• The Journal of the Acoustical Society of Korea
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• v.20 no.1
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• pp.21-29
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• 2001

In order to detect the precise port/starboard direction of arrival of target signal in real noisy ocean environments, Inverse beamforming (IBF) algorithm is surveyed theoretically and the detection performances of IBF are analyzed with simulations. Cardioid Inverse beamforming algorithm was proposed for port/starboard discrimination and the performance was studied with simulations. It is shown that IBF has a 3dB array gain advantage over Conventional beamforming (CBF) under ideal conditions. This 3 dB advantage is proven theoretically and illustrated with simulations. The fact that the IBF beamwidth is narrower than the CBF beamwidth by a factor of 0.68 proves the performance of defection and spatial resolution improvement. Comparing the simulation results of Cardioid Inverse beamforming and Conventional Cardioid beamforming, it is shown that Cardioid Inverse beamformer has enhanced performance in minimum detection level, detection accuracy and resolution. Due to the results of moving target bearing detection test in endfire, it is shown that Cardioid Inverse beamformer has better performance, comparing the Conventional Cardioid beamformer.

• Journal of Convergence for Information Technology
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• v.10 no.3
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• pp.16-21
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• 2020

This paper describes the jamming characteristics of a stand-off jammer jamming the LPI radar. The LPI radar reduces the side lobes of the receiving antenna to reduce the effect of jamming. It is easy a radar to predict the effect of jamming on a self-protection jammer where the jammer is in the same position as the target. However, for stand-off jammer jamming at different locations from the target, the prediction of jamming effect is complex. In this paper, the jamming effect of LPI radar is analyzed using signal to jamming ratio and burn-through range. Also, when the antenna's side lobe decreases below -30 dB, the stand-off jamming effect in the side lobe direction is weak. So we proposed a new jamming method for the main lobe and analyzed the jamming effect. This study is expected to be useful for the design and operation of aircraft jammers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4C
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• pp.217-225
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• 2011

In this paper, we propose an adaptive de-interlacing algorithm that is based on the degree of local complexity. The conventional intra field de-interlacing algorithms show the different performance according to the ways which find the edge direction. Furthermore, FDD (Fine Directional De-interlacing) algorithm has the better performance than other algorithms but the computational complexity of FDD algorithm is too high. In order to alleviate these problems, the proposed algorithm selects the most efficient de-interacing algorithm among LA (Line Average), MELA (Modified Edge-based Line Average), and LCID (Low-Complexity Interpolation Method for De-interlacing) algorithms which have low complexity and good performance. The proposed algorithm is trained by the DoLC (Degree of Local Complexity) for selection of the algorithms mentioned above. Simulation results show that the proposed algorithm not only has the low complexity but also performs better objective and subjective image quality performances compared with the conventional intra-field methods.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.211.1-211.1
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• 2012

The on-orbit test simulation for predicting the instrument directional responsivity was conducted by the Monte Carlo based integrated ray tracing (IRT) computation technique and analytic flux-to-signal conversion algorithms. For the on-orbit test simulation, the Sun model consists of the Lambertian scattering sphere and emitting spheroid rays, the Amon-Ra instrument is a two-channel including a broadband scanning radiometer (energy channel) and an imager with ${\pm}2^{\circ}$ FOV (visible channel). The solar radiation produced by the Sun model is directed to the instrument viewing port and traced through the dual channel optical train. The instrument model is rotated on its rotation axis and this gives a slow scan of the Sun model over the full field of view. The direction of the incident lights are fed with scanned images obtained from the visible channel instrument. The instrument responsivity was computed by the ratio of the incident radiation input to the instrument output. In the radiometric simulation, especially, measured BRDF of the 3D CPC was used for scattering effects on radiometry. With diamond turned 3D CPC inner surface, the anisotropic surface scattering model from the measured data was applied to ray tracing computation. The technical details of the on-orbit test simulation are presented together with field-of-view calibration plan.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.1
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• pp.12-22
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• 2016

Convenience and safety are the key words for the automotive driving and various sensor technologies have been studied for enhanced perception of driving environments. In frequency modulated continuous wave (FMCW) radar systems, single antenna is enough for range and velocity detection of multiple targets. Multiple array antenna is needed for estimating direction of arrival(DoA). Using DoA estimation algorithm in time domain as in the conventional systems, it is difficult to distinguish vehicles lie in the same angle. In order to facilitate the enhanced angle estimation, DoA estimation algorithm is applied in frequency domain. In this paper, the method for applying multiple signal classification(MUSIC) algorithm in frequency domain is suggested and the performance is analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1C
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• pp.23-33
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• 2007

