• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.6
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• pp.602-609
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• 2021

Aircraft radar has special function which is ranging from aircraft to ground of antenna boresight. Because ranging information is used to calibrate altitude of aircraft or to drop a conventional bomb, the measuring have to be precise and robust. Therefore, we propose a simple and efficient method using monopulse radar for ground ranging. Proposed method calculates balancing weight according to linearity of monopulse ratio and mixes two ranging measurements in proportional to the weight. By exploiting balancing weight, radar is able to react to various environment as monopulse ratio contains characteristics of clutter environment. As a result, robust ranging information can be achieved. We use DEM(Digital Elevation Model) in order to simulate heterogeneous environment. In experimental result, it is shown that proposed method shows better accuracy and precision in any environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7A
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• pp.603-610
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• 2005

Beam-forming method based on the estimated channel information at the base station degrade the performance mismatching directional vector in case of systems which Frequency Division Duplex (FDD) center frequency of uplink and downlink are different. Also blind estimation technique which is to obtain directional vector of reverse link through received signal has disadvantage of hardware complexity increase. To solve these problems, in present paper, a smart antenna algorithm which is to improve the beam-forming complexity increase due to user number by appling the spatial fourier transform to be able to beam- forming toward a wanted direction through adjusting a obtained uplink weight function by estimating Angle-of-Arrival (AoA) to the competable form at the downlink is proposed. The proposed algorithm is integrated to the CDMA downlink transmitter and simulations are performed to confirm the performance as frame error rate at the receiver. As a result, the beam forming effect is confirmed and the performance gain with the proposed algorithm is comparable to ordinary smart antenna system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1C
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• pp.72-80
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• 2003

This paper proposed the method of finding optimal weight vectors for enhancing the performance of an adaptive array antenna system by adopting a novel beam-forming algorithm in CDMA (code division multiple access) channel. This algorithm is a liberalized power method, based on power method, with the total computational load, O(4N). Where, N denotes the number of antenna elements. The performance of the proposed algorithm is shown in terms of SER (symbol error rates), allowable capacity, and the convergence characteristic in IS2000 1X CDMA channel. As a result of simulations, the adaptive way antenna system allows 6-10 times more users than the conventional one in a cell of a base station. Furthermore, the proposed algorithm shows superior performance to the conventional one regarding symbol error rates, converging characteristics, and computational load.

• Journal of IKEEE
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• v.17 no.2
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• pp.135-139
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• 2013

This paper presents the 8-channel active module operated in Ka-band. The module is designed for the mobile satellite communication antenna systems, and the module structure has the merit to minimize the size and weight of the antenna systems by 30% compared with the conventional systems using the active module composed of single channel. This module was designed to be optimally operated by prohibiting the electrical interference among the individual channels. From the test results of the fabricated 8-channel active module, it can be confirmed that the maximum channel gain error is ${\pm}1.3dB$, the minimum channel output power is 21.5dBm, and the maximum gain variation by phase control is ${\pm}1.0dB$.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.1 no.2
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• pp.209-220
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• 1997

DBS offers actual services to mass-media and communication system of very broad region in information society. Especially, the DBS is the only system to access TV broadcasting service on a sailing ship. But the ship's DBS receiver is required a complex antenna tracking system because ships are under complex moving such as pitch, roll, and yaw etc. This study is motivated to develop a tracking antenna system to receive the koreasat on small silo ship. Therefore, this system is researched to small size, light weight, simple operation, and low cost of the product. The mount structure have been a compact size and easy operation to the Az/El 2-axis type which is operated by step motor. And it is very useful on a ship in the around sea of korean peninsula. The antenna has a plate type of micro-strip array, and is a domestic production. The vibration sensor is selected to gyro sensor of ultra-sonic rate type for ship's moving control. Tracking method is used the step-tracking algorithm, and the ship's moving compensation is adapted to the closed loop control method by ship's moving detection of gyro sensor. Tracking test is operated by the ship's moving simulator, we examined the actual receiving state on sailing shipboard in the near sea of korean peninsular.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.11
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• pp.868-877
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• 2018

In this paper, we propose a new beamforming algorithm for a conformal array antenna based on support vector regression(SVR). While the conventional least squares method(LSM) considers all sample errors, SVR considers errors beyond the given error bound to obtain the optimum weight vector, which has a sparse solution and the advantage of the minimization of the overfitting problem. To verify the performance of the proposed algorithm, we apply SVR to the experimentally measured active element patterns of the conformal array antenna and obtain the weights for beamforming. In addition, we compare the beamforming results of SVR and LSM.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.451-455
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• 2003

Major concern in modern industry is how to reduce the time and cost for product efficient production. Among many mechanical parts of a satellite, bracket plays an important role to support the load when the satellite is launched to space. so enough strength and stiffness. A designer could add unnecessary material and strength it so as not to fail when it used. But if mechanical part of satellite is over-designed, cost will rise and it also goes against to the aim of lightness. To achieve lightness and enough strength and stiffness, optimization algorithm should be introduced in design process. In this study, conceptual design of bracket is carried out to increase the performance of satellite. Some parameter which could change the weight of this part are selected as design variables. Total weight of bracket is to be minimized while displacement and stress should not exceed limit. Size optimization is done with 3D solid element and PLBA, the RQP algorithm. The weight of 0.262kg of initial model is reduced to 0.241kg after optimization process, so 9.8% of weight reduction is obtained.

• International Journal of Aerospace System Engineering
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• v.7 no.1
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• pp.1-6
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• 2020

A deployment mechanism is designed to stow into a small volume efficiently. The panels are fabricated by carbon fiber reinforced plastics (CFRPs). The parameters for the deployment are determined by considering the number of panels, the folding/twisting angles, and the driving force for a deployment device. In addition, a surface accuracy of the manufactured reflector is measured through a photogrammetry methodology. The deployment behavior of CFRP reflector is observed by using the zero-gravity device which compensates the gravity effect during the deployment. The zero-gravity device is constructed wire, motor, controller and loadcell. During the deployment of the reflector panel, the wire and motor compensate for its weight by the feedback process of the controller. Tests result show that a zero-gravity device compensates for the weight of the panel during the deployment of the CFRP reflector.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.509-513
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• 2002

This paper presents a semi-blind Minimum Mean Square Error (MMSE) beamforming adaptive algorithm used far OFDM/CDMA combined system. The proposed algorithm exploits the transmitting pilot signal in the initial period of the transmission to update the weight vector. Then it applies the blind adaptive period to update the weight vector, in which the pilot signal is no longer used. The derivation of the algorithm based on the Mean Square Error (MSE) criterion is also presented. Computer simulation is carried out to verify the performance of the proposed approach.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.3
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• pp.407-416
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• 2021

An active phased array antennas can not only electrically steer the beam by controlling the weighting of the excitation signal, but can also form a pattern null in the direction of the interference source. The weight of the excitation signal to steer the main beam can be easily calculated based on the position of the radiating element. In addition, the weight of the excited signal for pattern null formation can also be calculated by setting the required radiation pattern and using WLSM(Weighted Least Squares Method). However, in a general wireless communication network environment, the location of the interference source is unknown. Therefore, an adaptive pattern null synthesis is needed. In this paper, it was confirmed that pattern null synthesis according to the required radiation characteristic was possible. And based on this, adaptive pattern null synthesis into the direction of an interference source was studied using a binary search algorithm based on observation area. As a result of conducting a simulation based on the presented technique, it was confirmed that adaptive pattern null forming into the direction of an interference is possible in efficient way.