• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.1
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• pp.52-60
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• 1997

A 23GHz 2-stage LNA was designed using MPIE numerical analysis and microwave CAD EEsof softwares. The basic circuit was designed by EEsof tools but analyzed more precisely using numerical MPIE tools and modified. The matching sections of the input and output terminals were designed with paralledl coupled filter-type lines, these matching sections perform impedance matching and DC blocking, more over have the advantages of small discontinuities and small errors in the design process. The FET chip is directly attached to the ground metal. The designed LNA gives 15.2dB gain and 2.7dB noise figure. without considering 1.8dB loss of connectors. These results validate our design process and matching schemes and fabrication technologies over the 20GHz frequency range.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.3
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• pp.699-706
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• 2010

We have studied to obtain the slanted finger interdigital(SFIT) type filter was formed on the Langasite substrate and was evaporated two IDT electrode by Aluminum-Copper alloy respectively. We can fabricate that the block weighted type IDT as an input transducer of the filter and the withdrawal weighted type IDT as an output transducer of the filter from the results of our computer-simulation. Also, we have performed to obtain the properly design conditions about phase shift conditions of the SPIT type filter. We have employed that the number of pairs of the input and output IDT are 50 pairs and the thickness and the width of reflectors are $5000\;{\AA}$ and $3.6{\mu}m$ respectively. At the first sample, we have employed that the distance from the hot electrode to the reflectors is $2.4{\mu}m$ distance from the ground electrode to the reflectors is $1.8{\mu}m$ and the distance from the hot electrode to the ground is $1.5{\mu}m$ respectively. At the other sample, we have also employed that the distance from the hot electrode to the reflectors and the distance from the ground electrode to the reflectors are $2.4{\mu}m$. Frequency response of the fabricated SAW filter has the property that the center frequency is about 190MHz and bandwidth at the 3dB is probably 7.3 MHz. And we could obtain that return is less than -20dB, ripple characteristics is probably 3dB and triple transit echo(TTE) is less than -22dB after when we have matched impedance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.2
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• pp.127-134
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• 2015

In this paper, we propose 2.6 GHz single band dual polarization MIMO omni antenna for in-building applications. The proposed antenna operates at 2.6 GHz single LTE band, Up-link 2.52~2.54 GHz and Down-link 2.64~2.66 GHz. Horizontal and vertical polarizations of the antenna has been, respectively, constructed by the synthesis of four folded loop antennas and the folded monopole antenna. The height of the MIMO omni-directional antenna is minimized to be less than ${\lambda}/13.5$ from the ground. The measurement results show excellent MIMO omni antenna performance of 2.85 dBi vertical polarization gain, 2.29 dBi horizontal polarization gain, and 19.25 dB port isolation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.594-601
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• 2019

A true MSEW abutment is an abutment type that directly supports the load of a superstructure. Metal strips, which are in-extensile reinforcements, should be used to minimize abutment deformation. A study to derive the application conditions of a True MSEW abutment was carried out by Zevogolis(2007). As a result, the pullout factor of safety of the uppermost reinforcement was estimated to be the smallest. Therefore, the pullout factor of safety of the uppermost reinforcement is the most important design factor. Parameter analysis was conducted with the abutment length, abutment heel, and abutment height as variables. The pullout factor of safety increased with increasing abutment length and abutment heel length. This is because the contact area increases and the superstructure is dispersed as the abutment length and abutment heel length increase. The pullout factor of safety converges at an abutment length of 1.2m and an abutment heel length of 0.9m. This is because the effective length of the reinforcement is reduced due to the increase in contact area. On the other hand, the extension of the superstructure will increase if the abutment length and abutment heel length are increased excessively. In addition, earth-volume is increased if the abutment height increases excessively. This acts as an upper load on the MSE wall. Therefore, it needs to be examined carefully.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.3
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• pp.25-31
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• 2003

In this paper, we proposed a novel compact microstrip lowpass filter with an ultra-wide stopband and a sharp cutoff frequency response. To improve the cutoff response of the conventional filter, the coupling effect between two open stubs is used. The slot on the ground with conventional shunt open stubs plays an important role of increasing the stopband at a high frequency. The combination of these structures gives the filter the characteristics of an ultra-wide stopband with a prominent cutoff sharpness. The fabricated microstrip lowpass filter with the size of 19.2 mm $\times$ 14.9 mm has -3 dB cutoff frequency at 1.1 GHz and -20 dB stopband from 1.5 GHz to over 30 GHz. The insertion loss is less than -0.15 dB in the passband.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.11
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• pp.85-92
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• 2003

