Shi-Wei Qu

Tohoku University, Sendai-shi, Miyagi-ken, Japan

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Publications (36)51.57 Total impact

  • Xue Bai, Shi-Wei Qu, Huan Yi
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    ABSTRACT: Spoof planar plasmonic waveguides (SPPWs) show potential applications in many microwave and terahertz systems, e.g. imaging, communication and sensing, due to their capability of highly confining spoof surface plasmon polaritons (SPPs) and relatively low propagation loss. Meanwhile, efficient electromagnetic emission from the SPPWs is one of the dominant factors in the practical applications. In this article, we demonstrate a beam-scanning circularly polarized (CP) antenna based on the SPPW of blind-hole array, which can efficiently convert spoof SPPs propagating in the SPPW into free-space emissions. Several centre-inclined rectangular patches are adopted to achieve the CP emission. The antenna array was designed and fabricated in the microwave frequency band, and the measured results validate the good emission performance of the proposed array, e.g. high gain and wide-scan angle. Finally, the proposed idea can be further extended into the terahertz frequency band.
    Journal of Physics D Applied Physics 07/2014; 47(32):325101. · 2.53 Impact Factor
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    ABSTRACT: This paper presents two kinds of novel elements to design single-layer dual-band reflectarray, with identical polarization in two closely separated bands. Several degrees of freedom of the proposed elements are tuned to match the desired phase compensations at two center frequencies simultaneously. It is noted that the dual-band characteristics are realized by a single integrated element rather than conventional dual-band elements with independent tunable components corresponding to two center frequencies. A 10 × 10-element offset-fed reflectarray operating at 9 and 13.5 GHz, with a ratio of the center frequencies 1.5, is designed and fabricated to validate the performance of the element, and the measured results show reasonable agreements with simulations. Due to the incompleteness of reflection phase distribution at the two center frequencies of the presented element, a complementary element with four resonances is introduced. Then, a 20 × 20-element reflectarray composed of both kinds of elements is also designed, and the measured results demonstrate a good availability of the proposed elements.
    IEEE Transactions on Antennas and Propagation 01/2014; 62(1):199-205. · 2.33 Impact Factor
  • Huan Yi, Shi-Wei Qu, Xue Bai
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    ABSTRACT: This letter presents an efficient and simple way to excite a microstrip patch antenna array in K-band. This array is formed by a spoof planar plasmonic waveguide for excitation and several circular patches for radiation. The optimized proposed 2 × 4 patch array, operating in 18.1 ~ 19.4 GHz, features an average gain of 15.2 dBi with a maximum of 16.5 dBi at 18.2 GHz. An experiment was performed, and the measured results prove validity of the design. This method opens up a new kind of feeding method for patch antenna array, which can be broadly engineered in millimeter-waves (MMW) region even to terahertz (THz) region.
    IEEE Antennas and Wireless Propagation Letters 01/2014; 13:1227-1230. · 1.67 Impact Factor
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    ABSTRACT: Effective downhole-to-surface transmission of the logging signals is one of the critical techniques for logging while drilling (LWD). This letter aims to evaluate an advanced scheme of signal transmission for the LWD proposed by Novatek, with an emphasis on the electromagnetic (EM) coupling between two adjacent pipes and the impedance matching between the coupler and the coaxial cables imbedded in drilling pipes. The numerical modeling of the EM coupling structure has been made by first using the full-wave simulation tool, and then the influence of the parameters of the coupler on the coupling coefficient has been discussed based on circuit simulation software. The optimization of the critical parameters has been made based on the given analysis. It has been found from the analysis that the air gap between the upper and the lower ferrite cores in the coupler is a key factor with remarkable influences on the impedance matching and the coupling coefficient.
