• 한국소음진동공학회논문집
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• 제14권2호
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• pp.111-118
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• 2004

A number of researchers have attempted to measure the reverberation time of a passenger car, ut the reverberation time of passenger car is too short to measure with the traditional band pass filter. And if the reverberation time is very short, the product of the reverberation time (T) and the bandwidth (B) of the traditional band pass fitter becomes small. The low limit of BT product required for the measurement of reverberation time with the traditional band pass filter is 16. In order to overcome this problem, the wavelet filter bank was developed. In this study, this new wavelet filter was employed to measure the reverberation times of five different classes of passenger cars. The low limit of BT product required for the measurement of reverberation time with the wavelet filter is 4. The reverberation times of five passenger cars were measured successfully with the new wavelet filter bank. The reverberation times measured in most passenger cars was found to be around 0.04. Compared with general acoustic rooms like concert halls, this is a very short reverberation time

• 한국전자파학회논문지
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• 제23권4호
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• pp.457-467
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• 2012

본 논문에서는 도파관의 단면(waveguide transverse plane)에 아이리스(iris)를 갖는 구조들을 도파관의 진행 방향으로 일정한 간격으로 배치하여 소형의 대역 통과 여파기를 구현하는 방법을 제시하고자 한다. 이를 위하여 리지가 장하된 원형 개구 아이리스를 여파기 설계의 기본 공진기 구조로 활용하며, 임피던스 인버터(impedance inverter)로 동작하게 되는 L형 아이리스를 새롭게 제안하여 여파기의 길이 방향 크기를 줄이는데 사용하였다. 최종 제작된 여파기는 중심 주파수 10 GHz에서 400 MHz의 대역폭을 갖는데, 기존의 여파기 설계 방식에 비하여 70 %의 소형화를 달성하였다.

• ETRI Journal
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• 제37권5호
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• pp.945-950
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• 2015

A novel microstrip low-pass filter is presented to achieve an ultra-wide stopband with 11 harmonic suppression and very sharp skirt characteristics. The filter is composed of a modified U-shaped resonator (which creates two fully adjustable transmission zeroes), a T-shaped resonator (which determines a cut-off frequency), and four radial stubs (which provide a wider stopband). The operating mechanism of the filter is investigated based on a proposed equivalent-circuit model, and the role of each section of the proposed filter in creating null points is theoretically discussed in detail. The presented filter with 3 dB cut-off frequency ($f_c=2.35GHz$) has been fabricated and measured. Results show that a relative stopband bandwidth of 164% (referred to as a 22 dB suppression) is obtained while achieving a high figure-of-merit of 15,221.

• Nuclear Engineering and Technology
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• 제39권6호
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• pp.725-730
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• 2007

This paper describes recently developed techniques for effective filtering of neutron detector signal noise. In this paper, three kinds of noise filters are proposed and their performance is demonstrated for the estimation of reactivity. The tested filters are based on the unilateral kernel filter, unilateral kernel filter with adaptive bandwidth and bilateral filter to show their effectiveness in edge preservation. Filtering performance is compared with conventional low-pass and wavelet filters. The bilateral filter shows a remarkable improvement compared with unilateral kernel and wavelet filters. The effectiveness and simplicity of the unilateral kernel filter with adaptive bandwidth is also demonstrated by applying it to the reactivity measurement performed during reactor start-up physics tests.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2005년도 춘계학술대회논문집
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• pp.368-371
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• 2005

In this paper, a small band pass filter is designed using new probe type for wireless communication system. In order to provide a band pass filter which can be reduced in dimension, can be reduced in height, and can be surface-mounted. The filter was fabricated using $TE_{01{\delta}}$ mode dielectric resonator. The input/output probes are attached to coner portion of the rectangular metal cavity. Results of the manufactured filter$(12{\times}12{\times}8mm)$ show that the center frequency is 9.953GHz, the insertion loss is -2.98 dB, the 3dB-bandwidth is 15 MHz, and the lode Q is 663.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.939-951
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• 2019

A novel empirical mode decomposition strategy based on Fourier transform and band-pass filter techniques, contributing to efficient instantaneous vibration analyses, is developed in this study. Two key improvements are proposed. The first is associated with the adoption of a band-pass filter technique for intrinsic mode function sifting. The primary characteristic of decomposed components is that their bandwidths do not overlap in the frequency domain. The second improvement concerns an attempt to design narrowband constraints as the essential requirements for intrinsic mode function to make it physically meaningful. Because all decomposed components are generated with respect to their intrinsic narrow bandwidth and strict sifting from high to low frequencies successively, they are orthogonal to each other and are thus suitable for an instantaneous frequency analysis. The direct Hilbert spectrum is employed to illustrate the instantaneous time-frequency-energy distribution. Commendable agreement between the illustrations of the proposed direct Hilbert spectrum and the traditional Fourier spectrum was observed. This method provides robust identifications of vibration modes embedded in vibration processes, deemed to be an efficient means to obtain valuable instantaneous information.

