• Title, Summary, Keyword: array

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Iterative Polynomial Fitting Technique Using Polynomial Coefficients for the Nonlinear Line Array Shape Estimation (비선형 선배열 형상 추정을 위한 계수 반복 다항 근사화 기법)

  • Cho, Chom Gun
    • Journal of the Korea Institute of Military Science and Technology
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    • v.9 no.2
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    • pp.20-25
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    • 2006
  • Low frequency towed line array with high array gain and beam resolution is a long range surveillance sensor for anti-submarine warfare. The beam characteristics is however deteriorated due to the distorted line array sensor caused by low towing speed, wind, current, and towing ship maneuvering. An adaptive beamforming method is utilized in this paper to enhance the distorted line array beam performance by estimating and compensating the nonlinear array shape. A polynomial curve fitting in the least square sense is used to estimate the array shape iteratively with the distributed heading sensors data along the array. Real time array shape estimation and nonlinear array beam calculation is applied to a very long towed line array sensor system and the beam performance is evaluated and compared to the linear beamformer for the simulation and sea trial data.

Spatial Spectrum Estimation of Incident Signal Via Measured Array Manifold (측정 Array Manifold를 적용한 입사 신호의 공간 스펙트럼 추정)

  • 강흥용;이성윤;김영수;김창주;박한규
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.15 no.3
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    • pp.223-230
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    • 2004
  • A method for measuring array manifold which is the array antenna response of incident signal is presented. Array manifold measurement procedure by the presented method is explained for UCA(Uniform Circular Array), and spatial spectrum of 300 ㎒ tone signal incident on UCA is estimated by MUSIC algorithm in which spatial spectrum peak is searched with measured array manifold. Spatial spectrum estimation using array manifold measured by the proposed method shows superior performance to calculated array manifold.

Performance Analysis of Array Processing Techniques for GNSS Receivers under Array Uncertainties

  • Lee, Sangwoo;Heo, Moon-Beom;Sin, Cheonsig;Kim, Sunwoo
    • Journal of Positioning, Navigation, and Timing
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    • v.6 no.2
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    • pp.43-51
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    • 2017
  • In this study, the effect of the steering vector model mismatch due to array uncertainties on the performance of array processing was analyzed through simulation, along with the alleviation of the model mismatch effect depending on array calibration. To increase the reliability of the simulation results, the actual steering vector of the array antenna obtained by electromagnetic simulation was used along with the Jahn's channel model, which is an experimental channel model. Based on the analysis of the power spectrum for each direction, beam pattern, and the signal-to-interference-plus-noise ratio of the beamformer output, the performance deterioration of array processing due to array uncertainties was examined, and the performance improvement of array processing through array calibration was also examined.

Design of an Optimal Planar Array Structure with Uniform Spacing for Side-Lobe Reduction

  • Bae, Ji-Hoon;Seong, Nak-Seon;Pyo, Cheol-Sig;Park, Jae-Ick;Chae, Jong-Suk
    • Journal of electromagnetic engineering and science
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    • v.3 no.1
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    • pp.17-21
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    • 2003
  • In this paper, we design an optimal planar array geometry for maximum side-lobe reduction. The concept of thinned array is applied to obtain an optimal two dimensional(2-D) planar array structure. First, a 2-D rectangular array with uniform spacing is used as an initial planar array structure. Next, we modify the initial planar array geometry with the aid of thinned array theory in order to reduce the maximum side-lobe level. This is implemented by a genetic algorithm under some constraint, minimizing the maximum side-lobe level of the 2-D planar array. It is shown that the optimized planar array structure can achieve low side-lobe level without optimizing the excitations of the array antennas.

Performance Analysis of AGC Applebaum Array for Multiple Narrowband Interference (다중의 협대역 간섭 신호에 대한 AGC Applebaum어레이의 성능 분석)

  • 윤동현;이규만;한동석
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.6B
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    • pp.1092-1099
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    • 2000
  • An adaptive array system can effectively remove all received interferences by using adaptive algorithms even though the received signal condition is not known. The conventional adaptive array systems, however, cannot remove all interferences adaptively and converge very slowly when the eigenvalue spread of the input covariance matrix is large. In the paper, a new adaptive array system called an automatic gain controller (AGC) Applebaum array and its control algorithm are proposed to overcome the performance degradation of conventional Applebaum array in multiple interference conditions. The performance analysis of the proposed AGC Applebaum array is described under the condition of multiple narrowband interferences. Simulation results show the array output signal-to-noise ratio (SNR) of the AGC Applebaum array increases by 30dB compared to that of the conventional Applebaum array in the simulation condition. The gain of the AGC Applebaum array in the incident direction of a weaker interference is also shown to be lower than that of the conventional Applebaum array.

