• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.9 s.112
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• pp.811-820
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• 2006

Ultra wideband CPW batons are proposed in this paper. The proposed talons are consisted of ultra wideband multi-stage Wilkinson dividers and 'X'-shaped $180^{\circ}$ out-of-phase generator. Bottom-bridges and via-holes are used to connect CPW ground lines instead of the conventional air-bridges which require troublesome manual working in fabrication with HMIC(Hybrid Microwave Integrated Circuits) substrates. The proposed CPW batons have ultra wideband of 3 or $10(=F_{figh}/F_{low})$ theoretically, the wideband characteristics and S-parameters of the basis Wilkinson divider are directly converted to those of the proposed batons. The proposed batons are so compact and small compared to the conventional Wilkinson batons because no additional area for out-of-phase section is required. So the size of the proposed batons is exactly the same as that of the basis Wilkinson dividers. As examples, 3-stage and 7-stage wideband Wilkinson dividers are converted to the proposed batons. Their measured operating bandwidth are $1\sim3GHz$ and $0.8\sim5GHz$, respectively, with excellent matching, isolation and power division performances. The measured magnitude and phase balance errors are ${\pm}0.5dB\;and\;0.45\;dB,\;and\;{\pm}5^{\circ}\;and\;{\pm}10^{\circ}C$ over $1\sim3GHz\;and\;0.8\sim5GHz$, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.3
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• pp.461-470
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• 1999

This paper presents the description of a 4-bit digital p-i-n diode phase shifter that was designed for quasimillimeter wave band satellite receiver to use in phased-array systems. 180$^{\circ}$ and 90$^{\circ}$ cells are designed in reflection type that consists of a 3-dB rat-race hybrid coupler, 45$^{\circ}$ and 22.5$^{\circ}$ cells are designed in loaded-line type to reduce the size of circuit and the number of diode to be used. The 4-bit phase shifter uses eight p-i-n diodes mounted in the microstrip circuit. The average insertion loss for the 16 phase states is 6.92dB over the 19.8~20.3 GHz band and maximum phase error is 6.2$^{\circ}$ at 20 GHz.

• Journal of Mushroom
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• v.3 no.3
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• pp.109-114
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• 2005

Attempts were made to control Diatrype stigma occurred on the bed-log of shiitake by resistant shiitake strains. In selection test of resistant shiitake strains, 67 out of 77 strains tested were proved to be resistant to D. stigma. Among them, 13 strains including KFRI 5 were effective to inhibit the access of D. stigma, and 7 strains including KFRI 180 remarkably invaded the territory of D. stigma. Among 31 shiitake strains made by hybridization of resistant strains for D. stigma, 8 strains including KFRI 537 inhibited the access of D. stigma, and 4 strains including KFRI 545 invaded the territory of D. stigma. The effects of temperatures and inoculation orders to the resistance were confirmed in PDA plates and test tubes filled with sawdust of Quercus acutissima. Four kinds of temperature treatments as follows were tested: (1) continuous incubation at $14^{\circ}C$, (2) continuous incubation at $25^{\circ}C$, (3) changing of incubation temperature from $14^{\circ}C$ to $25^{\circ}C$ as soon as mycelia of both shiitake and D. stigma meet together, (4) changing of incubation temperature from $25^{\circ}C$ to $14^{\circ}C$ as soon as mycelia of both shiitake and D. stigma meet together. Three kinds of inoculation procedure were tested: (1) inoculation of shiitake 3 days ahead of D. stigma inoculation, (2) inoculation of D. stigma 3 days ahead of shiitake inoculation, (3) simultaneous inoculation of both fungi. In PDA plate test, the strain KFRI 137 showed outstanding ability to inhibit mycelial growth of D. stigma and the strain KFRI 180 invaded into the territory of D. stigma in most of treatments. Hybrid strains, KFRI 545, 546, and 547 were more resistant than their parent strains, KFRI 488 and 405. In test tube examinations, all the strains of shiitake showed high resistance at the treatment of change in temperature from $14^{\circ}C$ to $25^{\circ}C$ when mycelia of both shiitake and D. stigma meet together. On the other hand, resistance of all the strains growing at $25^{\circ}C$ decreased when the temperature was changed into $14^{\circ}C$ after mycelia of both fungi. In these cases, the resistance reached to 7~20% of the highest resistance. The strain KFRI 259 invaded the territory of D. stigma, contrary to PDA plate test. Among the strains, KFRI 393 strain was the most resistant under the continuous incubation at $25^{\circ}C$.

