• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.340-341
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• 2010

Noise reduction is an important factor to design low noise sensor array. In this paper three layers of the de-coupler in the conformal sensor array were used to investigate noise reduction. Conformal sensor array is positioned in the layers and the distance from the layer is 0.25cm~1.5cm. Transfer function in the frequency density function is investigated according to the three different positions. When increasing the embedded distance the flow noise decreased in the region of the kx>10.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.29-29
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• 2010

기존의 반도체 공정을 기반으로 하는 소자구조는 주로 평면의 웨이퍼상에 만들어져왔다. 그러나, 제작된 소자 어레이를 늘림이 가능한 (stretchable) 폴리머 기판에 프린팅 전이하는 방식을 이용하면 어떤 형태의 곡면에도 소자 제작이 가능해진다. 이러한 프린팅 방식으로, 다양한 곡면에 실리콘 소자 어레이를 제작한 연구결과를 발표하고자 한다. 한 응용 예로 사람의 눈과 같은 반구형 표면에 실리콘 나노 리본으로 만든 광다이오드 어레이를 배열하여 전자 눈 카메라를 제작하여 성능을 확인하였다. 또한 수차를 최소화할 수 있는 포물면에 전자눈 카메라를 제작하여 평면카메라에 비해 이미지의 균일성이 우수함을 보여주고자 한다.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.269-269
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• 2016

최근, 플렉서블 광전자소자 제작 기술의 눈부신 발전으로, 기존의 평면형 이미지 센서가 가지고 있는 여러가지 한계를 극복하기 위해 곡면형 이미지 센서 제작에 대한 다양한 연구가 진행되고 있다. 리소그래피, 물질 성장, 도포, 에칭 등의 대부분의 반도체 공정은 평면 기판에 기반한 공정 방법으로 곡면 구조의 이미지 센서를 제작하기에는 많은 어려움이 있다. 본 연구에서는 곡면형 이미지 센서의 제작을 위해 곡면 구조 위에서의 직접적인 공정 대신 평면 기판에서 단결정 실리콘을 이용해 전사 인쇄가 가능하고 수축이 가능한 초박막 구조의 이미지 센서를 제작한 후 이를 떼어내는 방식을 이용하였다. 이온 주입 및 건식 식각 공정을 통해 평면 SOI (Silicon on Insulator) 기판 위에 단일 광다이오드 배열 형태의 소자를 제작한 후 수 차례의 폴리이미드 층 도포 및 스퍼터링을 통한 금속 배선 공정을 통해 초박막 형태의 광 검출기를 완성한다. 이후 습식 식각 및 폴리디메틸실록산(PDMS) 스탬프를 이용한 전사 인쇄 공정을 통해 기판으로부터 디바이스를 분리하여 변형 가능한 형태의 이미지 센서를 얻을 수 있다. 이러한 박막형 이미지 센서는 유연한 재질로 인해 수축 및 팽창, 구부림과 같은 구조적 변형이 가능하게 되어 겹눈 구조 카메라, 튜너블 카메라 등과 같이 기존 방식의 반도체 공정으로는 구현할 수 없었던 다양한 이미징 시스템 개발에 적용될 수 있을 것으로 기대된다.

• 대한공업교육학회지
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• v.33 no.2
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• pp.273-286
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• 2008

Underwater acoustic sensor array can detect acoustic signal in underwater and the sensor array can be mounted in each left, right or front side of the UUV(Unmanned Underwater Vehicle). The sensor array could be conformal array and effected turbulent boundary layer flow noise. Therefore, in this paper numerical simulations were performed to know the how the outer flow noise affect the hydrophone which embedded in the elastomer. Corcos wall pressure model was used as turbulent boundary layer flow noise and this model was applied to the frequency density function. Characteristics of transfer function according the kx wave number were simulated and design parameters were thickness of elastomer, density, and modulus of elasticity. Based on the simulation results when increasing the thickness of elastomer noise reduction was increased. This results can be applied to the design of conformal array of UUV.

