• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.2
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• pp.212-215
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• 2016

In this paper, a 5.08 GHz Ring Voltage Controlled Oscillator(Ring VCO) was implemented using $0.18{\mu}m$ standard CMOS technology. The proposal Ring VCO is 3-stage structure. This research confirmed that the each stage's different transistor size ratio influence the current change and alter power consumption consequentially. This circuit is formed to control the current thereby adding the Current Mirror and to tune the frequency by supplying control voltage. It has an 65.5 %(1.88~5.45 GHz) tuning range. The measured output power is -0.30 dBm. The phase noise is -87.50 dBc/Hz @1 MHz offset with operating frequency of 5.08 GHz fundamental frequency. The total power consumption of Ring VCO is 31.2 mW with 2.4 V supply voltage.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.5
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• pp.510-519
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• 2013

In this study, the spray characteristics of a pressure swirl atomizer classified into a liquid sheet-type swirl nozzle for Urea-SCR system were investigated experimentally with the variation of injection pressure. The length to diameter ratio ($l_o/d$) of the nozzle was 3.1, and the swirler was set inside the nozzle tip to give injecting fluid angular momentum. The injection duration of the nozzle was controlled by PWM (pulse width modulation) modes. The development processes of the spray were imaged by a 2-D PIV system, and the change of spray angle was measured. The atomization characteristics, including axial velocity and SMD, were measured using a 2-D PDA system with the injection pressures at room temperature and ambient pressure conditions. As the experimental results, the injection pressure had a significant impact on the spray structure showing a different shape around the spray leading edge, and the smaller SMD was observed with increasing injection pressures, which was similar to that of the previous work.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.12
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• pp.83-91
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• 1998

Fiber Bragg grating which has a blazed ang1e to the plane of incident wave generates a side-mode as well as main-mode. The side-mode has an identical characteristics with a long period grating that couples with a cladding mode, so rejects the special wavelength. We experimented on the side-mode characteristics with two fibers which Ge doped depressed index fiber and very high photosensitive H$_2$ loaded step index fiber according to the tilted angle. Also, using a phase mask equipped with rotation plate which has 0.02$^{\circ}$ resolution, we can control the bandwidth and the peak value of a total loss spectrum by aligned tilted grating in a fiber and using this, tried to compose the ASE band rejection filter of the Erbium doped fiber amplifier.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.8
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• pp.598-609
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• 2003

This paper describes a CMOS IF PLL frequency synthesizer. The designed frequency synthesizer can be programmed to operate at various intermediate frequencies using different external LC-tanks. The VCO with automatic amplitude control provides constant output power independent of the Q-factor of the external LC-tank. The designed frequency divider includes an 8/9 or 16/17 dual-modulus prescaler and can be programmed to operate at different frequencies by external serial data for various applications. The designed circuit is fabricated using a 0.35${\mu}{\textrm}{m}$ n-well CMOS process. Measurement results show that the phase noise is 114dBc/Hz@100kHz and the lock time is less than 300$mutextrm{s}$. It consumes 16mW from 3V supply. The die area is 730${\mu}{\textrm}{m}$$\times$950${\mu}{\textrm}{m}$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.7
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• pp.768-773
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• 2012

A branch-line hybrid using microstrip artificial transmission lines(ATLs) with slotted-triangular patches is proposed. The proposed artificial transmission line is compact in structure as well as easy to adjust the characteristic impedance and electrical length of equivalent transmission line by changing the slot's parameters; hence, it is useful for miniaturizing conventional transmission lines. The designed branch-line hybrid, because of the use of the right angled isosceles triangular shaped artificial transmission lines as building blocks, has no useless empty space, and hence optimally miniaturized. A fabricated 3 dB branch-line hybrid shows the coupling variation of ${\pm}0.5$ dB and the phase difference between two output ports of $91^{\circ}{\pm}4^{\circ}$ within 15 % bandwidth at 2.45 GHz center frequency. The size of proposed branch-line hybrid is only 38% of the conventional branch-line hybrid.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.1
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• pp.37-43
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• 1996

