Changwon Jung

Seoul National University of Science and Technology, Sŏul, Seoul, South Korea

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Publications (18)11.15 Total impact

  • Seonghun Kang · Insu Yeom · Changwon Jung
    09/2014; 15(9):5796-5800. DOI:10.5762/KAIS.2014.15.9.5796
  • Jinyoung Kim · Jaeyoung Jung · Youngbae Jung · Changwon Jung
    05/2014; 15(5):3107-3113. DOI:10.5762/KAIS.2014.15.5.3107
  • Insu Yeom · Seonghun Kang · Changwon Jung
    05/2014; 15(5):3074-3078. DOI:10.5762/KAIS.2014.15.5.3074
  • Byeonggwi Mun · Changwon Jung · M.-J. Park · Byungje Lee
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    ABSTRACT: A compact frequency-reconfigurable multiple-input–multiple-output (MIMO) antenna on a laptop is proposed for multiband LTE services. Each MIMO antenna consists of two planar inverted-F antenna (PIFA) elements, using a T-shaped dc line and two p-i-n diodes (D1 and D2), in conjunction with the proximity-coupled feed structure. By effectively minimizing its dimension and its interference with antenna performance, the proposed T-shaped dc line is designed to fit within the proximity-coupled feed structure. The proposed MIMO antenna covers the LTE 17/13 bands (704–787 MHz, ${rm VSWR} < 3$) at State 1 (D1 and D2: on state), and the LTE 20/7 bands (791–862 MHz, 2500–2690 MHz, ${rm VSWR} < 3$) at State 2 (D1 and D2: off state). The proposed antenna obtains high isolation ( $ > 20~hbox{dB}$), low envelope correlation coefficient (${rm ECC}< 0.0161$), and total efficiency of greater than 51%, for all operating frequency bands.
    IEEE Antennas and Wireless Propagation Letters 01/2014; 13:1389-1392. DOI:10.1109/LAWP.2014.2339802 · 1.58 Impact Factor
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    ABSTRACT: In this letter, a reconfigurable radiation pattern antenna for multiple-input–multiple-output (MIMO) applications on mobile devices is proposed. The operating frequency band of the antenna is 5.15–5.35 GHz for a wireless local area network (WLAN) 802.11a service. Each antenna is composed of a loop-and-dipole structure, as well as two switches for the reconfigurable radiation pattern, to generate a beam in three different directions. The proposed antenna is designed to have an orthogonally directional radiation pattern with high isolation and a low-correlation coefficient in the MIMO environment.
    IEEE Antennas and Wireless Propagation Letters 01/2014; 13:1373-1376. DOI:10.1109/LAWP.2014.2339012 · 1.58 Impact Factor
  • Source
    Insu Yeom · Junghan Choi · Sung-su Kwoun · Byungje Lee · Changwon Jung
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    ABSTRACT: The RF front-end performances in the far-field condition of reconfigurable antennas employing two commonly used RF switching devices (PIN diodes and RF-MEMS switches) were compared. Two types of antennas (monopole and slot) representing general direct/coupled feed types were used for the reconfigurable antennas to compare the excited RF power to the RF switches by the reconfigurable antenna types. For the switching operation of the antennas, a biasing circuit was designed and embedded in the same antenna board, which included a battery to emphasize the antenna’s adaptability to mobile devices. The measurement results of each reconfigurable antenna (radiation patterns and return losses) are presented in this study. The receiving power of the reference antenna was measured by varying the transmitting power of the reconfigurable antennas in the far-field condition. The receiving power was analyzed using the “Friis transmission equation” and compared for two switching elements. Based on the results of these measurements and comparisons, we discuss what constitutes an appropriate switch device and antenna type for reconfigurable antennas of mobile devices in the far-field condition.
    International Journal of Antennas and Propagation 01/2014; 2014:1-14. DOI:10.1155/2014/385730 · 0.66 Impact Factor
  • Source
    Jinyoung Kim · Changwon Jung
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    ABSTRACT: We implemented double-negative metamaterials using cross-polarized split-ring resonators in a microstripline. The split-ring resonators comprised quad ring structures and were connected with the microstripline in series. Four different structures, with the shorted rings in varying locations, were fabricated to demonstrate reconfigurable band-pass characteristics. The effective permittivities and permeabilities were extracted using the Ziolkowski method. Excellent agreement between the developed circuit model and the measurement was observed up to 10 GHz.
    07/2013; 14(7). DOI:10.5762/KAIS.2013.14.7.3450
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    ABSTRACT: A compact handset multiple-input multiple-output (MIMO) antenna for long-term evolution (LTE) 700 band (746~787 MHz) applications is proposed. The proposed antenna consists of two symmetrical PIFAs. Without the usage of any additional coupling elements between closely mounted antennas, a high isolation (>15 dB) and a low enveloped correlation coefficient () are achieved by the optimum location and arrangement of MIMO antenna elements.
    International Journal of Antennas and Propagation 05/2013; 2013(2). DOI:10.1155/2013/850489 · 0.66 Impact Factor
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    ABSTRACT: A half-wavelength loop structure on the ground plane for mobile handset applications is proposed to mitigate the user's hand effect on antenna radiation efficiency. The proposed loop structure makes a major portion of electric field distribution on the ground plane shift away from the user's hand. This considerably improves the antenna radiation efficiency compared to an antenna without a loop structure under the influence of the user's hand.
    IEEE Antennas and Wireless Propagation Letters 12/2012; 11:450-452. DOI:10.1109/LAWP.2012.2195289 · 1.58 Impact Factor
