• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1807-1810
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• 2002

This paper presents a technique for avoid- ing indefiniteness in Maximum Likelihood (ML) criteria for Direction-of-Arrival (DOA) finding using a sensor ar- ray with arbitrary configuration. The ML criterion has singular points in the solution space where the criterion becomes indefinite. Solutions fly iterative techniques for ML bearing estimation may oscillate because of numerical instability which occurs due to the indefiniteness, when bearings more than one approach to the identical value. The oscillation makes the condition for terminating iterations complex. This paper proposes a technique for avoiding the indefiniteness in ML criteria.

• Journal of Biomedical Engineering Research
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• v.14 no.3
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• pp.221-226
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• 1993

Modules of hemodiafilter were manufactured by using MC-Hp200 and RC-HP4DOA hoi low fiber membranes of Enka Co. in a unique design. The performances of she hemodiafillers were evaluated by measuring the molecular weight cut-off, ultrafiltration rate, clearance, and pressure drop across the hemodiafiter. As a whole, the performances of the RC-HP400A module were superior to those of the MC-Hp200 module. The modules prepared in thls study showed the satisfactory performances for hemodiafiltration.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1654-1659
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• 2003

In this paper, the performance evaluation of the JADE-MUSIC estimation based on the indoor channel is presented. By means of the JADE-MUSIC algorithm, DOA and time delay can be obtained simultaneously. In the JADE-MUSIC method, the channel impulse response is first estimated from the received samples and then this impulse response is employed to estimate DOAs and time delays of multipath waves. Moreover, according to the JADE-MUSIC characteristics, it can work in cases when the number of impinging waves is more than the number of antenna elements, unlike the traditional parametric subspace-based method, such a case is not true. Therefore, we employ the JADE-MUSIC algorithm applying for the real indoor environment where is rich of the multipath propagation waves and can imply that the number of waves is very possibly higher than that of the array element. The experiment is carried out in our laboratory considered to be the real indoor environment. The performance of the JADE-MUSIC algorithm is evaluated in terms of the comparison between the simulation and experiment results by using the simulated channel model and the real indoor channel model, respectively. It is clear that the joint angle and delay estimation using the simulated channel model are in good agreement with the estimation using the real indoor channel model. Therefore, we can say that the JADE-MUSIC algorithm accomplishes the high performance to jointly estimate the angle and delay of the arriving signal for the indoor environment.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.8
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• pp.95-104
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• 2016

Subspace-based direction-of-arrival (DOA) estimation algorithms have a difficulty in dealing with coherent signals caused by multi-path environment. As one of attempts to solve this problem, a spatial differencing method is known to be useful for not only estimating DOAs of the coherent signals but also improving the number of resolvable wavefronts even more than the number of antenna elements. However, since the conventional spatial differencing method uses only the partial statistics of the observed data, this method suffers from the performance degradation in estimation accuracy caused by the residual correlation between the uncorrelated signals. To cope with this problem, in this paper, a generalized spatial differencing method is proposed. Unlike the conventional method, the proposed method utilizes the entire statistics of the received signals. Therefore, the additional performance enhancement in both estimation accuracy and the number of resolvable wavefronts can be achieved. The performance analyses with computer simulations show that the proposed method outperforms the conventional method in terms of the estimation accuracy and the number of resolvable wavefronts.

• The Journal of the Acoustical Society of Korea
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• v.39 no.3
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• pp.179-190
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• 2020

In this paper, we estimated the Direction of Arrival (DOA) using Conventional BeamForming (CBF), adaptive beamforming and compressive beamforming. Minimum Variance Distortionless Response (MVDR) and Multiple Signal Classification (MUSIC) are used as the adaptive beamforming, and grid-free compressive sensing is applied for the compressive sensing beamforming. Theoretical background and limitations of each technique are introduced, and the performance of each technique is compared through simulation and real experiments. The real experiments are conducted in the presence of reflected signal, transmitting a sound using two speakers and receiving acoustic data through a linear array consisting of eight microphones. Simulation and experimental results show that the adaptive beamforming and the grid-free compressive beamforming have a higher resolution than conventional beamforming when there are uncorrelated signals. On the other hand, the performance of the adaptive beamforming is degraded by the reflected signals whereas the grid-free compressive beamforming still improves the conventional beamforming resolution regardless of reflected signal presence.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.8
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• pp.917-920
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• 2016

