• Title/Summary/Keyword: uniform array

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A Study on Maximum Posterior Probability Estimator for Direction of Arrival Estimation of Incoming Signal (입사신호의 도래방향 추정을 위한 최대 사후 확률 추정기에 대한 연구)

  • Lee, Kwan-Hyeong;Park, Sung-Kon;Jeong, Youn-Seo
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.9 no.2
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    • pp.190-195
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    • 2016
  • In this paper, we are comparative analysis both class method and proposal method in order to estimation of incident signal direction on uniform array antenna system. Proposal method of this paper decrease error probability for a signal direction of arrival estimation using maximum posterior probability estimator. If it decrease to signal estimation direction error probability, signal direction of arrival can correctly estimate. Through simulation, we were comparative analysis proposed method and class method. Also, we were comparative analysis about signal estimation error probability with increasing array antenna element. We show the superior performance of the proposed method relative to the class method to decrease of signal estimation error probability about 12%.

Design and fabrication of a 20 MHz high frequency linear array ultrasonic transducer for medical use (20 MHz 의료용 고주파 선형 배열 초음파 트랜스듀서의 설계 및 제작)

  • Lee, Wonseok;Roh, Yongrae
    • The Journal of the Acoustical Society of Korea
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    • v.35 no.6
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    • pp.466-472
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    • 2016
  • In this work, a medical linear array ultrasonic transducer working in the range of 20 MHz has been developed for high-resolution ultrasonic imaging. After devising the structure of the transducer suitable for the transmission of high-frequency waves, we optimized the dimension of constituent components. Then, the process to fabricate the transducer was developed to realize the designed structure, and a prototype of the transducer was fabricated and characterized. The center frequency of the fabricated transducer was measured to be 19 MHz, and the fractional bandwidth to be 84.5 %, and the standard deviation of the sensitivity over the entire channels to be 0.74 dB. These measurement results showed good agreement with design data, which confirmed the validity of the high frequency ultrasonic transducer structure developed in this work. It was confirmed that the developed transducer with new structure had wider frequency bandwidth and uniform sensitivity than a conventional 20 MHz transducer.

Real Time AOA Estimation Using Neural Network combined with Array Antennas (어레이 안테나와 결합된 신경망모델에 의한 실시간 도래방향 추정 알고리즘에 관한 연구)

  • 정중식;임정빈;안영섭
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2003.05a
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    • pp.87-91
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    • 2003
  • It has well known that MUSIC and ESPRIT algorithms estimate angle of arrival(AOA) with high resolution by eigenvalue decomposition of the covariance matrix which were obtained from the array antennas. However, the disadvantage of MUSIC and ESPRIT is that they are computationally ineffective, and then they are difficult to implement in real time. The other problem of MUSIC and ESRPIT is to require calibrated antennas with uniform features, and are sensitive to the manufacturing facult and other physical uncertainties. To overcome these disadvantages, several method using neural model have been study. For multiple signals, those require huge training data prior to AOA estimation. This paper proposes the algorithm for AOA estimation by interconnected hopfield neural model. Computer simulations show the validity of the proposed algorithm. The proposed method does not require huge training procedure and only assigns interconnected coefficients to the neural network prior to AOA estimation.

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One-dimensionally Ordered Array of Co and Fe Nanoclusters on Carburized-W(110) via Template Assisted Self-Assembly

  • Kim, Ji-Hyun;Yang, Serlun;Kim, Jae-Sung;Lukashev, Pavel;Rojas, Geoffrey;Enders, Axel;Sessi, Violetta;Honolka, Jan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.02a
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    • pp.135-136
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    • 2012
  • Carbon atoms near the surface of W(110) induce reconstructions such as $R(15{\times}12)$ -C/W(110) which consists of two characteristic parts, one square shaped and bright protrusion and two smaller ones. In the atomic resolution STM image, the bigger protrusion shows the periodicities of clean W(110), indicating that it is almost carbon poor region. The smaller protrusion contains hexagonal carbide surface layer of ${\alpha}$-W2C on W(110). Employing this carburized W(110) as templates, we grow Co and Fe clusters of less than ten atoms. Due to the selectivity of bonding sites, growth of larger cluster is highly unfavorable for Co and the size of clusters is very uniform. Since Co atoms prefer to sit on the bigger protrusion rather than smaller one, Co cluster can be arranged one-dimensionally in $R(15{\times}12)$-C/W(110) with quite uniform size distribution. However, Fe clusters sit on both sites without favored site, but still with uniform size distribution. On the other hand, Fe clusters can be grown with quasi one-dimensional order in $R(15{\times}3)$-C/W(110), which consists of only smaller protrusions. We investigate the magnetic properties of the ordered nano-sized clusters. Experiments using XMCD reveals little magnetic moment of Co cluster on $R(15{\times}12)$-C/W(110). This observation is consistent with the predictions of our first principles calculations that small Co clusters can be nonmagnetic or antiferromagnetic with low mean magnetic moment per atom.