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    ABSTRACT: A novel fabrication process for a fixed-fixed membrane structure in RF microelectromechanical-systems switches is implemented to alter the stress-distribution and deformation of the membrane and thus vary the required actuation force. This two-step process removes UV-light-exposed photoresist first by wet dissolution of a sacrificial photoresist layer and then by oxygen reactive ion etching. During wet release, the patterned but unexposed photoresist above the membrane helps prevent stiction. Further designs of photoresist-aided membranes are demonstrated to control the measured pull-down voltage level of the switches, which is consistent with the multiphysics simulation work.
    Journal of Microelectromechanical Systems 07/2010; 19(3-19):715 - 717. DOI:10.1109/JMEMS.2010.2046138 · 1.75 Impact Factor
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    ABSTRACT: An internal PIFA/slot antenna for quad-band mobile handset applications is presented. The quad-band operation for the bar-type mobile handset is obtained by the resonant modes of the slot antenna in conjunction with those of the PIFA. The proposed antenna has a compact size of 42 times 10 times 4 mm<sup>3</sup>. The quad-band operation includes GSM850 (824-894 MHz), GSM900 (880-960 MHz), DCS1800 (1710-1880 MHz), and PCS1900 (1850-1990 MHz).
    Antennas and Propagation Society International Symposium, 2009. APSURSI '09. IEEE; 07/2009
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    ABSTRACT: This paper presents a structure of the frequency selective surface (FSS) to improve the isolation between donor antenna and coverage antenna for indoor WCDMA repeater systems. The repeater system has two linearly polarized antennas backed with the reflectors. The proposed FSS is embedded into reflectors aligned with the cross-polarization of each antenna. The isolation with the FSS is enhanced overall more than 6 dB at WCDMA band, compared to that without the FSS.
    06/2009; DOI:10.1109/APS.2009.5171995
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    ABSTRACT: A compact ultrawideband (UWB) antenna with a band-notch function is proposed for laptop applications. The band-notch function is realized by a half-wavelength parasitic element printed on the rear side of the substrate. The impedance bandwidth (VSWR < 2) of the antenna is 3.1 ~ 11.4 GHz (114%) with a notched frequency from 5.05 to 5.90 GHz. The antenna has a fairly good omnidirectional pattern, and the average gain is -3.0 ~ -1.2 dBi over the UWB frequency band except for the notched frequency band. The performance of the proposed antenna is confirmed by simulation and measurement results.
    IEEE Antennas and Wireless Propagation Letters 02/2009; 8(8):580 - 582. DOI:10.1109/LAWP.2009.2021286 · 1.58 Impact Factor
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    ABSTRACT: By using a multilayered ferrite substrate, a compact internal DTV (digital television) antenna is proposed. The antenna is constructed on the ground plane of a clamshell-type mobile phone. It is suitable for a DVB-H band (VSWR<3), and it has over -10 dBi gain which is acceptable for a practical digital television signal reception.
    Antennas and Propagation Society International Symposium, 2008. AP-S 2008. IEEE; 08/2008
  • Seunghwan Yoon · Changwon Jung · Young-eil Kim · F. De Flaviis
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    ABSTRACT: In this paper, a novel multi-port, multi-band small planar antenna is presented. It has three input ports; each of them has their own frequency bands, 2.4 GHz, 3.5 GHz and 5.5 GHz. These three antennas are printed on a small area, 250 mm<sup>2</sup>. The proposed antenna is printed on a cheap organic material substrate with other RF components. It requires enough isolation among the antennas since each frequency band ought to operate at the same time. Polarizations of monopole antennas are all orthogonal as best as possible to minimize mutual couplings and open stubs are used at feed points to block the other frequency band signals. The antenna proposed in this paper is a solution to the onboard configuration of handset system needed multiple wireless services and they can be used simultaneously.
    Microwave Conference, 2007. APMC 2007. Asia-Pacific; 01/2008
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    ABSTRACT: First Page of the Article
    Antennas and Propagation Society International Symposium, 2007 IEEE; 07/2007
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    ABSTRACT: This paper describes an improved manufacturing technology for the fabrication of radio frequency (RF) microelectromechanical systems switches on a laminated printed circuit board (PCB). The process simplifies the fabrication process without sacrificing the RF performance of switches on the PCB. The proposed process patterns a 17.5-μm-thick copper layer on the PCB; as a result, the surface becomes highly nonplanarized. Polyimide is then used to planarize the PCB's patterned copper layer. The use of polyimide for planarization has not only made the fabrication process simpler, but it has also reduced the formation of voids in the photoresist sacrificial layer where metallic membrane is deposited and patterned. The switches fabricated with this technology demonstrate a low insertion loss (less than 0.06 dB at 10 GHz) and good isolation (less than 20 dB at 10 GHz).
    IEEE Sensors Journal 11/2005; 5(5-5):950 - 955. DOI:10.1109/JSEN.2005.854148 · 1.76 Impact Factor
  • Source
    Sunan Liu · Ming-Jer Lee · Changwon Jung · G.-P. Li · F. De Flaviis
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    ABSTRACT: A microstrip antenna with integrated RF microelectromechanical system (MEMS) switches is proposed and demonstrated to operate at dual frequencies with circular polarization. The switches are incorporated into the diagonally fed square patch for controlling the operating frequency and a rectangular stub attached to the edge of the patch acts as the perturbation to produce the circular polarization at 6.69 GHz and 7.06 GHz.
    Antennas and Propagation Society International Symposium, 2005 IEEE; 08/2005

Publication Stats

85 Citations
11.15 Total Impact Points


  • 2009–2013
    • Seoul National University of Science and Technology
      Sŏul, Seoul, South Korea
    • Kwangwoon University
      • Department of Radio Sciences & Engineering
      Seoul, Seoul, South Korea
  • 2008
    • Samsung Advanced Institute of Technology
      Usan-ri, Gyeonggi-do, South Korea