• Journal of Advanced Marine Engineering and Technology
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• v.32 no.8
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• pp.1248-1256
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• 2008

In this paper, basic characteristics of transmission line employing PPGM (periodically perforated ground metal) were investigated using theoretical and experimental analysis.According to the results, unlike the conventional PBG (photonic band gap) structures, the characteristic impedance of the transmission line employing PPGM structure showed a real value, which exhibited a very small dependency on frequency. The transmission line employing PPGM structure showed a loss (per quarter wave length) higher by $0.1{\sim}0.2\;dB$ than the conventional microstrip line. According to the investigation of the dependency of RF characteristic on ground condition, the RF characteristic of the transmission line employing PPGM structure was hardly affected by the ground condition in the frequency lower than Ku band, but fairly affected in the frequency higher than Ku band, which indicated that coplanar waveguide employing PPGM structure was optimal for RF characteristic and reduction of size. Considering above results, impedance transformer was developed using coplanar waveguide with PPGM structure for the first time, and good RF characteristics were observed from the impedance transformer. In case that {\lambda}/4$ impedance transformer with a center frequency of 9 GHz was fabricated for a impedance transformation from 20 to10 {\Omega}$, the line width and length were 20 and $500\;{\mu}m$, respectively, and its size was only 0.64 % of the impedance transformer fabricated with conventional microstrip lines. Above results indicate that the transmission line employing PPGM is a promising candidate for a development of matching and passive elements on MMIC.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.10 s.113
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• pp.993-999
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• 2006

This paper presents the design simulation, implementation, and measurement of a miniaturized DCS, PCS / Satellite DMB dual-band stacked chip antenna with double coupled line for mobile communication terminals. A stacked meander is realized by using a via hole with height of 0.8 mm and a diameter of 0.35 mm to connect upper- and lower-layer meander sections for a reduction of the dimensions of the antenna. In addition the stacked meander chip antenna is extended by a double coupled-line to achieve two different radiation modes. A ratio of the first frequency and second frequency vary with the geometrical parameter of coupled lines. The fabricated antenna used FR-4 substrate with relative permittivity of 4.2. And its dimensions are $15.2{\times}7{\times}0.8mm^3$. The measured impedance bandwidth(VSRW<2) are 244 and 120 MHz at the operating frequency, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.10 s.113
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• pp.929-934
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• 2006

In the paper, we suggest a simpler synthesis technique for capacitively-coupled match circuit(CCMC) which have a function of DC block and impedance matching simultaneously, and introduce a stability margin analysis technique for designing microwave amplifier under conditionally stable state. Stability margin analysis is used to determine optimum match point that ensure maximum gain under the given stability margin. It can reduce time consuming work for selecting match points in the conditionally stable state. Also, suggested miniaturization scheme of matching network is distinguished from previous work with respect to reducing deterministic parameters for CCMC synthesis. To verify utility of suggested method, 24 GHz gain block is fabricated under conditionally stable state using an internal thin-film fabrication process, Measured results show a stable gain of 10 dB and flatness of 1 dB, which is well coincident with simulated one.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.3
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• pp.284-290
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• 2016

As the recently advanced scientific developments result in high lever of the usability and the needs for the electrical equipment and devices in various situations, the safety technologies protecting malfunction and electrical critical damages including soft and hardware from the unexpectedly radiated electromagnetic interferences are required gradually. In addition, the numerical analysis for the miniaturized electrical components and equipments as well as the conventional electrical devices installed inside the electrically large enclosures and structures requires the memory requirement and time consumption too big to be handled in a realistic situation, which will result in a limitation in solving the complete set of maxwell's equations. In this paper, PWB method based on statistical theory and topological modeling with appropriate zoning concepts are introduced for the EM analysis of an electrically large complex structures.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.8
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• pp.900-904
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• 2010

In this paper, a frequency tunable zeroth-order resonant(ZOR) antenna has been implemented. The ZOR characteristics of the proposed antenna is realized by using a composite right-and left-handed(CRLH) transmission line which consists of a rectangular slot on the ground plane of a mushroom structured antenna in order to minimize the antenna size. In addition, the tunable devices are introduced on the slotted ground plane for frequency tuning capability. Depending on the on and off states of the tunable device on the slotted ground plane, a shunt inductance value of the CRLH transmission line is changed and its resonant frequency becomes tunable. From the experimental results, the resonant frequency of the proposed antenna is changed from 4.92 GHz to 2.96 GHz. Additionally, the proposed antenna's size is reduced by 94.24 % compared with the half-wavelength patch antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.5
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• pp.397-400
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• 2018

