• The Journal of the Acoustical Society of Korea
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• v.21 no.3E
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• pp.126-131
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• 2002

Ultrasonic measurements are made in egg white to study the properties of the solution of the natural protein. The high-Q ultrasonic resonator method is used to get the ultrasonic absorption spectra over the range 0.2-10 ㎒ at 20℃. It is proportional to the 1.25th power of the frequency. The gelation process caused by heat is studied from the change in the velocity and the absorption. at 3 ㎒ using the pulse echo overlap technique over the range of 10-80℃. The absorption decreases with increasing temperature up to 60℃ where it turns up sharply and rapidly increases thereafter. The strong absorption in the gel region is described by the interaction between the solution and the network structure made of protein. Very slow variation in time elapse is observed after the temperature is quickly raised. It would be a real-time observation of the network building process and the characteristic time for the process is shown to be 400 min. A hysteresis phenomenon with respect to the temperature is observed. This phenomenon is associated with the memorizing effect of the network structure of protein of the gel.

• The Journal of the Acoustical Society of Korea
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• v.25 no.1E
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• pp.14-19
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• 2006

Ultrasonic absorption and velocity spectra in bovine serum albumin (BSA) aqueous solutions have been measured at $20^{\circ}C$ over the frequency range 0.2-3 MHz in the pH range 1.5-13.2. The high-Q ultrasonic resonator and pulse-echo overlap methods were used. At acid pH's, excess absorption over that of pH 7 was explained by double relaxation. The pH dependences of the relaxation frequency and maximum absorption per wavelength, showed that the relaxation at about 200 kHz was related to the expansion of molecules and that about 3 MHz resulted from the proton transfer reaction of carboxyl group. At alkaline pH's, the excess absorption was explained by double relaxation. The relaxation at about 300 kHz was associated with a helix-coil transition, and that about 3 MHz was attributed to the proton transfer reaction of phenolic group. The rate constants and volume changes associated with these processes were estimated.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.183-186
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• 1999

The Ultra-miniature and low phase noise Colpitts VCO of 0.06㏄ in size has been developed using the high Q resonator and phase compensation technique. This type is one transistor VCO without a buffer. To design and simulate the VCO accurately, nolinear model parameters of a bipolar transistor are extracted using the measured I-V data and S parameters based on the Gummel-Poon model. Design and simulation have been done by Serenade 7.5 design tool using the extracted nonlinear model parameters. The wideband VCO has been designed using two varactor diodes and open loop gain compensation technique to improve the operating frequency range. The ultra-miniature VCO has shown the phase noise of -91㏈c/Hz at 10KHz offset and output power of -3㏈m The wideband VCO has shown the tuning frequency bandwidth of 150MHz phase noise of -95㏈c/Hz at 10KHz offset and output power of 5㏈m.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.382-385
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• 2001

In the previous study, a new LTCC material in the $PbWO_{4}-TiO_{2}-B_{2}O_{3}-CuO$ system was introduced. The developed material can be sintered at $850^{\circ}C$ and its dielectric properties are $\varepsilon_{r}=20-25$, $Q{\times}f_{o}=30000\sim50000GHz$, and $\tau_{f}=0.2{\sim}30ppm/^{\circ}C$, respectively. Therefore this material can be used as a LTCC substrate material for fabrication of multilayered high frequency communication module set. In present study, using this material, tape casting condition was established. With this condition, a multilayered resonator was fabricated and its electrical properties were examined. In present study, an antenna-duplexer module was also fabricated. Frequency characteristics of as-fabricated antenna-duplexer module was compared with simulation results.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.621-625
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• 2001

In this article, piezoelectric films and their application for film bulk acoustic resonator (FBAR) devices are presented. The FBAR is composed of piezoelectric film sandwiched between top and bottom electrodes and an acoustic reflector of SiO$_2$/W slatted multilayers. Various FBAR devices were fabricated and evaluated through simulation and measurement. The insertion loss, return loss and Q-factor were observed to be reasonably high and good. The FBAR technology seems very promising particularly for RF band filter application.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06d
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• pp.35-39
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• 1998

