• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 제5회 영호남 학술대회 논문집
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• pp.35-38
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• 2003

In this paper, we investigated the electric and acoustic properties of piezoelectric composites, which were fabricated using polymer and piezoelectric ceramics, when the volume fraction of PZT varies. Practically, the shrinkage rate of polymer is an important factor in ultrasonic transducer fabrication. When 10 wt% filler A was added into polymer(Epofix), the lowest shrinkage was resulted. The electromechanical coupling factor($k_t$) of the fabricated piezoelectric composites showed its highest when the volume fraction PZT was 0.6. It decreased if the volume fraction was higher than the value. The relative permittivity and acoustic impedance of piezoelectric composites decreased linearly when PZT volume fraction was decreased. The lowest acoustic impedance was 3.2 when the volume fraction of PZT was 0.2.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 추계학술대회 논문집
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• pp.69-72
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• 2008

This paper presents the transient and conventional grounding impedance behaviors of large grid grounding system associated with the injection point of impulse current The measurement methods consider two possible errors in the grounding-system impedances: (1) ground mutual resistance due to current flow through ground from the ground electrode to be measured to the current auxiliary, (2) ac mutual coupling between the current test lead and the potential test lead The test circuit was set to reduce the error factors. The transient grounding impedance depends on the rise time and injection point of impulse current It is effective that grounding conductor is connected to the center of the large grid grounding system.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 제4회 영호남학술대회 논문집
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• pp.146-149
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• 2002

In this study, 2-2 type piezocomposites were made and characteristics as volume fraction of PZT were investigated. The accoustic impedance of 2-2 piezoelectric composites was linearly decreased with decreasing PZT volume fraction. when the volume fraction of PZT was 0.2 the acoustic impedance was 3.2 Mrayl. The electromechanical coupling factor was favourable in comparison with the single phase PZT, and that was about uniformed about 0.68 in the 0.2 to 0.6 of PZT volume fraction.

• Transactions on Electrical and Electronic Materials
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• 제17권2호
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• pp.118-120
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• 2016

A coplanar waveguide employing periodic 3D coupling structures (CWP3DCS) was developed for application in miniaturized on-chip passive components on silicon radio frequency integrated circuits (RFIC). The CWP3DCS showed the shortest wavelength of all silicon-based transmission line structures that have been reported to date. Using CWP3DCS, a highly miniaturized impedance transformer was fabricated on silicon substrate, and the resulting device showed good RF performance in a broad band from 4.6 GHz to 28.6 GHz. The device as was 0.04 mm² in size, which is only 0.74% of the size of the conventional transformer on silicon substrate.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2003년도 기술심포지움 논문집
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• pp.260-264
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• 2003

In this paper, a $\lambda/4$ hairpin resonator is proposed to reduce the size of planar resonators for a LTCC MLC bandpass filter. The $\lambda/4$ hairpin resonator operates as stepped impedance resonator (SIR) without changing the width of the planar resonator. It is composed of two sections those are parallel coupled line and transmission line. The characteristic impedance of two sections is different each other. The design formulas of the bandpass filter using the coupling element at the arbitrary position are derived from even and odd-mode analysis. The formulas can take account of the arbitrary coupling of lumped ana/or distributed resonators. The advantage of this filter is its abilities to change freely the coupling structure between two resonators. Experimental bandpass filters for 2.4GHz Band are implemented and their performances are shown.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.957-959
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• 2014

The wave analysis of cylinders combined rigidly with a finite plate to identify the effect of the plate on the wave propagation. This paper uses the mobility and impedance coupling method to combine a infinite-length cylinder with the plate, and obtains the coupling forces induced by the vibration of the structure. The waveguide finite element method is used to calculate the wave characteristics of the cylinder excited by the forces. From the results, the dispersion diagram can be obtained. It contains the characteristics induced by the vibration and length of the internal plate. It also shows the wave propagation of elastic waves sustained in the cylinder.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.662-668
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• 1997

Since the structural impedance is much greater than that of medium in the most cases, we often assume that the structure is rigid and that the structural vibration is independent of medium, i.e. we usually calculate the vibration of the structure first, and then obtain the radiation sound from it. This assumption is no longer satisfied when the structural stiffness is small or the fluid impedance is comparable to it. This situation often happens in underwater acoustics. Although many researchers have studied about structural-fluid coupling, we have difficulties in solving the problem analytically. Therefore the numerical method using powerful computation leads us to obtain the various coupling problem. To understand the physical coupling phenomena, visualization of sound field by a geometrically simple system(plate-cavity coupled system) is performed experimentally. Acoustic holographic method is used to estimate sound field.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.184-187
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• 2005

Physical changes in a structural system may cause changes in mechanical impedance of the system. Due to the electro-mechanical coupling effect in piezoelectric materials, this change can be monitoring by the electrical impedance of the piezoelectric sensor. In this paper, the variability of electro-mechanical impedance caused by temperature effect is assessed to adjust impedance data used for EMI based damage detection in beams. First experiments on beams are described. Next, experiments were performed under the temperature varying condition, in the range of $3^{\circ}C\;to\;23^{\circ}C$. Finally, the relationship between temperatures and impedance signatures is analyzed empirically temperature-frequency patten for the test structure.

• Journal of Power Electronics
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• 제19권6호
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• pp.1575-1581
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• 2019

Due to the mismatched line impedance among distributed generation units (DGs) and uncontrolled harmonic current, the droop controller has a number of problems such as inaccurate reactive power sharing and voltage distortion at the point of common coupling (PCC). To solve these problems, this paper proposes a resistive-capacitive virtual impedance control method. The proposed control method modifies the DG output impedance at the fundamental and harmonic frequencies to compensate the mismatched line impedance among DGs and to regulate the harmonic current. Finally, reactive power sharing is accurately achieved, and the PCC voltage distortion is compensated. In addition, adaptively controlling the virtual impedance guarantees compensation performance in spite of load changes. The effectiveness of the proposed control method was verified by experimental results.

• 한국ITS학회 논문지
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• 제4권3호
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• pp.73-78
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• 2005

본 논문에서는 상호 캐패시터 (Bypass coupling Capacitor)를 이용하여 Transmission Zero를 구현함으로써 우수한 차단 응답 특성을 보이며, 또한 IDC (Interdigital Capacitor)을 사용함으로써 더욱 향상된 고조파 특성을 갖는 대역 통과 여파기를 설계 및 구현하였다. 지능형 교통시스템에 사용되고 있는 5.85 GHz의 중심 주파수에서 3 %의 대역폭을 갖도록 설계된 SIR (Stepped Impedance Resonator) 대역 통과 여파기는 1.8 dB의 삽입 손실과 20 dB의 반사 손실 특성을 갖도록 설계 되었으며, 제작된 대역 통과 여파기는 대역폭이 4.2 %로 1.9 dB의 삽입 손실과 15.4 dB의 반사 손실을 측정 결과에서 나타내었다.