This paper presents a miniaturized 65 nm CMOS 30~46 GHz wideband amplifier. To minimize the chip area, coupled inductors are used in the matching networks. The measurement shows that the fabricated amplifier exhibits 9.3 dB of peak gain, 16 GHz of 3 dB bandwidth, and 42 % fractional bandwidth. The measured input and output return losses were more than 10 dB at 35.8~46.0 GHz and 28.6~37.8 GHz, respectively. The chip consumes 42 mW at 1.2 V. The measured group delay variation is 19.1 ps within the 3 dB bandwidth and the chip size excluding the pads is $0.09mm^2$.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.3
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• pp.429-436
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• 2013

In this study, we researched a pendant-type aspherical optical system, which could be applied to street lighting and security lighting in Europe. The goal of this research was eco-friendly artificial lighting that could be used for the one-to-one replacement of ordinary lighting. LED lighting was miniaturized by using one COB LED Module and one aspherical optical system, which could control the luminosity of the LED. Through the aspherical optical system, the light distribution angle could be controlled in a range of $140^{\circ}$ for the X-axis and $40^{\circ}$ for the Y-axis. This means that this optical system is appropriate for catenary-type lighting, which is widely used in Europe on both narrow and broad roads. The performance was determined using a lighting simulation program. This lighting system simulation showed that road rates M4 and M5 could be satisfied, with the condition of a 13-m height and 50-m distance (U0 and TI). The simulation program estimated that light pollution, which disturbs sleep, could beeliminated in the European streetlight case. Determining methods for the light distribution control, performance, and optimal lighting setup conditions is very important to prevent light pollution. Moreover, the initial step of developing the lighting system design and post management will require an effort with much analysis.

• Journal of Sensor Science and Technology
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• v.21 no.4
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• pp.241-248
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• 2012

Recently healthcare industry such as pharmaceutical, medical device and healthcare service technology is growing significantly. Mobile healthcare has attracted big attention due to IT convergence technology. Paradigm of healthcare has been changed from the 1st generation(communicable disease prevention) and the 2nd generation(treatment of disease due to extended life expectancy) to the 3rd generation(extended life expectancy due to prevention and control). In our study, we suggest the 3rd generation mobile healthcare system using Bluetooth based wearable ECG monitoring system and smart phone technology. The mobile healthcare system consists of wearable shirts with Bluetooth communication module, ECG sensor, battery, and mobile phone. The ECG data is obtained by a miniaturized sensor and the data is transferred to a mobile phone using Bluetooth communication. Then, user can monitor his/her own ECG signal on an application using Android in mobile phone. The Bluetooth communication device is used due to highly reliable data transmission property and the Bluetooth chip is embedded in every mobile phone. The wearable shirts with chest belt of Bluetooth ECG module is designed with a focus on convenience in the daily life of a wearer. The ECG signal evaluation software in Android based mobile phone is developed for the health check and the ECG signal variation is tested according to the activities of the wearer such as walking, climbing stairs, stand up and sit down, and so on.

• Fire Science and Engineering
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• v.30 no.2
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• pp.106-113
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• 2016

Ultra-high pressure positive displacement pump can discharge high pressure water with mass volume, which depends on periodic changes in volume that made by rotation motor. Its high efficiency of discharge is one of the most strong point of positive displacement pump. Due to its simple system structure, it can be miniaturized and lightened. Positive displacement pump can discharge high pressure with stable flow rate, irrespective of pressure fluctuate. This is the reason that positive displacement pump was used instead of centrifugal pump. In this study, shutoff operating system was developed for positive displacement pump to secure safety of high pressure operate. This shutoff system contains controller system, electronic clutch, and relief valve, and each part is mutual supplementation. Speed test was carried out in order to check operation of controller program and electronic clutch and fluid flow, venting experiment of the relief valve. It was confirmed that segment system of ultra-high pressure positive displacement pump is operated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.124-127
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• 2005

As computer capability and test skill become more and more advanced, finite element method and modal test are being widely applied in engineering design. In order to correlate and reconcile the inevitable discrepancies between the analytical and experimental models, many techniques have been developed. Among these methods, multiple-system methods are known as the effective tools in that they can supply the rich modal data available which are experimentally obtained. These abundant modal data can help structural system parameters estimated well. Multiple-system methods can be classified into the structural modification methods and feedback controller methods. The structural modification methods need the physical attachment of structures and their concept may limit the application of them. To overcome this drawback, the feedback controller methods are addressed which enable us to get more modal data without the structural change. Mode decoupling controller(MDC), one of them, is to use acceleration out)ut feedback to perturb an open-loop system. The output feedback controller generally cannot guarantee the stability of a closed-loop system. However, MDC can solve this problem under the certain constraints. So far, MDC utilizes accelerations as the sensor signals. In this research, strain sensors are going to be picked up to apply to the MDC. Strain output is recently used for structural system identification due to the drastically improved and miniaturized strain sensor. In this paper, we show that the MDC using strain output has differences compared with acceleration output in estimating the structural system parameters. The associated simulation is performed to demonstrate the above mentioned characteristics.