• Title, Summary, Keyword: phased array

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One-Channel Phased-Array Quadrature RF Coil for Spine Magnetic Resonance Imaging (척추 MRI를 위한 One-Channel Phased-Array Quadrature RF 코일)

  • 양윤정;김선경
    • Journal of Biomedical Engineering Research
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    • v.19 no.2
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    • pp.129-132
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    • 1998
  • A new one-channel phased-array quadrature RF coil is developed for spine MR imaging. Quadrature RF coils for MRI have been used to improve the signal-to-noise ratio (SNR) by$"\squt{2}"$ using two orthogonal RF coils in combination. More recently, the phased-array RF coil has been proposed for more improvement of SNR by using an array of reduced-size RF coil elements. Two schemes proposed for the new phased-array quadrature RF coil are:(1) Proper overlapping of two quadrature RF coils thus removing the mutual inductance and (2) Attaching preamplifiers right after the coil section and combining the signal with proper phase delays. The coil has been implemented for receive-only mode, and tested by phantom and volunteer imaging. The experimental results show the utility of the proposed RF coil.d RF coil.

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The Radiation Characteristics of a Linear Phased Array Antenna using a Pin Array Patch Antenna as an Element (핀 배열 안테나를 단위 안테나로 사용한 선형 위상 배열 안테나의 방사 특성)

  • Kim, Tae-Young;Kim, Gun-Su;Kim, Boo-Gyoun
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.46 no.12
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    • pp.44-51
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    • 2009
  • The radiation characteristics of a pin array patch antenna phased array are compared to those of a conventional patch antenna phased array. The performance of a pin array patch antenna phased array is much improved than that of a conventional patch antenna phased array because the mutual coupling between the adjacent pin array patch antennas is very small compared to that between the adjacent conventional patch antennas. The radiation characteristics of a pin array patch antenna phased array show the superior performance such as low variation of the gain of the main beam and the side lobe level for the variation of the direction of the main beam.

A study on the active phased array antennas with slotline coupling (슬롯라인 결합을 이용한 능동 위상배열안테나에 관한 연구)

  • Mun, Cheol;Kim, Seon-Taek;Yoon, Young-Joong;Park, Han-Kyu
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.22 no.5
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    • pp.981-989
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    • 1997
  • In this paper, the 5-element active phased array antennas coupled through slotline between elements are designed and fabricated. A recent studies on the active phased array antennas using the transmission line coupling which can be designed to provide strong coupling and the appropriate coupling phase. But this sturucture has limitation of expanding in two dimensions for planar active phased array antennas and distortion of the radiation pattern caused by coupling network. Thus our work proposes the slotline coupling structure asthe broadband coupling network for the active phased array antenna. In experiment, 5-elements active phased array antenas have steering range from -30.deg. to 20.deg. off broadside as the free-running frequencies of end elements are controlled. The overall results show that the proposed slotline coupling structure is suited for the coupling network in the actie phased array antenna system. And the proposed coupling structire solves the expansion problem and eliminates the distortion of the radiation pattern caused by the spurious radiation of the transmission line coupling network. Thus thiscan be expanded to two dimensional coupling network for the planar active phased array antenna system.

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Basic Experiment for Lamb Wave Focusing by Phased Magnetostrictive Transducers in a Plate (자기변형 트랜스듀서의 위상차를 이용한 평판에서의 Lamb파 집속 기초 실험)

  • Lee, Joo-Kyung;Kim, Hoe-Woong;Lee, Ho-Cheol;Kim, Yoon-Young
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.3
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    • pp.227-233
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    • 2011
  • The ultrasonic guided wave phased array using magnetostrictive patch transducers is proposed. The magnetostrictive transducer has received much attention because it is cost-effective and capable to generate ultrasonic waves with a simple configuration. However, it has not been used for ultrasonic guided wave phased array applications until now. In this paper, we propose a magnetostrictive transducer based phased array system consisting of a multi-channel function generator, power amplifiers and Lamb wave magnetostrictive transducers. To check the performance of the ultrasonic guided wave phased array, several Lamb wave focusing experiments were carried out in an aluminum plate. The results demonstrated the capability of the developed array to focus the Lamb waves at specific target points.

