• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권1호
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• pp.40-44
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• 2006

In this paper, the distortion characteristics of an electrical pulse which has a rise/fall time due to the dispersion and the reflection, on nonuniform tapered microstrip lines has investigated in time domain. The transmission characteristics on uniform microstrip lines in time domain had represented already, but the results for the nonuniform tapered microstrip lines not represented yet. We investigated the transmission characteristics for pulse signal on the nonuniform tapered microstrip lines, and the result applied to design of wide band impedance matching circuit in design of MMIC. The voltage and current transfer functions are shown for the tapered line. The dispersion and distortion obtained by using these transfer functions are represented for the nonideal square pulse.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2004년도 춘계종합학술대회
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• pp.472-474
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• 2004

본 연구에서는 변형된 Folded 다이폴 안테나의 특성을 모멘트법을 이용하여 조사하였다. 안테나의 중심주파수는 200MHz, 도선의 반지름은 0.5mm이고 두 개의 선형 다이폴 사이의 간격은 2cm이다. 시뮬레이션 결과 18cm 정도의 내부 sub 변화와 4.5cm 정도의 외부 stub 변화는 SWR 기준으로 3 미만을 유지한다. 이는 변형된 Folded 다이폴 안테나가 추가적인 정합회로 없이 광대역 특성을 보이는 것을 의미한다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.273-277
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• 1999

A cold cathode flourescent lamp for the backlight in the notebook computer requires high input voltage about 1300(V) when it turns on. But once a discharge starts, the input voltage can be dropped by about one-third for continued output. The equivalent impedance also varies from open to several dozens of kilo-ohms. The piezoelectric transformer converts electrical energy into mechanical energy and then converts it back to electrical energy at a high voltage. Its high output voltage, high efficiency and small size are suitable for driving the LCD backlight in the notebook computer. The piezoelectric transformer operates near the resonance frequency and the output waveform is close to sine wave with very little noise. This paper suggests an inverter for LCD backlight of notebook computer using piezoelectric transformer that includes voltage to frequency converter for gate signal which is useful for tracking of variable resonance frequency depending on load impedance.

• ETRI Journal
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• 제46권4호
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• pp.716-726
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• 2024

An ultrawide stopband lowpass filter is reported using three stepped impedance resonators with high selectivity. The filter extends the stopband frequency range and attenuation, and two quarter-wave open stubs and three circular ground slots are introduced. The lumped and distributed equivalent models are derived and analyzed. The corresponding results are validated experimentally in a fabricated prototype. The prototype lowpass filter has a 3 dB cutoff frequency (f_c) of 2.9 GHz, and the stopband is extended up to 35 GHz (12.07f_c), with an attenuation level better than 20 dB throughout. The passband-to-stopband transition (3 dB-20 dB) bandwidth is 0.18 GHz, and the roll-off factor is 135 dB/GHz at 30 dB. The insertion loss is 0.3 dB at 1.6 GHz. The normalized circuit size of the proposed filter with respect to the guided wavelength is 0.04.

• 한국전산구조공학회논문집
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• 제20권1호
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• pp.39-50
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• 2007

본 논문은 다중 적층지반상의 지반-구조물 상호작용 해석을 위한 3차원 무한요소를 소개한다. 본 무한요소는 Cartesian 좌표계에서 정식화되었으며, 수평, 수평모서리, 수직, 수직 모서리 그리고 수평 수직 모서리 무한요소로서 총 5개의 무한요소로서 구성된다 적용한 형상함수 내부의 파동함수들은 적층지반의 파동문제를 효과적으로 모사하며 다중파동성분을 포함하고 있다. 본 요소의 성능을 검증하기 위하여 주파수영역에서 여러 가지 예제해석을 수행하였다. 균질 및 적층지반상 강체기초와 묻힌 케이슨 기초의 무차원 동적 거동(compliance & impedance)을 구하였으며, 기연구자들의 값과 비교 검토하였다.

• 한국항행학회논문지
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• 제15권5호
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• pp.774-780
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• 2011

본 논문은 저속파 특성을 갖고 있는 오픈 스터브가 연결된 전송선로를 이용하여 배글리(Bagley) 다각형과 지셀(Gysel) 분배기 설계를 제안한 것이다. 이러한 저속파 특성을 갖고 있는 구조는 짧은 길이의 전송선로와 병렬로 연결된 오픈 스터브의 캐패시턴스 때문에 특성 임피던스와 위상 속도의 감소 때문에 회로의 소자의 크기를 작게 구현할 수 있다. 이러한 특성을 확인하여 위하여 중심주파수 2.1 GHz에서 기존의 배글리 다각형과 지셀 분배기를 저속파 특성을 이용하여 분배기를 구현하였으며, 그 전기적 특성은 두 종류의 분배기가 동일하지만 저속파 특성을 이용한 분배기의 크기를 각각 15 % 이상 줄일 수 있음을 확인하였다.

