• Title/Summary/Keyword: 표적 근사화

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Application of Approximate FFT Method for Target Detection in Distributed Sensor Network (분산센서망 수중표적 탐지를 위한 근사 FFT 기법의 적용 연구)

  • Choi, Byung-Woong;Ryu, Chang-Soo;Kwon, Bum-Soo;Hong, Sun-Mog;Lee, Kyun-Kyung
    • The Journal of the Acoustical Society of Korea
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    • v.27 no.3
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    • pp.149-153
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    • 2008
  • General underwater target detection methods adopt short-time FFT for estimate target doppler. This paper proposes the efficient target detection method, instead of conventional FFT, using approximate FFT for distributed sensor network target detection, which requires lighter computations. In the proposed method, we decrease computational rate of FFT by the quantization of received signal. For validation of the proposed method, experiment result which is applied to FFT based active sonar detector and real oceanic data is presented.

Improvement of a Planning Technique Based on Heuristic Target Shaping for Stereotactic Radiosurgery (방사선 수술시 경험적 표적 근사화에 근거한 최적화 방법 개선)

  • Oh Seungjong;Choi Kyoung-Sik;Song Ju-Young;Suh Tae-Suk
    • Progress in Medical Physics
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    • v.16 no.4
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    • pp.176-182
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    • 2005
  • Stereotactic radiosurgery (SRS) is a technique to deliver a high dose to a target region and a low dose to a critical organ through only one or a few irradiation. The SRS must be planned exactly. Currently the surgery plan is peformed by trial and error method. There are many questions about the reliability and reproducibility of the plan result. This study Improve each step of the Oh's method based on heuristic target shaping to obtain the better result. The target was reconstructed using cylinders with same height and the neighbored cylinders were combined according to the difference of each center and diameter. Then, spheres were packed within each cylinders by the packing rules. Two virtual targets were used to compare this method with Oh's method. As a result, the numbers of isocenter were successfully reduced - more than $35\%$ and $26\%$ - without serious differences of proscription isodose to tumour volume ratio (PITV) and maximum dose to proscription dose ratio (MDPD). This technique using cylinder piling and sphere packing will be a helpful tool to planner in stereotactic radiosurgery.

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Development of Ideal Model Based Optimization Procedure with Heuristic Knowledge (정위적 방사선 수술에서의 이상표적모델과 경험적 지식을 활용한 수술계획 최적화 방법 개발)

  • 오승종;송주영;최경식;김문찬;이태규;서태석
    • Progress in Medical Physics
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    • v.15 no.2
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    • pp.84-93
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    • 2004
  • Stereotactic radiosurgery (SRS) is a technique that delivers a high dose to a target legion and a low dose to a critical organ through only one or a few irradiations. For this purpose, many mathematical methods for optimization have been proposed. There are some limitations to using these methods: the long calculation time and difficulty in finding a unique solution due to different tumor shapes. In this study, many clinical target shapes were examined to find a typical pattern of tumor shapes from which some possible ideal geometrical shapes, such as spheres, cylinders, cones or a combination, are assumed to approximate real tumor shapes. Using the arrangement of multiple isocenters, optimum variables, such as isocenter positions or collimator size, were determined. A database was formed from these results. The optimization procedure consisted of the following steps: Any shape of tumor was first assumed to an ideal model through a geometry comparison algorithm, then optimum variables for ideal geometry chosen from the predetermined database, followed by a final adjustment of the optimum parameters using the real tumor shape. Although the result of applying the database to other patients was not superior to the result of optimization in each case, it can be acceptable as a plan starling point.

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Multiple Target Angle Tracking Algorithm Using Angular Innovation Extracted from Signal Subspace (신호 부공간에서 구한 방위각 이노베이션을 이용한 다중표적 방위각 추적 알고리즘)

  • Ryu, Chang-Soo;Lee, Su-Hyoung;Lee, Kyun-Kyung
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.36S no.12
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    • pp.20-26
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    • 1999
  • In this paper, a multiple target angle tracking algorithm that can avoid data association problem and has a simple structure is proposed by obtaining the angular innovation of the targets from a signal subspace. The signal subspace is recursively estimated by a signal subspace tracking algorithm, such as PAST. A nonlinear matrix equation which satisfy the estimated signal subspace and the angular innovation is induced and expanded into a Taylor series for linear approximation. The angular innovation is obtained by solving the approximated linear matrix equation in the least square sense. The good performance of the proposed algorithm is demonstrated by various computer simulations.

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Terminal Guidance for Aerial Vehicles through Nadir-Looking Image Formation Using an Imaging Radar with a Rotating Antenna (회전하는 안테나를 가진 레이다를 이용하여 비행체 종말 유도를 위한 직하 방향 레이다 영상형성)

  • Lee, Hyukjung;Song, Sungchan;Chun, Joohwan
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.30 no.4
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    • pp.328-331
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    • 2019
  • A linear frequency modulated pulse train waveform can be cost-effective in achieving high range resolution, and thus the synthetic aperture radar may be benefited by using the mixer output of the received signal. However, the image formation process from a mixer output is vulnerable to errors caused by stop-and-go approximation. In this paper, a nadir-looking imaging radar based on time domain correlation is proposed. Furthermore, to prevent the occurrence of ghosting effect in images, antenna placement on a rotating disk is proposed. Simulation results indicate that ghosting effect can be eliminated by employing the proposed antenna placement structure.

