• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.217-217
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• 2009

This paper describes the characteristics of polycrystalline 3C-SiC doubly clamped beam micro resonators. The polycrystalline 3C-SiC doubly clamped beam resonators with 60 ~ 100 ${\mu}m$ lengths, $10\;{\mu}m$ width, and $0.4\;{\mu}m$ thickness were fabricated using a surface micromachining technique. Polycrystalline 3C-SiC micro resonators were actuated by piezoelectric element and their fundamental resonant frequency was measured by a laser vibrometer in vacuum at room temperature. For the 60 ~ 100 ${\mu}m$ long cantilevers, the fundamental frequency appeared at 373.4 ~ 908.1 kHz. The resonant frequencies of doubly clamped beam with lengths were higher than simulated results because of tensile stress. Therefore, polycrystalline 3C-SiC doubly clamped beam micro resonators are suitable for RF MEMS devices and bio/chemical sensor applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.1
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• pp.14-19
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• 2003

In this paper, a λ/4 hair-pin resonator is proposed to reduce the size of resonators. A LTCC MLC bandpass filter is designed using the λ/4 hair-pin resonators. The electromagnetic coupling structure between two planar resonators is analysed. The equivalent circuit is derived to explain the behavior of the LTCC MLC bandpass filter using λ/4 hair-pin resonators. A design procedure is also described. The simulated and measured results of 1.8 GHz band 2-pole bandpass filter are presented.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.86-91
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• 2007

A study was performed to understand self-excited pressure fluctuations in the lean premixed flames and to evaluate the effect of Helmholtz resonator on the pressure fluctuations. As low-frequency pressure fluctuations have been reported to cause fatal damage to the combustor and the entire system, Helmholtz-type resonators, which reduce the damage by low-frequency pressure fluctuation in the combustor, are attached to the channel of unburned mixture flow. It is found that the range of low-frequency pressure fluctuations of flame mode 2 is narrowed by the attachment of Helmholtz resonators. From this result, if Helmholtz-type resonators are applied to actual gas turbine combustor, it is confirmed that Helmholtz resonators attached on the fuel discharge hole are also effective for narrowing the range of flame mode 2

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.4
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• pp.303-306
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• 2009

This paper describes the characteristics of polycrystalline 3C-SiC doubly clamped beam micro resonators. The polycrystalline 3C-SiC doubly clamped beam resonators with $60{\sim}100{\mu}m$ lengths, $10{\mu}m$ width, and $0.4{\mu}m$ thickness were fabricated using a surface micromachining technique. Polycrystalline 3C-SiC micro resonators were actuated by piezoelectric element and their fundamental resonant frequency was measured by a laser vibrometer in vacuum at room temperature. For the $60{\sim}100{\mu}m$ long cantilevers, the fundamental frequency appeared at $373.4{\sim}908.1\;kHz$. The resonant frequencies of doubly clamped beam with lengths were higher than simulated results because of tensile stress. Therefore, polycrystalline 3C-SiC doubly clamped beam micro resonators are suitable for RF MEMS devices and bio/chemical sensor applications.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1154-1161
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• 2015

This paper presents a semi-lumped balun transformer using conventional PCB process and its design theory and geometry for the maximally flat response and wide bandwidth using magnetically coupled LC resonators. The proposed balun is comprised of two pairs of coupled resonators which share one among three LC resonators. It provides an identical magnitude and phase difference of 180° between two balanced ports with DC isolation and an impedance transformation characteristic. Theoretical design and analysis were performed to optimize the inductance and capacitance values of proposed balun device for obtaining the wide bandwidth and maximally flat response in its pass-band. Three balun transformers with a center frequency of 500 MHz were demonstrated for proving the concept of design proposed. They were fabricated by using lumped chip capacitors and planar inductors embedded into a conventional 4-layered PCB substrate. They exhibited a maximum magnitude difference of 0.8 dB and phase difference within 2.4 degrees.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.130-130
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• 2009

