• 한국전자파학회논문지
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• 제26권2호
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• pp.196-203
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• 2015

곡면 위상 배열 안테나나 곡면 주파수 선택 구조 등의 전파 특성을 해석하기 위해서는 원통형 배열 구조의 효율적인 해석방법에 대한 연구가 필요하다. 원통형 배열 구조가 실제 적용되는 구조는 유한 배열 구조지만, 대부분 전자기 해석은 무한 배열 구조라 가정하므로 실제 구조의 특성과 근사화한 구조의 특성 간의 오차가 발생하게 된다. 따라서 원통형 무한 배열 구조와 유한 배열 구조의 전파 특성의 비교와 분석이 필요하다. 본 논문에서는 원통형 무한 배열 구조를 해석하기 위해 원통형 Floquet harmonics 해석 방법을 적용하였으며, 원통형 유한 배열 구조를 해석하기 위해서는 너비가 좁은 스트립(strip)이 배열된 배열 구조를 가정하여 thin wire approximation을 적용한 method of moments(MoM)를 이용하였다. 본 논문에서는 원통형 유한 배열 구조와 무한 배열 구조의 전파 특성을 비교하기 위하여 투과 특성과 전류 분포를 계산하였다.

• Steel and Composite Structures
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• 제17권5호
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• pp.561-572
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• 2014

In this paper, we present the scattering characteristics of infinite and finite array using method of moment (MoM) with Floquet harmonics and asymptotic waveform evaluation (AWE) technique. First, infinite cylindrical dipole array is analyzed using the MoM with entire domain basis function and cylindrical Floquet harmonics. To provide the validity of results, we fabricated the cylindrical dipole array and measured the transmission characteristics. The results show good agreements. Second, we analyzed the scattering characteristics of finite array. A large simulation time is needed to obtain the scattering characteristics of finite array over wide frequency range because Floquet harmonics can't be applied. So, we used the MoM with AWE technique using Taylor series and Pade approximation to overcome the shortcomings of conventional MoM. We calculated the radar cross section (RCS) as scattering characteristics using the proposed method in this paper and the conventional MoM for finite planar slot array, finite spherical slot array, and finite cylindrical dipole array, respectively. The compared results agree well and show that the proposed method in this paper is good for electromagnetic analysis of finite FSS.

• 전자공학회논문지
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• 제50권6호
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• pp.43-55
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• 2013

본 논문에서는 원통형태의 배열구조에서 수평면(H-plane), 수직면(E-Plane) 빔조향 특성을 갖는 원통형 능동위상배열 안테나를 제안하였다. 상호결합특성이 우수한 접힌 다이폴 안테나를 원통의 배열구조에 적합하도록 설계하고, 수직과 수평으로 $8{\times}8$ 원통 배열구조를 갖는 지향성 배열안테나와 전력 분배를 위한 결합분배기를 설계 및 제작하였다. 원통배열 안테나의 복사소자 배열 간격은 반전력 빔폭과 빔 조향 시 그레이팅로브가 발생하지 않도록 결정하였다. 안테나의 빔 조향은 송수신장치 내부의 6비트 위상변위기를 이용하여 구현하였으며, 안테나 빔조향 시 수평면으로 -24도 ~ 24도, 수직면 기준으로 0도 ~ 36도의 빔조향 특성을 갖도록 고안되었다.

• 한국소음진동공학회논문집
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• 제25권6호
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• pp.440-446
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• 2015

Acoustic signal is emitted from a vessel and received by a cylindrical array sensor at some distance from the vessel. Acoustic signal is the source for a cylindrical array sensor which is designed to detect the acoustic signal. Cylindrical array sensors seldom have an ideal hydrodynamic shape and are not sufficiently robust to survive without some protection and they are normally housed in a sonar dome. Reflected signals by some structure inside a sonar dome make unwanted signals. Therefore, an acoustic baffle is used to minimize unwanted signals. The performance of the acoustic baffles can be determined from the acoustic numerical analysis at the design stage. In this study, finite element method was used to analyze the acoustic field around the cylindrical array sensor and baffle effects. The baffle performance can be defined the echo reduction. To show the baffle performance, the specimens were made for pulse tube test and echo reductions were measured during the test. In this paper, the effect of echo reduction of the acoustic baffle was discussed.

