• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.32 no.4
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• pp.421-431
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• 1996

From comparing the impact dynamic absorber with the impact damper in the auxiliary vibration system with the conventional dynamic absorber, the following conclusions are obtained as follows ; 1. Recognizing that the amplitude restraining effect of the impact dynamic absorber become resonable in a comparison of conventional one development of an improved dynamic absorber may be probable. 2. With increasing the frequency ratio, the 1st resonance peak is higher but the 2nd one gets lower. In addition, the frequency ratio is peak located at the same resonance. 3. The optimum impact clearance is smaller and the vibration constraining effect becomes better with and increase in the mass of impact ball. And it is recognizable that the optimum tuning frequency ratio and impact clearance in an accordance with the mass ratio are varied. 4. The optimum tuning condition becomes gradually lower than the case of r=1 and maximum amplitude becomes lower with an increment in the mass ratio. However, the impulse clearance is larger and the working range of restraining vibration amplitude become smaller with a decrement in the mass of impact ball.

• ETRI Journal
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• v.31 no.3
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• pp.271-281
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• 2009

This paper presents a novel multiband microstrip-fed right angle slot antenna design technique for multiple independent frequency bands. The new technique uses various slot sizes at various appropriate positions. We first propose a tri-band slot antenna consisting of three right angle slots. Then, a quad-band slot antenna is developed with four right angle slots which achieves slant ${\pm}45^{\circ}$ linear polarization, omnidirectional pattern coverage, good antenna gain, and acceptable impedance bandwidths over all the operating frequency range. Moreover, an open-circuited tuning stub is introduced to achieve good impedance matching. Both proposed antennas are designed on a ground plane of RT/duroid 5880 substrate with a thickness of 1.575 mm. The real measurable results show that the desired frequencies used in wireless communication systems, namely, WLAN and WiMax, are efficiently achieved.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.10
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• pp.940-950
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• 2011

This paper reports a filtered velocity feedback(FVF) controller, which is an alternative to direct velocity feedback(DVFB) controller. The instability problems at high frequencies due to non-collocated sensor/actuator configuration with the DVFB can be alleviated by the proposed FVF controller. The FVF controller is designed to filter out the unstable high frequency response. The dynamics of a clamped plate under forces and moments and the FVF controllers are formulated. The stability of the control system and performance are investigated with the open loop transfer function(OLTF). It is found that the FVF controller has a higher gain margin than the corresponding DVFB controller owing to the rapid roll-off behavior at high frequencies. Although the gain margin cannot be fully utilized because of the enhancement at the high frequencies, the vibration at the modes lower than the tuning frequency is well controlled. This performance of the FVF controller is shown to be improved from that of the DVFB controller. It is, however, noted that the stability around the tuning frequency is very sensitive so that the enhancement in vibration level should be followed. The reduction performance at low frequencies using the FVF controller should be compromised with the enhancement in the vibration at high frequencies while designing the controller.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.98-100
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• 2007

This paper proposes a robust digital controller for PWM voltage source inverter using CRA method. The usual inverter controller for the operation of constant voltage and constant frequency consists of a double looped PI controller for the outer voltage controller and the inner current controller, of which the order of characteristic polynomial is high and so the gain tuning is difficult. Considering the limited switching frequency of the devices and sampling frequency of the digital controller, the gain tuning is usually based on the engineering experiences with the try and error method. In this paper, the error-space approach is used to get the system model including the controller with low order, and the characteristic ratio assignment (CRA) method is proposed for the design of robust controller which has the advantage to design the optimal gain to meet the referenced response and overshoot within the limit range. The PSiM simulation and experience results are shown to verify the validity of the proposed controller.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.1
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• pp.69-75
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• 2010

In this paper, with using the clapp type VCO(Voltage Controlled Osillator) configuration a wideband frequency synthesizer in UHF band is proposed. In order to design a wideband frequency synthesizer, the variation of phase in the negative resistance circuit as well as the load circuit was analyzed. Based on this result we propose a method to widen the operation range of the VCO. A frequency synthesizer using the proposed wideband VCO was designed and fabricated. It is shown that the synthesizer has the operating frequency range of 740~1,530 MHz by 0~5 V varactor tuning voltage, and it had the output power of 2~-6 dBm. Moreover, the phase noise measured as -77 dBc/Hz at 10 kHz offset, and as -108 dBc/Hz at 100 kHz offset from the oscillation frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.5
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• pp.468-474
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• 2010