This paper describes the temperature characteristics of polycrystalline 3C-SiC micro resonators. The 1.2 ${\mu}m$ and 0.4 ${\mu}m$ thick polycrystalline 3C-SiC cantilever and doubly clamped beam resonators with 60 ~ 100 ${\mu}m$ 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 temperature range of $25{\sim}200^{\circ}C$. The TCF(Temperature Coefficient of Frequency) of 60, 80 and 100 ${\mu}m$ long cantilever resonators were -9.79, -7.72 and -8.0 $ppm/^{\circ}C$. On the other hand, TCF of 60, 80 and 100 ${\mu}m$ long doubly clamped beam resonators were -15.74, -12.55 and -8.35 $ppm/^{\circ}C$. Therefore, polycrystalline 3C-SiC resonators are suitable with RF MEMS devices and bio/chemical sensor applications in harsh environments.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.355-358
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• 2006

A linear acoustic analysis is conducted to examine bituning of acoustic resonators for acoustic damping in a combustion chamber of liquid rocket engine. Bituned resonators are tuned to the two principal modes, the first tangential(1T) and the first radial(1R) modes. First, the acoustic-damping effect of monotuned resonators is investigated. The damping capacity is quantified by damping factor as a function of the number of the resonators monotuned to 1T or 1R mode. Next, the damping characteristics of the bituned resonators are investigated. From the numerical data, the number of resonators, to be tuned to 1T and 1R modes, respectively, can be selected properly.

• ETRI Journal
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• v.36 no.3
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• pp.510-513
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• 2014

A Q-band pHEMT image-rejection low-noise amplifier (IR-LNA) is presented using inter-stage tunable resonators. The inter-stage L-C resonators can maximize an image rejection by functioning as inter-stage matching circuits at an operating frequency ($F_{OP}$) and short circuits at an image frequency ($F_{IM}$). In addition, it also brings more wideband image rejection than conventional notch filters. Moreover, tunable varactors in L-C resonators not only compensate for the mismatch of an image frequency induced by the process variation or model error but can also change the image frequency according to a required RF frequency. The implemented pHEMT IR-LNA shows 54.3 dB maximum image rejection ratio (IRR). By changing the varactor bias, the image frequency shifts from 27 GHz to 37 GHz with over 40 dB IRR, a 19.1 dB to 17.6 dB peak gain, and 3.2 dB to 4.3 dB noise figure. To the best of the authors' knowledge, it shows the highest IRR and $F_{IM}/F_{OP}$ of the reported millimeter/quasi-millimeter wave IR-LNAs.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.8
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• pp.756-762
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• 2012

A method of the low-frequency noise reduction in an enclosure by using an array of Helmholtz resonator is presented. An integral form of equation, which represents the acoustical coupling between the internal sound field and the resonator array, is formulated so that the boundary element method can be applied to solve the coupling problem. It is shown that the resonator array on the surface of the enclosure can be regarded as impedance patches on the boundary element. Experiments on a simple enclosure acoustically coupled with an array of resonators are conducted to verify the method. The predicted noise reduction by the boundary element method shows good agreement with the measured one. The effects of the resistance of resonators as well as the number of resonators on the noise reduction are demonstrated. As a practical example, the presented method is applied to the payload fairing of a space launcher with resonator arrays. It is demonstrated that the resistance of resonators affects significantly the required number of resonators to achieve a desired noise reduction.

• Journal of electromagnetic engineering and science
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• v.16 no.4
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• pp.232-234
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• 2016

In this paper, the power transfer efficiencies (PTEs) of magnetic resonance (MR) wireless power transmission (WPT) and radio frequency (RF) WPT are compared as a function of the distances between resonators (or antennas). The PTE of the C-loaded loop resonators during MR WPT was theoretically calculated and simulated at 6.78MHz, showing good agreement. The PTE of the patch antennas, whose area is the same as the C-loaded loop resonator during MR WPT, was theoretically calculated using the Friis equation and the equation by N. Shinohara and simulated at 5.8 GHz. The three results from the Friis equation, the equation by N. Shinohara, and from a full wave simulation are in strong agreement. The PTEs, when using the same size resonators and antennas are compared by considering the distance between the receiver and transmitter. The compared results show that the MR WPT PTE is higher than that of the RF WPT PTE when the distance (r) between the resonators (or antennas) is shorter. However, the RF WPT PTE is much higher than that of the MR WPT PTE when the distance (r) between the resonators (or antennas) is longer since the RF WPT PTE is proportional to $r^{-2}$ while the MR WPT PTE is proportional to $r^{-6}$.