• Title/Summary/Keyword: 공진기 섭동방법

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The Microwave Dielectric Properties of Sintering Condition of ZST Ceramics for Movile Telecommunication System (이동 통신용 ZST세라믹스의 소결조건에 따른 고주파 유전 특성)

  • Seo, Jung-Chull;Lee, Hee-Young
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.05b
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    • pp.257-260
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    • 2000
  • 소결온도 및 소결시간의 변화가 ZST세라믹의 유전상수 $\varepsilon_{\tau}$, 품질계수 $Q{\cdot}f$ 및 공진주파수의 온도계수 $\tau_f$에 미치는 영향에 대하여 연구하였다. 소결온도를 $1420^{\circ}C$까지 올렸을 때 공진기 섭동방법으로 1.6GHz에서 측정한 품질계수 Q가 가장 높았으나, 소결밀도 및 유전상수는 오히려 감소하였다. 소결시간의 증가에 따른 품질계수 Q는 $1300^{\circ}C{\sim}1380^{\circ}C$ 온도 범위에서는 소폭 상승하였으며, 소결밀도 및 유전상수는 거의 일정하였다. 공진주파수의 온도계수 $\tau_f$는 소결온도 및 소결시간의 변화에는 거의 의존하지 않았다.

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A Numerical Study on Combustion-Response Parameters of Impinging-Jet Injectors for Stability Rating (충돌형 분사기의 연소응답 인자 정량화에 관한 수치해석적 연구)

  • Son, Jin Woo;Kim, Chul Jin;Sohn, Chae Hoon
    • Journal of the Korean Society of Propulsion Engineers
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    • v.17 no.2
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    • pp.1-8
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    • 2013
  • This study presents relations between the time lag and interaction index of the impinging-jet injectors using the time lag model in a model chamber. The response of the flame is analyzed to artificial perturbation with 5% amplitude of oxidizer speed at a resonance frequency. At the mixing point of fuel and oxidizer, which determines the characteristic length, the relationship between velocity perturbation and heat release rate is quantified by combustion parameters of interaction index and time lag. In this method, time lag or delay is calculated by the characteristic length and the average velocity obtained from numerical results. The tendency that the time delay decreases with axial jet velocity has been observed.

Permittivity Measurement of Thin Film Using a Waveguide-type Resonator with a Slot (슬랏을 갖는 도파관형 공진기를 이용한 박막 필름의 유전율 측정)

  • Cho, Chihyun;Kang, Jin-Seob;Kim, Jeng-Hwan
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.24 no.2
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    • pp.214-217
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    • 2013
  • In this paper, a waveguide-type resonator with a slot is proposed to measure permittivity of thin film from resonant frequency shifting by an attached MUT(Material Under Test). The MUT on the slot shifts resonant frequency by perturbation of electromagnetic field. Amount of shifting resonance frequency is dependent on the permittivity of MUT, and that relation is obtained from numerical simulation. The measured relative permittivity of a thin film with thickness of $65{\mu}m$ is 3.3492 with standard error of ${\pm}0.0605$ in the frequency range of 2 GHz to 3 GHz. Also the proposed method is compared with other measuring methods such as dielectric resonator and waveguide probe systems.

Complex Permittivity and Linewidth Measurements of Microwave Ferrites Using the Cavity Perturbation Method (공진기 섭동방법을 이용한 마이크로파 페라이트의 복소 유전율과 선폭 측정)

  • 엄동진;오호석;박동철;윤상원
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.30A no.4
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    • pp.11-19
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    • 1993
  • The complex permittivity and the linewidth of microwave ferrites are measured using the well known cavity perturbation method. The cavity perturbation method has been widely used for the measurement of complex permittivity and conductivity of low loss magnetic and dielectric materials at microwave frequencies. TT1-2000, TT73-2200, and G-113 samples ordered from Trans-Tech Inc, are tested. TE$_{103}$ and TE$_{106}$ rectangular waveguide cavities are fabricated and the ferrite sample of cylidrical rod and sphere shapes are prepared. The error between the measurement values and the supplier's data is less than 1 percent in case of $\varepsilon$’ and about 10 percent in case of linewidth ($\Delta$H). Worst case error analysis shows that our measured results are well within the error bound calculated from the accuracy specification of the measuring instruments.

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Introduction of Numerical Simulation Techniques for High-Frequency Combustion Instabilities (고주파 연소불안정 예측을 위한 해석기술 개발 사례)

  • Kim, Seong-Ku;Joh, Miok;Han, Sanghoon;Choi, Hwan-Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2017.05a
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    • pp.68-77
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    • 2017
  • High-frequency combustion instability results from a feedback coupling between the unsteady heat release rate and the acoustic waves formed resonantly in the combustion chamber. It can be modeled as thermoacoustic problems with various degrees of the assumptions and simplifications. This paper presents numerical analysis of self-excited combustion instabilities in a variable-length lean-premixed combustor and designs of passive control devices such as baffle and acoustic resonators in a framework of 3-D FEM Helmholtz solver. Nonlinear behaviors such as steep-fronted shock waves and a finite amplitude limit cycle are also investigated with a compressible flow simulation technique.

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The Study of Near-field Scanning Microwave Microscope for the Nondestructive Detection System (비파괴 측정을 위한 근접장 마이크로파 현미경 연구)

  • Kim, Joo-Young;Kim, Song-Hui;Yoo, Hyun-Jun;Yang, Jong-Il;Yoo, Hyung-Keun;Yu, Kyong-Son;Kim, Seung-Wan;Lee, Kie-Jin
    • Journal of the Korean Society for Nondestructive Testing
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    • v.24 no.5
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    • pp.508-517
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    • 2004
  • We described a near-field scanning microwave microscope which uses a high-quality dielectric resonator with a tunable screw. The operating frequency is f=4.5 5GHz. The probe tip is mounted in a cylindrical resonant cavity coupled to a dielectric resonator We developed a hybrid tip combining a reduced length of the tapered part with a small apex. In order to understand the function of the probe, we fabricated three different tips using a conventional chemical etching technique and observed three different NSMM images for patterened Cr films on glass substrates. We measured the reflection coefficient of different metal thin film samples with the same thickness of 300m and compared with theoretical impedance respectly. By tuning the tunable screw coming through the top cover, we could improve sensitivity, signal-to-noise ratio, and spatial resolution to better than $1{\mu}m$. To demonstrate the ability of local microwave characterization, the surface resistance of metallic thin films has been mapped.