four Elements With Similar Radiation Characteristics and Isolation Structure2009In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 8, p. 1107-1110Article in journal (Refereed)
    Abstract [en]

    A compact planar multiple-input-multiple-output (MIMO) antenna system of four elements with similar radiation characteristics is proposed for the whole 2.4-GHz WLAN band. It consists of two proximity-coupled fed microstrip square ring patch antennas and two lambda/4 microstrip slot antennas of the same linear polarization. These two types of antennas are printed on different sides of the substrate to reduce mutual coupling. With a novel isolation structure etched on the ground plane of the FR4 substrate, high port isolation (below -25 dB) and good MIMO performance are achieved. The overall lateral size of the MIMO system is only 0.64 lambda X 0.48 lambda, and good impedance matching (S11 < 10 dB) is achieved across the operating band for all the antenna elements. Full spherical radiation patterns are measured for the MIMO system, showing similar radiation characteristics, and the gains are above 2.3 dB across the operating band.

  • 7. Liu, Qi
    et al.
    Yu, Yufeng
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Capacitively Loaded, Inductively Coupled Fed Loop Antenna With an Omnidirectional Radiation Pattern for UHF RFID Tags2013In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 12, p. 1161-1164Article in journal (Refereed)
    Abstract [en]

    A capacitively loaded, inductively coupled fed loop antenna with an omnidirectional radiation pattern for UHF radio frequency identification (RFID) tags is proposed. The inductively coupled feed structure is beneficial for conjugate impedance matching. The loaded capacitors in the radiating and feeding loops allow for easy control of the resonant frequency and the antenna reactance, respectively. The omnidirectional radiation pattern on the horizontal plane makes the proposed tag insensitive to be mounted on different target objects. With a small size of 43 x 43 mm(2), the measured maximum reading range of the prototype is 9.5 m with a total transmitted power of 4.0 W effective isotropic radiated power (EIRP).

  • 8.
    Malmström, Johan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering. Saab Surveillance, S-17588 Stockholm, Sweden.
    Derivation of Reaction Theorems for Scattered Fields2018In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 17, no 10, p. 1876-1880Article in journal (Refereed)
    Abstract [en]

    Two novel formulations of the reaction are derived. The formulations decompose the electromagnetic fields in scattered components based on the location of the sources of the scattered fields. It is shown that some of the scattering components do not contribute to the reaction. The novel formulations of the reaction are derived by excluding these noncontributing components from the classical reaction formulations. The correctness of one of the formulations is verified with a numerical example. It is observed from one of the novel formulations that the first-order scattered fields do not contribute to the reaction. This result legitimizes the approximation to neglect multiple scattering, which is a common assumption when using reaction theorems. The novel formulations are also important for a conceptual understanding of the reaction.

  • 9.
    Mattsson, Martin
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Kolitsidas, Christos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Dual-Band Dual-Polarized Full-Wave Rectenna Based on Differential Field Sampling2018In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 17, no 6, p. 956-959Article in journal (Refereed)
    Abstract [en]

    A dual-band rectenna for radio frequency (RF) energy harvesting is presented in this letter. The proposed antenna has two concentric square patches electrically connected with a small microstrip line connection. Four ports are located in the inner patch. The configuration of the ports enables a differential field sampling scheme and dual polarization. The antenna operates for the WiFi frequency bands of 2.4 and 5.5 GHz with 7.52 and 7.26 dBi gain, respectively, for each frequency. A full-wave Greinacher voltage doubler rectifier for each polarization has been employed for RF-to-dc conversion. The proposed novel topology utilizes the differential field sampling for each polarization and quadruples the overall output voltage by the rectification process. The differential output voltage source from the rectenna can directly act as a power source as typically electronics require differential source for their operation.

  • 10.
    Moteasselian, Alireza
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ellgardt, Anders
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A Helix Excited Circularly Polarized Hollow Cylindrical Dielectric Resonator Antenna2013In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 12, p. 535-538Article in journal (Refereed)
    Abstract [en]

    In this letter, we use a helix to excite two orthogonal HE11 delta modes in phase quadrature in a hollow cylindrical dielectric resonator antenna to generate circular polarization. As compared to our previous work, it is shown that replacing the cylindrical dielectric resonator antenna with a hollow cylindrical-shaped one leads to a significant enhancement in the 3-dB axial-ratio bandwidth. A design guideline is provided, and three design cases are presented. A prototype for one of the designs is fabricated and measured. Measured and simulated data are presented and discussed. It is shown that the 3-dB axial-ratio bandwidth increases as the wall thickness of the hollow cylindrical dielectric resonator decreases. Furthermore, a reduction in the wall thickness requires a longer helix exciter for similar performance.

