• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 하계학술대회 논문집
• /
• pp.377-382
• /
• 2000

Film bulk acoustic resonator (FBAR) using AIN reactively sputtered at room temperature was fabricated. The FBAR is composed of a piezoelectric aluminium nitride thin film, top electrode of Al and bottom electrode of Au connected by a short (200${\mu}{\textrm}{m}$) transmission line on both sides and reflector layers of SiO$_2$- W Pair. The active areas of Al and Au were patterned using 150${\mu}{\textrm}{m}$ diameter shadow mask. The series resonance frequency (fs) and the parallel resonance frequency (fp) were measured at 1.976 GHz and 2.005 GHz, respectively. The minimum insertion loss and return loss were 6.1 dB and 37.19 dB, and the quality factor (Q) was 4261.

• 동력기계공학회지
• /
• 제9권3호
• /
• pp.26-32
• /
• 2005

The volumetric efficiency is significantly affected by the behavior of pressure wave in induction system and exhaust pipe. By the motion of the piston, there exist pressure fluctuation in induction system which produce waves. Waves are propagated along a pipe bi-directional as they propagated through it, making compression wave and rare-faction(expansion) wave. These wave phenomena can affect to the volumetric efficiency. As a method of improvement of the volumetric efficiency, fuel economy and pollutant emission reduction particularly in low engine speeds, a side-branch additional tunable helmholtz resonator on the secondary pipe of intake system is proposed by use of their acoustic vibrations. Some of results are presented which deal with their physical phenomena for the wave action of intake system in a four-stroke three cylinders diesel engine.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2005년도 춘계학술대회논문집
• /
• pp.786-789
• /
• 2005

An acoustic total or partial enclosure is widely used to reduce the sound pressure level propagating from a noise source. However, the performance of the acoustic enclosure is decreased by its inherent limitations such as temperature rise or acoustic pressure build up inside the enclosed acoustic field. In general, a silencer is installed to overcome these limitations, for large amount of air can be exchanged through the silencers. In this reason, a parallel baffle type duct silencer with acoustic resonators is studied to reduce the transmitted noise from a transformer. In this silencer, the high frequency components of the transmitted noise over 360Hz are effectively absorbed by the parallel baffles and the other ones, 120 and 240 Hz, are reduced due to the presence of Helmholtz resonators. Large sound attenuation is achieved by applying the sound resonating barrier to the large transformers in a substation.

• Journal of Mechanical Science and Technology
• /
• 제18권1호
• /
• pp.145-152
• /
• 2004

Effects of various baffle designs on acoustic characteristics in combustion chamber are numerically investigated by adopting linear acoustic analysis. A hub-blade configuration with five blades is selected as a candidate baffle and five variants of baffles with various specifications are designed depending on baffle height and hub position. As damping parameters, natural-frequency shift and damping factor are considered and the damping capacity of various baffle designs is evaluated. Increase in baffle height results in more damping capacity and the hub position affects appreciably the damping of the first radial resonant mode. Depending on baffle height, two close resonant modes could be overlapped and thereby the damping factor for one resonant mode is increased exceedingly. The present procedure based on acoustic analysis is expected to be a useful tool to predict acoustic field in combustion chamber and to design the passive control devices such as baffle and acoustic resonator.

• 한국세라믹학회지
• /
• 제38권11호
• /
• pp.980-986
• /
• 2001

5.2GHz 중심 주파수를 갖는 Bragg reflector형 FBAR를 제작하여 주파수 응답 특성을 측정하고, 공진기 구조에서 각 층의 탄성 손실(acoustic loss)을 고려한 주파수 응답의 수치적 계산을 통해서 그 특성을 분석하였다. W과 $SiO_2$쌍을 선택하여 RF sputtering법으로 총 9층의 Bragg reflector를 제작하였고, 공진기의 압전층으로 pulsed dc 전원에 의한 sputtering법으로 AlN과 Al 전극을 증착하여 제작하였다. 제작된 공진기의 반사손실( $S_{11}$)은 중심주파수 5.38GHz에서 12dB이었고 직렬 공진 주파수( $f_{s}$)는 5.376GHz, 병렬 공진 주파수 ( $f_{p}$)는 5.3865GHz로 관찰되었다. 공진기의 성능지수인 유효 전기기계결합계수( $K_{ef{f^2}}$)값이 약 0.48%, 품질계수 ( $Q_{s}$) 값이 411이었다. 수치적으로 계산된 주파수 응답 특성으로부터 AlN 박막의 acoustic 상수들과 Bragg reflector의 반사계수를 도출한 결과 AlN 박막의 material acoustic impedance와 wave velocity는 AlN 고유의 값보다 감소되었으며, AlN 박막의 전기기계 결합계수( $K^2$)값은 c축 배향성 저하에 의해 매우 작은 값(0.49%)을 가졌다. 주파수 대역에서 Bragg reflector의 반사계수는 약 0.99966으로 계산되었으며 약 2.5 GHz에서 9.5 GHz까지의 넓은 반사대역을 나타내었다.다.었다.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2008년도 춘계종합학술대회 A
• /
• pp.59-62
• /
• 2008

In this paper, we study ZnO-based a film bulk acoustic resonator (FBAR) using a multi-layered Bragg reflector. We insert chromium adhesion layers of 0.03 mm-thick to the Bragg reflector and improve the performance using thermal treatments. At operating frequency about 2.5 GHz, excellent resonance characteristics are observed in terms of good return loss and high quality factor.

• Journal of information and communication convergence engineering
• /
• 제3권4호
• /
• pp.167-171
• /
• 2005

In this paper, the resonance characteristics of SMR-type FBAR devices annealed by three different annealing methods are investigated and compared. The resonance characteristics could be effectively improved by the proposed efficient annealing method which optimizes the annealing conditions. It seems very useful for improving the performance of the SMR-type FBAR devices as a cost-effective way.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2012년도 춘계학술대회 논문집
• /
• pp.942-943
• /
• 2012

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2004년도 제26회 학술발표회 초록집
• /
• pp.177-177
• /
• 2004

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2002년도 추계학술발표강연 및 논문개요집
• /
• pp.92-92
• /
• 2002