• Title/Summary/Keyword: Multi-aperture

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The Multi-Aperture Transmit Horn Antenna for Radar Space Feeder (레이다 공간급전용 다중-개구 송신 혼 안테나)

  • 조용문;박동철
    • Journal of the Korea Institute of Military Science and Technology
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    • v.6 no.3
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    • pp.113-121
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    • 2003
  • In this paper, the transmit antenna for the space feeder used for the phased array antennas is investigated. The multi-aperture horn antenna is proposed as the transmit antenna and the characteristics are verified with the Matlab coding, HFSS of Ansoft Corp., and MWS of CST Corp., The E-plane and H-plane beam patterns of the multi-aperture horn antenna are nearly symmetrical and the sidelobe level of the I-plane beam pattern is lower than that the of general pyramidal horn antenna. The fabricated multi-aperture horn antenna is measured using the near-field measurement system. The measured results show good agreement with the simulated ones.

Volume-sharing Multi-aperture Imaging (VMAI): A Potential Approach for Volume Reduction for Space-borne Imagers

  • Jun Ho Lee;Seok Gi Han;Do Hee Kim;Seokyoung Ju;Tae Kyung Lee;Chang Hoon Song;Myoungjoo Kang;Seonghui Kim;Seohyun Seong
    • Current Optics and Photonics
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    • v.7 no.5
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    • pp.545-556
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    • 2023
  • This paper introduces volume-sharing multi-aperture imaging (VMAI), a potential approach proposed for volume reduction in space-borne imagers, with the aim of achieving high-resolution ground spatial imagery using deep learning methods, with reduced volume compared to conventional approaches. As an intermediate step in the VMAI payload development, we present a phase-1 design targeting a 1-meter ground sampling distance (GSD) at 500 km altitude. Although its optical imaging capability does not surpass conventional approaches, it remains attractive for specific applications on small satellite platforms, particularly surveillance missions. The design integrates one wide-field and three narrow-field cameras with volume sharing and no optical interference. Capturing independent images from the four cameras, the payload emulates a large circular aperture to address diffraction and synthesizes high-resolution images using deep learning. Computational simulations validated the VMAI approach, while addressing challenges like lower signal-to-noise (SNR) values resulting from aperture segmentation. Future work will focus on further reducing the volume and refining SNR management.

Tx/Rx Bidirectional Beamforming Using Multi - Element Defocusing (Multi-Element Defocusing을 이용한 Tx/Rx 양방향 빔포밍)

  • Lee, Y.H.;Hwang, J.S.;Song, T.K.;Ahn, Y.B.
    • Proceedings of the KOSOMBE Conference
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    • v.1998 no.11
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    • pp.219-220
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    • 1998
  • Although a single-element synthetic aperture system can produce high-resolution beam profile, it is not a highly practical system because of its low signal to noise ratio against conventional system's. A multi-element synthetic aperture processing has been proposed with defocusing in this paper. A multi element subaperture defocused to emulate a single element spatial response with high acoustic power. The results have higher signal to noise and better contrast resolution than conventional synthetic aperture method.

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Ultrasound Synthetic Aperture Beamformer Architecture Based on the Simultaneous Multi-scanning Approach (동시 다중 주사 방식의 초음파 합성구경 빔포머 구조)

  • Lee, Yu-Hwa;Kim, Seung-Soo;Ahn, Young-Bok;Song, Tai-Kyong
    • Journal of Biomedical Engineering Research
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    • v.28 no.6
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    • pp.803-810
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    • 2007
  • Although synthetic aperture focusing techniques can improve the spatial resolution of ultrasound imaging, they have not been employed in a commercial product because they require a real-time N-channel beamformer with a tremendously increased hardware complexity for simultaneous beamforming along M multiple lines. In this paper, a hardware-efficient beamformer architecture for synthetic aperture focusing is presented. In contrast to the straightforward design using NM delay calculators, the proposed method utilizes only M delay calculators by sharing the same values among the focusing delays which should be calculated at the same time between the N channels for all imaging points along the M scan lines. In general, synthetic aperture beamforming requires M 2-port memories. In the proposed beamformer, the input data for each channel is first upsampled with a 4-fold interpolator and each polyphase component of the interpolator output is stored into a 2-port memory separately, requiring 4M 2-port memories for each channel. By properly limiting the area formed with the synthetic aperture focusing, the input memory buffer can be implemented with only 4 2-port memories and one short multi-port memory.