  • 11.
    Osipov, Andrei
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Evaluation of the Electric Polarizability for Planar Frequency-Selective Arrays2018In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 17, no 7, p. 1158-1161Article in journal (Refereed)
    Abstract [en]

    This letter presents a method to evaluate the static electric polarizability of 2-D infinitely periodic metal patch arrays with dielectric substrate. Static polarizabilities are used in several design applications for periodic structures such as estimation of the bandwidth limitations for frequency-selective structures or prediction of the radiation properties for antenna arrays. The main features of the proposed method are its numerical efficiency and a deep insight into the physics of the fields interacting with the structure. We provide derivation and analysis of the method, and its verification against two another commercial solver-based approaches for various structure geometries. Additionally, we suggest the guidelines for applying the method to bandwidth optimization of frequency-selective structures and illustrate this with an example.

  • 12.
    Osipov, Andrei
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Q-factor and bandwidth of periodic antenna arrays over ground plane2020In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 19, no 1, p. 158-162Article in journal (Refereed)
    Abstract [en]

    In this paper, the Q-factor expression for periodic arrays over a ground plane is determined in terms of the electric current density within the array's unit cell. The expression accounts for the exact shape of the array element. The Q-factor formula includes integration only over a volume of an element in a unit cell, and can thus be efficiently implemented numerically. The examples show good agreement between the proposed Q-factor, the full-wave-calculated tuned fractional bandwidth, and the input-impedance-based formula by Yaghjian and Best (2005) for the array of tilted dipoles and the loops array.

  • 13.
    Osseiran, Afif
    et al.
    Ericsson Research, Ericsson AB, Stockholm, Sweden.
    Logothetis, Andrew
    Ericsson Research, Ericsson AB, Stockholm, Sweden.
    A Method for Designing Fixed Multi-Beam Antenna Arrays in WCDMA Systems2006In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 5, no 1, p. 41-44Article in journal (Refereed)
    Abstract [en]

    In this paper, Simulated Annealing is used for designing a fixed multi-beam antenna array (AA) in a multi-user radio WCDMA system. The method can be used dynamically in a real system and/or in a radio planning tool. The proposed method is applied on a linear array by designing the Antenna Element (AE) pattern, the number of fixed beams, the AE spacing, and the AA transmit weights. The proposed method leads to a substantial BS power reduction which can be used to increase the system capacity or data throughput in a WCDMA system.

  • 14. Pan, T.
    et al.
    Zhang, S.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. South China Normal University (SCNU), China.
    Compact RFID tag antenna with circular polarization and embedded feed network for metallic objects2014In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 13, p. 1271-1274, article id 6843861Article in journal (Refereed)
    Abstract [en]

    A low-profile radio frequency identification (RFID) tag antenna is proposed with a compact size of 45 × 45~mm2 and circular polarization (CP) for metallic surfaces. A star-shaped slot is etched onto the antenna for the CP and antenna size reduction. A terminal-grounded L-shaped feedline is embedded in the etched slot to efficiently excite the wideband CP mode, complexly match the tag-antenna impedance, and further reduce the antenna size. The embedded feed structure also helps achieve a relatively higher gain, resulting in a longer reading range. The proposed antenna can cover the impedance bandwidth of 60 MHz (from 880 to 940 MHz) as well as the 3-dB CP bandwidth of 12 MHz (from 905 to 917 MHz). Further results demonstrate that the proposed tag antenna provides a stable reading range when mounted on metal plates of various sizes.

  • 15.
    Quevedo-Teruel, Oscar
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ebrahimpouri, Mahsa
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Kehn, Malcolm Ng Mou
    Ultrawideband Metasurface Lenses Based on Off-Shifted Opposite Layers2016In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 15, p. 484-487Article in journal (Refereed)
    Abstract [en]

    Metasurfaces have demonstrated to be a low-cost solution for the development of directive antennas at high frequency. One of the opportunities of metasurfaces is the possibility to produce planar lenses. However, these lenses usually present a narrow band of operation. This limitation on bandwidth is more restrictive when the required range of refractive index is high. Here, we present a novel implementation of metasurfaces with low dispersion that can be employed for the design of ultrawide-band planar lenses. The implementation consists of two mirrored metasurfaces that are displaced exactly a half unit cell. This displacement produces two effects: It increases the equivalent refractive index of the fundamental mode and flattens its frequency dependence.

  • 16.
    Quevedo-Teruel, Oscar
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Miao, Jingwei
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Mattsson, Martin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Algaba-Brazalez, A.
    Johansson, M.
    Manholm, L.
    Glide-Symmetric Fully Metallic Luneburg Lens for 5G Communications at Ka-Band2018In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 17, no 9, p. 1588-1592, article id 8410981Article in journal (Refereed)
    Abstract [en]

    Here, we propose a fully metallic implementation of a Luneburg lens operating at Ka-band with potential use for 5G communications. The lens is implemented with a parallel plate that is loaded with glide-symmetric holes. These holes are employed to produce the required equivalent refractive index profile of a Lune-burg lens. Glide symmetry and inner metallic pins are employed to increase the equivalent refractive index. The lens is fed with rectangular waveguides designed to match the height of the parallel plate, and it is ended with a flare to minimize the reflections. 