• 한국소음진동공학회논문집
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• 제19권10호
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• pp.987-995
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• 2009

As an experimental technique to analyze the far-field characteristics of underwater cylindrical array sensors, cylindrical acoustic holography is studied. Inside an laboratory water tank, far-field directivity patterns as well as near-field source images are reconstructed from the measured hologram by hydrophone array. Approximate equation for far-field directivity estimation is derived based on stationary phase method. The simulation and experiment show well usefulness of the proposed method in application of underwater array sensors.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.111-116
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• 2009

As an experimental technique to analyze the far-field characteristics of underwater cylindrical array sensors, cylindrical acoustic holography is studied. Inside an laboratory water tank, far-field directivity patterns as well as near-field source images are reconstructed from the measured hologram by hydrophone array. Approximate equation for far-field directivity estimation is derived based on stationary phase method. The simulation and experiment show well usefulness of the proposed method in application of underwater array sensors.

• 한국해양공학회지
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• 제18권5호
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• pp.7-14
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• 2004

The interaction of incident manochromatic waves with an array of N surface-piercing porous dual cylindrical structures is investigated in the frame of three-dimensional linear potential theory. The dual cylindrical structure is camposed of concentric two cylinders. The exterior cylinder is porous and the interior cylinder is impermeable. The fluid domain is divided into N+1 regions i.e. a single exterior region and N interior regions. The diffraction potentials in each region representing the scattering of incident waves by an array of porous cylindrical structures are expressed by the Fourier Bessel series. The unknown coefficients in each region are determined by applying the porous boundary condition and continuity of mass flux at the matching boundary. It is found that an array of porous cylindrical structures reduces both the wave forces and the wave run-up, and shows the excellent performance of wave blocking. The results show that various types of breakwater exchanging seawater are prospective by controlling the porosity and the configuration of cylindrical structures.

• 한국전자파학회지:전자파기술
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• 제5권2호
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• pp.46-54
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• 1994

본 논문에서는 원통변에 표면-정합된 마이크로스트럽 배열 안태나의 지향특성을 개선하기 위한 방볍을 제 시한다. 장방형 마이크로스트립 패치를 원통변에 횡방향으로 호(arc) 모양 배열하는 경우, 원통면윤 다각형의 각주로 끈사하고, 각각의 각주 평변에 임의 방향으로 주빔의 sqwnt를 가지는 Dolph - Tschebyscheff 배열, u uniform 배열 등의 부배열(sub-array)을 배치하므로써 전체 원통면 배열 안테나에 원하는 지향특성을 가지도 록 할 수 있음을 보이고, 원통면-공진기 모텔을 이용하여 복사패턴을 해석한다. 부배열의 종류에 따른 전체 배 열 얀테나의 복사패턴을 비교하고, 배열간격이 $\lambda_0$/2인 uniform 배열을 이용한 요소수 12인 원통면 배열 안테 나를 제작하여 반경이 6인 원통변에 정합시켰을 때 부엽 level -l3dB, 반전력범폭 $9^{\circ}$, 제일 null 사이각 $15^{\circ}$인 양호한 특성을 얻어 선형배열을 이용하는 경우보다 지향특성을 현저하게 개선시켰다

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제3B권4호
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• pp.179-187
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• 2003

In the machine tool industry, direct drive linear motor technology is of increasing interest as a means to achieve high acceleration and to increase reliability. This paper analyzes and compares the characteristics of the tubular linear actuator with the cylindrical Halbach and radial array, respectively. A tubular linear actuator with cylindrical Halbach array, consisting of parallel magnetized arc segments instead of ideal radial and axial magnetized rings, is manufactured. The magnetic field solutions due to the PMs and to the currents are established analytically in terms of vector potential, using the 2-D cylindrical coordinate system. Motor thrust, flux linkage and back emf are then derived. Thrust characteristics according to such design parameters as magnet height and air gap length are also given. The results are validated extensively by comparison with finite element analysis (FEA). Test results such as thrust measurements are also given to confirm the analysis.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.143-148
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• 2006

The goal of this paper is to analyze, through simulations and experiments, GNSS interference mitigation performance under various types of antenna structures against wideband and narrowband interferences using spatial-temporal adaptive signal processing (STAP) techniques. The STAP approach, which combines spatial and temporal processing, is a viable means of GNSS array signal processing that enhancing the desired signal quality and providing protection against interference. In this paper, we consider four types of 3D antenna array structure - Uniform Linear Array (ULA), Uniform Rectangular Array (URA), Uniform Circular Array (UCA), and the Single-Ring Cylindrical Array (SRCA) under an interference environment. Analytical evaluation and simulations are performed to investigate the system performance. This is followed by simulation GPS orbits in interfered environment are used to evaluate the STAP performance. Furthermore, experiments using a 2x2 URA hardware simulator data show that with the removal of wideband and narrowband interference through the STAP techniques, the signal tracking performance can be enhanced.