• Korean Journal of Optics and Photonics
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• v.25 no.1
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• pp.38-43
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• 2014

An external cavity laser supporting two wavelengths is demonstrated by incorporating polymer waveguide Bragg reflectors and a superluminescent light-emitting diode. An oversized rib waveguide structure and Bragg gratings are designed by using the effective-index and transmission-matrix methods. Bragg gratings with different periods are inscribed on a polymer waveguide through double-exposure laser interferometry. In order to tune the cavity loss affected by the reflectivity of Bragg gratings, a Bragg reflectors with varying length is incorporated. Two-wavelength-mode lasing is achieved for the device consisting of 2-mm long, 537-nm period gratings and 2.2-mm long, 540-nm period gratings; the lasing wavelengths are 1554 nm and 1564 nm, with an output power close to 0 dBm, a 20-dB bandwidth of 0.2 nm, and a side-mode suppression ratio of 45 dB.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1086-1087
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• 2015

본 논문에서는 태양전지 모듈의 표면 오염으로 인한 태양광발전량의 감소를 사전 예방하기 위해 영상기술을 이용한 표면 오염도 자동검출 기술에 대해 논의하였다. 일반적인 태양광발전시스템의 경우 태양전지 모듈의 표면 오염원 제거를 위해 사람에 의한 수동적인 방법에 의존하는 것이 현실이나, 커다란 규모의 태양광 발전시설의 경우는 인력으로 오염원을 제거하는 것은 거의 불가능 하다. 이러한 관점에서 태양전지 모듈 표면에 떨어진 오염 물질로 인한 출력감소를 사전에 예방하고, 시스템을 효율적으로 운영하기 위해 이미지 영상기술이 적용되었다. 본 기술은 기본적으로 레이저 광원과 먼지와 상호 interaction을 통해 생성된 반사파 및 이를 CCD 영상으로 획득하고 태양전지 모듈 표면의 오염원의 유무, 균일/불균일 분포 등의 3가지 서로 다른 조건을 설정하여 비교 시험을 수행하였고, 개발된 오염측정 시스템을 수상 태양광 발전 파일럿 설비에 적용하여 운전성능을 검증하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.11
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• pp.1019-1022
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• 2016

In this paper, a 2~16 GHz GaN wideband power amplifier MMIC s designed and fabricated using the nonuniform power amplifier design technique that utilizes drain shunt capacitors to simultaneously provide each transistor with the optimum load impedance and phase balance between input and output transmission lines. The power amplifier MMIC chip that is fabricated using the $0.25{\mu}m$ GaN HEMT foundry process of Win Semiconductors occupies an area of $3.9mm{\times}3.1mm$ and shows a linear gain of larger than 12 dB and an input return loss of greater than 10 dB. Under a continuous-wave mode, it has a saturated output power of 36.2~38.5 dBm and a power-added efficiency of about 8~16 % in 2 to 16 GHz.

• Journal of Satellite, Information and Communications
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• v.1 no.1
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• pp.59-64
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• 2006

The broadband power detector for power amplitude envelope detection of the direct-conversion Six-port output signal was designed and implemented in this paper. The power detector should be linearly operated to produce the linear amplitude and phase signal for input RF signals in required broadband frequency range. The power detector should be designed under conditions of matching circuit with low VSWR, which protect unbalanced phase signal from reflection signal due to mismatch between the output port of a six-port and the input port of a power detector. The designed power detectors, which were implemented in L-band with 50 ohm matching and Ku-band with multiple LC matching circuits and isolator, respectively, were analyzed in viewpoints of the utilization as a power detector of direct conversion Six-port. The dynamic range of designed power detectors were also measured and rvaluated as a power detector of Six-port circuit.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.4
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• pp.417-426
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• 2010