    IEEE Geoscience and Remote Sensing Letters 09/2013; 10(5):1001-1005. · 1.82 Impact Factor
  • Shi-Wei Qu, Kung Bo Ng, Chi Hou Chan
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    ABSTRACT: A broadband millimeter-wave short backfire antenna (SBA), excited by a bowtie dipole and fed by an E-band rectangular waveguide, is presented in this paper. Its subreflector is replaced by two simple strips printed on the opposite sides of the same supporting substrate of the bowtie exciter for ease and accuracy of fabrication. For reference of practical designs, detailed parametric studies are performed in this paper. Measurements and simulations show that the proposed antenna can feature an improved operating bandwidth and broadside gain compared to the previously reported conventional SBAs. The measured impedance bandwidth for SWR ≤2 is 57%, from 55.7 to 100 GHz, in which the measured broadside gain is from 13.8 to 18.5 dBi with the peak gain at 85 GHz. Finally, high illumination efficiency of the bowtie exciter is highlighted by comparisons with a straight dipole excited SBA.
    IEEE Transactions on Antennas and Propagation 04/2013; 61(4):1697-1703. · 2.33 Impact Factor
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    ABSTRACT: A novel single-layer reflectarray element with an I-shaped dipole encompassed by a circular ring, showing smooth phase-frequency response, is proposed in this letter. Based on this element, an optimization method is adopted to match the desired phase delays at two edge frequencies so as to get fixed phase difference between two adjacent elements in the optimized band. A low-profile X-band 6$,times,$10-element reflectarray with a scattering angle of 30$^{circ}$ for normal incidence of plane waves is designed and fabricated. Simulations and measurements show that a bandwidth of 22.3% for 3 dB directivity dropping and 15.2% for ${-}$10 dB sidelobe level (SLL) can be achieved.
    IEEE Antennas and Wireless Propagation Letters 01/2013; · 1.67 Impact Factor
  • Xue Bai, Shi-Wei Qu, Kung Bo Ng
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    ABSTRACT: A novel millimeter-wave antenna for circularly polarized (CP) radiation is presented. The proposed antenna is composed of a patch dipole and a slot dipole, and it is realized by a plated through-hole printed technique on a microwave substrate. Measurements show that the antenna can present a bandwidth from 56.2 to 65 GHz for a reflection coefficient S11 ≤ -10 dB as well as for an axial ratio (AR) ≤ 3 dB, and the 10.03-dBi average gain is achieved. This design yields good directional radiation patterns. Studies on several critical parameters are performed for practical designs.
    IEEE Antennas and Wireless Propagation Letters 01/2013; 12:1355-1358. · 1.67 Impact Factor
  • Huan Yi, Shi-Wei Qu
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    ABSTRACT: In this letter, a dual-band polarization-dependent electromagnetic band-gap (PDEBG) surface is designed as a reflector of a dual-band dipole antenna to realize dual-band circular polarization. Experimental and numerical results verify the concept of the low-profile dual-band circularly polarized antenna. The antenna features 10-dB return-loss bandwidths of 13.4% and 3.2% and 3-dB axial-ratio bandwidths of 2.4% and 3.5% in low and high frequency bands, respectively. The proposed antenna can present the same or different circular polarization in two bands based on different designs of the PDEBG.
    IEEE Antennas and Wireless Propagation Letters 01/2013; 12:1149-1152. · 1.67 Impact Factor
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    Shi-Wei Qu, Zai-Ping Nie
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    ABSTRACT: Future plasmonic integrated circuits with the capability of extremely high-speed data processing at optical frequencies will be dominated by the efficient optical emission (excitation) from (of) plasmonic waveguides. Towards this goal, plasmonic nanoantennas, currently a hot topic in the field of plasmonics, have potential to bridge the mismatch between the wave vector of free-space photonics and that of the guided plasmonics. To manipulate light at will, plasmonic nanoantenna arrays will definitely be more efficient than isolated nanoantennas. In this article, the concepts of microwave antenna arrays are applied to efficiently convert plasmonic waves in the plasmonic waveguides into free-space optical waves or vice versa. The proposed plasmonic nanoantenna array, with nanopatch antennas and a coupled wedge plasmon waveguide, can also act as an efficient spectrometer to project different wavelengths into different directions, or as a spatial filter to absorb a specific wavelength at a specified incident angle.