In this paper, a multiple U-shaped slot antenna on 5㎓ band is designed, fabricated, and measured. The prototype consists of a U-shaped slot and two Invert U-shaped slot. To obtain wide bandwidth, the foam layer is inserted between ground plane and substrate. After various parameters, length, width, position of U-shaped slot horizontal, interval length between two invert U-shaped slot, feeding position and airgap width, optimized, a multiple U-shaped slot antenna is fabricated and measured. The measured results of the antenna are compared with its simulated results. A 2:1 VSWR impedance bandwidth of 20.4% is achiedved by employing this technique. The gain is about 5.5㏈i. The experimental far-field patterns are stable across the pass band.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.8
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• pp.921-926
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• 2014

In this paper, the characteristics of inset fed microstrip antenna loaded with CSLR(complementary single loop resonator) are studied. Effective permeability parameters of the SLR unit cell is retrieved from simulated scattering parameters, and structure parameters of the SLR unit cell are selected so that effective permeability is negative value at the operating frequency. The optimized inset fed microstrip antenna loaded with SLR for a $3{\times}3$ array in the ground plane of a conventional patch antenna is designed and simulation results of return loss and radiation pattern are shown. At resonant frequency 2.82 GHz, the overall dimension of the proposed antenna is reduced by approximately 56.8% compared to the conventional inset fed antenna. Simulation results are obtained by 3D FEM solver(Ansoft's HFSS).

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.4
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• pp.327-334
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• 2010

This paper deals with a single-phase dynamic voltage restorer(DVR) with a quasi Z-source topology. The proposed system based on a single-phase quasi Z-source PWM ac-ac converter which have features such as the input voltage and output voltage are sharing ground, and input current operates in continuous current mode(CCM). For the detection of voltage sag-swell, peak voltage detection method is applied. Also, the circuit principles of the proposed system are described. During the 60% severe voltage sag and 30% voltage swell, the proposed system controls the adding or missing voltage and maintains the rated voltage of sinusoidal waveform at the terminals of the critical loads. Finally, PSIM simulation and experimental results are presented to verify the proposed concept and theoretical analysis.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.99-99
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• 2010

최근 집속이온빔을 이용한 미세회로 교정, MEMS 공정 및 이온 도핑 등에 대한 연구개발이 활발히 이루어지고 있다. 기존에 널리 사용되었던 액체 금속 이온 소스의 경우 비교적 큰 angular divergence 및 Ga 이온 소스에 의한 오염이 문제시 되고 있어 이를 대체할 수 있는 가스 이온 소스에 대한 연구를 진행하였다. 본 연구에서 사용된 가스 이온 소스는 2 turn 안테나(1/4 inch Cu tube)가 감긴 반경 4 cm 석영관 내부에 Ar 가스를 주입 후 RF(13.56MHz)-ICP 타입 방전을 이용하였다. 운전 압력은 $10^{-5}\;Torr$ 범위이며 인가된 RF 전력은 최대 150 W이다. 석영관 내 발생된 플라즈마로부터 Ar 이온을 인출하기 위해 2단 인출 전극 구조가 사용되었으며 상단 전극에 고전압이 인가되고 하단 전극이 접지되는 형태이다. 2단 인출 전극의 최대 인출 전압은 10 kV, 상단 및 하단 전극의 구멍 크기는 각각 0.3 mm, 2 mm이다. 이온빔의 퍼짐을 최소화하기 위해 전극 간 공간 내 이온 거동 전산모사를 통해 전극 구조를 설계하였으며 이를 통해 최대 $30\;mA/cm^2$의 이온 전류 밀도 값을 얻을 수 있었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.10
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• pp.1126-1135
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• 2007

This paper presents the varactor-tuned miniaturized hairpin tunable filter with a single control voltage. The previously proposed miniaturization method is a very straight-forward method to miniaturize a parallel coupled-line filter. In this paper, the miniaturized hairpin tunable filter is proposed with the constant ratio rule of that the capacitances of the each stage always have constant ratio without any dependency to miniaturized electrical length. To show the validity of the proposed method, a 3rd order 0.5 dB ripple Chebyshev fitter with a center frequency of 900 MHz and a fractional bandwidth(FBW) of 10 % was designed and fabricated. The fabricated filter was based on CER-10 substrate of Taconic Inc. with 1SV277 varactor diode of Toshiba Inc. The center frequency of the fabricated filter can be changed from 606 MHz to 944 MHz, 338 MHz with the control voltage from 0.5 V to 4 V. The insertion loss of the proposed filter is increased with the increment of the control voltage, and the filter characteristics are well reserved expect of slight change of the bandwidth with the various control voltage.