• Title/Summary/Keyword: 다중빔

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A Calibration Technique for Array antenna based GPS Receivers (배열 안테나 기반 GPS 수신기에서의 교정 방안)

  • Kil, Haeng-bok;Joo, Hyun;Lee, Chulho;Jeong, Eui-Rim
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.22 no.4
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    • pp.683-690
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    • 2018
  • In this paper, a new signal processing technique is proposed for calibrating gain, phase, delay offsets in array antenna based anti-jamming minimum variance distortionless response (MVDR) global-positioning-system (GPS) receivers. The proposed technique estimates gain, phase and delay offsets across the antennas, and compensates for the offsets based on the estimates. A pilot signal with good correlation characteristics is used for accurate estimation of the gain, phase and delay offsets. Based on the cross-correlation, the delay offset is first estimated and then gain/phase offsets are estimated. For fine delay offset estimation and compensation, an interpolation technique is used, and specifically, the discrete Fourier transform (DFT) is employed for the interpolation technique to reduce the computational complexity. The proposed technique is verified through computer simulation using MATLAB. According to the simulation results, the proposed technique can reduce the gain, phaes and delay offset to 0.01 dB, 0.05 degree, and 0.5 ns, respectively.

Wide Coverage Microphone System for Lecture Using Ceiling-Mounted Array Structure (천정형 배열 마이크를 이용한 강의용 광역 마이크 시스템)

  • Oh, Woojin
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.22 no.4
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    • pp.624-633
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    • 2018
  • While the multimedia lecture system has been getting smart using immerging technology, the microphone still relies on the classical approach such as holding in hand or attaching on the body. In this paper, we propose a ceiling mounted array microphone system that allows a wide reception coverage and instructors to move freely without attaching microphone. The proposed system adopts cell and handover of mobile communication instead of a complicated beamforming method and implements a wide range microphone over several cells with low cost. Since the characteristics of unvoiced speech is similar to Pseudo Noise it is shown that soft handover are possible with 3 microphones connected to delay-sum multipath receiver. The proposed system is tested in $6.3{\times}1.5m$ area. For real-time processing the correlation range can be reduced by 82% or more, and the output latency delay can be improved by using the delay adaptive filter.

A study on Intention Pulse Forming Network Generation of Pulse Nd:YAG Laser adopting Multi -Alienation Discharge (다중분할 방전방식을 적용한 펄스형 Nd:YAG 레이저의 임의 펄스성형 연구)

  • Whi-Young Kim
    • Journal of the Korea Computer Industry Society
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    • v.2 no.7
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    • pp.975-982
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    • 2001
  • In this study, a solid-state laser system adopting a new real time multi-discharge (RTMD) method in which three flashlamps are turned on consecutively was designed and fabricated to examine the pulse width and the pulse shape of the laser beams depending upon the changes in the lamp rum-on time. That is, this study shows a technology that makes it possible to make various pulse shapes by turning on three flashlamps consecutively on a real-time basis with the aid of a PIC one-chip microprocessor. With this technique, the lamp turn-on delay time can be varied more diversely from 0 to 10 ms and the real-time control is possible with an external keyboard, enabling various pulse shapes. In addition, longer pulses can be more widely used for industrial processing and lots of medical purposes

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Design and Verification of Far-field measurement system for W-band Millimeter-wave Antenna (밀리미터파(W대역) 안테나 측정을 위한 원-전계 측정 시스템 설계 및 검증)

  • Baek, Jong-Gyun;Hwang, In-June;Cho, Chi-Hyun;Joo, Joung-Myoung;Joo, Ji-Han;Park, Jong-Kuk;Kim, Jaesik;Kim, Sosu
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.22 no.2
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    • pp.43-50
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    • 2022
  • In this paper, we designed and verified a Far-field measurement system for measuring the performance of an antenna operating in millimeter wave(W-band). For the antenna test, a measurement system should be selected according to the type of antenna, measurement items, measurement environment and period, etc. In the case of near-field measurement, it takes a lot of time because the number of measurement items increases when the antenna has multiple channels or various beams. Such an antenna can reduce the measurement time through Far-field measurement, and only necessary measurement items can be measured. Therefore, this study secured precise alignment of the far-field measurement system using a high-power laser and improved the measurement accuracy by applying a double amplifier system. The designed system was built in the anechoic chamber and verified by comparison with the verified Near-field measurement system.