This paper describes the 6-way power divider to be used as a feeding structure of the waveguide array antenna generating the plane wave at the near distance. The SMA connector has been connected at the center of the power divider in order to feed the radiating element. The six output ports made of waveguide are positioned on the peripheral of the divider. This paper proposes the method utilizing the inductive post in order to decrease the return loss. The height of the feeding pin, the diameter of the inductive post, and the distance between the feeding pin and inductive post have been investigated, and as a result, the power divider has been optimized. The simulated and measured results show the low return loss of about -40 dB. The calculated and measured transmission coefficients are -7.78 dB and -8.06 dB, respectively. The output power of the six waveguide port show equal-amplitude and equal-phase distribution. Since the power divider proposed in this paper can be expanded to the divider having several output ports, it could be easily applied to the various array antennas.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.9
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• pp.987-994
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• 2010

In this paper, a simple and effective active load-pull method is proposed, and the method to improve the efficiency of X-band power amplifier using harmonic control circuit is presented. The proposed active load-pull system mainly consists of directional coupler, phase shifter, short circuit, and power amplifier, and allows a user to access reflection coefficients near the edge of the Smith chart($\Gamma$=1) easily. The device used in this paper is Mitsubishi's GaAs FET MGF1801, and the operating frequency of the power amplifier is 9 GHz, The amplifier had output power of 21.65 dBm and drain efficiency of 24.9 % at class-A, and had output power of 21.46 dBm and drain efficiency of 53.3 % at class-AB. Harmonic control circuit is designed only second and third harmonic components because of the bandwidth limitation of the microwave components. The drain efficiency is improved as much as 6.4 % compared with class-AB power amplifier.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.307-315
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• 2005

We have studied to obtain the SAW filter for the passband was formed on the Langasite substrate and was evaporated by Aluminum-Copper alloy and then we performed computer-simulated by simulator. We can fabricate that the block weighted type IDT as an input transducer of the filter and the withdrawal weighted type IDT as an output transducer of the filter from the results of our computer-simulation. Also, we have performed to obtain the properly design conditions about phase shift of the SAW filter for WCDMA. We have employed that the number of pairs of the input and output IDT are 50 pairs and the thickness and the width of reflector are 5000$\AA$ and 3.6$mu$m, respectively. Frequency response of the fabricated SAW filter has the property that the center frequency is about 190MHz and bandwidth at the 3dB is probably 8.2MHz. And we could obtain that return loss is less then 16dB, ripple characteristics is probably 4dB and triple transit echo is less then 18dB after when we have matched impedance.

• Journal of Advanced Navigation Technology
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• v.14 no.3
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• pp.391-396
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• 2010

This paper presents some important research result comparisons for multi function RF modules which use amplifier or frequency multiplier. By using multiplier, multi function module can be realized amply in comparison to multi band module which has separate block for each frequency band. Some com paring analysis among the switching method between separate amplifier and multiplier, the structure using frequency selective reflector, and the module using the defected ground structure. The multi function module which operates as amplifier or multiplier with input frequency is developed and input frequency suppression and output harmonics suppression can be improve d by using defected ground structure.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.11
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• pp.1075-1081
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• 2004

In this paper, a VCO of a general advance warning system for vehicle's speed limitation in the X-band used in Japan is designed using a small signal scattering coefficient of PHEMT. A varactor diode that wide tuning range and series resistance 0 H is used for designing the VCO and -85 dBc/Hz of phase noise at 10 kHz of offset frequency is obtained by adjusting the reflection coefficient between the micro-strip line and the varactor device which determines transistor's operation voltage and resonant frequency, In addition +4.5 dBm of basic frequency signal output level and -25.6 dEc of the second harmonic constraint are acquired. Sample that produce in this paper could confirm that more excellent special quality appears than existing products in sensitivity.

• Journal of Ocean Engineering and Technology
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• v.24 no.1
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• pp.47-52
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• 2010

This study presents a modified scheme for the radar image simulation of sea waves. A simulated radar image was obtained by taking into account the dot product of the directed vector from the radar and the normal vector of the sea surface. Moreover, to calculate the radar image, we used the radar received power and radar cross section. To demonstrate the effectiveness of the proposed scheme, the wave spectrum from field data was utilized to obtain the simulated sea waves. The radar image was simulated using numerically generated sea waves. The wave statistics from the simulation agrees comparatively with those of the original field data acquired by real radar measurements.