• Title, Summary, Keyword: Cavity resonator

Search Result 151, Processing Time 0.038 seconds

NOISE REDUCTION OF AN ENCLOSED CAVITY BY MEANS OF AIR-GAP SYSTEMS

  • Kang, S.W.;Lee, J.M.
    • International Journal of Automotive Technology
    • /
    • v.5 no.3
    • /
    • pp.209-213
    • /
    • 2004
  • The objective of this paper is to introduce the noise reduction characteristics of a double gap system, which is composed of two air-gaps and two partition sheets. The resonance of acoustic modes of an enclosed cavity can be effectively suppressed by installing the double gap system in the cavity. It is revealed from a simple, one-dimensional model that the double gap system is more effective than the single gap system that consists of one air-gap and one partition sheet, in that the former requires a smaller space than the latter. Finally, these theoretical conclusions are verified by comparison experiments using an actually manufactured enclosed cavity, of which the boundary surfaces are made of thick panels that can be assumed as rigid walls.

Design of a Low-Profile, High-Gain Fabry-Perot Cavity Antenna for Ku-Band Applications

  • Nguyen, Truong Khang;Park, Ikmo
    • Journal of electromagnetic engineering and science
    • /
    • v.14 no.3
    • /
    • pp.306-313
    • /
    • 2014
  • A Fabry-Perot resonator cavity antenna for Ku-band application is presented in this paper. The Fabry-Perot cavity is formed by a ground plane and a frequency selective surface (FSS) made of a circular hole array. The cavity resonance is excited by a single-feed microstrip patch located inside the cavity. The measured results show that the proposed antenna has an impedance bandwidth of approximately 13% ($VSWR{\leq}2$) and a 3-dB gain bandwidth of approximately 7%. The antenna produces a maximum gain of 18.5 dBi and good radiation patterns over the entire 3-dB gain bandwidth. The antenna's very thin profile, high directivity, and single excitation feed make it promising for use in wireless and satellite communication applications in a Ku-band frequency.

Electromagnetic Simulation of the Quality Factor and Microstructure of Microwave Dielectrics (마이크로파 유전체의 미세구조와 품질계수의 상관관계에 대한 컴퓨터 시뮬레이션)

  • Park, Jae-Hwan;Park, Jae-Gwan
    • Korean Journal of Materials Research
    • /
    • v.11 no.2
    • /
    • pp.146-150
    • /
    • 2001
  • Electromagnetic simulation was compared to the measurement with a network analyzer in the cavity resonator method which has been used for determining microwave quality factor. Scattering matrix $S_{12}$ obtained from the network analyzer was compared to the $S_{12}$ obtained from the simulation. The effects of the pore and the secondary phase of the dielectric resonator on the microwave quality factor were studied. From the simulated results, the dominant resonant $TE_{01\delta}$ mode was determined and the quality factor was observed to decrease with the pore and the secondary phase in the dielectrics.

  • PDF

Simultaneous Measurements of the Loss Tangent of Rutile ($TiO_2$) and the Microwave Surface Resistance of $YBa_2Cu_3O_{7-{\delta}}$ Films using Two Resonant Modes of Rutile -loaded cavity Resonator (루타일이 삽입된 유전체 공진기의 두 공진 모드를 이용한 루타일의 유전손실과 $YBa_2Cu_3O_{7-{\delta}}$ 박막의 마이크로파 표면저항 측정)

  • Lim, J.;Lee, J.H.;Kim, M.J.;Hur, J.;Lee, S.Y.
    • Progress in Superconductivity
    • /
    • v.4 no.2
    • /
    • pp.137-143
    • /
    • 2003
  • In measuring the microwave surface resistance of high-Tc superconductor (HTS) films using the dielectric-loaded cavity resonator method, one of the most important factors that limit the measurement sensitivity is the measurement error in the loss tangent ($tan\delta$) of the dielectric rod placed inside the cavity. We have measured the effective surface resistance ( $R_{S}$ $^{eff}$) of$ YBa_2$$_Cu3$$_{7-{\delta}}$ (YBCO) films and the $tan\delta$ of rutile ($TiO_2$) using the 'two-tone'method suggested by Kobayashi et at. [IEEE, MTT-S Digest, 495, (2001)], which enables simultaneous measurements of both the $R_{S}$ $^{eff}$ fof HTS films and the $tan\delta$ of the rutile with high sensitivity. A rutile-loaded cavity resonator with the $TE_{012}$ and $TE_{021}$ resonant frequencies at 13.67 - 14.01 GHz is used for this purpose. At temperatures where the two modes do not couple with other modes, the $R_{S}$ $^{eff}$ of YBCO films and $tan\delta$ of rutile measured by the two-tone method appear to match well with the corresponding values measured using the reported $tan\delta$ values of sapphire within 10 %. Usefulness of the 'two-tone' method for microwave characterization of HTS films and dielectrics is discussed.d.ielectrics is discussed.ussed.

  • PDF

Design of a Variable Resonator for the Sacred Bell of the Great King Seongdeok (성덕대왕신종을 위한 가변형 명동의 설계)

  • Kim, Seock-Hyun;Jeong, Won-Tae;Kang, Yun-June
    • The Journal of the Acoustical Society of Korea
    • /
    • v.31 no.5
    • /
    • pp.288-297
    • /
    • 2012
  • This study proposes a design model of the variable type resonator which corrects the temperature variance according to the season, in order to maximize the resonance effect in the Sacred bell of the Great King Seongdeok. In the bell, the 1st natural frequency (64 Hz) and the 2nd natural frequency (168 Hz) are the most important partial tones. Resonance conditions of the two components are determined for the internal acoustic cavity system, which consists of bell body cavity, gap and the resonator. Acoustic frequency response characteristics of the internal cavity are determined by the boundary element analysis using SYSNOISE. As an external factor, temperature variance according to the season largely influences the resonance condition and the length of the resonator should be controlled to maximize the resonance effect. As a measure, this study proposes a design model of the variable type resonator for the Sacred Bell of the Great King Seongdeok, which can control the length at the belfry according to the season.