Measurement of Numerical Aperture of Graded-index Plastic Optical Fiber by Using a Variable Aperture (입사광의 크기 조절을 통한 경사굴절률 플라스틱 광섬유의 수치구경 측정기법)

  • Kim, Dae-Kyu;Kim, Bo-Ram;Lee, Byoung-Hwak;Park, Seung-Han
    • Korean Journal of Optics and Photonics
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    • v.22 no.1
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    • pp.5-9
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    • 2011
  • There are technical difficulties in measuring the numerical apertures of multi-mode gradient-index plastic optical fibers (GI-POFs) due to their strong speckle noise originating from dopants, non-uniformity of gradient-index profile, and multi-mode interference. Therefore, we propose a new method of obtaining the numerical aperture by controlling the size of the incident laser beam and measuring the numerical aperture of GI-POF. The results show that we can get a value for the numerical aperture of GI-POF very similar to that measured by the conventional method. We can also obtain the optimum launching condition of input beam and maximum coupling efficiency.

High Power Single Mode Multi-Oxide Layer VCSEL with Optimized Thicknesses and Aperture Sizes of Oxide Layers

  • Yazdanypoor, Mohammad;Emami, Farzin
    • Journal of the Optical Society of Korea
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    • v.18 no.2
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    • pp.167-173
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    • 2014
  • A novel multi-oxide layer structure for vertical cavity surface emitting laser (VCSEL) structures is proposed to achieve higher single mode output power. The structure has four oxide layers with different aperture sizes and thicknesses. The oxide layer thicknesses are optimized simultaneously to reach the highest single mode output power. A heuristic method is proposed for plotting the influence of these variable changes on the operation of optical output power. A comprehensive optical-electrical thermal-gain self-consistent VCSEL model is used to simulate the continuous-wave operation of the multi-layer oxide VCSELs. A comparison between optimized VCSELs with different structures is presented. The results show that by using multi-oxide layers with different thicknesses, higher single-mode optical output power could be achieved in comparison with multi-oxide layer structures with the same thicknesses.

Digital Matting Using Multi-view Camera System (다시점 카메라 시스템을 이용한 디지털 매팅 방법)

  • Hyun, Myung-Han;Ho, Yo-Sung
    • Proceedings of the IEEK Conference
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    • 2007.07a
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    • pp.281-282
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    • 2007
  • In this paper, we propose a method for digital matting using a multi-view camera system. In order to generate multi-view synthetic aperture images, we first move all images obtained from the multi-view camera according to their disparities. After we obtain corresponding trimaps by taking a variance of the synthetic aperture images, we convert the trimaps into multi-view alpha mattes. Experimental results show that the proposed scheme can create the composite images successfully by combining foreground objects with multi-view background images.

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Current Trends of the Synthetic Aperture Radar (SAR) Satellite Development and Future Strategy for the High Resolution Wide Swath (HRWS) SAR Satellite Development (SAR(Synthetic Aperture Radar) 위성 개발현황 및 향후 HRWS(High Resolution Wide Swath) SAR 위성 개발전략)

  • Ko, Ungdai;Seo, Inho;Lee, Juyoung;Jeong, Hyunjae
    • Journal of Space Technology and Applications
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    • v.1 no.3
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    • pp.337-355
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    • 2021
  • This paper is made to suggest a future strategy for the Korean High Resolution Wide Swath Synthetic Aperture Radar (HRWS SAR) satellite development by surveying the current trends for the SAR satellite technologies. From the survey, the latest SAR technology trends are revealed of using Digital Beam-Forming (DBF), SCan-On-Receive (SCORE), Displaced Phase Center Antenna (DPCA), interferometry, and polarimetry for exploiting the SAR imagery. Based on the latest SAR technology trends and the foreign HRWS SAR development cases, the strategy for the future HRWS Korean SAR satellite development is suggested to develop the DPCA and SCORE technologies by using the KOrea Multi-Purpose SATellite-6 (KOMPSAT-6) which is going to launch in a few years, and consequently to develop the HRWS SAR satellites which can monitor the whole Earth at weekly intervals.