Dong-Hyuk Choi

Daejeon University, Daiden, Daejeon, South Korea

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Publications (8)6.17 Total impact

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    ABSTRACT: A novel wideband built-in antenna with resonance frequency variability for digital video broadcasting-handheld (DVB-H) is proposed. The tunable antenna consists of two channel matching networks and a spiral-shaped monopole type radiator. Based on the matching networks combined with the switches, wide bandwidth and good radiation gains are obtained. As a demonstration, a wideband tunable antenna is designed and measured. The proposed antenna has an approximately omnidirectional radiation pattern and its peak gain is 3 dB greater than the required antenna gain covering DVB-H band. These features are suitable for DVB-H applications.
    IEEE Antennas and Wireless Propagation Letters 02/2007; · 1.67 Impact Factor
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    Dong-Hyuk Choi, Seong-Ook Park
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    ABSTRACT: A patch antenna with dual-band and dual-polarization operation is proposed and discussed. For feeding the antenna, it is used the electromagnetically coupled microstrip-T junction and coplanar waveguide (CPW)-line. Since both ports of the antenna are electromagnetically coupled, the proposed antenna eliminates the need for capacitors in the RF path for active antenna applications. By using CPW resonant cell, the demonstrated approach results in a significant improvement in port isolation.
    Microwave Conference, 2006. APMC 2006. Asia-Pacific; 01/2007
  • Dong-Hyuk Choi, Se-Kun Oh, Seong-Ook Park
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    ABSTRACT: This paper describes new phase-shifterless beam steering techniques which exploit the synchronization properties of coupled nonlinear oscillator arrays. In each, the control parameters are the coupling phases of the local interactions between elements. The one-dimensional oscillator arrays under consideration are described by Phase Model- type equations, implying the assumption that the amplitude dynamics have achieved a steady state. Linear stability analyzes for each technique are provided which reveal significant differences in attainable scan angles.
    01/2007;
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    Dong-Hyuk Choi, Seong-Ook Park
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    ABSTRACT: This paper presents an active integrated antenna using a T-shaped microstrip-line-fed slot antenna which acts as DC isolation in the RF path and has a wide bandwidth. A fabricated parallel feedback antenna oscillator has a stable oscillation and a clean spectrum at the frequency of 10.05 GHz, which is only 0.5 % deviation from the designed frequency of 10 GHz. The measured EIRP is 37.79 mW, and the cross-polarization levels are at least -15 dB lower than the co-polarization ones for all directions.
    Antennas and Propagation Society International Symposium, 2005 IEEE; 08/2005
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    Dong-Hyuk Choi, Seong-Ook Park
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    ABSTRACT: A varactor-tuned active integrated antenna which is consisted of a series feedback voltage-controlled oscillator (VCO) and a matched slot antenna is proposed. The fabricated antenna has a stable oscillation at 5.8 GHz band, and the frequency varies form 5.73 GHz to 5.97 GHz, with less than 1.28 dB of amplitude deviation over the frequency range.
    Antennas and Propagation Society International Symposium, 2005 IEEE; 08/2005
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    Young-Il Cho, Dong-Hyuk Choi, Seong-Ook Park
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    ABSTRACT: In this letter, finite-difference time-domain analysis of the bow-tie antenna, including a feeding point, was studied by incorporating an approximated static field solution without additional computation time. By reformulating the static field solution in the rotated coordinate system, we can easily calculate the correction factors and obtain the result that shows a remarkable agreement with the method of moments result in spite of relatively coarse meshes.
    IEEE Antennas and Wireless Propagation Letters 01/2005; · 1.67 Impact Factor
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    ABSTRACT: This paper presents the radiation patterns of the monopole antenna mounted on the rectangular shaped structure and the coupling problem between transmit (Tx) and receiver (Rx) antennas obtained by using the FDTD method. A comparison of FDTD calculated results with the exact solution for cylindrical structure validates the accuracy of the algorithm. Using the developed FDTD code, the power radiated from the Tx port influences the Rx port at the nearby working frequency of 2 GHz. The magnitude of coupling effects in terms of scattering parameters has the highest value of about −40 dB within the 2–3.5-GHz frequency range. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 265–268, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11348
    Microwave and Optical Technology Letters 02/2004; 40(3):265 - 268. · 0.59 Impact Factor
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    Dong-Hyuk Choi, Seong-Ook Park