• Journal of the Korean Society for Precision Engineering
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• v.17 no.4
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• pp.226-232
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• 2000

This paper develops a finite element model for studying the crashworthiness analysis of a mid-size truck. A simulation for a truck frontal crash to a rigid barrier using the model is performed with PAM-CRASH installed in super computer SP2. Full vehicle model is composed of 86467 shell elements, 165 beam elements and 98 bar elements, and 86769 nodes. The model uses four material model such as elastic, elastic-plastic(steel), rigid and elastic-plastic(rubber) material model which are in PAM-CRASH. Frame and suspension system are modeled with 28774 shell elements and 31412 nodes. Cab is modeled with 34680 shell elements and 57 beam elements, and 36254 nodes. Bumper is modeled with 2262 shell elements, and 2508 nodes. Axle, steering shaft, etc are modeled using beam or bar elements. Mounting parts are modeled using rigid bodies. Bodies are interconnected using nodal constrains or joint options. To verify the developed model, frontal crash test with 30mph velocity to a rigid barrier is carried out. In the crash test, vehicle pulse at lower part of b-pillar is measured, and deformed shapes of frame and driver seat area are photographed. Those measured vehicle pulse and photographed pictures are compared those from the simulation to verify the developed finite element model.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4A
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• pp.250-259
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• 2012

This paper compared and investigated the choice of optimal algorithm affects on the directivity synthesis of linear array in the satisfaction to the design specification of the desired directivity, convergence characteristic, and adaptability. Optimal algorithms use a quasi-Newton method(DFP and BFGS method) for realizing the desired directivity, used a quasi-ideal beam, steering beam, and a multi-beam, chosen as desired directivity. In the numerical result, this paper verified the effectiveness of the quasi-Newton method to the directivity synthesis, and offered a solving approach of occurred problems in the numerical simulation process.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.1
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• pp.11-19
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• 2019

The waveguide slotted active phased array radar is characterized in that the beam is tilt in a specific direction when the feeding position of the antenna is not in the center of the antenna. If the beam deflection phenomenon is not properly compensated, error bias is generated in the target information collected by the radar, and the target accuracy is lowered. In this paper, we describe a technique to compensate the error of the target information that is collected in the active phased array radar of the waveguide slot type instead of the center of the antenna.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.1
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• pp.23-30
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• 2022

The active phased array antenna system performs beam steering, multi-beam formation and adaptive beam forming by controlling the amplitude and phase of signals fed to each radiating element. In order to obtain the desired radiation characteristics using an active phased array antenna system, the accurate amplitude and phase of the signal must be fed to each radiating element; however, due to various causes, the signal errors occurs in each radiating element. In this paper, a signal error estimation method of each radiating element is proposed. The proposed method simplifies the process of signal error estimation, and can quickly and accurately calculate the signal error.

• Journal of Korea Society of Industrial Information Systems
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• v.15 no.2
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• pp.11-16
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• 2010

In this papar, we have proposed a small electronically steerable parasitic array radiator with 180 degree azimuth beam coverage and high gain characteristics. The proposed antenna is composed of a uniplanar Yagi dipole as a feeding element and two dipoles as parasitic elements. The fabricated antenna is tested by electronically changing the reactance loaded on the parasitic dipoles and the results show that it has 5.2dB~6.7dB gain in $-90^{\circ}{\sim}90^{\circ}$wide azimuth range and -10dB return loss characteristics within 5.725GHz~5.825GHz UNII band.

• The Journal of the Acoustical Society of Korea
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• v.39 no.6
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• pp.559-567
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• 2020

This paper proposes a noise cancelling algorithm to remove own-ship noise for a towed array sonar. Extra beamforming is performed using partial channels of the acoustic array to get a reference beam signal robust to the noise bearing. Frequency domain Adaptive Noise Cancelling (ANC) is applied based on Normalized Least Mean Square (NLMS) algorithm using the reference beam. The bearing of own-ship noise is estimated from the coherence between the reference beam and input beam signals. Own-ship noise level is calculated using a beampattern of the noise with estimated steering angle, which prevents loss of a target signal by determining whether to update a filter so that removed signal level does not exceed the estimated noise level. Simulation results show the proposed algorithm maintains its performance when the own-ship gets out off its bearing 40 % more than the conventional algorithm's limit and detects the target even when the frequency of the target signal is same with the frequency of the own-ship signal.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2777-2784
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• 2011

In this paper, DOA(direction of arrival) of multiple incident signals received from linear array antenna and circular array antenna, which is based on nonparametric estimation algorithm, and adaptive beam-forming algorithm are studied and analyzed. In nonparametric estimation algorithm, we minimize a regularized objective function for finding a estimate of the signal energy as a function of angle, using nonquadratic norm which leads to supper resolution and noise suppression. And then, DOA is estimated by the signal and noise spatial steering vector, and adaptive beam-forming pattern is improved by weight vectors obtained from the spatial vector. Especially, the discrimination ability of DOA and the adaptive beam-forming ability according to antenna array methods and the number of array elements are compared and considered.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.155-161
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• 2018

Many short range weather radars with the low elevation search capability are needed for analysis and prediction of unusual weather changes or rainfall phenomena which occurs regionally. However, due to the characteristics of low elevation electromagnetic wave beam, it is highly probable that the received weather signals of these radars are contaminated by the ground and sea clutter. Since most of ground clutter appears around the very narrow low Doppler frequency region, it is somewhat easy to separate. However, the sea clutter removal is very difficult since it can occupy the broad Doppler frequency region according to weather conditions. Therefore, in this paper, the sea clutter removal capability is analyzed for a phased array weather radar which use vertical array elements for electronic elevation beam steering. Also, it is shown that the sea clutter removal can be achieved appropriately using the receiver beam forming technology in a phased array antenna.

• The Journal of the Acoustical Society of Korea
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• v.38 no.6
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• pp.678-686
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• 2019

Underwater communication performance is degraded by the influence of Inter-Symbol Interference (ISI) due to multipath. Passive time reversal processing is the most effective technique for mitigating multipath, and the diversity combining method can be used to improve its performance. This paper analyzed communication performance using the beam diversity combining method, which combines signals obtained through the beam steering to various angles. Directions of arrival were estimated through the beam-time migration, which, in turn, was estimated from probe signals received by a vertical line array. The performance was analyzed based on the number and type of combinations among the estimated angles. In this paper, the data obtained from the Biomimetic Long range Acoustic Communications 2018 (BLAC18) experiment, which was conducted in the East sea, ~50 km east of Pohang, in October 2018, were used for the analysis. The output Signal to Noise Ratio (SNR) was used as communication indicators.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.5
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• pp.568-573
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• 2019

Modern Radars are evolving into MFRs which can search multiple targets simultaneously and then track them. Additionally they should be able to avoid some external jamming signals. Applying to these MFRs, Antennas should be able to perform DBF including to not only real-time beam steering but also multi-beam forming simultaneously. And they can cancel the beam at the specific direction. In this paper, we describe the implementation of sub-array type antenna hardware which can be applying DBF. Also we propose the modified amplitude aperture distribution for suppressing the side lobe level and explain the sub-array receiver design with amplitude tapering. It consists in making the amplitude weighting in 2 steps. In order to compare two weighting cases, we investigate the G/T performance for the array antenna. At the conclusion, we make a comparative study for the dynamic range of every sub-array receiver and present the hardware implementation that is more advantageous for sub-array alignment and calibration in DBF.