• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.1
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• pp.79-87
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• 2019

Radar detection range is decreased with an increase in the noise levels and detection thresholds in adaptive CFAR of a radar signal processor to the weather clutter reflection signal in the rain. When a high-velocity plot is generated in weather clutter, what are detected are not targets but false plots. Detection opportunity is reduced by radar time resource consumption from additional confirmations regarding the false plots. In this paper, the received signals are saved using a radar-received signal storage device. Based on the analysis of the received signals from weather clutter, the influence of the rainfall reflection has been mitigated by front-end attenuation of the signal processor. The improvement in the detection performance is verified through received signal and simulation results.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.26 no.4
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• pp.360-364
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• 1990

To testy time division scheme, we performed some experiments in a circular water tank(13m in diameter and 1m deep). A result of that is shown in figure 4. The 2-dimensional position of the pinger was calculated by the method of hyperbolic line of position calculation. The resolution of the time difference on the base line is 2.5cm. In experiments, the multiple pingers of a single frequency were distinguished and tracked successfully. When the experiment is carried out in the water tank, some multi-path pulses always occur. To delete it, several 10 ms of time delay is inserted onto the program after a group of the normal signals are received. Some normal pulses are not received by the time delay, however there is no problem, practically, for the distinction and the tracking of the pulse. In 2-dimensional positioning, the pinger position can be calculated with three hydrophones. However, if four hydrophones are available, the positioning accuracy will be higher than three hydrophones only by some techniques. Another good feature of the use of four hydrophones is that the positioning of the pinger is capable if a hydrophone fails in receiving them. We also tested this distinguishing method in the field using another type pingers(APPENDIXA).

• Journal of Satellite, Information and Communications
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• v.2 no.2
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• pp.48-52
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• 2007

Recently, the research of GPS receiver which uses the Software-Defined Radio(SDR) technique is being actively proceeded instead of traditional hardware-based receiver. The software-based GPS receiver indicates that the signal acquisition and tracking treated by the hardware-based platform are processed as the software technique through a microprocessor. In this paper, GPS software receiver is designed by using SDR technique and then the signal acquisition, tracking, and the navigation message decoding parts are verified through the PC-based simulation. Moreover, the efficient algorithms are developed about the signal acquisition and tracking parts in order to obtain the accurate pseudorange. Finally, the pseudorange is calculated through the relative channel delay received through the different satellite of L1 frequency band. GPS software receiver proposed in this paper will be included in the element of GPS/Galileo complex system of development target and will provide not only the method that verifies the performance for Galileo Sensor Station standard but also usability by providing various debugging environments.

• Progress in Medical Physics
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• v.18 no.1
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• pp.42-47
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• 2007

Purpose: To evaluate the tracing of optic nerve tract using manganese enhanced magnetic resonance Imaging. Materials and Methods: After injecting $30{\mu}l$ of $MnCl_2(1mol)$ (1 mol) Into the retina of female New Zealand white rabbit, the contrast enhancements at major anatomical structures of optic nerve tract were evaluated by high resolution T1-weighted Images 12 hours, 24 hours, and 48 hours after $MnCl_2(1mol)$ Injection using 3D FSPGR (Fast Speiled Gradient Recalled echo) pulse sequence at 1.5T clinical MR scanner with high performance gradient system. Also, for quantitative evaluation, the signal-to-noise ratios of circular ROI on anatomical locations were measured. Results: The major structures on the optic nerve tract were enhanced after injecting $MnCl_2(1mol)$. The structures, which showed enhancement, were right optic nerve, optic chiasm, left optic tract, left lateral geniculate nucleus, left superior colliculus. The structures on the contralateral optic pathway to the right retina were enhanced whereas the structures on the ipsilateral pathway did not show enhancement. Conclusion: The Mn transport through axonal pathway of optic nerve sys)em was non- invasively observed after injecting injecting $MnCl_2$ at the retina, which is the end terminal of optic nerve system. This Mn transport seems to occur by voltage gated calcium $(Ca^{2+})$ channel and In case of direct Injection Into the retina, the fast transpori pathway of voltage gated calcium channel seems to be responsible for Mn transport.

• Journal of the Institute of Convergence Signal Processing
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• v.14 no.3
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• pp.191-204
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• 2013

In this paper, we investigated the correlation outputs of Daejeon correlator at the viewpoints of the buffer memory setting related to the fine delay tracking and the under/overflow issue in FFT modules, in order to eliminate DC-like component and phase concentration to 0 degree. As the ring buffer memory is being used for the fine delay tracking, the DC-like component in correlation outputs is generated by improper setting of data read/write address, and then that address setting method is modified to exclude a polluted FFT segment in correlation processing when crossing the port/stream boundary. The phase concentration to 0 degree at beginning of bandpass is caused by inadequate scaling factors, which may be the origins of under/overflow occurred at internal computation of FFT stage. With the revised method of the ring buffer memory setting and the scaling factors in FFT, we could obtain higher signal-to-noise ratio and flux density, compared to the previous method, through the correlation processing of true observational data.