The Design of Target Tracking System Using FBFE Based on VEGA (VEGA 기반 FBFE을 이용한 표적 추적 시스템 설계)

  • 이범직;주영훈;박진배
    • Journal of the Korean Institute of Intelligent Systems
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    • v.11 no.4
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    • pp.359-365
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    • 2001
  • In this paper, we propose the design methodology of target tracking system using fuzzy basis function expansion(FBFE) based on virus evolutionary genetic algorithm (VEGA). In general, the objective of target tracking is to estimate the future trajectory of the target based on the past position of the target obtained from the sensor. In the conventional and mathematical nonlinear filtering method such as extended Kalman filter(EKF), the performance of the system may be deteriorated in highly nonlinear situation. To resolve these problems of nonlinear filtering technique, by appling artificial intelligent technique to the tracking control of moving targets, we combine the advantages of both traditional and intelligent control technique. In the proposed method, after composing training datum from the parameters of extended Kalman filter, by combining FDFE, which has the strong ability for the approximation, with VEGA, which prevent GA from converging prematurely in the case of lack of genetic diversity of population, and by idenLifying the parameters and rule numbers of fuzzy basis function simultaneously, we can reduce the tracking error of EKF. Finally, the proposed method is applied to three dimensional tracking problem, and the simulation results shows that the tracking performance is improved by the proposed method.

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Performance Analysis of the Inversion Schemes in the Spotlight-mode SAR(Synthetic Aperture Radar) (Spotlight-mode SAR(Synthetic Aperture Radar)에서의 Inversion 기법 성능 분석)

  • 최정희
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.40 no.1
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    • pp.130-138
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    • 2003
  • The classical image reconstruction for stripmap-mode Synthetic Aperture Radar is the Range-Doppler algorithm. When the spotlight-mode SAR system was envisioned, Range-Doppler algorithm turned out to fail rapidly in this SAR imaging modality. Thus, what is referred to as Polar format algorithm, which is based on the Plane wave approximation, was introduced for imaging from spotlight-mode SAR raw- data. In this paper, we have studied for the raw data processing schemes in the spotlight-mode Synthetic Aperture Radar. We apply the Wavefront Reconstruction scheme that does not utilize the approximation in spotlight-mode SAR imaging modelity, and compare the performance of target imaging with the Polar format inversion scheme.

Analysis of Acoustic Target Strength for the Submarine with Alberich Anechoic Coating Effects (알베리히 무반향 코팅재 효과를 고려한 잠수함의 음향 표적강도 해석)

  • Kwon, Hyun-Wung;Hong, Suk-Yoon;Kim, Hwa-Muk;Song, Jee-Hun
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.19 no.4
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    • pp.410-415
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    • 2013
  • Acoustic target strength (TS) is one of the most considerable design elements for survival capacities of the submarine. It needs to reduce acoustic TS that submarines are getting larger and larger, Alberich anechoic coatings are widely used as the representative method. In this paper, the finite element method (FEM) is used to analyze the reflection and transmission coefficients of Alberich anechoic coatings, which have periodic unit cells. The FEM results are compared with experimental results in the literature. Moreover, acoustic TS for the submarine is analyzed by using that result. Finally, it is shown that acoustic TS (Case 1: 10dB, Case 2: 6dB) are reduced due to the use of Alberich anechoic coatings.

Optimal Scheduling of Detection and Tracking Parameters in Phased Array Radars (위상배열 레이다 검출 및 추적 매개변수의 최적 스케쥴링)

  • Jung, Young-Hun;Kim, Hyun-Soo;Hong, Sun-Mog
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.36S no.7
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    • pp.50-61
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    • 1999
  • \In this paper, we consider the optimal scheduling of detection and tracking parameters in phased array radars to minimize the radar energy required for track maintenance in a cluttered environment. We develop a mathematical model of target detection induced by a search process in phased array radars. In the mathematical development, we take into account the effect of unwanted measurements that may have originated from clutter or false alarms in the detection process. We use and analytic approximation of the modified Riccati equation of the probabilistic data association (PDA) filter to take into account the effect of clutter interference in tracking. Based on the search process and the tracking models, we formulate the optimal scheduling problem into a nonlinear optimal control problem. We solve a constrained nonlinear optimization problem to obtain the solution of the optimal control problem.

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Imaging Method for Array Structured Bistatic Ground-to-Air Radar (배열 구조 바이스태틱 지대공 레이다의 이미징 기법)

  • Choi, Sang-Hyun;Yang, Dong-Hyeuk;Song, Ji-Min;Yang, Hoon-Gee
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.29 no.8
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    • pp.599-607
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    • 2018
  • This paper presents a ground-to-air bistatic radar system and its implementation algorithm, which resembles an SAR(synthetic aperture radar) reconstruction algorithm. Via cooperative working between a standoff transmitting radar and an array of ground based receiving radars, it detects and images moving targets under clutter in the air. In the proposed system, the whole receiving antenna aperture is synthesized by physical ground based radars, and thus, unlike conventional SAR, it does not require long illumination time of the target area. The reconstruction algorithm uses planewave approximation based polar format processing, which alleviates the requirement of positioning the receiving radars, which can cause grating lobes if not chosen properly. We derive a reconstruction algorithm including clutter suppression and discuss implementation issues, such as the resolution of a reconstructed image and the method of compensation for the irregularity of the receiving radars' positions. A simulation that validates the proposed algorithm is also shown.