• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.3
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• pp.1-8
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• 2010

Acoustic tuning of quarter-wave resonator is investigated numerically to suppress combustion instability in liquid rocket engines. A model combustion chamber is adopted. First, basic acoustic characteristics are examined and acoustic damping is pursued by quarter-wave resonators. Next, for frequency tuning of the resonators, thermodynamic properties inside the acoustic resonators are estimated based on the numerical data. Maximum damping capacity is obtained when the resonators are designed to have the optimum length calculated with the properties. But, damping capacity induced by the resonators with the same length is comparable with it.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.3
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• pp.253-261
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• 2010

In this paper, the design and the fabrication of dual bandpass filter using heterogeneous resonators is presented. Each resonator would not have an effect on each resonant frequency. Two types of resonators are designed to have different fundamental resonant frequencies, one for the lower passband and the other for the upper passband. In the lower band, half and quarter wavelength resonators were used. In the upper band, a dual-mode resonator was used for adjusting bandwidth. In the upper pass band frequency, resonators of lower passband acts as the input and output. For WLAN, Proposed filters with different second passband frequencies at 2.45/5.2 GHz and 2.45/5.8 GHz are designed and fabricated.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.361-365
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• 2002

Three types of the coupling structures in combline resonators are presented: magnetic, electric, and mixed coupling structures. The magnetic coupling structure is provided by the window, and the electric coupling is provided by the electric probe. The mixed coupling structure which is the superposition of the magnetic and electric coupling structures, is proposed for the electric coupling in combline resonators with easy tuning capability. The responses of each coupling structure are shown. A 4-pole combline filter is designed and fabricated as an application of those coupling structures, and shows good filter responses.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.169-172
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• 2002

In this paper, the design formulas for bandpass filters using parallel coupled stepped impedance resonators(SIR) are derived. General content about basic feature of stepped impedance resonators(SIR) is represented. The filters and duplexer using stepped impedance resonators(SIR) have been designed and realized with the presented design method at IMT-2000 frequency band Simulations have used serenade circuit simulation and HFSS EM-simulation. We were showed excellent agreements between SIR design theory and simulation results on the multi-layer filter/duplexer.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.234-238
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• 2003

The LTCC bandpass filter using multilayer resonators is made of combline type and interdigital type parallel coupled-lines. The equivalent circuits of parallel coupled-lines are analysed. They are applied to make an equivalent circuit of LTCC bandpass filter using multilayer resonators. The 3-pole bandpass filter of the center frequency of 2.45GHz with 250Hz bandwidth is designed and fabricated. The simulated result of the bandpass filter are presented.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.5
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• pp.211-213
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• 2005

[$SiO_2$] film coated as a passivation layer for YBCO based electronic devices is investigated by measuring the micro wave properties of micro strip line resonators. The $SiO_2$ film coated resonators are compared with coated resonators for two degradation conditions, a $200^{\circ}C$ annealing in air and an exposure to air at $85^{\circ}C\;85\%$ relative humidity. The $SiO_2$ film reduces the YBCO thin film degradation caused by oxygen stoichiometry change and reaction with water.

• Journal of Mechanical Science and Technology
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• v.18 no.8
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• pp.1461-1469
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• 2004

Acoustic characteristics in an industrial gas-turbine combustor are numerically investigated by a linear acoustic analysis. Spatially non-homogeneous temperature field in the combustor is considered in the numerical calculation and the characteristics are analyzed in view of acoustic instability. Acoustic analyses are conducted in the combustors without and with acoustic resonator, which is one of the acoustic-damping devices or combustion stabilization devices. It has been reported that severe pressure fluctuation frequently occurs in the adopted combustor, and the measured signal of pressure oscillation is compared with the acoustic-pressure response from the numerical calculation. The numerical results are in good agreement with the measurement data. In this regard. the phenomenon of pressure fluctuation in the combustor could be caused by acoustic instability. From the numerical results for the combustor with present acoustic resonators installed, the acoustic effects of the resonators are analyzed in the viewpoints of both the frequency tuning and the damping capacity. It is found that the resonators with present specifications are not optimized and thus, the improved specification or design is required.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.1069-1072
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• 2001

We described a method resonant mode identification in dielectric-rod loaded cylindrical cavity resonators. Resonant frequency of dielectric loaded cavity is calculated by analyzing the characteristic equation. The characteristic equation is solved by using the ContourPlot graph of Mathematica. As the result of comparing calculation value and experimental value of resonant frequencies, we know that the field representation of non-decaying mode is exact. The contour graph method is not a method using approximated representation of electromagnetic field variation at the outer area of dielectric in the resonators but a method using exact representation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12
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• pp.1077-1079
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• 2003

This paper describes the development of bulk acoustic wave (BAW) resonators using a PolyVinyliDene Fluoride (PVDF). The resonators have an air gap between a substrate for acoustic isolation without surface micromachining. We measured the resonance frequency and the input reflection coefficient (S$\sub$11/) of resonators using vector network analyzer. The fundamental resonance in this experimental result was measured at 1.4 ㎓ with a return loss of -23.2 ㏈. We can confirm a possibility of resonator application as using a PVDF because it can fabricate the resonator without etching process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.250-250
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• 2008

This paper describes the resonant characteristics of polycrystalline SiC micro resonators. The $1{\mu}m$ thick polycrystalline 3C-SiC cantilevers with different lengths were fabricated using a surface micromachining technique. Polycrystalline 3C-SiC micro resonators were actuated by piezoelectric element and their fundamental resonance was measured by a laser vibrometer in vacuum at room temperature. For the 100 ~ $40{\mu}m$ long cantilevers, the fundamental frequency appeared at 147.2 kHz - 856.3 kHz. The $100{\mu}m$ and $80{\mu}m$ long cantilevers have second mode resonant frequency at 857.5 kHz and 1.14 MHz. Therefore, polycrystalline 3C-SiC micro resonators are suitable for RF MEMS devices and bio/chemical sensor applications.