• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.217-218
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• 2008

Since the digital TV signal band is very wide ($54{\sim}806MHz$), the VCO used in the frequency synthesizer must also have a wide frequency tuning range. Multiple LC VCOs have been used to cover such wide frequency band. However, the chip area increases due to the increased number of integrated inductors. A general method for achieving both reduced VCO gain(Kvco) and wide frequency band is to use the switched-capacitor bank LC VCO. In this paper, a scheme is proposed to cover the full band using only one VCO. The RF VCO block designed using a 0.18um CMOS process consists of a wideband LC VCO with reduced variation of VCO gain and frequency steps. Buffers, divide-by-2 circuits and control logics the simulation results show that the designed circuit has a phase noise at 100kHz better than -106dBc/Hz throughout the signal band and consumes $9.5{\sim}13mA$ from a 1.8V supply.

• Journal of Power Electronics
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• v.12 no.4
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• pp.677-688
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• 2012

The vibratory conveyors with electromagnetic drive are used for performing gravimetric flow of granular materials in processing industry. By realizing free vibrations of variable intensity and frequency over a wide range through application of the electromagnetic actuator, suitable power converter, and the corresponding controller, continuous conveyance of granular materials have been provided for various operating conditions. Standard power output stages intended for control of vibratory conveyance using thyristors and triacs. Phase angle control can only accomplish tuning of amplitude oscillations, but oscillation frequency cannot be adjusted by these converters. Application of current controlled transistor converters enables accomplishing the amplitude and/or frequency control. Their use implies the excitation of a vibratory conveyor independent of the supply network frequency. In addition, the frequency control ensures operation in the region of mechanical resonance. Operation in this region is favourable from the energy point of view, since it requires minimal energy consumption. The paper presents a possible solution and advantages of the amplitude-frequency control of vibratory conveyors by means of a current controlled power converter.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.5 s.120
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• pp.511-521
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• 2007

In this paper, we designed and fabricated a Ka-band synthesizer module. In addition, the systematic layout procedure and the test procedure were presented for the construction of compact synthesizer. To implement the Ka-band synthesizer, X-band VCO is employed as VCO and its frequency was multiplied by 3 with frequency tripler. The fabricated frequency synthesizer shows a frequency tuning range of 500 MHz, output power of about 14 dBm, and a phase noise of -96.17 dBc/Hz at the 100 kHz offset frequency.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.535-540
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• 2004

In this paper, We proposed a rectangular slot antenna with CPW feeder. Slot antennas fed by CPW are attractive due to the simple fabrication simplicity and ease of integration with active devices. This antenna consists of two parts, inner patch and outer patch to realize wide-band antenna by multi-frequency. Also, We fabricated a proposed rectangular slot antenna, confirm characteristics of multi-frequency by tuning antenna parameters, inner antenna's location and size. The experimental results show that each resonant frequency of a fabricated antenna is measured at almost 1, 9GHz, 2.8GHz, 3, 5GHz, 4, 9GHz. In radiation patterns each resonant frequency, radiation pattern 4-th resonant frequency is the same ad that of TM11 in patch antenna. Therefore, the experimental and theoretical results shows that a proposal rectangular slot antenna have triple resonant frequencies.

• Smart Structures and Systems
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• v.13 no.2
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• pp.319-341
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• 2014

A family of smart tuned mass dampers (STMDs) with variable frequency and damping properties is analyzed under harmonic excitations and ground motions. Two types of STMDs are studied: one is realized by a semi-active independently variable stiffness (SAIVS) device and the other is realized by a pendulum with an adjustable length. Based on the feedback signal, the angle of the SAIVS device or the length of the pendulum is adjusted by using a servomotor such that the frequency of the STMD matches the dominant excitation frequency in real-time. Closed-form solutions are derived for the two types of STMDs under harmonic excitations and ground motions. Results indicate that a small damping ratio (zero damping is the best theoretically) and an appropriate mass ratio can produce significant reduction when compared to the case with no tuned mass damper. Experiments are conducted to verify the theoretical result of the smart pendulum TMD (SPTMD). Frequency tuning of the SPTMD is implemented through tracking and analyzing the signal of the excitation using a short time Fourier transformation (STFT) based control algorithm. It is found that the theoretical model can predict the structural responses well. Both the SAIVS STMD and the SPTMD can significantly attenuate the structural responses and outperform the conventional passive TMDs.

• Journal of electromagnetic engineering and science
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• v.16 no.3
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• pp.191-193
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• 2016

This paper proposes a voltage-controlled oscillator (VCO) that has broadband turning and low-level of phase noise characteristics. Due to the micro-strip line resonant circuit with a low Q value, which is applied to the broadband tuning range, the depreciated phase noise performance is compensated by restraining the harmonics of the oscillating frequency. The VCO was designed according to the proposed structure as well as the conventional structure, and the superiority of the proposed structure was verified through its simulation, fabrication, and measurement.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.56-57
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• 2002

일정한 파장 간격을 가지는 다파장 광원은 WDM 시스템에서 중요한 소자중의 하나로 부각되고 있다. 다파장 광원에서 요구되는 주요 특징은 넓은 파장대역과 많은 수의 채널이며 각 채널들의 출력이 크고 균일해야 할 필요가 있다. 또한 각 채널의 파장이 ITU frequency grid와 일치해야 한다. 반도체 레이저와 광섬유레이저를 이용하여 이런 요구들을 만족하는 다파장 광원에 대한 다양한 연구들이 이루어져 왔다. (중략)

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.175-178
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• 2004

Power supply technique for electrodeless lamps, especially self-oscillation method, is presented in this paper for Endura of Osram. The power supply uses different method for high efficiency at high frequency operation compared to the conventional method using saturable transformer. Exact parameter tuning using simulation is suggested for effective design for real applications.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.3-6
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• 2001

This paper presents optimal robust PID controller design method for second order systems to satisfy the design specifications in time domain. The parameters of PID controller are determinated by the weighting factors Q and R of cost function. It is suggested that the selection of Q and R matrix can be determinated by its relationship with the natural frequency of ITAE criterion.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.1067-1072
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• 2003

Generally dual mass flywheel(DMF) is used as a solution to reduce noise and vibration of power train system and to improve the comfortability of passenger car. In this paper, design concept of new DMF model, analytical/numerical model, test procedure and tuning results are presented. Design parameters are studied by some numerical methods and tests. As the result, we can find more efficient model of DMF and reduce vibration level in power train system.