Effect of Cavity Material on the Q-Factor Measurement of Microwave Dielectric Materials (캐비티 재질이 마이크로파 유전체 공진기의 Q값 측정에 미치는 영향)

  • Park, Jae-Hwan;Park, Jae-Gwan
    • Journal of the Microelectronics and Packaging Society
    • /
    • v.18 no.3
    • /
    • pp.39-43
    • /
    • 2011
  • Effects of cavity material on the Q-factor measurement of microwave dielectric materials were studied by HFSS simulation and the measurements using metal cavity. $TE_{01\delta}$ mode resonant frequency was determined from the electric and magnetic field patterns and the loaded Q-factor was calculated from 3dB bandwidth of $S_{21}$ spectrum. When the cavity metal materials were Cu, SUS and Au cavity, the level of Q-factor was similar. However, Q-factor was significantly decreased when the cavity metal material was CuO. The Q-factor measurements of dielectric resonator by network analyzer using various metal cavity exhibits consistent behavior.

Investigation on the characteristics of a cavity-dumped Nd:glass laser (Cavity-dumping형 Nd:glass laser의 제작 및 특성 조사)

  • 차용호;강응철;남창희
    • Korean Journal of Optics and Photonics
    • /
    • v.6 no.2
    • /
    • pp.130-134
    • /
    • 1995
  • A small signal gain coefficient of Nd:glass was measured and a cavity-dumped laser was constructed. To measure the small signal gain coefficient, we constructed a resonator consisting of Nd:glass, Pockels cell, polarizing beam splitter. The measured small signal gain coefficient was $0.088 cm_{-1}$ when the input energy was 100 J and the round-trip internal loss of the resonator was 56%. The cavity-dumped laser was constructed using Nd:glass. 2 m radius of curvature HR-mirrors, Pockels cell, polarizinig beam splitter and $\lambda/4$ plate. The output energy of cavity-dumped laser was 0.85 J at 140 J input energy and the laser pulse width was 8 ns.s 8 ns.

  • PDF

Control of Sound Pressure inside a Flow Excited Cavity by Regulation of Vorticity Shedding (와류진동 조절에 의한 유동가진 공동 내부의 음압 제어)

  • Park, Jong-Beom;Hwang, Cheol-Ho
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.17 no.12
    • /
    • pp.1223-1229
    • /
    • 2007
  • Flow traveling over a cavity opening forms a vortex due to unstable shear layer and induces an aerodynamic pressure excitation from the diffusion of the vortex convecting out of the trailing edge of the opening. The interaction between the excitation force and the cavity response sustains resonance in the resonator(cavity) and locked-in vortex shedding at the leading edge of the opening. The aerodynamic excitation force can be described from the diffusion of the vortex over the trailing edge and the level of its diffusivity is related to the strength of vorticity seeded at the leading edge. In this study, the control scheme of the internal pressure oscillation was proposed from regulating the vorticity at the leading edge by use of an oscillating spoiler. It was found that the relative motion between the spoiler and the air mass at the cavity opening influenced vorticity strength and the control was achieved by direct feedback of the cavity pressure fluctuation to the actuator.

A Study on the Design Parameter of a Resonance type Absorber (공명형 흡음기의 설계인자에 관한 연구)

  • Song, Hwa-Young;Lee, Young-Chul;Lee, Sun-Ki;Lee, Dong-Hoon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • /
    • pp.964-968
    • /
    • 2007
  • A helmholtz resonator has been widely used for the purpose of suppressing low frequency noises propagated from various heat and fluid machineries. However, the resonator has demerits that the absorption bandwidth at resonance frequency is very small and a large cavity is necessary. In order to overcome these problems, in this paper, a resonator with perforated panels at the neck and/or in the cavity is proposed. The absorption performances of resonators are measured by two-microphone method and are estimated by transfer matrix method. The experimentally measured values of normal absorption coefficients are agreed well with the corresponding values from the transfer matrix method. By introducing perforated panels at the neck of a resonator, it is shown that the absorption performances and bandwidth have a significant improvement.

  • PDF

Noise Reduction Characteristics of a High-performance Air-gap Resonator (고효율 에어갭 공명기의 소음 저감 특성)

  • Kang, Sang-Wook;Lee, Jang-Moo;Lim, Won-Sik
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.28 no.2
    • /
    • pp.118-124
    • /
    • 2004
  • The objective of the paper is to demonstrate the noise reduction characteristics of an air-gap resonator, which is composed of an air gap and a partition sheet. By means of installing the air-gap resonator in an enclosed cavity, acoustic resonance can be effectively suppressed using a small space. In particular, it is revealed from a simple, one-dimensional model that the air-gap resonator serves as the Helmholtz resonator that generally absorbs acoustic resonance energy at its resonance frequency. As a result, the air-8ap resonator also has a resonance frequency, which can be predicted with a simple frequency equation derived in the paper. Finally, verification experiments show that the air-gap resonator can be effectively designed by predicting a reasonable gap thickness using the simple frequency-equation.