• Journal of Magnetics
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• 제22권2호
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• pp.238-243
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• 2017

In this research, we report the preliminary results of an insertional type parallel transmission (pTx) array that has 7-elements that are placed in the space above a patient table as a transmit (Tx) coil to give an RF transmission ($B_1{^+}$) field for the body object of a 3 Tesla (T) MRI system. In previous research, we have tried to compare the performances of different coil elements and array geometries for a pTx body image. Based on these results, we attempt to obtain a human image with the proposed pTx array. Through the simulation and experimental results, we introduce a possible structure of multi-channel Tx array and verify the utility of a multi-channel Tx body image using $B_1{^+}$ shimming. The insertional pTx array, combined with a receiver (Rx) array coil, provides an enhanced $B_1{^+}$ field homogeneity in a large ROI image as a result of $B_1{^+}$ shimming applied over the full body size object. Through this research, we hope to determine the usefulness of the proposed insertional type RF coil combination for 3 T body imaging.

• Current Optics and Photonics
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• 제7권3호
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• pp.248-253
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• 2023

An efficient global optimization approach for a periodic plasmonic nanoslit array based on extraordinary optical transmission within an acceptable time range is proposed using 𝚀 factor analysis method. The particle swarm optimization is employed as a global optimization tool. The figure of merit is defined as a product of transmission peak value and 𝚀 factor. The design variables are the slit width, height, and period of the slit array, respectively. The optical properties such as transmission spectrum and bandwidth are calculated rigorously using the finite element method.

• 반도체디스플레이기술학회지
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• 제17권2호
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• pp.20-25
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• 2018

In this paper, we have designed circularly polarized array antenna for 5.8GHz microwave wireless power transmission. To obtain high antenna gain, we studied a single patch antenna, a $2{\times}1$ array antenna, a $2{\times}2$ array antenna, a $2{\times}4$ array antenna, and a $4{\times}4$ array antenna. Commonly, characteristics of each antenna have a frequency of 5.8 GHz and Right Hand Circular Polarization(RHCP) of circular polarization. Also, the results were obtained with the design to each antenna that the return loss was less than -10dB and the axial ratio was less than 3dB. The gain of the antennas was 6.08dBi for a single patch antenna, 9.69dBi for a $2{\times}1$ array antenna, 12.99dBi for a $2{\times}2$ array antenna, 15.72dBi for a $2{\times}4$ array antenna and 18.39dBi for a $4{\times}4$ array antenna. When the elements of the array antenna were increased, it was confirmed that it increased by about 3dBi.

• 전자공학회논문지A
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• 제31A권10호
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• pp.31-38
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• 1994

In this paper, the leaky wave readiation characteristics of a microstrip rectangular patch array is presented. The reflection and transmission characteristics are analyzed using the equivalent transmission line method. Since the leaky wave is generated from the periodic array, using the Floquet'theorem, leaky wave frequency range is predicted and confirmed by the measured reflection and transmission characterstics of the array. A 17 element microstrip patch array at X-Band is designed and tested. Teh scattering Characteristics show good agreement woth those obtained from the equivalent transmission line analysis. The radiatio characteristics at 10GHz using this method show about 3${\circ}$ shift in main lobe angle compared with measured results.

• 한국광학회지
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• 제30권2호
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• pp.67-73
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• 2019

본 논문에서는 다양한 배열을 가지는 기판에서의 특이 광 투과 센서 시스템의 센싱 성능을 조사하였다. 보조파장 홀 어레이 구조는 어레이의 주기와 격자 배열을 달리하여 제작하였고, 특이 광 투과 센서 시스템으로 제작한 기판에서의 투과 스펙트럼을 측정하였다. 굴절률이 다른 유전물질을 이용하여 투과 스펙트럼을 관찰한 결과 어레이의 주기가 증가할수록 센서의 민감도가 높아짐을 보았다. 또한 육각형 어레이에서 측정한 결과와 비교하였을 때 정사각형 어레이에서 센서의 성능이 향상됨을 입증하였다.

• International journal of advanced smart convergence
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• 제11권4호
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• pp.41-46
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• 2022

This study is a Ku-band array antenna for the manufacture of low-orbit satellite communication terminals, designed to have miniaturization, high gain, and wide beam width. The transmission of low-orbit satellite communication has a right-rotating circularly polarized wave, and the reception has a left-rotating circularly polarized wave. The 4×8 array antenna was separated for transmission and reception, and it was combined with the RF circuit part of the transmitter and receiver, and was terminated in the form of a waveguide for RF signal impedance matching in the form of a transition from the microstrip line to the waveguide. The 30° beam width of the receiver maximum gain of 19 dBi and the 29° beam width of the transmitter maximum gain of 18 dBi are shown. Through this antenna configuration, the system was configured to suit the low-orbit satellite transmission/reception characteristics.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권3호
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• pp.175-181
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• 2004

In order to increase the coupling efficiency of the Power and Phase of the active Phase way antenna, we have fabricated the active phased-array antenna which is coupled by the transmission line, and investigated the relationship between the length of the coupling transmission line and coupling power and phase. The following three types of driving method -(1) giving the frequency difference between the two active antenna, (2) applying the input signal to the one side of the two antennas, and changing the eigen frequency of the other side antenna, (3) appling the different phase inputs to the active antennas was investigated. The experimental results showed that the interval of the antenna elements has not affected the power and the phase of the antenna.

• 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.

• 한국전자파학회논문지
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• 제23권10호
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• pp.1188-1195
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• 2012

향후 레이더는 능동 위상 배열레이더(Active Phased-Array Radar System)로 발전하는 추세이다. 특히, 다채널 수신 시스템에서 실시간 신호처리를 위해서 신호처리용 보드의 처리 속도와 개수와의 trade-off는 최적화 되어야 한다. 본 논문에서는 많은 양의 수신 데이터를 안테나부에서 신호처리부로 전달하기 위한 전송 기법에 대하여 소개하고자 한다. 그 결과, 기존 방법에 비해 신호처리부의 S/L 보드 개수는 절반(1/2) 수준으로 감소하였고, 통신 전송 속도 여유 마진은 약 2배 더 증가되는 효과가 있다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 ICEIC The International Conference on Electronics Informations and Communications
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• pp.302-309
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• 2004

The transmission capacity of wireless communication systems may become dramatically high by employ multiple transmit and receive antennas with space-time coding techniques appropriate to multiple transmit antennas. For large number of transmit antennas and at high bandwidth efficiencies, the receiver may become too complex whenever correlation across transmit antennas is introduced. Reducing decoding complexity at receiver by combining array processing and space-time codes (STC) helps a communication system using STC to overcome the big obstacle that prevents it from achieving a desired high transmission rate. Multi-carrier CDMA (MC-CDMA) allows providing good performance in a channel with high inter-symbol interference. Antenna array, STC and MC-CDMA system have a similar characteristic that transmit-receive data streams are divided into sub-streams. Thus, there may be a noticeable reduction of receiver complexity when we combine them together. In this paper, the combination of array processing and STC in MC-CDMA system over slow selective-fading channel is investigated and compared with corresponding existing MC-CDMA system using STC. A refinement of this basic structure leads to a system design principle in which we have to make a trade off between transmission rate, decoding complexity, and length of spreading code to reach a given desired design goal.