• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.2 s.7
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• pp.81-87
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• 2005

In this paper, a VCDRO(Voltage Control Dielectirc Resonator Oscillator) for signal source of doppler radar system is designed and fabricated. The proposed VCDRO is made with new tuning mechanism using CPW line. The coplanar waveguide of $\lambda_{g}$/2 in length with varactor diode is placed on the metallization side under the dielectric resonator and coupled to it. Tuning varactor diode is mounted at one end of the CPW. The proposed circuit tuned by a CPW allows one more varactor diode to be mounted on the optimized CPW, where a greater sensitivity of frequency tuning is needed. With varying the biasing voltage for the varactor diode from 0 V to 15 V, output frequency tuning of 12 MHz is obtained. The PLDRO exhibits output power of 16.5 dBm with phase noise in the phase locked state characteristic of -115 dBc/Hz at 100 Hz, -105 dBc/Hz at the 10 kHz, and -102 dBc/Hz at 1 Hz offset from 10.525 GHz , respectively.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.12
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• pp.14-21
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• 2009

In this paper, a Ka-band 10 W power amplifier module with seven power MMIC bare dies is designed and fabricated using MIC technology which combines multiple MMIC chips on a thin film substrate. Modified Wilkinson power dividers/combiners and CBFGCPW-Microstrip transitions for suppressing resonance and reducing connection loss are utilized for high-gain and high-power millimeter wave modules. A new TTL pulse timing control scheme is proposed to improve output power degradation due to large bypass capacitors in the gate bias circuit. Pulse-mode operation time is extended more than 200 nsec and output power increase of 0.62 W is achieved by applying the proposed scheme to the Ka-band 10 W power amplifier module operating in the pulsed condition of 10 kHz and $5\;{\mu}sec$. The implemented power amplifier module shows a power gain of 59.5 dB and an output power of 11.89 W.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.6
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• pp.623-632
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• 2013

Electromagnetic topology simplifies a complex analysis area in accordance with electromagnetic coupling. And then electromagnetic topology divides the simplified continuous area into sub-areas and analyzes electromagnetic problems at the sub-areas. Therefore electromagnetic topology has a merit to analyze the electromagnetic coupling in large and complex systems, however simplified modeling technique can generate large errors. In this paper, power balance method is used to estimate errors and subdivide junctions in the electromagnetic topology. The method is applied to analyze conducted and radiated electromagnetic coupling in two kinds of cavity models. Improvement of accuracy was accomplished in accordance with junction subdivision. Moreover we could save computation time and memory comparing with FDTD results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.10
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• pp.745-751
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• 2018

This paper reports on the design of a multiband multiple-input and multiple-output(MIMO) antenna for long-term evolution(LTE) vehicular communication and includes an analysis of the throughput field test results that were acquired by mounting the antenna to a vehicle. The antenna used for the field test was designed as a planar structure and included multiple stubs to obtain multiband resonant characteristics operating in the LTE(0.8~0.9 GHz, 1.7~2.2 GHz), Wi-Fi(2.4~2.48 GHz), and wireless access in vehicular environments (WAVE)(5.8~5.9 GHz) frequency bands. For the field test, antenna prototypes were mounted on the dashboard and roof of a vehicle and connected to the experimental LTE modem. The data transfer rate(throughput), signal-to-interference-plus-noise ratio(SINR), and reference signal received quality(RSRQ) were measured and analyzed in various real-world radio wave environments. Based on these results, the relationship between the SINR and throughput according to the field intensity is confirmed.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.11
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• pp.1047-1052
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• 2016

In this paper, we propose the CSLR(: Complementary Single Loop Resonators)-loaded inset fed patch antenna with a conducting reflector to improve the radiation patterns. Reflector of the proposed antenna is located below about ${\lambda}_0/4$ from the ground plane of the patch, the size is about two times of the patch. The proposed antenna is designed and fabricated on the substrate which has a dielectric constant and thickness with 2.5 and 0.787 mm, respectively. Simulation results are obtained by using the HFSS, 3D EM Solver based Finite Element Method(: FEM). The resonant frequency and matching characteristics of the antenna with reflector are substantially the same as when there is no change in the antenna without reflector, it is confirmed that radiation patterns are significantly improved by the reflector.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.3
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• pp.10-16
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• 2005