Video compression is essential technique for fast and efficient transmission of a large amount of video data maintaining high quality. Also, motion estimation and motion compensation is most important technique for efficient video compression. A proposed method is improved diamond search method which uses split diamond pattern and rotated diamond pattern. In particular, the proposed method shows superb result when it is used for the sequence with a direction of camera moving. Moreover when it is used for the sequence with little motion, complexity is reduced considerably by using fewer search points. Also, by varying the number of initial search points, the propose method can provide several options in terms of duality or speed. Simulation results shows that the proposed method sustains better visual quality compared with diamond search method and HEXBS even by using fewer search points. Besides, compared with existing methods, it is able to conduct a motion estimation more efficiently by changing the number of search points adaptively according to motion of video data.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.11
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• pp.748-754
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• 1999

Micromirrors supported by S-shape girders were fabricated and their angular deflections were measured using a laser-based system. A micromirror consists of a $50\mum\times50\mum$ aluminum plate, posts and an S-shape girder. Two electrodes were deposited on two corners of the substrate beneath the mirror plate. $50\times50$micromirror array were fabricated using the Al-MEMS process. The electrostatic force caused by the voltage difference between the mirror plate and one of the electrodes causes the mirror plate to tilt until the girder touches the substrate. Bial voltage of the mirror plate is between 25~35V and signal pulse voltage on both electrodes is $\pm5V$. A laser-based system capable of real-time two-dimensional angular deflection measurement of the micromirror was developed. The operation of the system is based on measuring the displacement of a HeNe laser beam reflecting off the micromirror. The resonant frequency of the micromirror is 50kHz when the girder touches the substrate and it is 25 when the micromirror goes back to flat position, since the moving mass is about twice of the former case. The measurement results also revealed that the micromirror slants to the other direction even after the girder touches the substrate.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.7
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• pp.1539-1545
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• 2015

GPS (global positioning system) is a popular system that provides location information by measuring arrival time difference at the receiver between several GPS satellite signals. GPS is widely used in commercial area as well as military systems. Reliable GPS signal reception is more important in the military systems. However, since the carrier frequencies of the GPS signals are well known, the GPS receivers are vulnerable to intentional jamming attacks. To remove jammers but maintain GPS signals at the received signals, a popular technique is an adaptive beam steering method based on array antenna. Among adaptive beam steering techniques, this paper considers MVDR (minimum variance distortionless response) algorithm, and proposes a new adaptive technique that preserves the received signals at desired direction, but removes the jamming signals adaptively. The performance of the proposed method is verified through computer simulation.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.5
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• pp.52-61
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• 2010

The use of the friction coefficient is known to provide good discrimination ability in the classification of human constitutions, which are used in alternative medicine. In this study, a system that uses a multi-axis load cell and a hemi-circular probe is designed. The equipment consists of a sensor (load cell type, manufactured by the authors), an x-axis linear-bush guide motorized mobile stage that supports the hand being analyzed, and a signal conditioner. Using the proposed system, the friction coefficients from different constitutions were compared, and the relative repeatability error for the friction coefficient measurement was determined to be less than 2 %. The direction along the ring finger line was determined to be the optimum measurement region for a constitutional diagnosis between Tae-eumin and Soyangin types using the proposed system. There were some differences in the friction coefficient between the two constitutions, as reported in ancient literature. The proposed system is applicable to a quantitative constitutional diagnosis between Tae-eumin and Soyangin types within an acceptable level of uncertainty.

• Korean Journal of Remote Sensing
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• v.11 no.3
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• pp.129-145
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• 1995

SeaBeam2000, a multibeam echo sounder, is a new generation seabed mapping system of which a single swath covers an angular range of -60.deg. to 60.deg. from the vertical direction with 121 beams. It provides high-density and high-quality bathymetric data along with sidescan acoustic data. The purpose of the research is to develop a system for processing multibeam underwater acoustic and bathymetric data using digital signal processing techniques. Recently obtained multibeam echo sounder data covering a survey area in the East Sea of Korea ($37{\circ}$.00'N to $37{\circ}$30'N and $129{\circ}$40'E to $130{\circ}$30'E) are preliminarily processed using the developed system and reproduced in the raster image format as well as three dimensionally visualized form.