• Title, Summary, Keyword: Cavity resonator

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An Approach to Estimate Dielectric Constant of Low-Loss Materials Using Dielectric Slab Loaded Cylindrical Cavity Resonators (유전체 슬랩이 삽입된 원통형 공진기를 이용한 저손실 물질의 유전 상수 측정)

  • Lee, Won-Hui
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.19 no.10
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    • pp.1115-1121
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    • 2008
  • In this paper, dielectric slab loaded cylindrical cavity resonator measurement technique is presented to determine the dielectric constant of a dielectric material. The dielectric constant is measured by the resonant frequency deviation of empty and dielectric slab loaded cavity. Characteristic equations are derived by th exact field analysis. The measurement configurations are formed using HP8719A vector network analyzer and an experimental cylindrical metallic cavity with circular cross-section. The validity of the theory is confirmed by experiments and CST MWS 4.0(3D simulator). The results were in the whole satisfactory. The measured dielectric constant of teflon and bakelite are 2.03 and 4.44, respectively.

Study on 5.8 GHz DR Duplexer using Cavity Filter (캐비티 필터를 이용한 5-8 GHz DR 듀플렉서의 연구)

  • 배창호;조평동;조병훈;김영성;장호성
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.26 no.12B
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    • pp.1712-1723
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    • 2001
  • This paper presents a design procedure and manufacturing techniques realizing of a 5.8 GHz duplexer based on cylindrical coaxial dielectric resonator. Upto Q$\times$f$\_$o/=30,000 cylindric coaxial dielectric resonator was developed control by addition of dielectric materials. This resonator shows attenuation characteristics -40 dB for transmitter and -50 dB for receiver by consisting of two sets of 4-stage cavity resonator within f$\_$o/$\pm$10 MHz bandwidth which was requirement of DSRC. Employing the measurement results, design procedure to characterize the transmission and reflection properties are presented.

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Acoustic resonance and refrigerating capability of a Hofler type thermoacoustic refrigerating system (Hofler 타입 열음향 냉장시스템의 공진특성과 냉장성능)

  • Hah, Zae-Gyoo
    • The Journal of the Acoustical Society of Korea
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    • v.16 no.1
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    • pp.76-80
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    • 1997
  • Acoustic resonance characteristics were analyzed and their effect on the refrigerating capability were experimentally verified on a fabricated Hofler-type thermoacoustic refrigerating system. Factors governing the overall resonance are the resonator composed of a cavity and two pipes, the loudspeaker driving the resonator, and rear side impedance characteristics of speaker housing. All these are coupled with electric constants of the speaker to exhibit electric resonance. Also the 'wall-effect' within the resonator causes attenuation to reduce the sharpness of the resonance. Analysis and experiments showed housing and the wall-effect of the resonator reduce the sharpness of resonance. Maintaining the accuracy of the resonance is, therefore, very important for efficient refrigeration.

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The Limitation and Applicabilitity of Helmholtz Resonator, Regarding as Equivalent Single-Degree of Vibration System (1자유도 등가 진동계로 이해하는 헬름홀츠 공명기 특성의 한계점과 응용)

  • 하상태;김양한
    • Journal of KSNVE
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    • v.4 no.2
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    • pp.209-219
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    • 1994
  • Classical method calculates the resonance frequency of Helmholtz resonator by postulating that there is a moving mass in neck and a stiffness which expresses the compressibility of cavity. This has been widely accepted as reasonable to determine the resonant frequency, provided that the wave length of interest is longer that any length scale of resonater. Nevertheless, it has been often recognized that this classical method sometimes does not well predict the resonant frequency. This paper decribes the way in which the dynamics of resonator very often does care about the detail geometries of resonator; location of the neck, diameter ratio of the neck to that of cavitty, length of resonator compared with that of neck, etc. This rather unexpected observations have been proved theoretically; 3 dimensional analysis of acoustic wave equation, as well as experimentally by comparing the resonant frequencies, transmission loss, and insertion loss of resonator.

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Nonlinear Impedance Characteristics of Helmholtz Resonator with Tapered Neck (경사진 목을 가지는 헬름홀쯔 공명기의 비선형 임피던스 특성)

  • Seo, Sang-Hyeon;Chung, Hoe-min;Kim, Yang-hann
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.75-80
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    • 2012
  • Helmholtz resonator is widely used acoustic instrument which has high absorption characteristics at its resonance frequency. Particularly it maintains good performance even in the low frequency region that is difficult to control by general porous absorptive materials. However, under severely high sound pressure level, the absorption characteristics are changed by increase of resistance due to nonlinear behavior of neck impedance. Because of this nonlinear behavior, it is difficult to obtain the expected absorption performance under high sound pressure environment. Thus, in order to prevent excessive rise of resistance, the resonator with neck having cross section dimension decrease away from the entry of the resonator cavity could be suggested. This paper introduces the experiment method and results about nonlinear characteristics of Helmholtz resonator with tapered neck and proposes the approximate nonlinear impedance model.

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A simple Q measurement method of a lossy coupled cavity resonator (손실결합 공동공진기의 간편한 Q 측정 방법)

  • Han, Dae-Hyun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.22 no.7
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    • pp.1015-1020
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    • 2018
  • The cavity resonator is one of the widely used components in the microwave applications. The unloaded Q, the resonant frequency, and the coupling factor are basic parameters of a cavity. A simple unloaded Q factor measurement procedure of a cavity is proposed in a lossy coupling. The equivalent circuit of a cavity with coupling loss at near the resonant frequency is presented. The coupling loss resistance was found by the measurement of a cavity impedance. The cavity impedance compensated coupling loss was redrawn on the Smith Chart. The loaded Q and coupling factor were obtained based on the compensated impedance locus and then the unloaded Q factor was calculated. To verify the proposed procedure, the cavity with lossless coupling was measured. The two measurement results in the lossy and lossless coupling agree well. The results confirm the proposed procedure is valid.