This paper suggested the sulfur lamp power supply using Fuzzy Gain Scheduling(FGS), which was designed and confirmed the performance through manufacturing. it was based on Series Resonant Half Bridge Inverter(SRHBI), so that was applied Pulse Frequency Modulation(PFM), Zero Voltage Switching(ZVS), soft switching and soft start for input power variation and output power compensation. In order to get the lengthened life time of magnetron and stabilized output or power, power ratter and efficiency were improved by fuzzy gain algorism. It also made it possible to get not the existing foxed output power but continuous variable output power$(900\~1250[W])$. The manufactured power supply showed good results in input power $220[V]{\pm}15[\%]$ with stabilized output of power, luminous efficiency 97[1m/W] and power factor $96[\%]$.

• Journal of the Korean GEO-environmental Society
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• v.14 no.2
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• pp.5-11
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• 2013

This study introduces a densification technique of controlled low strength materials (CLSM) made with coal ashes by pump discharge pressure. Based on a small-scale laboratory test results, unit weight of CLSM around discharge pipe is greater than that of relatively some distant area from discharge pipe. It is also found that densification of CLSM depends on not only mixture rate of pond ash but also fly ash and location of discharge pipe.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.9
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• pp.1643-1653
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• 1992

A method, which uses analytical or numerical modal analysis results, e.g. from finite element analysis, to select desirable response measurement and excitation points for an efficient modal testing is introduced. First, points of master degree of freedom(DOP) are determined so as to statistically minimize errors between responses of a full order model and those estimated from the reduced order model. Such master DOF's are selected as the response measurement points. Then a criterion named 'driving point model constant(DPMC)' related to the magnitudes of resonance peaks of the driving point freqency response functions used to select the point of excitation out of the master DOF's. In this work, the method is demonstrated through applications to modal testing on a one dimensional cantilever beam and an aluminum plate and the results are compared with those by another technique. also, the method is applied to a two dimensional structural component of a passenger car.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.5
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• pp.369-375
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• 2010

This paper presents a design and implementation of 3.3 kW on-board battery charger for electric vehicles or plug-in hybrid electric vehicles. Considering characteristics of the electric vehicles, a series-loaded resonant dc-dc converter and frequency control scheme are adopted to improve efficiency and reliability, and to reduce volume and cost. The developed on-board battery charger is designed and implemented by using high frequency of 80-130 kHz and zero voltage switching method. The experimental result indicates 92.5% of the maximum efficiency, 5.84 liters in volume, and 5.8kg in weight through optimal hardware design.

• Electrical & Electronic Materials
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• v.10 no.9
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• pp.901-908
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• 1997

The microwave dielectric properties of (Na.$_{1}$2//Sm$_{1}$2/)TiO$_3$and (Li$_{1}$2//Nd$_{1}$2/)TiO$_3$ceramics were investigated. Dielectric constant quality factor and temperature coefficient of resonant frequency of (Li$_{1}$2//Nd$_{1}$2/)TiO$_3$ceramics sintered at 145$0^{\circ}C$ for 2 hours were 86.2, 2780(at 3.8GHz) and 215ppm/$^{\circ}C$respectively. The solid solution of X(Na.$_{1}$2//Sm$_{1}$2/)TiO$_3$-(1-X)(Li$_{1}$2//Nd$_{1}$2/)TiO$_3$increased delectric constant and quality factor were decreased. Whereas temperature coefficient of resonant frequency was optimized to zero at the composition of 0.6(Li$_{1}$2//Sm$_{1}$2/)TiO$_3$-0.4(Li$_{1}$2//Nd$_{1}$2/)TiO$_3$where dielectric constant and quality factor were 86.2, 95-(at 3.8GHz) respectively. Also band-pass filters made of this material were examined.