• Title/Summary/Keyword: 다중빔

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Development of Multi-channel Fiber Laser and Beam Alignment Method (다채널 광섬유 레이저 및 다중 빔 정렬 기술 개발)

  • Kim, Youngchan;Ryu, Daegeon;Noh, Young-Chul
    • Korean Journal of Optics and Photonics
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    • v.33 no.6
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    • pp.245-251
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    • 2022
  • We have developed a multi-channel fiber laser for tiled laser beam combining and a laser output array system for multi-beam alignment. The fiber laser is a master oscillator power amplifier configuration that has a common seed, a preamplifier, and a 7-channel amplifier. The output power of each channel is more than 10 W. The laser output array system is a packed cylindrical configuration for a high fill-factor, and it has capabilities for collimation and tilt control with built-in PZT. Multi-beam alignment to a target is successfully implemented using PZT controlled with a stochastic parallel gradient descent (SPGD) algorithm.

Development of a Seabed Mapping System using SeaBeam2000 Multibeam Echo Sounder Data (SeaBeam2000 다중빔 음향측심기를 이용한 해저면 맵핑시스템 개발)

  • 박요섭;김학일;이용국;석봉출
    • 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.

High resolution nulling limitations for a multi-beam antenna : A Case Study for Korean Peninsula (다중 빔 안테나를 이용한 한반도지형에서의 국소 지역 재밍 신호 제거 연구)

  • Cheong, Chi-Hyun;Seo, Jong-Woo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.44 no.10
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    • pp.904-910
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    • 2016
  • The choice of nulling antenna type to be used for a given specification of user locations usually centers on whether to use a phased array antenna(PAA) or a multiple-beam antenna(MBA) for a satellite payload. This paper considers a MBA to analysis the nulling effect in the Korean peninsula jamming circumstance. First, the nulling performance and characteristics on the region of the earth coverage are confirmed with respect to the case of 7 beams. Then, optimum results are derived and compared to what can be accomplished with a fixed set of beams(the case of 10 and 19 beams are considered) for null steering to reject interference is investigated for a MBA.

Study on Multibeam Forming with Improved Accuracy of Steering Angle and Sidelobe Control (높은 조향 정확도 및 부엽 제어가 가능한 다중 빔 형성 연구)

  • Chi, Sang Wook;Lee, Chang-Hyun;Lee, Jeong-Hae
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.29 no.6
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    • pp.449-456
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    • 2018
  • Herein, several multibeam forming methods that can be applied to microwave wireless power transmission are presented. Because the conventional multibeam forming methods do not consider an active element pattern(AEP), an intended beam shape will contain a steering angle error when applied to an actual system. To solve this problem, a method of considering the average of the AEP and a method of considering all the AEPs by the modified Fourier series method have been proposed. We confirmed that the proposed method reduces the error with the intended beam shape in the multibeam formation. In addition, for the side lobe level(SLL) and null control, a method of multibeam forming by applying the superposition principle to the Dolph-Tschebyscheff method is proposed. We also confirmed that SLL control can be simultaneously achieved with the multibeam formation.

Simplified Near Optimal Downlink Beamforming Schemes in Multi-Cell Environment (다중 셀 환경에서 적은 복잡도를 갖는 준 최적 하향 빔형성)

  • Yang, Jang-Hoon;Kim, Dong-Ku
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.12C
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    • pp.764-773
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    • 2011
  • Despite enormous performance gain with multi-antenna transmission in the single cell environment, its gain diminishes out in the multi-cell environment due to interference. It is also very hard to solve the efficient downlink beamforming with low complexity in multi-cell environment. First, this paper shows that the asymptotically sum rate optimal downlink beamformings at low and high SNR are maximum ratio transmit (MRT) and zero forcing (ZF) beamforming in the multi-cell system, respectively. Secondly, exploiting the asymptotically optimal downlink beamforming, we develop simple two types of near optimal downlink beamforming schemes having the form of minimum mean squared error (MMSE) beamforming obtained from the dual uplink problem. For each type, three different subclasses are also considered depending on the computational complexity. The simulation results show that the proposed near optimum algorithms provide the trade-off between the complexity and the performance.