    Scientific Reports 01/2013; 3:3172. · 5.08 Impact Factor
  • Shi-Wei Qu, Kung Bo Ng
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    ABSTRACT: A broadband millimeter-wave cavity-backed antenna, excited by a rounded bowtie dipole, is reported in this letter. To improve the radiation patterns and the broadside gains, its aperture is optimized by cutting the sections with higher-order modes at lower frequencies away from a large aperture, forming a specific open cavity structure. Simulations show that the antenna can present an impedance bandwidth from 28 to over 50 GHz for ${\rm SWR} \leq 2$, and a bandwidth from 28 to 49 GHz for ${-}$ 10-dB sidelobe level. Measurements agree reasonably well with simulations. Comparisons between the antennas with and without the improved aperture in terms of electric field distribution and radiation patterns clearly show performance enhancement.
    IEEE Antennas and Wireless Propagation Letters 01/2012; 11:697-700. · 1.67 Impact Factor
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    ABSTRACT: This letter presents a reflectarray antenna composed of a combination of concentric open rings and an I-shaped dipole on a conductor-backed substrate. Two classes of elements with different variable dimensional parameters are introduced to realize linear phase-frequency characteristic in a wide frequency band and a phase range of over 360° . It is worth noting that the wideband performance is figured by the proposed reflectarray with a low profile of 0.065λ0 ( λ0 is the free-space wavelength at the center frequency), rather than thick substrate employed in common wideband designs. A prototype is fabricated and measured to verify the availability of the elements, and the measured results show good agreement with simulations.
    IEEE Antennas and Wireless Propagation Letters 01/2012; · 1.67 Impact Factor
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    ABSTRACT: A passive repeater (PR), comprising a four-element folded-patch antenna (FPA) array, a planar Yagi-Uda antenna, and a power combiner, was fabricated to experimentally investigate the multiple-input-multiple-output (MIMO) performance in multipath environment. It was found that the PR could realize polarization transition and broad-angle scattering. The received power and the MIMO channel capacity, which reflect MIMO performance, were discussed to demonstrate the effectiveness of the four-unit PR in improving the propagation channel in MIMO communications. It was found that the medians of the received power of Rx1 and Rx2 were improved by about 17 dB as compared to those without the PR. Also, when the received noise level was supposed to be -120 dBm/Hz, the median of the MIMO channel capacity with the PR was increased by 6.4 bps/Hz as compared to that without the PR.
    IEEE Antennas and Wireless Propagation Letters 02/2011; · 1.67 Impact Factor
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    ABSTRACT: A dual-antenna system (DAS) is developed as a reflector to improve the propagation channel of wireless com- munications in a a non-line-of-sight (NLOS) environment. The DAS includes a folded-patch antenna array, a power transmission network, and a plannar Yagi-Uda antenna. A 4-element array of the dual-antenna is evaluated by numerical analysis and experiment to demonstrate the performance and effectiveness of the DAS array in improvement of the receiving signal noise ratio (SNR) and channel capacity in the MIMO communications under the NLOS environment. I. INTRODUCTION In this research, a dual-antenna system (DAS) is developed to be used as a reflector instead of the reflectarray. The DAS is a passive device includes a folded-patch antenna array, a power transmission network, and a plannar Yagi- Uda antenna. The DAS has a broad scattering angle, and is caperble of polarization transition, and these features are required in solving the blind spots problem in urban area. A 4-element array of the dual-antenna is evaluated by numerical analysis and experiment to demonstrate the performance and effectiveness of the DAS array for improving the receiving SNR and channel capacity in MIMO communications under a non-line-of-sight (NLOS) environment.
    01/2011;
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    ABSTRACT: The loss and cost introduced by the feeding network and the associated components, e.g., T/R modules or phase shifters and so on, of a large array antenna are the main issue limiting its efficiency and applications. A novel idea in order to build a sparse periodic patch array is presented while keeping similar aperture efficiency by taking advantage of mutual coupling between array elements, and then the total cost of the array can be obviously decreased. Operating principles are carefully addressed based on electric field distributions and impedance matrix. Simulations and measurements show that when the active element spacing is as large as $1.67\lambda_{0}$ ($\lambda_{0}$ is the free-space wavelength at the operating frequency), approximately equal directivity can be achieved, compared to an ideal conventional array with a half-element spacing $(0.835\lambda_{0})$ and an identical total size.