• 대한공업교육학회지
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• v.34 no.1
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• pp.238-251
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• 2009

The noise itself that affects the sensor array is defined as the noise which happens in the place where the system is installed and the circumference noise which comes from the ocean. The array structure for detecting acoustic signal in the underwater effected turbulent layer flow noise. In this paper to design the conformal array spectral density function was introduced and several cases of flow induced noise which affect transfer function were simulated. Modified Corcos wall pressure model was used as turbulent boundary layer flow noise. The effect of noise has been reduced as integrated sum of transfer function has been reduced by decreasing elastomer thickness and density when kx is in low wave number area. Also the characteristics of transfer function by Corcos wall pressure displayed the product of frequency density function. This simulation results can be applied to the conformal array design in unmmaned underwater vehicle in the near future.

• Journal of IKEEE
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• v.16 no.4
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• pp.328-334
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• 2012

In this paper, we analyzed the electromagnetic characteristics of the spherical frequency selective surface with different arrangement of crossed dipole slot elements for reducing the RCS(radar cross section). The three dimensional MOM(method of moment) with RWG basis is used to analyze the proposed structure. To reduce the simulation time, we applied the BiCGSTab(Biconjugate Gradient Stabilized) algorithm as an iterative method and presented the comparison results with Mie's theoretical results for PEC sphere to show the validity of this paper. From the simulation results, the different arrangement of elements array showed the difference RCS that cannot be negligible. The arrangement method of element in frequency selective surface will be one of variables for the design of curved frequency selective structures.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.673-674
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• 2011

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.12
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• pp.1031-1043
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• 2015

This paper describes the pattern synthesis method of two kinds of conformal array antenna using the Enhanced Adaptive Genetic Algorithm (EAGA). One is the $1{\times}16$ conformal array antenna on a curved cylindrical metallic surface with quadratic function, and the other is the 18-element conformal arrary antenna on a metallic surface obtained by the rotation of a quadratic function curve around the axis. The active element pattern is utilized in the pattern synthesis. Especially for the case of the rotated-type conformal array antenna the transformed active element pattern obtained from the Euler's angle rotation of the active element pattern of the planar concentric array is utilized, which reduces the synthesis time a lot. To verify the validity of the proposed synthesis method the MATLAB results are compared with the MWS results. Furthermore, for the case of $1{\times}16$ conformal array antenna the measured results are compared with the MATLAB synthesized results.

• Journal of Biomedical Engineering Research
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• v.23 no.5
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• pp.351-364
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• 2002

Conventional 3D ultrasound imaging using mechanical ID arrays suffers from poor elevation resolution due to the limited depth-of-focus (DOF). On the other hand, 3D imaging systems using 2D phased arrays have a large number of active channels and hence require a very expensive and bulky beamforming hardware. To overcome these limitations, a new real-time volumetric imaging method using curved 2-D arrays is presented, in which a small subaperture, consisting of 256 elements, moves across the array surface to scan a volume of interest. For this purpose, a 2-D curved array is designed which consists of 90$\times$46 elements with 1.5λ inter-element spacing and has the same view angles along both the lateral and elevation directions as those of a commercial mechanical 1-D array. In the proposed method, transmit and receive subapertures are constructed by cutting the four corners of a rectangular aperture to obtain a required image qualify with a small number of active channels. In addition the receive subaperture size is increased by using a sparse array scheme that uses every other elements in both directions. To suppress the grating lobes elevated due to the increase in clement spacing, fold-over array scheme is adopted in transmit, which doubles the effective size of a transmit aperture in each direction. Computer simulation results show that the proposed method can provide almost the same and greatly improved resolutions in the lateral and elevation directions, respectively compared with the conventional 3D imaging with a mechanical 1-D array.

• The Journal of the Acoustical Society of Korea
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• v.21 no.7
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• pp.592-599
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• 2002

In this study, an ultrasonic transducer was designed with a commercial finite element analysis (FEA) code, PZFlex, and fabricated based on the design. The transducer has the dimension and shape suitable for abdomen diagnosis working at 5 ㎒ and consists of 128 piezoelectric elements disposed in a convex linear array form. The transducer is composed of two impedance matching layers, one backing layer, and kerfs placed between the piezoelectric elements. Validity of the design with the FEA was illustrated through experimental characterization of a sample transducer. Comparison with the design results by equivalent circuit analysis method was also made to check the superiority of the FEA design.