• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.1
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• pp.99-106
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• 2001

In this paper, an 1-Watt amplifier for IMT-2000 was designed and fabricated using feedfarward method which has the highest linearity and wide bandwidth. Since feedforward is sensitive to surroundings for example heat, input power level, time and so on, adaptive controller using micro controller is adopted. We fabricated a HPA with 35 dB gain, 40 dBm of 1-dB compression point, and utilized variable attenuator and variable phase shifter using reflection type to cancel loop signal. From the measured results, the fo11owing facts were obtained, in signal loop, main carrier over 35 dB was suppressed and error signal over 30 dB is cancelled in error loop, IMD characteristics above 60 dBc were obtained.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.6
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• pp.31-39
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• 2009

This paper proposes an ultrasonic sensor based intelligent automatic door system which improves the performance of conventional door systems by adding more intelligent functions such that it offers more convenience to passersby and reduces power loss. The conventional automatic door systems employed passive and active infrared sensors for detecting objects and human bodies. But, they have problems such as power loss in door closing, not sensing fast approaching objects, and safety. The proposed automatic door system with ultrasonic sensors prevents unnecessary door closings to save the power and senses fast approaching objects to open the door at proper time, and improves safety. Thus, the proposed system improves the performance of the conventional systems in terms of operation, economy, and safety.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.59-63
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• 2004

In this paper, we have developed a 2-port resistive frequency mixer for the retrodirective active array. The circuit topology is consisted of 2-port to avoid the complexity of LO and RF signal combination, using a pseudomorphic HEMT device. The operating frequencies are 4.0 GHz, 2.01 GHz, and 1.99 GHz for LO, RF, and IF, respectively. Conversion loss is measured to be -1㏈ and 1-㏈ compression point -15 ㏈m at the LO power of -10 ㏈m.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.4
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• pp.331-339
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• 2013

LiDAR has been one of the widely used and important technologies for 3D modeling of ground surface and objects because of its ability to provide dense and accurate range measurement. The objective of this research is to develop a method for automatic detection and modeling of railroad power lines using high density LiDAR data and RANSAC algorithms. For detecting railroad power lines, multi-echoes properties of laser data and shape knowledge of railroad power lines were employed. Cuboid analysis for detecting seed line segments, tracking lines, connecting and labeling are the main processes. For modeling railroad power lines, iterative RANSAC and least square adjustment were carried out to estimate the lines parameters. The validation of the result is very challenging due to the difficulties in determining the actual references on the ground surface. Standard deviations of 8cm and 5cm for x-y and z coordinates, respectively are satisfactory outcomes. In case of completeness, the result of visual inspection shows that all the lines are detected and modeled well as compare with the original point clouds. The overall processes are fully automated and the methods manage any state of railroad wires efficiently.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.819-830
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• 2017

An FM radio based PCL system is a passive radar technique for detecting the multiple moving targets from FM radio signals and tracking the trajectories of the targets by calculating the cross-correlation function of direct-path signal and target echo signals. However, the interference signals are received from a surveillance channel, which is designed to receive the target echo signals. Because of this problem, the target echo signals are masked by the strong interference signals and this makes it difficult to detect the true targets from the cross-correlation function. Adaptive filters are known as effective methods for suppressing the interference signals but there is a problem to present their accurate performances in the PCL system because many literatures used the cross-correlation function and the ratio of input and output power as a measure of the performance analysis. In this paper, a performance analysis method is proposed to evaluate the performance of interference cancellation algorithms. By using the property that each component of the filter weight vector is adjusted to suppress the specific interference signal, a performance measure of the interference signal suppression is defined by a function of adaptive filter weights. Based on the proposed method, we compare the performance of the adaptive filters used in the PCL system. Simulation results show that the proposed method can be very effective for evaluating the performance of interference cancellation algorithms.