In this paper, a VCHO(Voltage Controlled Harmonic Oscillator) for K-band application has been designed and implemented. The proposed oscillator has a structure of two hair-pin resonators placed on input and output of active device. Using in/out common frequency tuning structure, the VCHO yields some advantages of the enhanced fundamental frequency suppression characteristic as well as the improved output power of second harmonic. According to implementation and measurement results, it was shown that a VCHO provides an output power of -2.41 dBm, a fundamental frequency suppression of -21.84 dBc, and phase noise of -101.44 dBc/Hz at 100 kHz offset. In addition, as for the bias voltage from 0 V to -10 V for the varactor diode, output frequency range of 10.58 MHz is obtained with a power variation of ${\pm}0.19\;dB$ over its frequency range.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.6
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• pp.30-38
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• 1998

In this paper, a new CMOS current-mode integrator is proposed that can apply the basic building block of the low-voltage high frequency current-mode active filter. And tuning circuits that control the gain and unity gain frequency of them is designed. The proposed integrator is composed of the CMOS complementary circuit which can extend transconductance of an integrator. Therefore, the unity gain frequency which is determined transconductance and MOSFET gate capacitance can be expanded by the proposed integrator. The unity gain frequency of the proposed integrator is increased about two times larger than that of the conventional continuous-time integrator with NMOS-gm. And also, cut-off frequency and gain of the active filter can be controlled with the designed tuning circuit. From the result, we can reduce errors on fabrication. And then, 3rd-order low-pass active filter is designed as an application circuits. These results are verified by the small signal analysis and the 0.8$\mu\textrm{m}$ parameter HSPICE simulation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.5
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• pp.522-527
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• 2011

In this work, a 54 GHz divide-by-3 injection-locked frequency divider(ILFD) based on ring oscillator has been developed in a 0.13-${\mu}M$ Si RFCMOS technology for phase-locked loop(PLL) application. The free-running frequency is 18.92~19.31 GHz with tuning range of 0~1.8 V, consuming 70 mW with a 1.8 V supply voltage. At 0 dBm input power, the locking range is 1.02 GHz(54.82~55.84 GHz) and, with varactor tuning of 0~1.8 V, the total operating range is 2.4 GHz(54.82~57.17 GHz). The fabricated circuit size is 0.42 mm${\times}$0.6 mm including probing pads and 0.099 mm${\times}$0.056 mm for core area.

• Structural Engineering and Mechanics
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• v.72 no.6
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• pp.747-762
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• 2019

Based on the ball-screw mechanism, a tuned viscous mass damper (TVMD) has been proposed, which has functions of amplifying physical mass of the system and frequency tuning. Considering the sensitivity of a single TVMD's effectiveness to frequency mistuning like that of the conventional tuned mass damper (TMD) and according to the concept of the conventional multiple tuned mass damper (MTMD), in the present paper, multiple tuned mass viscous dampers (MTVMD) consisting of many tuned mass dampers (TVMD) with a uniform distribution of natural frequencies are considered for attenuating undesirable vibration of a structure. The MTVMD is manufactured by keeping the stiffness and damping constant and varying the mass associated with the lead of the ball-screw type inerter element in the damper. The structure is represented by its mode-generalized system in a specific vibration mode controlled using the mode reduced-order method. Modal properties and fundamental characteristics of the MTVMD-structure system are investigated analytically with the parameters, i.e., the frequency band, the average damping ratio, the tuning frequency ratio, the total number of TVMD and the total mass ratio. It is found that there exists an optimum set of the parameters that makes the frequency response curve of the structure flattened with smaller amplitudes in a wider input frequency range. The effectiveness and robustness of the MTVMD are also discussed in comparison with those of the usual single TVMD (STVMD) and the results shows that the MTVMD is more effective and robust with the same level of total mass.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.2
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• pp.73-78
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• 2011

A frequency synthesizer for DAB applications is designed using $0.18{\mu}m$ CMOS process with 1.8V supply. NP-core type is chosen for VCO core to improve low power characteristic and symmetric characteristic of output waveform. VCO range is 1302.34 MHz - 1949.51 MHz using switchable capacitor bank and varactor bank. Varactor biases that improve varactor capacitance characteristics were minimized as two, $K_{vco}$(VCO gain) is maintained using technique of varactor bank switching. Intervals of $K_{vco}$ are maintained adding VCO frequency compensation logic. Each block of VCO and frequency synthesizer designed $0.18{\mu}m$ CMOS process with 1.8V supply is verified by Cadence Spectre, measured VCO consumes 9mA current, and is 39.8% tuning range, total power consumption of the frequency synthesizer is 18mW.