• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.12
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• pp.19-23
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• 1991

A method for suppressing unwanted resonance modes by attaching an electromagnetic wave absorber onto a metal case was studied to prevent performance deterioration of electronic devices. The electromagnetic wave absorber fabricated for this study had an attenuation characteristics above 20dB in the frequency band from 450MHz, 1150MHz. A rectangular cavity resonator whose resonance frequencies of TE$_{101}$, TE$_{102}$ modes were 900MHz, 1250MHz, respectively, was made to measure attenuation for the electromagnetic wave absorber-metal assembly. The result showed that the resonance mode for high attenuation was sensitive to the location of electromagnetic wave absorber, and the attenuation characteristics above 20dB could be obtained when electromagnetic wave absorber was properly positioned.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.761-763
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• 2004

최근에 위성용 필터로서 유전체 공진기 내장 도파관 필터가 많이 연구되고 있다. 이 필터의 튜닝을 위하여 튜닝 스크류가 일반적으로 사용되어져 왔는데 튜닝 스크류의 사용은 복잡한 필터의 튜닝 시 너무 소모적인 작업을 야기시키고 미세한 튜닝에 어려움이 있어서 다른 해결책을 필요로 한다. 또한 제품의 사용 시에는 온도등의 외부환경의 변화에 대하여 대처를 하기 위하여 전기적인 튜닝을 이용한 튜닝의 자동화에 대한 필요성이 대두되었다. 이에 대한 해결책으로 BST($Ba_xSr_{1-x}TiO_3$)라는 강유전체를 이용하는 튜닝에 대하여 소개하고 한 경우에 대하여 FDTD 방시의 EM 시뮬레이션을 구하여 그 결과로서 전기저인 필터 튜닝의 가능성을 보여준다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.8
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• pp.752-758
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• 2013

The effect of external leakage on the acoustic performance of Helmholtz resonators is experimentally and numerically investigated. The transmission loss of the Helmholtz resonator with a circular perforated hole is measured by using an impedance tube setup. The experimental results are then compared with one-dimensional analytical and three-dimensional numerical results. As the size of the hole increases, the peak of the transmission loss shifts to higher frequency, especially for the holes on the cavity. While the transmission loss is almost independent of the location of the hole on the cavity, the impact of the hole location on the neck on the transmission loss is not negligible. The results show that one-dimensional analytical method can predict the overall trends, whereas three-dimensional numerical method is necessary for more accurate predictions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.4
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• pp.468-474
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• 2012

A low phase-noise microwave oscillator is presented by a substrate integrated waveguide(SIW) loading a complementary split ring resonator(CSRR) in this paper. The unloaded $Q$-factor of the SIW cavity is increased by loading a complementary split ring resonator(CSRR) and its value exhibits 1960. It is theoretically and experimentally demonstrated that the proposed circuit generates 11.3 dBm of output power at 9.3 GHz and a phase-noise of -127.9 dBc/Hz at 1-MHz offset.

• Proceedings of the Korean Vacuum Society Conference
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• 2008.02a
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• pp.223-223
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• 2008

• 한국초전도학회:학술대회논문집
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• v.12
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• pp.47-47
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• 2002

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.173-178
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• 2000

A prototype for a highly sensitive, automated measurement system for the microwave surface resistance of high-T$_c$ superconductor films was set up, and tested by measuring the microwave surface resistances of high-T$_c$ YBa$_2$Cu$_3$O$_{7-{\delta}}$(YBCO) films at the frequency of about 19.6 GHz and the temperature of 30 K ${\sim}$ 90 K. An open-ended TE$_{011}$ mode sapphire-loaded cylindrical cavity resonator was used as the measurement probe, where YBCO films were used as the endplates of the cylindrical cavity. The characteristics of the measurement system include functions to display the unloaded ${\varrho}$ and the resonant frequency of the TE$_{011}$ mode resonator as well as the microwave surface resistance of the YBCO films, all simultaneously as a function of temperature. Applicability of the measurement system for investigating the homogeneity in the microwave properties of large high-T$_c$ superconductor films is discussed.

• Progress in Superconductivity
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• v.2 no.1
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• pp.27-32
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• 2000

A prototype for a highly sensitive, automated measurement system for the microwave surface resistance of high-$T_c$ superconductor films was set up, and tested by measuring the microwave surface resistances of high-$T_c$ $YBa_2Cu_3O_{7-\delta}$ (YBCO) films at the frequency of about 19.6 GHz and the temperature of 30 K $\sim$ 90 K. An open-ended $TE_{011}$ mode sapphire-loaded cylindrical cavity resonator was used as the measurement probe, where YBCO films were used as the endplates of the cylindrical cavity. The characteristics of the measurement system include functions to display the unloaded Q and the resonant frequency of the $TE_{011}$ mode resonator as well as the microwave surface resistance of the YBCO films, all simultaneously as a function of temperature. Applicability of the measurement system for investigating the homogeneity in the microwave properties of large high-$T_c$ superconductor films is discussed.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.7
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• pp.14-21
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• 2001

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? diameter considering the conductor loss. The resonant frequency of the DR cavity is calculated with non decaying mode analysis. Conventionally, cylindrical dielectric resonator is analysed by Cohn's model which use the decaying 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 has about 1dB insertion loss, 20MHz bandwidth and more than 30dB attenuation at $f_0+15MHz$.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.1
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• pp.16-24
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• 2008

Near-field scanning microwave microscope (NSMM) has been used to characterize the electromagnetic properties of samples based on a cavity perturbation technique. We used a NSMM using a waveguide cavity to couple a metallic probe tip as a point like evanescent field emitter. We explained the quality of our NSMM system by applying the cavity perturbation theory. First, to make a shape perturbation, we inserted linear and loop probes in the waveguide resonator. To check up electric and magnetic field distribution inside the waveguide resonator by shape perturbation, we confirmed the field distribution by using a HFSS simulation. Second, to make material perturbation, we located a dielectric sample in front of the probe tip and measured reflection coefficient $(S_{11})$. We found that the resonance frequency$(f_r)$ was changed linearly as the dielectric constant of resonator$({\varepsilon}_r)$ increased when ${\Delta}{\varepsilon}\;and\;{\Delta}{\mu}$ were small.