A Study on Noise Reduction of Rotary Compressor (공조용 로터리 압축기의 소음 저감에 관한 연구)

  • Ahn, B.H.;Kim, Y.S.
    • Journal of the Korea Society For Power System Engineering
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    • v.3 no.3
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    • pp.60-69
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    • 1999
  • The noise and vibration sources of rotary compressor for room air-conditioner are pressure pulsation of compression process, cavity resonance of inner space, structural radiation noise of shell and impact noise of discharge valve. Among them, pressure pulsation is very important noise and vibration source. Because it transferred various kinds of noise and vibration like as mentioned above. In this reason, muffler and resonator are used in order to absorb and remove these noises. But an analytical prediction using acoustic analysis does not coincident with the experimental result. The difference between analysis and actual state is due to the assumption of analysis. This paper covered with new concept of muffler design based on the turbulence kinetic energy of flow by using CFD. From this analysis, it is possible to decide the best position of discharge port of muffler. Therefore $2{\sim}3dB$ noise reduction effect is acquired in rotary compressor of 5000 BTU grade. Also new approach of resonator design is suggested. From this study, the characteristics of resonator and surge hole (a kind of resonator without pipe length) are identified. The former is useful for pure tone noise (narrow frequency band), and the latter is effective for broad frequency band. This paper shows that it is very available to use 3 dimensional analysis of resonator in order to predict more exact tuning frequency. The result is proved by a lot of experiments. From combination of fluid analysis and acoustic analysis, up stream position is effective location of resonator concerning turbulence motion of fluid.

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A Study on the Detection of the Rain Using Open-Ended Coaxial Cavity Resonator (한쪽 면이 열린 동축 공동 공진기를 이용한 빗물 감지에 관한 연구)

  • Lee, Yun-Min;Kim, Jin-Kuk;Hur, Jung
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.24 no.9
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    • pp.944-950
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    • 2013
  • This paper is a study of a rain sensor using an open-ended coaxial cavity resonator which senses the amount of rain drops linearly. It shows that it will be used as a sensor to sense the amount of rain dropped on the windshield of an automobile based on the principle of varied resonant frequency and the loss according to the amount and characteristics of an dielectric lied on the open side of a resonator. The input and output ports are built in the both sides of the resonator and the input and output coupling probes are formed like 'ㄱ' shape. The response of rain drops were simulated by the radius of inner conductor of 2 mm, 5 mm, and 10 mm respectively and it showed that the raindrop was sensed most linearly and sensitively when the radius of inner conductor is 5 mm, We have measured that the resonant frequency have varied from 3.55 GHz to 3 GHz and the Q value have varied from 42.38 to 24.3 according to the variation of rain drop amount on the fabricated resonator. Therefore, it shows that the designed resonator can be applied as a rain sensor that measures the amount of rain drops linearly by using the resonant frequency as a measurement parameter.

A Study on the Coupling Performance Improvement of Cylindrical DR Bandpass Filter using Travelling Wave Mode Analysis (진행모드 해석을 이용한 유전체 공진기 대역통과 필터의 결합 특성 개선에 관한 연구)

  • Lee, Won-Hui;Park, Chang-Won;Yang, Jae-Hyuck;Hur, Jung;Lee, J. H.;Lee, Sang-Young
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • pp.125-129
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    • 2000
  • In this paper, We designed and fabricated C-band bandpass filter using dielectric resonators. From waveguide cutoff frequency which applied the region between adjacent dielectric resonators, the height of cavity is determined. The cavity's diameter is determined to the twice of dielectric resonator's diameter considering the conductor loss. The resonant frequency of the DR-cavity is calculated with travelling wave mode analysis. Conventionally, circular cylindrical dielectric resonator is analysed by Cohn's model which use the evanescent mode in the region between dielectric resonator wall and circular cavity wall, which is an approximated method. The external quality factor, Q$_{ex}$ has found with simulation result using Ansoft's Maxwell simulation tool. The designed filter using dielectric resonators with dielectric constant of 45 has the passband center at 5.065GHz. The bandpass filter using dielectric resonators have about 1dB insertion loss. 20MHz bandwidth and more than 30dB attenuation at f$_{0}$$\pm$15MHz.z.z.

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A Measurement Method of Dielectric Properties of Dielectric Materials using $TE_{011}$ mode of Cylindrical Cavity Resonators (원통형 공동 공진기의 $TE_{011}$ 모드를 이용한 유전체의 전자기적 특성 측정 방법)

  • Lee, Won-Hui;Kim, Tai-Shin;Hur, Jung;Lee, Sang-Young
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.38 no.5
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    • pp.9-15
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    • 2001
  • This paper describes measurement method of dielectric properties of dielectric materials using cylindrical cavity resonator's. Dielectric properties of concern here are relative permittivity, loss- tangent, quality factor and so on. An analysis of $TE_{011}$mode in dielectric properties of concentric dielectric-rod inserted cylindrical cavity resonator is presented. The frequency variation by the air gap at $TE_{011}$ mode turns out to be the least sensitive. A technique using a $TE_{011}$ mode of concentric dielectric-rod inserted cylindrical cavity resonator and an exact field representation of neo non-decaying mode are introduced for measurement of dielectric properties.

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