Methyl과 ethyl formate의 초음파 흡수계수를 0.15-2 MHz의 주파수 범위, 온도 5-3$0^{\circ}C$에 걸쳐 1MHz 이하에서 정확한 초음파 흡수측정이 가능한 광 회절 초음파 공명법을 이용하여 측정하였다.그 결과, cisdhk trans 에 의한 초음파 완화 현상은 전형적인 단일 완화현상을 보였고, 그 스페트럼으로부터 완화주파수와 완화강도를 결정할 수 있었다. 완화 주파수와 완화강도의 온도 의존성으로부터 활성화 에너지(ΔH#)와 에너지 차(ΔH)를 구하였다. 측정된 methyl과 ethyl formate의 활성화 에너지는 각각 9.8과 8.9kcal/mol 이었고, 에너지 차는 각각 2.3 과 2.2kcal/mol로 나타났다

• Journal of the Korean Magnetic Resonance Society
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• v.23 no.3
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• pp.81-86
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• 2019

Overhauser dynamic nuclear polarization (O-DNP) has been an efficient method to boost the thermal nuclear polarization in liquids at room temperature. However, O-DNP for a benchtop NMR using a permanent magnet has remained unexplored yet. In this work, we report the development of an O-DNP system adopting a permanent magnet of 1.6 T. Q-band (~43 GHz) high-power amplifier produced 6 W microwave for saturation. Instead of resonator, we used an open-type antenna for the microwave irradiation. For several representative small molecules, we measured the concentration and frequency dependences of the enhancement factor. This work paves the way for the development of a benchtop DNP-NMR system overcoming its disadvantage of low quality signal when using a permanent magnet.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.12
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• pp.1167-1172
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• 2013

This paper presents a X-band doppler radar with high conversion gain using a self-oscillating-mixer(SOM) that oscillation and frequency mixing is realized at the same time. To improve phase noise of the SOM oscillator, a ${\lambda}/2$ slotted square patch resonator(SSPR) was proposed, which shows high Q-factor of 175.4 and the 50 % reduced circuit area compared to the conventional resonator. To implement the low power system, low biasing voltage of 1.7 V was supplied. To enhance the conversion gain of the SOM, bias circuit is configured near the pinch-off region of transistor, and the conversion gain was optimized. The output power of the proposed SOM was -3.16 dBm at 10.65 GHz. A high conversion gain of 9.48 dB was obtained whereas DC Power consumption is relatively low about 7.65 mW. The phase noise is -90.91 dBc/Hz at 100 kHz offset. The figure-of-merit(FOM) of the proposed SOM was measured as -181.8 dBc/Hz, which is supplier to other SOMs by more than about 7 dB.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.4
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• pp.41-54
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• 2002

In this study, we have analyzed the effects of the membrane layer and the bragg reflector layers on the resonance characteristics through comparing the characteristics of the membrane type FBAR (Film Bulk Acoustic Wave Resonator) and the one type bragg reflector layers with those of the ideal FBAR with top and bottom electrode contacting air by using equivalent circuit technique. It is assumed that ZnO is used for piezoelectric film, $SiO_2$ are used for membrane layer and low acoustic impedance layer, W are used for the high acoustic reflector layer and Al is used for the electrode. Each layer is considered to have a acoustic propagation loss. ABCD parameters are picked out and input impedance is calculated by converting 1-port equivalent circuit to simplified equivalent circuit that ABCD parameters are picked out possible. From the variation of resonance frequency due to the change of thickness of electrode layers, reflector layers and membrane layer it is confirmed that membrane layer and the reflector layer just under the electrode have the greatest effect on the variation of resonance frequency. From the variation of resonance properties, K and electrical Q with the number of layers, K is not much affected by the number of layers but electrical Q increases with the number of layers when the number of layers is less than seven. The electrical Q is saturated when the number of layers is large than six. The electrical Q is dependent of mechanical Q of reflector layers and membrane layer. Both ladder filter and SCF (Stacked Crystal Filters) show higher insertion loss and out-of-band rejection with the increase of the number of resonators. The insertion loss decreases with the increase of the number of reflector layers but the bandwidth is not much affected by the number of reflector layers. Ladder Filter and SCF with membrane layer show the spurious response due to spurious resonance properties. Ladder filter shows better skirt-selectivity characteristics in bandwidth but SCF shows better characteristics in insertion loss.

• 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.