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최순우(Swoon-Woo Choi),노재우(Jae-Woo Noh),임주영(Ju-Young Lim),정용선(Yong-Sun Jung),안병철(Bierng-Chearl Ahn) 한국정보기술학회 2016 한국정보기술학회논문지 Vol.14 No.7
This paper proposes a 210-m high eLoran transmitting antenna. The proposed antenna consists of a ground, a center post, four slant wires, four horizontal wires, a feeding post and a shorting post. Four slant wires are connected to the end of the center post for top loading and their ends are connected by four horizontal wires for structural support and connected to the ground by insulated wires. The feeding post and the shorting post are connected to a horizontal wire at suitable points. A 1/550 scale model of the optimally designed antenna is fabricated and measured. Measurements show that the fabricated antenna has reflection coefficient of less than -6dB over 4.23 MHz bandwidth centered around 57.3MHz and maximum gain of 1.1dBi.
김영민(Young-Min Kim),최순우(Swoon-Woo Choi),이광원(Kwang-Won Lee),방재훈(Jae-Hoon Bang),안병철(Bierng-Chearl Ahn) 한국정보기술학회 2015 한국정보기술학회논문지 Vol.13 No.5
This paper presents a high-efficiency method for the wireless charger by adjusting the geometries of Tx/Rx coils surrounded by ferrite sheets. The proposed charger consists of a transmitting module, a receiving module and two coils for transmitting and receiving the wireless power. The transmitting module has a series capacitance for resonance of the Tx coil at 100 kHz, two half-bridge circutis based on the MOSFET technology for suppling the AC voltage by switching mechanism and a wireless power transmitting management chipset(bq500211A) for controlling overall structure. The receiving module is realized by a fabricated chipset(bq5101xB) having a rectifier, a voltage conditioning circuit and a controller. Two chipsets employed in the transmitting/receiving modules are controlled by a MCU program. The maximum charging efficiency of the charger is acquired by experimental methods which adjust the geometries of ferrite sheets around the Tx and Rx coils. From the fabrication and measurements, it is confirmed that the maximum charging efficiency is greater than 92% and the charging time is less than 200 minutes in the such case.
이광원(Kwang-Won Lee),최순우(Swoon-Woo Choi),박철수(Cheol-Su Park),이주(Shu-Li),정용선(Yong-Sun Jung) 한국정보기술학회 2015 한국정보기술학회논문지 Vol.13 No.6
In this paper, We propose a prime-focus reflector antenna having a low back-radiation pattern at 18-GHz. The proposed antenna consists of a parabolic reflector, a small feed, a metallic shroud, a radio absorber and a sheet radome. The commercial software, Microwave Studio<SUP>TM</SUP> v. 2012 by CST, is employed in the design of the reflector antenna and the feed. In the initial design, the design specifications of the feed is acquired from the information of the reflectors diameter and focal length. The feed is minimized by employing a choke, a slit and a dielectric slab on the circular waveguide. The metallic shroud and radio absorber are employed on the reflectors edge for reducing the sidelobe and back-radiations. The feed and reflector antenna are fabricated and measured. The fabricated feed has a -10dB reflection coefficient over 15.7-20.6GHz. The fabricated reflector antenna has a -10dB reflection coefficient over 15.8-20.7GHz and satisfies the radiation envelope of the ETSI class-2. The measured efficiencies of the reflector are above 48% from 17.5GHz to 19.5GHz.
유상길(Sang-Gil Yu),최순우(Swoon-Woo Choi),김동현(Dong-Hyun Kim),김대오(Dae-Oh, Kim),안병철(Bierng-Chearl Ahn) 한국정보기술학회 2016 한국정보기술학회논문지 Vol.14 No.5
This paper presents precise measurement techniques for waveguide components at microwave band. The error parameters are presented in the network analyzer and the calibrated results are shown by using the SOLT(Short-Offset short-Load-Thru) kit when measuring waveguide components. A method is proposed to obtain the performances of the circular-rectangular waveguide transition by in order connecting 3 offset shorts. The scattering parameters of the transition are calculated from the measured reflection coefficients with 3 offset shorts. The waveguide transition has a reflection coefficient of less than -18dB and a transmission coefficient of more than –0.16dB. Next, a method utilizing a low-reflection horn at the common port of an OMT is introduced. The electric performances between the straight and side ports are measured by employing connecting a low-reflection horn at the common port of the OMT. The measurements agree well with the designed results.
유상길(Sang-Gil Yu),박철수(Cheol-Su Park),최순우(Swoon-Woo Choi),방재훈(Jae-Hoon Bang),안병철(Bierng-Chearl Ahn) 한국정보기술학회 2015 한국정보기술학회논문지 Vol.13 No.10
This paper proposes a Ka-band monopulse feed horn having four input rectangular waveguides. The proposed feed consists of four input waveguides, two H-moders, a E-moder and a flared horn. Two H-moders and the E-mode having waveguide discontinuous structures are designed by using the DFT function in the commercial software. The lengths of each moder and the flared horn are determined to satisfy in-phase conditions of the multi modes at the feeds aperture. Five-step waveguide transformers are designed and employed to connect the input waveguide of the feed to the WR-28 rectangular waveguide. The optimally designed monopulse feed is fabricated with 3 split blocks. The fabricated horn has a reflection coefficient of less then -10dB over 34.55-36.56GHz and a -15dB beamwidth of 100°. In the difference patterns over the azimuth and elevation planes, the null is less than -22dB at the center of the feed.
최순우,안병철 충북대학교 컴퓨터정보통신연구소 2014 컴퓨터정보통신연구 Vol.22 No.2
This paper presents a dual-feed circularly-polarized ceramic patch antenna for satellite positioning applications at 1.227GHz. The antenna consists of a metal ground plane, a ceramic block, a square patch and two coaxial feed lines. The patch is miniaturized by using a dielectric material with a dielectric constant of 21. The capacitive feeding is employed to increase the isolation between two feeding ports instead of the conventional probe feeding. The designed antenna has the following characteristics : 3.9dB gain at 1.227GHz, a reflection coefficient of less than -5dB and an isolation of greater than 30dB at 1.213-1.241GHz. The antenna shows an axial ratio of less than 3dB over ±60° from the boresight when fed with signals of equal amplitude and 90° phase difference.