Slope Stability and Development of Debris Flow Deposit in the Ulleung Basin, East Sea (동해 울릉분지의 사면안정성 및 쇄설류 퇴적체의 발달)

  • Lee, Sun-Jong;Lee, Jeong-Min;Yoo, Dong-Geun;Lee, Go-Eun;Park, Soo-Chul
    • Economic and Environmental Geology
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    • v.50 no.2
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    • pp.129-143
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    • 2017
  • The shallow sediments in the southwestern Ulleung Basin consist of mass flow deposits such as slide/slump and debris flow deposits (DFD), caused by slope failure. These sediments are proven to be important in studying geological disaster and stability of the seafloor. In this paper, we analysised the flow accumulation and slope failure susceptibility of the Ulleung Basin on the basis of multi-beam data, collected in this area. We also studied the distribution pattern and the seismic characteristics of the DFD in the uppermost layer of the Ulleung Basin on the basis of seismic data. The slope susceptibility was calculated as the frequency ratio of each factors including slope, aspect, curvature and stream power index (SPI), which causes the slope failure. These results indicate that the slope failure is frequently to occur in the southern and western continental slope of the Ulleung Basin. The sediment flow (mass flow) caused by the slope failure converges to the north and northwest of the Ulleung Basin. According to the seismic characteristics, the uppermost layer in study area can be divided into four sedimentary unit. These sedimentary units develop from the south and southwest to the north and northwest in association with slope susceptibility and flow accumulation.

Time-delay Estimation Method for Performance Enhancement of Underwater Source Localization using Doublet Array (Doublet 센서배열의 수중음원 위치 추정 성능 향상을 위한 시간지연 추정 기법)

  • Sim, Min-Seop;Lee, Ji-Hyeog;Lee, Hyeong-Sin
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.5
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    • pp.69-76
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    • 2020
  • The sound signal radiated from an underwater source is received by the hydrophone of the system, including multi-path time-delay and multi-path signal by sea surface and bottom reflection. The system using a time-delay between received signals for the source localization shows performance degradation due to incoherence by the multi-path propagation environment and the disturbance of a marine environment. Various types of array and signal processing have been used for robust source range and bearing estimation in this environment. In this paper, we use a line array composed of doublet array and an estimated time-delay correction method for robust localization performance in a multi-path propagation environment. Three doublet arrays are located on the same line, and the time-delay between signals received on each doublet array is estimated in a two-step procedure. The estimated time-delay value is obtained by the cross-correlation function and corrected by the interaction formula between the center-frequency of received signal and the geometry of the array with respect to aperture. By this proposed procedure, the range and bearing of source from array were calculated. In order to confirm the validity of the proposed method and array, we simulated localization and estimation using the Monte-Carlo method.

Innovative Geostationary Communication and Remote Sensing Mutli-purpose Satellite Program in Korea-COMS Program

  • Baek, Myung-Jin;Park, Jae-Woo
    • Journal of Satellite, Information and Communications
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    • v.2 no.2
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    • pp.29-35
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    • 2007
  • COMS satellite is a multipurpose satellite in the geostationary orbit, which accommodates multiple payloads of the Ka band Satellite Communication Payload, Meteorological Imager, and Geostationary Ocean Color Imager into a single spacecraft platform. In this paper, Korea's first innovative geostationary Communication, Ocean and Meteorological Satellite (COMS) program is introduced which is fully funded by Korean Government. The satellite platform is based on the Astrium EUROSTAR 3000 communication satellite, but creatively combined with MARS Express satellite platform to accommodate three different payloads efficiently for COMS. The goals of the Ka band satellite communication mission are to in-orbit verify the performances of advanced communication technologies and to experiment wide-band multi-media communication service. The Meteorological Imager mission is to continuously extract meteorological products with high resolution and multi-spectral imager, to detect special weather such as storm, flood, yellow sand, and to extract data on long-term change of sea surface temperature and cloud. The Geostationary Ocean Color Imager mission aims at monitoring of marine environments around Korean peninsula, production of fishery information (Chlorophyll, etc.), and monitoring of long-term/short-term change of marine ecosystem. The system design difficulties are in the different kinds of payload mission requirements of communication and remote sensing purposes and how to combine them into one to meet the overall satellite requirements. In this paper, Ka band communication payload system is more highlighted.