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Novel Maskless Bumping for 3D Integration

  • Choi, Kwang-Seong;Sung, Ki-Jun;Lim, Byeong-Ok;Bae, Hyun-Cheol;Jung, Sung-Hae;Moon, Jong-Tae;Eom, Yong-Sung
    • ETRI Journal
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    • v.32 no.2
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    • pp.342-344
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    • 2010
  • A novel, maskless, low-volume bumping material, called solder bump maker, which is composed of a resin and low-melting-point solder powder, has been developed. The resin features no distinct chemical reactions preventing the rheological coalescence of the solder, a deoxidation of the oxide layer on the solder powder for wetting on the pad at the solder melting point, and no major weight loss caused by out-gassing. With these characteristics, the solder was successfully wetted onto a metal pad and formed a uniform solder bump array with pitches of 120 ${\mu}m$ and 150 ${\mu}m$.

Directivity Characteristics of Wide-Band One-Shot Beam Formed with Gaussian Weighting (가우시안 가중치에 의한 광대역 단일빔의 지향 특성)

  • 도경철;손경식
    • The Journal of the Acoustical Society of Korea
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    • v.18 no.1
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    • pp.25-31
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    • 1999
  • This paper proposes a new wide-band beamforming algorithm which has Gaussian weighting at nested linear array for acoustic measurement. The beamforming is performed one-shot by using all sensors simultaneously, not octave-by-octave. Gaussian weighting of frequency-dependent function is applied to each sensor before time-delay compensation so as to control the frequency receiving band of each sensor. As the results of the simulations, it is confirmed that the proposed algorithm can form the one-shot beams having uniform directivity index and also it can be applied to the broad-band acoustic measurement.

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RF Shimming Considering Coupling Effects for High-Field MRI

  • Heo, Hye-Young;Cho, Min-Hyoung;Lee, Soo-Yeol
    • Journal of Biomedical Engineering Research
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    • v.29 no.4
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    • pp.267-271
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    • 2008
  • The RF shimming technique has been used to improve the transmit RF field homogeneity in highfield MRI. In the RF shimming technique, the amplitude and phase of the driving currents in each coil element are optimized to get homogenous flip angle or uniform image intensity. The inductive and capacitive coupling between the coil elements may degrade the RF field homogeneity if not taken into account in the optimization procedure. In this paper, we have analyzed the coupling effects on the RF shimming using a sixteen-element TEM RF coil model operating at 300 MHz. We have found that the coupling effects on the RF shimming can be reduced by putting high dielectric material between the active rung and the shield.

Estimation of Distributed Signal's Direction of Arrival Using Advanced ESPRIT Algorithm (개선된 ESPRIT 알고리즘을 이용한 퍼진 신호의 신호도착방향 추정)

  • Chung, Sung-Hoon;Lee, Dong-Wook
    • Proceedings of the KIEE Conference
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    • 1999.11c
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    • pp.703-705
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    • 1999
  • In this paper, we introduce the direction of arrival(DOA) estimation of distributed signal based on the improved ESPRIT algorithm. Most research on the estimation of DOA has been performed based on the assumption that the signal sources are point sources. However, we consider a two-dimensional distributed signal source model using improved ESPRIT algorithm. In the distributed signal source model, a source is represented by two parameters, the azimuth angle and elevation angle. We address the estimation of the elevation and azimuth angles of distributed sources based on the parametric source modeling in the three-dimensional space with two uniform linear arrays. The array output vector is obtained by integrating a steering vector over all direction of arrival with the weighting of a distributed source density function. We also develop an efficient estimation procedures that can reduce the computational complexity. Some examples are shown to demonstrate explicity the estimation procedures under the distributed signal source model.

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Micro Pattern Forming on Polymeric Circular Tubes by Hydrostatic Pressing (폴리머 원형 튜브 대상 미세 패턴 정수압 성형)

  • Rhim, S.H.
    • Transactions of Materials Processing
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    • v.23 no.8
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    • pp.507-512
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    • 2014
  • The objective of the current investigation is to establish techniques in micro pattern forming operations of polymeric circular tubes by using hydrostatic pressing. This method was developed and successfully applied to the micro pattern forming on polymeric plates. The key idea of the new technique is to pressurize multiple vacuum-packed substrate-mold stacks above the glass transition temperature of the polymeric substrates. The new process is thought to be a promising micro-pattern fabrication technique for two reasons; first, (hydro-) isostatic pressing ensures a uniform micro-pattern replicating condition regardless of the substrate area and thickness. Second, multiple curved substrates can be patterned at the same time. With the prototype forming machine for the new process, micro prismatic array patterns, 25um in height and 90 degrees in apex angle, were successfully made on the PMMA circular tubes with diameters of 5~40mm. These results show that this process can be also used in the micro pattern forming process on curved plates such as circular tube.

Convolutional Neural Network Based Source Separation Using a Non-uniform Linear Microphone Array (비균등 선형 마이크로폰 어레이를 활용한 합성곱 신경망 기반의 음원분리)

  • Moon, Jung Min;Park, In Young;Kim, Hong Kook
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 2017.11a
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    • pp.44-45
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    • 2017
  • 본 논문에서는 비균등 선형 마이크로폰 어레이를 활용한 convolutional neural network (CNN) 기반의 음원분리 방법을 제안한다. 우선, 주어진 어레이 배치에 따라 채널간의 시간차를 분석하고, 분석된 시간차에 따라 주파수별로 방사각과 넓이에 따라 입력 오디오 신호의 spectral magnitude를 예측한다. 그러고 나서, CNN 분류기로부터 최적의 방사각과 넓이를 선별하고 이를 통해 음원을 분리한다.

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