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A Fast Battery Charger for USN Applications
Otgonbaatar Gombo, Bieng-Chearl Ahn 충북대학교 컴퓨터정보통신연구소 2013 컴퓨터정보통신연구 Vol.21 No.1
This paper presents an implementation of a supercapacitor-based fast battery charger for USN sensor nodes. Our goal is to charge the sensor node battery in as short as possible time. In order to shorten the charging time, we first charge a pack of supercapacitors, which will slowly charge a battery in the sensor node. The implemented charging system consists of two parts, a portable charger and a battery unit. The portable charger includes a 200-F pack of supercapacitors and two supercapacitor chargers. The battery unit includes a 400-F pack of supercapacitors, a step-up converter, a lithium battery charger and a lithium battery. The supercapacitor packs in the portable charger and the battery unit are charged up to 10V and 5V respectively. The sensor node battery unit can be charged in 6 minutes.
A 3‐20GHz Vivaldi Antenna with Modified Edge
Bieng-Chearl Ahn, Otgonbaatar Gombo 충북대학교 컴퓨터정보통신연구소 2013 컴퓨터정보통신연구 Vol.21 No.1
A wideband elliptically-tapered-aperture Vivaldi antenna is proposed in this paper. The tapered aperture improves the lowfrequency impedance matching. The antenna is printed on a Teflon substrate and fed by a microstrip line. The size of the antenna is 92.9mm x 100.4mm x 0.787mm. The design, fabrication and measurement of the proposed antenna are presented.
이제선(Jea-Sun Lee),Gombo Otgonbaatar(오곤바타 검보),윤금노(Keum-No Yoon),방재훈(Jae-Hoon Bang),안병철(Bierng-Chearl Ahn) 한국정보기술학회 2011 한국정보기술학회논문지 Vol.9 No.1
In this paper, a planar dipole with a quasi-isotropic radiation pattern is proposed for use in 2.45㎓ ZigBee communications. A quasi-isotropic radiation pattern is realized by employing a C-shaped dipole electrode pattern on the FR-4 substrate. The antenna electrode shape is optimized using a commercial software so that the dipole shows minimum gain difference, wide frequency bandwidth and good impedance matching performances. The designed antenna is fabricated and its performance is measured. Measured performances of the fabricated antenna are 1.9㏈i maximim gain, 6.9㏈ gain difference, and 310㎒ bandwidth, which are in good agreement with the design goal.
Design of an E-plane Ring Hybrid Coupler in a Rectangular Waveguide
Tsend Shijirbaatar,Dong-Kook Lee,Otgonbaatar Gombo,Jae-Hoon Bang,Bierng-Chearl Ahn 한국정보기술학회 2012 한국정보기술학회논문지 Vol.10 No.7
Rectangular waveguide ring hybrid couplers are often used in combining, subtracting and dividing microwave signal in waveguides. In this paper, we present the optimum design and experimental verification of an E-plane 180° ring hybrid coupler in a rectangular waveguide. Using an electromagnetic simulation tool, the optimum dimensions of the ring hybrid coupler are obtained for a wideband performance at various operating frequencies of the standard WR-28 rectangular waveguide. The resultant design data can be used for an E-plane ring hybrid coupler in any standard rectangular waveguide. To verify the validity of the design, a ring hybrid coupler operating at 35GHz is fabricated using the split-block technique and its performance is measured. Measured results agree well with the simulation. Measurements of the fabricated coupler show a reflection coefficient less than -20 dB, an isolation greater than 20dB, an amplitude deviation within +0.3/-0.6dB and phase deviation within +6.5°/-5.5° over 33.4-37.2GHz(10.8% bandwidth).