• Composites Research
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• v.30 no.6
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• pp.416-421
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• 2017

The structural adhesive have been manufactured for improvement of bonding process between CFRP and metal. The optimal condition for bonding process were investigated by evaluating the lap shear strength with amount of adhesive and curing time and the surface treatment of the CFRP. To confirm proper adhesion conditions, the fracture sections between CFRP and metal was observed using reflection microscope. Not only the improvement of the adhesion condition was important, but surface treatment on CFRP was also important. The optimal curing temperature was at $180^{\circ}C$ for 20 minutes. The improvement for adhesive property was confirmed After surface treatment on CFRP. The optimal amount of structural adhesive for bonding between CFRP and metal was $1.5{\times}10^{-3}g/mm^2$. Through the optimization of bonding process, the improvement of mechanical property over 10% is confirmed in comparison with existing adhesive.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.2
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• pp.257-262
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• 2012

The Ministry of Information-Communication assigned 18~19GHz frequency band for communication of cabins and platform to link between subway/train and it's station. In this paper, we propose wireless transmission devices which are 2 stage hybrid low noise amplifier of 18GHz band and mixer for 18GHz as well to apply for RF receiver. We designed LNA to be noise matched its 1st stage and gain matched for 2nd stage and mixer using $180^{\circ}$ hybrid coupler to suppress the spurious signal. The transistors of 18 GHz LNA and mixer are NE3210S01 of NEC and KMB-N51-1, respectively. As the result of simulation, we get 19.92dB gain and 2.06dB noise figure with LNA and 8.61dB conversion loss with mixer.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.7
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• pp.678-685
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• 2013

In this paper, we propose a design of dual-band patch antennas for Global Positioning System(GPS) applications, and the designed antenna is used as an individual element of GPS arrays. A low distortion and a high isolation of the array are achieved by adjusting rotating angles of each array element. The antenna consists of two radiating patches that operate in the GPS $L_1$ and $L_2$ bands, and the two ports feeding network with a hybrid chip coupler is adopted to achieve a broad circular polarization(CP) bandwidth. The rotating angles of each antenna element are varied with four directions(${\phi}=0^{\circ}$, ${\phi}=90^{\circ}$, ${\phi}=180^{\circ}$, ${\phi}=270^{\circ}$) in order to minimize the pattern distortion and maximize the isolation among array elements. The measurement shows bore-sight gains of 0.3 dBic($L_1$) and -1.0 dBic($L_2$) for the center element. Bore-sight gains of 1.6 dBic($L_1$) and 1.0 dBic($L_2$) are observed for the edge element. This results demonstrate that the proposed antenna is suitable for GPS array applications.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.512-515
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• 2003

We have studied a novel vertical alignment liquid crystal cell. At initial state of a cell with rubbed parallel on top and bottom substrates, the vertically aligned LCs are twisted by $180^{\circ}$. However, after a critical voltage is applied to the cell, the configuration of the LC changes to optically compensated splay form, where the mid-director lies parallel to the substrate and thus the LC has two hybrid alignments around center.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.66-70
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• 2003

In this paper a plannar singly balanced diode Miter for 24GHz band application is designed and implemented using a microstrip line and two schottky barrier beam lead mixer diodes. The implemented mixer have a conversion loss of 6 [dB], LO/RF isolation of 23 [dB], input 1dB compression point of 4 [dBm]. this diode mixer would be useful for homedyne radar.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.164-165
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• 2007

Si(중간층)/DLC(diamond-like carbon)막은 스퍼터와 이온소스(ion source)법에 의한 복합방식(hybrid method)을 이용하여 3mTorr의 반응가스 벤젠($C_6H_6$)분위기에서 Si wafer에 기판온도 $130^{\circ}C$로 180분간 증착하였다. 평가는 표면과 단면에 대해 주사전자현미경(scanning electron microscopy, SEM)과 투자전자현미경(trasmission electron microsope, TEM)으로 관찰하였다. 경도와 마찰계수는 나노인텐터(nanoindetor)와 마모시험기를 이용하였으며, 박막의 구조는 라만스펙트럼으로 분석하였다. 그 결과 박막의 두께는 약 $0.9{\mu}m$, 표면조도는 약 $0.34{\sim}1.64nm$로 평탄한 표면을 가지며 경도는 약 $35{\sim}37GPa$, 마찰계수는 약 $0.02{\sim}0.07$로 관찰되었다. 라만분광법과 전자회절패턴에 의해 IG/ID의 함량비는 $0.54{\sim}0.59$로 $sp^2$와 $sp^3$가 혼재된 전형적인 비정질 구조임을 확인하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1248-1258
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• 2010

In this paper, a method for simultaneously realizing the sum and difference patterns which are required in the monopulse radar sensor systems, is presented by using single taper array antenna with rectangular microstrip patches. The widths of patches are first determined by the voltage weights which are synthesized for the fundamental array factor patterns to be applied to the monopulse operation by using the sidelobe levels(SLLs) control technique. As the bi-directionally series-fed technique is applied and the lengths of connecting lines between patches are appropriately adjusted, the single array generates two phase-shifted beams which activates out-of-phase and in-phase ports of a $180^{\circ}$ hybrid coupler to synthesize the sum and difference patterns. The simulated results on the configuration designed at 9.5 GHz are compared with measured results showing the validity of the proposed method.