Breaking waves were generated in a 2-D flume. A piston-type wavemaker was operated in accordance with signals which consist of elementary harmonics with appropriate phase differences. These phase differences were estimated by using a linear wave theory so that wave crests were to be concentrated at the same position. The stroke of wavemaker was controlled to create plunging-type breaking waves. The signal with small amplitude could not generate breaking waves. In the case of moderate amplitudes, various breaking waves could be obtained. Most of breaking waves were spilling type. Only when the wavemaker was operated with appropriate amplitude, plunging-type breaking waves were generated. The parameters of breaking waves are the wave steepness and the frequency bandwidth. If the central frequency was low, breaking waves were not generated. Based on experimental data, we found that the wave height of breaking inception was H = 0.0113 gT$^2$. We also made computations by using a mixed Euler-Lagrangian scheme under the assumption of potential flow. The numerical results show good agreements with tank measurements.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.1861-1868
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• 2014

In wireless communication systems, a frequency offset exist at the received signal due to the transmitter-receiver oscillator mismatch and Doppler effect in mobile environments. Those offsets rotate the received signal's phase and degrade the receiver performance. Hence, estimation and compensation of the frequency offset is crucial at the receiver. This paper proposes a new frequency offset estimation technique based on partial correlation. The proposed method requires less computational complexity than that of the conventional method. In addition, since the proposed one can estimate a wide range of frequency offset without estimation accuracy loss, the application of the method is desirable for the communication environments that have a large frequency offset. In order to verify the performance of our proposed scheme, a series of computer simulations have been carried out and compared against those of the conventional method.

• Korean Journal of Optics and Photonics
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• v.13 no.5
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• pp.400-407
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• 2002

Two dimensional solitary waves are stably propagated in a saturable medium which has a saturable nonlinear index as input intensity. However, in the case of low intensity. a negative fifth-order nonlinear medium has properties of a saturable medium. So a Gaussian beam travels stably. The propagation process into the fifth order nonlinear medium of the Gaussian beam with a weak intensity is investigated by using the computer simulation of the two-dimensional nonlinear Schrodinger equation. As a result, it is confirmed that the two-dimensional spatial solitary waves are stably propagated in this medium when the incident powers are self-trapping powers. In the condition of the phase difference and collisional angle between two input beams of 180 degree and 0.05 degree, respectively, we can confirm that all optical switching is as simple as controlling the incident power of one input beam.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.5
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• pp.48-59
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• 2019

In recent years, the type of bridge where cables such as suspension bridge and cable-stayed bridge are the main factors in the construction of long-range bridges has been soaring. The effects of cables on these structures are very large, and for structural analysis, it is necessary to study the cable and the structural changes according to the mode characteristics of the cables. In particular, cables are directly connected to camber adjustment, which conveys load effects on girders to tower, and are important components in the overall structure, and since the initial tension on the construction is compared with the tension over time, this study was conducted to help identify the condition of the bridge's aging and abnormalities. Therefore, in this study, the characteristics of the mode from the mode analysis through the impact hammer to the mass of the cable and the change in the length of the cable are analyzed.

• Korean Journal of Optics and Photonics
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• v.32 no.4
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• pp.187-194
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• 2021

This paper presents a study of laser output characteristics. We fabricated a MOPA (master oscillator power amplifier)-type high-power, narrowbandwidth fiber laser with a bidirectional pumping configuration in its main amplifier. As signal beams, light sources with bandwidths of 3 GHz and 10 GHz-phase-modulated through a PRBS (pseudo-random binary sequence)-were used interchangeably. Furthermore, the characteristics of the SBS (stimulated Brillouin scattering) were analyzed using a signal beam with 3 GHz bandwidth, by adjusting the forward to backward pumppower ratio. Moreover, the characteristics of the transverse mode instability were analyzed by adjusting the forward to backward pump-power ratio, using a signal beam with 10-GHz bandwidth. Finally, the output power from 10 GHz bandwidth was amplified to more than 1 kW using a forward to backward pump-power ratio of 1.6. The beam quality M² was measured to be approximately 1.36, and the optical-to-optical efficiency was 80% at maximum output power.