• 조명전기설비학회논문지
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• 제20권9호
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• pp.11-17
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• 2006

We have theoretically investigated the effects of the interplay between the driving voltage of Mach-Zehnder(MZ) modulators and the bandwidth of low-pass filters(LPF) in 10[Gb/s] duobinary modulation systems. For the change of driving voltage ratios(driving voltage/switching voltage), the transmission performance has been evaluated over 200[km] of single-mode fiber(SMF) systems. For driving voltage ratios with smaller than 100[%], the transmission performance has been maintained and greatly affected by the bandwidth of LPFs than the driving voltage. For driving voltage ratios with larger than 100[%], the transmission performance has been degraded and is not sensitive to the bandwidth of LPFs. To see the limitation of driving voltage, we have reduced the driving voltage ratio to 50[%]. Our results suggest that 10[Gb/s] duobinary signals with driving voltage ratio with smaller than 100[%] have been transmitted over 200[km] SMF within 2[dB] power penalty without dispersion compensation. For the driving voltage ratio with 50[%], we have verified that the transmission performance was maintained.

• 한국정보통신학회논문지
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• 제4권3호
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• pp.557-564
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• 2000

교차결합 마이크로스트립 헤어핀 공진기 여파기는 통과대역과 저지대역에서 리플이 나타나며 이러한 리플들은 주파수 선택도와 삽입손실을 개선시킬 수 있다. 교차결합 여파기는 구조가 간단할 뿐 만 아니라 여러가지 형태로 구성할 수 있으므로 그에 따라 여파기 크기가 달라진다. 본 연구에서는 중심주파수가 1.8GHz이고 대역폭이 5.0%를 갖는 대역통과 여파기를 Ensemble 소프트웨어로 설계하였다. 제작된 여파기의 대역폭은 중심 주파수 1.8GHz에서 약 4.53%를 나타내었다.

• 한국전자파학회논문지
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• 제18권7호
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• pp.704-709
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• 2007

본 논문에서는 UWB 시스템에 적용하기 위한 CPW 대역 통과 여파기를 제안하였다. 제안된 여파기는 특성 임피던스 $50{\Omega}$을 갖는 전송 선로에 슬롯만을 형성하여 대역 통과 특성을 갖도록 구현하였다. 설계된 대역 통과 여파기는 무선 랜 주파수 대역에서의 협대역 저지 특성을 얻기 위해 CPW 접지면에 두 쌍의 반파장 슬롯 공진기를 이용한 대역 저지 여파기와 결합하였다. 제작된 대역 통과 여파기는 $15.35{\times}13.60mm$의 작은 크기로 주파수 통과 대역은 3-dB 삽입 손실을 기준으로 $2.8{\sim}9.8GHz$이며 $5.15{\sim}5.71GHz$의 협대역 저지 대역을 갖는다. 또한, 군 지연 특성은 저지대역을 제외한 통과 대역 내에서 400 psec 이하를 나타낸다.

• 한국전자파학회논문지
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• 제12권6호
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• pp.899-905
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• 2001

본 논문에서는 저손실 필터의 소형(경량화를 목적으로 간단한 구조의 3중모드 유전체 공진기를 제안하였다. 대역통과 필터(BPF)의 설계에 있어서는 유한 요소법(FEM)을 근거로 하는 HPSS의 시뮬레이션 결과를 사용하였으며, 세라믹 유전체 공진기를 사용하여 시제작 하였다. 이와 같은 방법으로 3단의 BPF를 설계 제작한 결과, 중심주파수 1.93 GHz에서의 삽입손실은 약 0.9 dB, 대역폭은 25 MHz를 나타냈다. 한편, 보다 복잡한 특성이 요구되는 경우에는3중모드 유전체 공진기간에 슬롯을 사용하여 결합시킬 수 있는 방법을 제시했다. 이와 같은 BPF는 차세대 이동 통신인 IMT-2000시스템에 응용될 수 있다.