The Intensity Scale of Multiple Scattering of X-rays in Non-Crystalline Solids (비정질 고체에 대한 X선의 다중 산란 강도)

  • 박성수;장윤식;류봉기;박희찬
    • Journal of the Korean Ceramic Society
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    • v.34 no.1
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    • pp.109-113
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    • 1997
  • When the intensity of X-rays scattered from amorphous materials (very weakly absorbing materials) is measured using standard diffractometric technique, the intensity caused by multiple scattering is obtained in the measured X-ray intensity. Computer programs have been developed to estimate the intensity of the mul-tiple scattering obtained in vitreous SiO2 and B2O3 with various X-rays. Using the above computer program, the intensity ratios of multiple scattering to single scattering in vitreous SiO2 were 0.10~0.16% at CuK$\alpha$, 0.98~5.87% at MoK$\alpha$, and 1.88~17.86% at AgK$\alpha$ in the range of 2$\theta$=0~180$^{\circ}$. Therefore, pri-or to the structural analysis of vitreous SiO2 and B2O3 performed experimentally using X-ray diffractometric technique, the intensity data measured in MoK$\alpha$ and AgK$\alpha$ radiations must be corrected for multiple scattering effect.

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Area storage density in holographic disk memories using rotational, angular, and spatial multiplexing methods in combination (회전, 각, 그리고 공간 다중화 방법을 결합 사용하는 홀로그래픽 디스크 메모리에서의 면적저장밀도)

  • 장주석
    • Korean Journal of Optics and Photonics
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    • v.11 no.5
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    • pp.371-376
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    • 2000
  • For multi-hologram recording especially in a dIsk-shaped storage medium. we had studied a simple cost-effective method to unplement the rotational, angular, and ,patial multiplexmg techniques together in order to enhance the area storage density. Holographic storage with both rotational and angular multIplexing was realized by controlling the rderence beam directly with a pair of wedge prisms. whlie the storage WIth spatIal multlplexmg by shIfting the storage medium. In thIS paper \ve show that lhe area storage density of our system is strongly dependent on f numbers of the lenses in the srgnal and reference anns, and also show that the area storage densrly becollles maximal when the f number of the lens in the signal arm is approximately twice as long for a given f number of the lens in the reference emn. e emn.

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Channel Estimation and Analog Beam Selection for Uplink Multiuser Hybrid Beamforming System (상향링크 다중사용자 하이브리드 빔포밍 시스템에서 채널 추정과 아날로그 빔 선택 방법)

  • Kim, Myeong-Jin;Ko, Young-Chai
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.3
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    • pp.459-468
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    • 2015
  • In this paper, we consider an uplink multiuser hybrid beamforming system where an access point (AP) communicates with multiple users simultaneously. The performance of the uplink multiuser hybrid beamforming system depends on the effective channel which is given by the product of the channel matrix and the analog beams. Therefore, to maximize the performance, we need to obtain the channel information and then select the analog beams appropriately by using the acquired channel information. In this paper, we propose the channel estimation method and low complexity analog beam selection algorithm for the uplink multiuser hybrid beamforming system. Additionally, our analysis shows that the proposed low complexity analog beam selection algorithm provides much less complexity than the optimum analog beam selection algorithm. From the numerical results, we confirm that the proposed low complexity analog beam selection algorithm has little performance degradation in spite of much less complexity than the optimum analog beam selection algorithm under the equal system configuration.

Piezoelectric Beam Rotating Actuator for Multiple Beam Disk Drives (압전소자률 이용한 다중빔 광디스크용 빔 회전 구동기)

  • 김병준;김수현;곽윤근
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.5
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    • pp.154-159
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    • 2000
  • A multi-beam optical disk drive is presented as a method for improving the effective data transfer rate by increasing the beam spot number formed on an optical disk. The beam rotating actuator is necessary for putting multi-beam on more than one track. The beam rotating actuator is made up of piezoelectric material, high stiffness wire hinge and dove prism. The actuator has good frequency response above 1KHz and suitable operational range. The dynamic equation for the actuator is derived.

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Orthogonal Code Sharing and Radio Resource Allocation in Multibeam Satellite Communication Systems (다중빔 위성 통신 시스템에서 빔간 직교 코드 공유 기법과 동적 무선 자원 할당)

  • Lim, Kwang-Jae;Kim, Soo-Young;Oh, Deok-Gil;Kim, Jae-Moung
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.3A
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    • pp.140-150
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    • 2003
  • In this paper, we propose a novel code sharing method for downlink transmission of mobile satellite communication systems using a multibeam geosynchronous-orbit satellite. In the proposed system, spreading codes are shared among downlink beams in order to increase the system capacity. We also propose efficient radio resource and transmit power allocation schemes for the proposed system. Simplified analysis and simulation results on the system capacity show the capacity improvement by the proposed scheme. The simulation results show that the capacity of the proposed system is more than 2 times as large as that of a conventional multibeam satellite system. In the frequency-selective fading channel, the capacity improvement increases as the interference between orthogonal spreading codes decrease.