• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.10
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• pp.1147-1158
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• 2008

In this paper, we designed a phase-looking circuit that locks the 16.8 GHz VTDRO to a 700 MHz SAW oscillator using SPD as a phase detector Direct phase locking with loop filter alone causes the problem of lock time, so VTDRO is phase leered by loop filter with the aid of time varying square wave current generator. The current generator is related to the loop filter and needs the systematic toning. In this paper, a systematic design of the current generator and loop filter is presented. The fabricated PLDRO shows a stabilized frequency of 16.8 GHz, a output power 6.3 dBm, and a phase noise of -101 dBc/Hz at the 100 kHz offset.

• Journal of electromagnetic engineering and science
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• v.12 no.4
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• pp.227-233
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• 2012

This paper describes a novel and compact biosensing platform using an RF active system. The proposed sensing system is based on the oscillation frequency deviation due to the biomolecular binding mechanism on a resonator. The impedance variation of the resonator, which is caused by a specific biomolecular interaction results in a corresponding change in the oscillation frequency of the oscillator so that this change is used for the discrimination of the biomolecular binding, along with concentration variation. Also, a Surface Acoustic Wave (SAW) filter is utilized in order to enhance the biosensing performance of our system. Because the oscillator operates at the skirt frequency range of the SAW filter, a small amount of oscillation frequency deviation is transformed into a large variation in the output amplitude. Next, a power detector is used to detect the amplitude variation and convert it to DC voltage. It was also found that the frequency response of the biosensing system changes linearly with three streptavidin concentrations. Therefore, we expect that the proposed RF biosensing system can be applied to bio/medical applications capable of detecting a nano-sized biomolecular interaction.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.2
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• pp.134-138
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• 1994

$LiTaO_3 (LT)$ single crystals (Y, X-axis) were grown from the congruent composition, 48.65 mole %, $Li_2O$ for SAW (Surface Acoustic Wave) applications. Basic SAW filters were fabricated on the RIST prepared LT wafers (Y-cut) using phtolithography. SAW filter performance was evaluated. The results were compared of the SAW characteristics between RIST prepared LT wafer (Y-cut) and commercial Yamaju wafer (Y-cut). The SAW filter prepared on the RIST grown LT wafer was shown better SAW performances than that of Yamaju wafer.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1767-1775
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• 2003

The SAW device is extensively used as a electro$.$mechanical band­pass filter in which a two­pairs of interdigital transducers are provided over the surface of the piezoelectric substrate. For the design requirement, the central frequency and the bandwidth of the passband, and the attenuation level of the stopband region are specified. The configuration is made so as to satisfy the specification given. The central frequency is mainly determined by the distance between the pair of the finger electrodes. The design is considered as an optimization problem with which the error norm, the distance between the desired characteristics and the calculated for a given model is to be minimized. The delta function model and the electrical equivalent circuit model are utilized to represent the SAW filter characteristics. Genetic algorithm is used for optimization in which apodization of the transducer fingers is chosen as a design variable.

• Journal of electromagnetic engineering and science
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• v.12 no.1
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• pp.37-44
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• 2012

This paper describes a compact and novel wireless vital sign sensor at 2.4 GHz that can detect heartbeat and respiration signals. The oscillator circuit incorporates a planar resonator, which functions as a series feedback element as well as a near-field radiator. The periodic movement of a human body during aerobic exercise could cause an input impedance variation of the radiator within near-field range. This variation results in a corresponding change in the oscillation frequency and this change has been utilized for the sensing of human vital signs. In addition, a surface acoustic wave (SAW) filter and power detector have been used to increase the system sensitivity and to transform the frequency variation into a voltage waveform. The experimental results show that the proposed sensor placed 20 mm away from a human body can detect the vital signs very accurately.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.2
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• pp.83-90
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• 2005

In this paper, we proposed the newly design method for extracting of the saw resonator characteristic. For the parameters of the proposed equivalent model, we adjusted and optimized the variables of several functions. As verification of proposed method, we firstly designed and fabricated cellular saw resonator by using the proposed model resonator. As the simulated and measured results of the proposed design method are almost equaled, we confirmed the usefulness of this method. we knew the usefulness of this method. Finally we designed the 800MHz cellular Tx/Rx band pass filter by using this designed resonator.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.152-153
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• 2001

파장 가변형 광 필터와 파장 선택형 광 스위치는 파장분할다중 광통신 및 광 교환 시스템을 구현하는데 매우 중요한 소자들 중의 하나이다. 특히 음향광학효과를 이용한 파장 가변형 광 필터(AOTF ： Acousto-Optic Tunable Filter)는 150nm 이상의 넓은 파장 가변범위, 1.5nm이하의 좁은 통과대역폭, 수 $\mu\textrm{s}$ 정도의 비교적 빠른 스위칭 속도 그리고 여러 개의 파장 채널을 동시에 선택할 수 있는 장점들을 가지고 있지만, 한편으로 표면 음향파(SAW： Surface Acoustic Wave) 구동에 필요한 RF 파워와 부 모드 (sidelobe)가 비교적 크다는 단점 때문에 실용화에 많은 제약을 받아왔다. (중략)

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.393-394
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• 2007

In this study, to minimize the above effect Zinc Oxide(ZnO) thin films on Si(100) substrate were deposited by RF magnetron sputter with changing sputtering conditions such as Ar/$O_2$ gas ratios, RF power, substrate temperature, chamber prsssure and target-substrate distance. To analyze a crystallographic properties of the films, ${\Theta}/2{\Theta}$ mode X-ray diffraction, rocking curve and Alpha-step were performed. SAW filters were fabricated to evaluate the feasibility of ZnO thin film as a piezoelectrical materials and the processes of ZnO SAW filters using etch and lift-off were compared.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.04b
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• pp.1239-1242
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• 2002

In this paper, the implementation of MAI(multiple access interference)-cancelled SSMA(spread spectrum multiple access) system using orthogonal carriers was presented. Employing the pseudo periodic spreading codes and orthogonal carriers frequency offset, proposed system have the features no MAI during a certain local time-duration. Spreading signals designed by pseudo periodic method and repetition, have zero correlation duration(ZCD) by orthogonal frequency shift method. The SSMA modem has been designed and implemented using surface-acoustic-wave(SAW) device as the matched filter of receiver. The effects of frequency offset on stability have been evaluated using computer simulation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.932-934
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• 2004

Due to the increasing variety and capacity of information and communication media, systems of microwave band communication have branched out extensively. Surface acoustic wave (SAW) devices fabricated FeSiB thin films on quartz substrate were deposited by RF magnetron sputter and by photolithographic processes. This device is with a center frequency 146MHz and the insertion loss as low as -43dB was obtained.