    IEEE Transactions on Antennas and Propagation 01/2011; 10:1317-1320. · 2.33 Impact Factor
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    ABSTRACT: The loss and cost introduced by the feeding network and the associated components, e.g. T/R modules or phase shifters and so on, of a large array antenna are the main issue limiting its efficiency and applications. In this paper, a novel idea in order to reduce the number of active elements is presented while keeping similar aperture efficiency by taking advantage of mutual coupling between array elements, and then the total cost of the array are greatly decreased. A simple way to control the mutual coupling of a patch array antenna is exampled in this paper, along with parametric studies. Simulations show that when the active element spacing is as large as 1.57λ (λ is the free-space wavelength at the operating frequency), a −13.8-dB side lobe level and an approximately equal aperture efficiency, compared to an ideal conventional array with a half element spacing (0.785λ) and an identical total size, can be achieved.
    01/2011;
  • Shi-Wei Qu, Chi Hou Chan, Quan Xue
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    ABSTRACT: A composite cavity-backed antenna excited by crossed triangular bowtie dipoles is proposed and investigated for circular polarization (CP) applications. It is fed by a novel balun, i.e., a transition from a microstrip line to double slot lines, providing symmetrical electric field distributions at the feeding port. Measurements of an optimized antenna prototype show that it can achieve an impedance bandwidth of over 57.6% for SWR ≤ 2, a 3-dB axial-ratio bandwidth of 39%, a broadside gain of 8-10.7 dBi, and symmetrical radiation patterns over the whole operating band. The operating principles of the proposed antenna are analyzed carefully and found quite different from crossed thin-wire dipoles with very weak coupling. Problems in the feeding balun, greatly deteriorating the CP performance at the resonance, are clearly addressed and solved. Detailed parametric studies are given in the final part of this paper.
    IEEE Transactions on Antennas and Propagation 11/2010; · 2.33 Impact Factor
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    ABSTRACT: In this paper, a type of novel reflectarray based on the GRIN lens is proposed. Basic idea about the new reflectarray is carefully addressed in next section, and then initial simulated results are given in the following part.
    Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE; 08/2010
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    Ieice Electronic Express. 01/2010; 7(9):647-651.
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    ABSTRACT: The dispersion relations of uniaxially anisotropic metamaterials (UAM) have been numerically investigated extensively, but their applications are still scarce. In this paper, a lens and a meta-reflector antenna made of the UAM are proposed and formulated, and design parameters versus different thickness or different incident/ deflected angles are given in details. Compared to the lens, the meta-reflector antenna presents only a half thickness or a half variation of permittivity or permeability. Simulated results of near-field distributions prove the validity of the two proposed antennas.
    01/2010;
  • Shi-Wei Qu, Chi-Hou Chan, Quan Xue
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    ABSTRACT: A composite cavity-backed folded sectorial bowtie antenna (FSBA) is proposed and investigated in this paper, which is differentially fed by an SMA connector through a balun, i.e. a transition from a microstrip line to a parallel stripline. The composite cavity as a general case, consisting of a conical part and a cylindrical rim, can be tuned freely from a cylindrical to a cup-shaped one. Parametric studies are performed to optimize the antenna performance. Experimental results reveal that it can achieve an impedance bandwidth of 143% for SWR les 2, a broadside gain of 8-15.3 dBi, and stable radiation pattern over the whole operating band. The total electrical dimensions are 0.66lambda<sub>m</sub> in diameter and 0.16lambda<sub>m</sub> in height, where lambda<sub>m</sub> is the free-space wavelength at lower edge of the operating frequency band. The problem about the distorted patterns in the upper frequency band for wideband cavity-backed antennas is solved in our work.
    IEEE Transactions on Antennas and Propagation 09/2009; · 2.33 Impact Factor