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A Study of the RCS Reduction by Pattern Synthesis for Singly Curved Structures (패턴 합성을 통한 단일 곡면 구조에서의 RCS 감소 기술에 관한 연구)

  • Kim, Woojoong;Seo, Hyeong Pil;Kim, Youngsub;Yoon, Young Joong
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.24 no.4
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    • pp.366-373
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    • 2013
  • This paper discusses the singly curved phased reflector for reduced RCS pattern, which has minimized RCS level at boresight with a null by phase cancelation and the lowered RCS level of main beam by splitting the main beam into multi directions. Considering the reduced level of boresight and main beam compared to the same sized reference PEC, this proposed multi-beam reflector can be adopted in the mono-static radar and the bi-static radar environment. The proposed reflector is a multi-beam reflector, which has different phase distributions at each row for different steering angle. It is designed through an intermediate stage of a single and dual-beam reflector. The behaviors of the designed reflectors are verified through full-wave simulation and experiment. The reflectors are designed in the frequency of 10 GHz and it has a size $240{\times}180mm^2$($8{\times}6\;{\lambda}^2$) with the curvature k=3.3. From the measured results, the proposed reflectors reduce the reflected power by 17 dB at boresight.

Seafloor Morphology and Surface Sediment Distribution of the Southwestern Part of the Ulleung Basin, East Sea (동해 울릉분지 남서부 해저지형 및 표층퇴적물 분포)

  • Koo, Bon-Young;Kim, Seong-Pil;Lee, Gwang-Soo;Chung, Gong Soo
    • Journal of the Korean earth science society
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    • v.35 no.2
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    • pp.131-146
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    • 2014
  • Multi-beam echosounder data and grain size analysis data of surface sediment were acquired and analyzed in order to investigate the shelf-to-slope morphology, geological character, and their geological controlling factors in the southwestern margin of the Ulleung Basin. According to the morphological character, the continental shelf can be divided into two parts: (1) shallow (~100 m) and steep ($0.5^{\circ}$) inner shelf, (2) deep (100-300 m) and gentle ($0.2^{\circ}$) outer shelf. The continental slope is featured with eight distinct topographic depressions of various spatial dimension (~121 $km^2$ in area) and head wall gradient (${\sim}24.3^{\circ}$). They are developed adjacent to each other and presumably formed by submarine landslides which have recurred under the strong influences of earthquakes and eustatic sea-level change. The inner continental shelf and the continental slope are dominated by fine-grained sediment, whereas the outer continental shelf is dominated by coarse-grained sediment. The surface sediment distribution seems dominantly influenced by eustatic sea-level change. The outer continental shelf is mostly covered by coarse relict sediment deposited during lowstand sea-level, while the inner shelf is covered with recent sediment during highstand sea-level. The surface of the continental slope is covered with fine-grained sediments which were supplied by hemipelagic advection process.

A Study on the Impact of Forklift Institutional, Technical, and Educational Factors on a Disaster Reduction (지게차의 제도적, 기술적, 교육적 요인이 재해감소에 미치는 영향에 관한 연구)

  • Young Min Park;Jin Eog Kim
    • Journal of the Society of Disaster Information
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    • v.19 no.4
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    • pp.770-778
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    • 2023
  • Purpose: In order to reduce forklift industrial accidents, it is necessary to classify them into institutional, technical, and educational factors and conduct research on whether each factor affects disaster reduction. Method: Descriptive statistical analysis, validity analysis, reliability analysis, and multiple regression analysis were conducted using SPSS 18 program based on an offline questionnaire based on a 5-point Likert scale. Result: As a result of multiple regression analysis, it was found that institutional, technical, and educational factors, which are independent variables for disaster reduction, explain about 62.5% of the variance in disaster prevention, which is the dependent variable. The regression model verification was found to be statistically significant with F=118.775 and significance probability p<0.01. Conclusion: First, there is a need to prevent disasters by including electric forklifts weighing less than 3 tons in the inspection system. Second, there is a need to make it mandatory to install front and rear cameras and forklift line beams to prevent forklift collision disasters. Third, there is a need to conduct special training related to forklifts every year, and drivers and nearby workers need to be included in the special training for forklifts.