  • 17.
    Shao, Botao
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Amin, Yasar
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Chen, Qiang
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Liu, Ran
    Zheng, Li-Rong
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Directly Printed Packaging-Paper-Based Chipless RFID Tag With Coplanar LC Resonator2013In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 12, p. 325-328Article in journal (Refereed)
    Abstract [en]

    This letter presents the design, simulation, fabrication, and characterization of an LC-resonator-based chipless RFID tag. The ID-generating circuit is designed based on a reconfigurable LC resonance circuit. Phase position modulation (PPM) coding is used for the enhancement of the coding capacity. The tag has been realized on packaging paper using all printing technique. In fabrication, overprinting process has been investigated as an effective pathway for the improvement of the conductivities. The tag with 4.25-bit coding capacity has been examined using a sweeping frequency signal transmitted from a vector network analyzer, and experimental results confirm the feasibility of the proposed chipless tag. With further optimizations, the tag can be used in the item-level tracking and identification applications, especially for the management of paper tickets and banknotes.

  • 18. Xiong, J.
    et al.
    Li, H.
    Jin, Y.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Modified TM020 Mode of a Rectangular Patch Antenna Partially Loaded With Metamaterial for Dual-Band Applications2009In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 8, p. 1006-1009Article in journal (Refereed)
    Abstract [en]

    In this letter, the TM020 mode of a rectangular patch antenna is modified by partially loading a mu-negative (MNG) or double-negative (DNG) metamaterial block. With proper constitutive parameters and filling ratio, the electric fields at two radiating edges of the patch can be out of phase, and a broadside radiation pattern is achieved. A novel dual-band rectangular patch antenna loaded with a pair of conventional double-positive (DPS) and MNG metamaterial blocks is proposed as an application example of the modified TM020 mode. Good impedance matching and similar patterns with broadside radiation are achieved simultaneously at both operating frequencies with a single-layer single-patch fed by a single coaxial line. Simulation shows that the modified TM020 mode gives an efficient radiator with sufficient gain and very low level of cross polarization. Partial loading of a DNG metamaterial block is also discussed for some special dual-band applications.

  • 19. Xiong, Jiang
    et al.
    Zhao, Mingyu
    Li, Hui
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    Wang, Bingzhong
    Collocated Electric and Magnetic Dipoles With Extremely Low Correlation as a Reference Antenna for Polarization Diversity MIMO Applications2012In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 11, p. 423-426Article in journal (Refereed)
    Abstract [en]

    In this letter, a magnetic dipole (M-dipole) and an electric dipole (E-dipole) are designed to form a collocated polarization-diversity-based dual-antenna system. The M-dipole is a modified shielded loop with multiple feed, and the E-dipole is a traditional lambda/2 dipole. Measured results show that both radiators have ideal impedance matching and port isolation and identical omnidirectional pattern with perfect orthogonal polarization at 860 MHz. The upper bound of the envelope correlation coefficient rho(emax), with the measured antenna efficiency taken into account, is only 0.018, and it is the lowest value when compared to some previous publications. Excellent effective diversity gain and channel capacity are also achieved at the operating frequency. The proposed dual-antenna system can mainly be used as a reference antenna for evaluating the performance of future collocated polarization-diversity-based multiple-input-multiple-output (MIMO) antennas.

  • 20. Yu, Y.
    et al.
    Shen, Z.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Compact omnidirectional antenna of circular polarization2012In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 11, p. 1466-1469Article in journal (Refereed)
    Abstract [en]

    A compact omnidirectional antenna of circular polarization (CP) is presented for 2.4-GHz WLAN access-point applications. The antenna consists of four bended monopoles, which are simultaneously excited through an associated feeding network. The radiated horizontal and vertical field components are derived based on an analytical model, and the 90° phase difference between them is shown to be naturally guaranteed. With a size of 0.22λ0× 0.22λ0× 0.076λ0 , the antenna exhibits a bandwidth (S11-10-dB and AR≤ 3-dB) of 3.56% and a left-handed CP average gain of 1.39 dB in the azimuth plane at 2.44 GHz.

  • 21. Yu, Yufeng
    et al.
    Xiong, Jiang
    Li, Hui
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    An Electrically Small Frequency Reconfigurable Antenna With a Wide Tuning Range2011In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 10, p. 103-106Article in journal (Refereed)
    Abstract [en]

    An electrically small frequency-reconfigurable antenna with a very wide tuning band is proposed. Three varactor diodes are used to achieve the tunable capacitance. With a modified feeding structure, the measured tuning range of the fabricated antenna reaches from 457.5 to 894.5 MHz, and the tuning band enhancement is also explained through an equivalent circuit analysis.

  • 22.
    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.

  • 23.
    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.

  • 24.
    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.

  • 25.
    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.

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