• Journal of IKEEE
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• v.15 no.1
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• pp.76-85
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• 2011

In this paper, we analysed RSS characteristics by external factors and presented an efficient algorithm for real-time location tracking and its hardware system. The proposed algorithm enhanced the ranging accuracy using Kalman Filter based on the RSS DB. The location tracking system that consists of the tag, AP(Access Point), a data collector(Data Receiver) with IEEE 802.15.4(ZigBee) network environment, and location tracking application that reveal locations of each tag is implemented for the test environment. The location tracking system presented in this paper is implemented with MSP430 microprocessor manufactured by TI(Texas Instrument), CC2420 RF chipset and the location tracking application. With the results of the experiment, the proposed algorithm and the system can achieve the efficiency and the accuracy of location tracking with the average error of 19.12cm, and its standard deviation of 5.31cm in outdoor circumstance. Also, the experimental result shows that exact tracking of position in indoor circumstance cannot achieve because of vulnerable RSS with external circumstance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.1
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• pp.207-214
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• 2016

RFID technology is a technology perceiving information with the device called reader and tag which is now used in public transportation such as Hi-pass. In this paper, we design a system which tracks indoor location using this technology. GPS, the most frequently used location-tracking system, has a defect that its accuracy decreases when the device is indoor. In suggested experiment, we simulate signals according to the moving of located objects, then compare with the result of the experiment. Based on the extracted data, we inform data which is for the purpose of tracking system based on analysis of the route and errors. Simulations for the tracking were performed with relocation of real objects. In the real experiment, we arrange the readers around the room and move the tagged object that we like to know the location, then analyze the data from the equipment. This paper suggests the analyzed data for the future indoor tag tracking applications. We expect that the RFID based location positioning data will be used for other indoor positioning research and development.

• Journal of Satellite, Information and Communications
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• v.10 no.4
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• pp.146-150
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• 2015

The COSPAS-SARSAT committee decides MEOSAR (Medium-Earth Orbit for search and rescue) service development for installing 406MHz SAR instruments on their respective MEO navigation satellite system of the United States, EU, and Russia, since 2000. The transmitted beacon signal is separately arrived by satellites with different FOA (Frequency of Arrival) and TOA (Time of Arrival). It is directly transferred to MEOLUT. In MEOLUT, a LUT track at least 3 or 4 satellites simultaneously and estimate location of beacon using time difference of arrival (TDOA) and frequency difference arrival (FDOA). But the transmitted distress signals may be overlapped each other because the distress beacons transmit signal on mean interval of 50 seconds in arbitrary time. It's difficult that simultaneously estimate location of beacon by current scheme for several overlapped distress signal. So we use cross ambiguity function (CAF) Map algorithm and present Multi-CAF MAP scheme in order to satisfy performance requirement of system. The performance is analyzed for COSAPS-SARSAT MEOSAR.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.1
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• pp.93-100
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• 2012

A telemetry signal occurs the line-of-sight problem by the effect of geography in flight test. A fixed relay system or a mobile relay system is used to solve that problem in general but we propose an airborne telemetry relay system using aircraft in this paper. An airborne telemetry relay system receives the telemetry signal of the test vehicle and then retransmits it to the ground system. The receiving antenna which is a phased array antenna can be tilted to ${\pm}30^{\circ}$ beam direction by beam-forming and track the rapidly moving test vehicle in effect. The relay pod which is mounted to an aircraft consists of the front antenna and the side antenna. It receives S-band signal and then down-converts the frequency to L-band signal. As a result, that can remove the frequency interference on an aircraft while retransmitting.

• Journal of Korea Multimedia Society
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• v.16 no.6
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• pp.667-677
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• 2013

With the huge success of Social Network Services, studies on social network analysis to extract the current issues or to track the symptoms of epidemic disease are being carried out actively. On Twitter, tweets reflect people's reaction to an event and users' individual status well, so it is possible to detect an event regarding a tweet as a sensory value. Recently, social signals are used to detect the spread of illness like the flu as well as the occurrence of disaster event like an earthquake in early stages. In this paper, we set up a cold as a target event and regarded tweets as Cold Signals. To evaluate the reliability of Cold Signals, we analyzed correlations between weather factors and the cold index provided by Korea Meteorological Administration.