• Current Optics and Photonics
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• v.1 no.4
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• pp.372-377
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• 2017

We demonstrate that the local resonance of metamaterials can be tuned by the effects of organic thin films under photoexcitation. Tris (8-hydroxyquinolinato) aluminum ($Alq_3$) layers are deposited on metamaterial/silicon hybrid structures. By varying the thickness of the $Alq_3$ layer on the subwavelength scale, the resonant peak of the metamaterial becomes very adjustable, due to the effect of a thin dielectric substrate. In addition, under photoexcitation all the spectral peaks of the resonance shift to higher frequencies. This originates from the reduction of the capacitive response generated inside the gaps of split-ring resonators. The adjustability of the electromagnetic spectrum may be useful for developing optical systems requiring refractive-index engineering and active optical devices.

• Korean Journal of Optics and Photonics
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• v.29 no.3
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• pp.104-109
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• 2018

We explain the basic principle of transformation optics, and introduce several design techniques for transformation cavities that can maintain the characteristics of whispering gallery modes (WGMs) even if the cavity is strongly deformed from a circular shape. As a method of obtaining various transformation cavities under a specific conformal mapping, we suggest a method of parallel movement of the initial cavity domain, and a method of rotating the ellipse as a cavity domain. The internal wave pattern and the far-field output characteristics of several designed resonant modes are numerically calculated. From these results, it is confirmed that a variety of GRIN resonators are possible for a given conformal coordinate transformation.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.3
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• pp.69-75
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• 2001

Photoimageable thick film technology is a new technology in that the lithography process such as exposure and development is applied to the conventional thick film process. Line resolution of 25 $\mu\textrm{m}$ width and 25 $\mu\textrm{m}$ space could be obtained by laminating green sheet, printing photoimageable Ag paste, exposing the test patterns, developing, and co-firing. In case of using the alumina substrate, 20 $\mu\textrm{m}$ fine line could be also obtained by similar process. Test results showed that exposing power density and developing time were the most important processing parameters for the fine line formation. Microstrip and series gap resonators with well-defined line morphology and good transmission characteristics in high frequency were formed by this new technology, and thereby dielectric constant and loss of test substrate were calculated.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.2
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• pp.13-18
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• 2001

In this paper, a four-pole quasi-elliptic function bandpass filter of 1.95GHz center frequency with 60 MHz bandwidth for IMT-2000 using miniaturized square SIR(Stepped Impedance Resonator) is designed and fabricated. The simulation of NUFDTD(Nonuniform Finite Difference Time Domain) is used to design the resonator and to calculate the coupling coefficient of three basic structures. The size reduction of miniaturized square SIR resonator is about more than 50% compare with a square open loop resonator. Bandpass filter using this resonator shows good microwave characteristic with the harmonic suppression of about 19dB. The results of measurements are almost similar to those of simulation.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.3
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• pp.210-220
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• 2008

We review three examples (an on-chip transmission line resonator [1], a phase-locked loop [2], and an analog-to-digital converter [3]) of design tradeoffs which can in fact be circumvented; the key in each case is that the parameters that seem to trade off with each other are actually separated in time or space. This paper is an attempt to present these designs in such a way that this common approach can hopefully be applied to other circuits. We note reader that this paper is not a new contribution, but a review in which we highlight the common theme from our published works [1-3]. We published a similar paper [4], which, however, used only two examples from [1] and [2]. With the newly added content from [3] in the list of our examples, the present paper offers an expanded scope.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.5
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• pp.697-706
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• 2000

In this paper, new bandpass filters that are composed of microstrip ring resonators with the center frequency of 5.775 GHz and the bandwidth of 100 MHz are presented. For the suppression of the unnecessary harmonics, lowpass filters are inserted into the feedlines and ring resonator itself, respectively These bandpass filters show good microwave characteristics with the harmonic suppression ratio of about 39 dB and 35 dB, respectively. Also, the varactor-tuned microstip ring bandpass filter with harmonic suppression is suggested and the tuning bandwidth of more than 450 MHz is obtained.

• 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.

• Journal of the Korean Ceramic Society
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• v.55 no.5
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• pp.419-439
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• 2018

Piezoelectric materials are essential parts of the electronics and electrical equipment used for consumer and industrial applications, such as ultrasonic piezoelectric transducers, sensors, actuators, transformers, and resonators. In this review, the development of piezoelectric materials and the figures of merit for various electromechanical applications are surveyed, focusing on piezoelectric crystals, i.e., the high-performance relaxor-$PbTiO_3$-based perovskite ferroelectric crystals and nonferroelectric high-temperature piezoelectric crystals. The uniqueness of these crystals is discussed with respect to different usages. Finally, the existing challenges and perspective for the piezoelectric crystals are discussed, with an emphasis on the temperature-dependent properties, from cryogenic temperatures up to the ultrahigh-temperature usage range.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.3
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• pp.202-206
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• 2003

In this study, modified PbTi $O_3$ ceramics was manufactured to apply for 30MHz SMD type ceramic resonator with the variations of electrode weight. To investigate the effects of electrode weight on resonant characteristics of ceramic resonator using 3$^{rd}$ overtone thickness vibration mode, ceramic wafers for resonator were fabricated by evaporating electrode weights of 0.66, 1.765, 2.32, 3.87$\times$ 10$^{-4}$ g/c $m^2$ with silver, respectively. And then, SMD type ceramic resonators were fabricated with the size of 3.7$\times$3.1mm and electrode radius size of 0.77mm. With increasing electrode weight, resonant resistance was gradually decreased. At the electrode weight of 2.32$\times$10$_{-4}$ g/c $m^2$, mechanical quality factor( $Q_{mt3}$) and dynamic range(D.R) showed the maximum value of 2,152 and 49dB, respectively.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1643-1648
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• 2004

When a shock wave propagates into a Helmholtz resonator, very complicated wave phenomena are formed both inside and outside the resonator tube. Shock wave reflection, shock focusing phenomena and shock-vortex interactions cause strong pressure fluctuations inside the resonator, consequently leading to powerful sound emission. In the present study, the wave phenomena inside and outside the Helmholtz resonator are, in detail, investigated with a help of CFD. The Mach number of the incident shock wave is varied below 2.0 and several types of resonators are tested to investigate the influence of resonator geometry on the wave phenomena. A TVD scheme is employed to solve the axisymmetric, compressible, Euler equations. The results obtained show that the configuration of the Helmholtz resonator significantly affects the peak pressure of shock wave focusing, its location, the amplitude of the discharged wave and resonance frequency.