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2D Sparse Array Transducer Optimization for 3D Ultrasound Imaging

  • Choi, Jae Hoon;Park, Kwan Kyu
    • Journal of the Korean Society for Nondestructive Testing
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    • v.34 no.6
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    • pp.441-446
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    • 2014
  • A 3D ultrasound image is desired in many medical examinations. However, the implementation of a 2D array, which is needed for a 3D image, is challenging with respect to fabrication, interconnection and cabling. A 2D sparse array, which needs fewer elements than a dense array, is a realistic way to achieve 3D images. Because the number of ways the elements can be placed in an array is extremely large, a method for optimizing the array configuration is needed. Previous research placed the target point far from the transducer array, making it impossible to optimize the array in the operating range. In our study, we focused on optimizing a 2D sparse array transducer for 3D imaging by using a simulated annealing method. We compared the far-field optimization method with the near-field optimization method by analyzing a point-spread function (PSF). The resolution of the optimized sparse array is comparable to that of the dense array.

Circularly Rotated Array for Dual Polarized Applicator in Superficial Hyperthermia System

  • Kim, Ki Joon;Choi, Woo Cheol;Yoon, Young Joong
    • Journal of electromagnetic engineering and science
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    • v.15 no.1
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    • pp.20-25
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    • 2015
  • A circularly rotated array for a dual polarized applicator in a superficial hyperthermia system is proposed. The applicator has a wider effective treatment area due to the $180^{\circ}$ phase shift. The dual polarized circularly rotated array (DPCRA) suppresses overheating at the center of the array and helps evenly distribute the heat. This array provides a more effective treatment area than a lattice array when a $2{\times}2$ dual polarized array is fitted to the treatment area. The treatment area is 71.5% of the aperture, whereas the effective treatment areas of the $2{\times}2$ dual polarized lattice array (DPLA) and the single polarized array (SPA) are 57.2% and 38.6% of the same aperture, respectively. The measurement matches the simulation results without blood circulation effects. In a $2{\times}2$ array applicator, the proposed DPCRA has more heat uniformity than the DLA and the SPA.

Localization of Two Monopole Sources with Identical Frequency Using Phased Microphone Array (마이크로폰 어레이를 이용한 두 개의 동일 주파수 소음원의 위치 규명에 관한 연구)

  • 황선길;최종수;이재형
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.735-741
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    • 2003
  • A simplified view of array design and application process was introduced. Array design is critical to achieve a successful phased array measurements. A planar microphone array is designed to produce optimum performance and also to fit economic requirement in integrating data acquisition system. Certain performance characteristics are of primary concern when designing arrays. These characteristics include array resolution, spatial aliasing and array sidelobe suppression. Every array has its directional pattern that shows such characteristics. Assuming that a monopole source is located in center, beam-patterns have been simulated varying measurement conditions such as number of sensors. array aperture size, distance between array and source, frequency of interest and so on. Sensor correction was conducted on very channel using magnitudes and phased of FRF with respect to a reference microphone channel. Then with a spiral type array, measurements have been made with two point sources of same frequency in order to investigate array resolving abilities. It is observed that higher frequency source achieves better resolution than lower one does.

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New Elements Concentrated Planar Fractal Antenna Arrays for Celestial Surveillance and Wireless Communications

  • Jabbar, Ahmed Najah
    • ETRI Journal
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    • v.33 no.6
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    • pp.849-856
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    • 2011
  • This research introduces three new fractal array configurations that have superior performance over the well-known Sierpinski fractal array. These arrays are based on the fractal shapes Dragon, Twig, and a new shape which will be called Flap fractal. Their superiority comes from the low side lobe level and/or the wide angle between the main lobe and the side lobes, which improves the signal-to-intersymbol interference and signal-to-noise ratio. Their performance is compared to the known array configurations: uniform, random, and Sierpinski fractal arrays.

On Performance of Adaptive Array and Sidelobe Canceller (간섭 신호 제거를 위한 Adaptive Array 및 측엽 제거 기법의 특성 분석)

  • Seo, Jeong-Uk;Lee, Sang-Cheol;Choe, Yeong-Gyun
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.21 no.2
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    • pp.61-70
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    • 1984
  • This paper examines the array antenna theory, basic relations between the array size (aperture) and its beamwidth and resultant patterns. This paper also provides array antenna system design criteria, mainly maximizing the signal-to-noise ratio (SNR) and its corresponding optimum array structure and weight functions. Explicit new expressions for array performance are also illustrated in terms of the array output SNR. An example is provided for a 37-element planar array to explicitly illustrate the beam-forming and nulling operations of the array. Fundamentals of sidelobe canceller (SLC) systems have been discussed along with a derivation of new SLC equations for optimum weights.

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