• Journal of Astronomy and Space Sciences
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• 제37권1호
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• pp.19-27
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• 2020

Pc1 pulsations are important to consider for the interpretation of wave-particle interactions in the Earth's magnetosphere. In fact, the wave properties of these pulsations change dynamically when they propagate from the source region in the space to the ground. A detailed study of the wave features can help understanding their time evolution mechanisms. In this study, we statistically analyzed Pc1 pulsations observed by a Bohyunsan (BOH) magneto-impedance (MI) sensor located in Korea (L = 1.3) for ~one solar cycle (November 2009-August 2018). In particular, we investigated the temporal occurrence ratio of Pc1 pulsations (considering seasonal, diurnal, and annual variations in the solar cycle), their wave properties (e.g., duration, peak frequency, and bandwidth), and their relationship with geomagnetic activities by considering the Kp and Dst indices in correspondence of the Pc1 pulsation events. We found that the Pc1 waves frequently occurred in March in the dawn (1-3 magnetic local time (MLT)) sector, during the declining phase of the solar cycle. They generally continued for 2-5 minutes, reaching a peak frequency of ~0.9 Hz. Finally, most of the pulsations have strong dependence on the geomagnetic storm and observed during the early recovery phase of the geomagnetic storm.

• 한국전기전자재료학회논문지
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• 제17권12호
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• pp.1259-1263
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• 2004

In this paper, the optimum design of ultrasonic dry cleaning head was investigated. The transducer instead of mechanical dynamic structure was used to generate ultrasonic wave and the horn-shape amplifier was utilized to solve the energy decaying problem of ultrasonic wave with propagating it through the media. The analyses of ultrasonic wave and a fluid for the selected structure of a cleaning head were carried out using SYSNOISE and ANSYS simulators, respectively. Based on simulator results, the distance between a horn and the substrate of 4 mm and the horn diameter of 10 mm were determined to maximize the energy of ultrasonic waves. The cooling structure was also considered to reduce the heat from the transducer and the horn. The equivalent circuit for the fabricated horn was deduced from HP4194A impedance/gain/phase analyzer and the frequency of an ultrasonic wave of 20.25 kHz was confirmed using the parameters of the equivalent circuit.

• Coupled systems mechanics
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• 제2권1호
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• pp.53-83
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• 2013

Sea waves induce significant pressures on coastal surfaces, especially on rocky vertical cliffs or breakwater structures (Peregrine 2003). In the present work, this hydrodynamic pressure is considered as the excitation acting on a piezoelectric material sheet, installed on a vertical cliff, and connected to an external electric circuit (on land). The whole hydro/piezo/electric system is modeled in the context of linear wave theory. The piezoelectric elements are assumed to be small plates, possibly of stack configuration, under a specific wiring. They are connected with an external circuit, modeled by a complex impedance, as usually happens in preliminary studies (Liang and Liao 2011). The piezoelectric elements are subjected to thickness-mode vibrations under the influence of incident harmonic water waves. Full, kinematic and dynamic, coupling is implemented along the water-solid interface, using propagation and evanescent modes (Athanassoulis and Belibassakis 1999). For most energetically interesting conditions the long-wave theory is valid, making the effect of evanescent modes negligible, and permitting us to calculate a closed-form solution for the efficiency of the energy harvesting system. It is found that the efficiency is dependent on two dimensionless hydro/piezo/electric parameters, and may become significant (as high as 30 - 50%) for appropriate combinations of parameter values, which, however, corresponds to exotically flexible piezoelectric materials. The existence or the possibility of constructing such kind of materials formulates a question to material scientists.

• 한국전자파학회논문지
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• 제24권7호
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• pp.722-729
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• 2013

본 논문에서는 밀리미터파 대역에서 저손실 전송 선로로 많이 사용되고 있는 구형 도파관의 단면 치수 변화가 전송 특성에 미치는 영향을 검토하였다. 도파관 내부의 그린 함수를 고유 모드 함수 전개법으로 구하고, 도파관 내부에 포스트를 설치한 구조의 내부 임피던스로부터 반사 계수 표현식을 도출하였으며, 도파관의 단면 치수 변화가 반사 계수에 미치는 영향을 검토하였다. 이론 해석의 타당성을 검증하기 위해 반사 계수를 측정하고, 이론치와 비교하였다.