• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.9
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• pp.38-48
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• 2000

This paper presents the photonic bandgap structure that has a defect mode within a broad stopband. In order to create a broad stopband, we eliminated one of periodic stopbands of PBG structure by using a quarter-wavelength transformer and cascaded another PBG structure having a center frequency corresponding to the eliminated stopband. We have demonstrated that it is a simple and effective method that can solve an overlapping problem of periodic stopband in two cascaded PBG structures.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.7
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• pp.644-652
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• 2004

In this paper, we designed a cascaded microstrip lowpass filter using the lowpass filters previously proposed. The previously proposed lowpass filters have a ultra-wide stopband and prominent cutoff sharpness using the combined characteristics of slot and microstrip open stub, respectively, and they are catagorized into 2 types by the method that determining their passband characteristics. The first type is determined its passband characteristics by open stub characteristics and the second is by slot characteristics. By cascading these structures with impedance adjustment of each element, the deeper out-of-band rejection and the sharper skirt response were achieved. The fabricated cascaded lowpass filters have -3㏈ cutoff frequencies at 1.035㎓ and 1.286㎓ respectively and -20㏈ stopband is over 20㎓ for both structures.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7A
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• pp.852-857
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• 2004

In this research, we suggested a new PBG cell with wide stopband. In order to improve the characteristics of the insertion loss, return loss, and ripple, we used two overlapped cells. One is small cell which is made in inside and the other is large cell which is made in outside. The inner cell stops the high band and the outer cell stops the low band. As a result, the new PBG cell had a wide stop band. Insertion loss was about 40dB in stopband and the ripple, and the return loss was improved. Also, the passband is broaden by employing new PBG cells.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.3
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• pp.439-444
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• 2020

In this paper, the analysis of the FSCS (frequency-selected coupling structure) as the coupling coefficient and multi-stage FSCS for enhanced bandstop bandwidth is suggested. The FSCS is composed by the connected coupled-line and open-stub. Basically, the resonance frequency of the FSCS is given by the electrical length of the stub, and the bandwidth is controlled by the coupling coefficient. Multi-stage FSCS is made by addition of another FSCS with the half electrical length. Manufactured bandstop filter using 3 stage FSCS is measured with the stopband of 177.3% and the maximum return loss of 1dB.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.87-89
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• 2006

U-물류/유통, U-항만에 핵심적인 기술이 될 Ultra-Wide(UWB)통신을 위한 광대역 안테나를 설계, 개발하였다. 설계된 안테나는 UWB 주파수 대역인 3.1$^{\sim}$11.7GHz 대역에서 안테나 특성을 만족하고, IEEE 802-11a와HIPERLAN/2에 의해 사용이 제한된 5.15${\sim}$5.825GHz 대역에서 주파수 저지 대역을 가지기 위하여 U모양의 얇은 슬롯을 복사 패치 위에 구현 하였다. 제작한 안테나는 5${\sim}$595GHz 대역을 제외하고는 안테나의 특성을 만족한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6C
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• pp.777-784
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• 2004

In this paper, a new filter structure to improve frequency response characteristics in decimation filter using CIC(Cascaded Integrator-Comb) filters and half band filters is proposed. Conventional filters improve only passband characteristics, but we propose a new filter which can improve stop band and pass band characteristics simultaneously. Since proposed filter needs only two multiplication, additional implementation cost is not much. And overall linear phase characteristics are maintained since the proposed filter is also linear phase. Finally, filter coefficients quantization effects ate discussed after Verilog-HDL coding.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.5
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• pp.69-74
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• 2010

In this paper, we proposed a compact arbitrary dual-band band-stop filter using CRLH transmission line. The proposed filter used CRLH transmission line as stub and it developed dual-band band-stop characteristics using non-linear phase response of CRLH transmission line. The size of proposed filter is compact. And it can control arbitrary dual stop band. In this paper, designed band-stop filter at GPS band and ISM band As result, the S(2,1) is about -30dB at GPS band and about -29dB at ISM band. The fabricated filter is very compact. Its dimension is 10mm*15mm.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.434-444
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• 2002

본 논문에서는 기존의 RF 여파기가 대역 내에서만 정합이 되는 특성을 개선하여 대역 외에서도 50$\Omega$ 정합 특성을 가지는 여파기 설계 기술을 제안하였다. 대역 외에서 정합 시켜 주는 방법으로 결합기와 대역 통과 여파기로 구성된 Balance Type과 결합기와 대역 저지 여파기로 대역 통과 여파기 특성을 가지는 Reflection Type을 제시하여 그 특성을 확인하였다. 각각의 형태는 광대역 90도 3-㏈ 결합기를 사용한 것으로 결합기의 대역폭과 진폭 및 위상 오차에 따라 저지 대역에서의 정합 특성이 좌우되며, 이에 광대역의 3-㏈ 결합기를 설계 및 적용하여 광대역의 반사 손실 개선 효과를 얻을 수 있었다. 제작 결과 Balance type의 경우 1.2 GHz~2.6GHz까지 대역 내에서 -10㏈에서 -15 ㏈의 반사 손실 특성을 가지고 대역 저지 특성이 우수하며, Reflection type은 DC에서 3.3GHz까지 반사손실이 -15 ㏈ 내외로 광대역 정합 특성을 가진다. 특히, 저주파 반사 특성이 우수하여 저주파 발진 가능성이 큰 회로 설계에 유용하다.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1414-1415
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• 2008

본 논문에서는 고출력 극초단파(High Power Microwave)가 쏘아지는 대상이 방어장비를 갖추고 있을 때 외부대상이 어떤 영향을 받는지를 규명하는데 목적이 있다. 입력펄스를 변조(modulation)시켜 저지대역(Stop Band) 주파수 대역에 맞추고, 펄스(Pulse)를 저대역 통과 필터의 저지대역에 통과시킨다. 이때 출력펄스의 응답(response)을 시간영역(Time-domain)에서 분석하여 정상상태(steady state)보다는 과도응답(Transient Response)을 확인하는 것을 제안한다. 이 방법은 저지대역의 파형이 필터를 통과해도 과도응답 때문에 필터가 제 역할을 하지 못한다는 이론을 규명한다. 이 이론은 고출력 극초단파가 외부대상에 미치는 영향에 있어서 전자파를 방어하려고 하여도 과도응답 상태 응답 때문에 타격을 받을 수 있다는 것을 규명한다.

• 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.