• Journal of Software Assessment and Valuation
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• v.16 no.1
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• pp.55-63
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• 2020

Lasers for optical broadband communication systems should have excellent frequency selectivity and modal stability. DFB lasers have low lasing frequency shift during high speed current modulation. In this paper, when a refractive index grating and a gain grating are simultaneously present in a DFB laser having a wavelength of 1.55 ㎛, the dielectric film is coated so that reflection does not occur on the right mirror surface, so that ρ_r=0. For the first mode, which requires a minimum gain at the threshold, the beam distribution of the oscillation mode in the longitudinal direction and the radiated power ratio P_l/P_r were analyzed and compared for the cases of the phase of ρ_l=π and π/2. If the phase of ρ_l=π, in order to obtain a low threshold current and high frequency stability, κL should be greater than 8. In the case of the phase of ρ_l=π/2, for low threshold current, κL is necessary to be 1.0, where the oscillation frequency coincides with the lattice frequency. DFB lasers with an anti-reflection coated mirror have excellent mode selectivity than 1.55um DFB lasers with two mirror facets

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.11
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• pp.1072-1081
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• 2012

For Ka-band satellite communication system, a new flexible payload technologies which can compensate rain attenuation have to be developed. The Ka-band satellite output power control technology enables to adjust downlink output power of satellite payload in Ka-band (19.8 ~ 22.2 GHz). In this paper, we introduce multi-beam antenna with multi-port amplifiers for Ka-band flexible output power allocation system. We have designed multi-beam antenna with array-fed reflector to form 8 beams on the Korean Peninsula. The target EIRP per beam is more than 59 dBW. The system is designed to present 6 dB boost beams for rainfall areas. Individual beams were optimized by the excited amplitude and phase of feed elements of the feed cluster. The multi-port amplifier(MPA) is one of effective approaches for flexible power allocation in combination with multi-beam antenna. In case of using MPA in multi-beam system, the inter-port isolation characteristic of MPA is important parameter to avoid interference among the output ports. In this paper, we propose a new MPA structure that consists of two $4{\times}4$ Buttler matrixes and phase/amplitude controllable power amplifier modules.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.8
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• pp.1188-1195
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• 2022

The 6-port phase correlator consists of one in-phase power divider and three 3-dB 90-degree phase difference power dividers, and is mainly used in a demodulation circuit that determines the phase of an input signal. This paper proposes the wideband 6-port phase correlator that consists of an in-phase power divider using a wideband 2:1 impedance transformer with three 37.5-Ω coaxial cables, and a 3-dB 90-degree phase difference power divide using Wireline. The proposed wideband phase correlator fabricated at a center frequency of 1000MHz has the value of the input reflection coefficient(S₁₁ and S₂₂) -14dB or less in the frequency range of 640~1270MHz. Also, the signal transmission characteristic(S_i1), from the in-phase power divider input port to four output ports, has the amplitude of -6.5±0.6dB and the phase error of within ±3.4°, and the signal transmission characteristic(S_i2), from the 90 degree phase difference power divider input port to four output ports, has the amplitude of -6.1±0.6dB and the phase error of within ±6.2°.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.8
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• pp.1220-1225
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• 2009

In this paper, a tunable fiber feedback laser based on the use of Sagnac loop filter and fiber Bragg grating (FBG) is proposed. The Sagnac loop filter using a high birefringence fiber provides precise 0.33-nm channel spacing as a multi-wavelength grid filter. Ni-Cr wire wound on the FBG is useful to induce the thermo-optic effect of the fiber. Two types of FBG structures, which have a different length of wire, are demonstrated to show the wavelength shift and separation. To tune FBG by resistant heat, some current is supplied into the wire. When the wavelength matched with one of the cavity modes of Sagnac loop filter, the mode-locked lasing is occurred. The electrical power sensitivity of the resonant wavelength is measured to 1.75pm/mW. This laser configuration can be applied the electrical power system for monitoring the power fluctuation.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.6
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• pp.128-134
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• 2009

In this paper, we propose a new lumped Wilkinson power divider which is designed to have lower quality-factors in the impedance transformation. Therefore, it can provide wider bandwidth than the conventional one. Moreover, the proposed power divider consists of fewer number of elements so that the circuit size can be further reduced. Simulation results show that the proposed lumped power divider allows a 50% wider bandwidth in the return loss and isolation performance. The conventional and new Wilkinson power was designed and fabricated based on the derived equations at 2.0 GHz. In the measurement, the proposed divider achieved a good performance with an input return loss ($S_{11}$) of -23.0 dB, an isolation ($S_{23}$) of -29.0 dB and an insertion loss ($S_{21}$) of -3.12 dB at the design frequency with wider bandwidth than the conventional one.