SpSF algorithm is direction-of-arrival estimation algorithm based on sparse representation of incident signlas. Cost function to be optimized for DOA estimation is multi-dimensional nonlinear function, which is hard to handle for optimization. After some manipulation, the problem can be cast into convex optimiztion problem. Convex optimization problem tuns out to be constrained optimization problem, where the parameter in the constraint has to be determined. The solution of the convex optimization problem is dependent on the specific parameter value in the constraint. In this paper, we propose a rule-of-thumb for determining the parameter value in the constraint. Based on the fact that the noise in the array elements is complex Gaussian distributed with zero mean, the average of the Frobenius norm of the matrix in the constraint can be rigorously derived. The parameter in the constrint is set to be two times the average of the Frobenius norm of the matrix in the constraint. It is shown that the SpSF algorithm actually works with the parameter value set by the method proposed in this paper.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.12
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• pp.1284-1291
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• 2014

For detection and parameter estimation, a multicarrier radar should discriminate a channel containing jamming signal and either leave it out or regenerate jammer suppressed target signal. To discriminate jamming channels, we use the angular spectrum of an eigenvector that embeds target echoes and jamming signals. We propose a criteria to discriminate the jammer channels and its basis through mathematical analysis. Moreover, we show some procedures to regenerate the jammer suppressed target echoes. Finally, the validity of the proposed method is demonstrated through simulation results showing improved performance in terms of direction of arrival(DOA) estimation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.9
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• pp.2157-2163
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• 2010

This paper includes the study of DOA(Direction of Arrival). CVDF(Correlative Vector Direction Finding) algorithm using at the phase difference each antenna needs to obtain ideal sinusoidal phase difference patterns. However, the phase difference patterns of circular array antennas may be interfered on a specific frequency band and to particular angle. The effect of installing each array antenna circularly and the effect of the interference by center pole (located in the center of a circular array antennas) may distort the phase difference patterns. This paper propose how to change the combination of antennas to measure phase difference patterns in real-time and how to use antenna beam patterns for minimizing the degradation phenomena with old CVDF algorithm. According to the test result, the capability of direction finding is improved.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.6
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• pp.1123-1129
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• 2003

The noise of maneuvering submarines or vessels can be divided into the tonal signals and broadband ambient noise. Tonal signals are from the revolution of motors and engines of vessels, and broadband ambient noise is from the bubbles which are generated by the propellers and the flow of water around vessels. We can analyze the kinds and the speed of vessels if we analyze the tonal signals and ambient noise. But, it is difficult to divide the tonal signals form the ambient noise when the power of tonal signal is much weaker than the power of ambient noise. In this paper, we detect the direction of arrival(DOA) of the noises generated by vessels with the automatic tracking window(ATW) preprocessing algorithm, and make a beam to the direction of the targets. We suggest a method which can separate weak tonal signals from broadband ambient noise with the ATW algorithm.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.1
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• pp.53-64
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• 2004

This paper proposes a monopulse beamforming network to estimate a target angle in interference conditions. The proposed system estimates the target direction of arrival (DOA) with two separate beamformings for azimuth and elevation with a planar may. The elevation is extracted from adaptive beamforming in the azimuth direction and the azimuth from adaptive beamforming in the elevation direction. Unlike conventional monopulse beamforming techniques using complex correction formulas or a cascaded architecture of an adaptive array and a mainlobe canceller, the proposed system is very efficient from the computational complexity. The advantage is from fact that the monopulse ratio of the proposed system does not depend on the adapted weights. Moreover, the proposed system can estimate the DOA of the target even for multiple mainlobe interferences since it does not need my kinds of mainlobe maintenance technique.