A Study on Ultrasonic Image Diagnosis Methods of Tooth Defect with Phased-Array Techniques (위상배열기법을 이용한 치아결함 초음파이미지 진단기술개발)

  • Oh, Yun-Jung;Hwang, In-Nam;Park, Su-Jung;Im, Kwang-Hee;Cho, Hyun-Joon;Cho, Young-Tae
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.18 no.6
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    • pp.604-613
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    • 2009
  • Recently, researches to develop phased array ultrasonic examination techniques are proceeded to diagnose dental caries and the status of surgical operation of dental implant. Sound field analysis of phased array ultrasonic transducers were carried out in order to characterizing the ultrasonic phased array beams. The sound field of ultrasonic radiation was calculated for the sample called "gypsum-improved stone" with the similar characteristics of dental materials. Industrial phased array ultrasonic devices were utilized for the insptriion of the artificial flaws machined in the gypsum-improved stone. Dental implants were made at the pig jaw bone and defect images were confirmed for the dental implants.

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Determination of Focal Laws for Ultrasonic Phased Array Testing of Dissimilar Metal Welds

  • Jing, Ye;Kim, Hak-Joon;Song, Sung-Jin;Song, Myung-Ho;Kang, Suk-Chull;Kang, Sung-Sik;Kim, Kyung-Cho
    • Journal of the Korean Society for Nondestructive Testing
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    • v.28 no.5
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    • pp.427-435
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    • 2008
  • Inspection of dissimilar metal welds using phased array ultrasound is not easy at all, because crystalline structure of dissimilar metal welds cause deviation and splitting of the ultrasonic beams. Thus, in order to have focusing and/or steering phased array beams in dissimilar metal welds, proper time delays should be determined by ray tracing. In this paper, we proposed an effective approach to solve this difficult problem. Specifically, we modify the Oglivy's model parameters to describe the crystalline structure of real dissimilar metal welds in a fabricated specimen. And then, we calculate the proper time delay and incident angle of linear phased array transducer in the anisotropic and inhomogeneous material for focusing and/or steering phased array ultrasonic beams on the desired position.

Simulation Based Investigation of Focusing Phased Array Ultrasound in Dissimilar Metal Welds

  • Kim, Hun-Hee;Kim, Hak-Joon;Song, Sung-Jin;Kim, Kyung-Cho;Kim, Yong-Buem
    • Nuclear Engineering and Technology
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    • v.48 no.1
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    • pp.228-235
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    • 2016
  • Flaws at dissimilar metal welds (DMWs), such as reactor coolant systems components, Control Rod Drive Mechanism (CRDM), Bottom Mounted Instrumentation (BMI) etc., in nuclear power plants have been found. Notably, primary water stress corrosion cracking (PWSCC) in the DMWs could cause significant reliability problems at nuclear power plants. Therefore, phased array ultrasound is widely used for inspecting surface break cracks and stress corrosion cracks in DMWs. However, inspection of DMWs using phased array ultrasound has a relatively low probability of detection of cracks, because the crystalline structure of welds causes distortion and splitting of the ultrasonic beams which propagates anisotropic medium. Therefore, advanced evaluation techniques of phased array ultrasound are needed for improvement in the probability of detection of flaws in DMWs. Thus, in this study, an investigation of focusing and steering phased array ultrasound in DMWs was carried out using a time reversal technique, and an adaptive focusing technique based on finite element method (FEM) simulation. Also, evaluation of focusing performance of three different focusing techniques was performed by comparing amplitude of phased array ultrasonic signals scattered from the targeted flaw with three different time delays.

Wideband Capon Beamforming for a Planar Phased Radar Array with Antenna Switching

  • Lee, Moon-Sik
    • ETRI Journal
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    • v.31 no.3
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    • pp.321-323
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    • 2009
  • A wideband beamforming algorithm for estimating the azimuth angle, elevation angle, velocity, and range using a planar phased radar array with antenna switching is proposed. It uses the time-variant steering vector model. Simulation results illustrating the performance of the proposed beamformer are presented.

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Detection Performance of Noncoherent Radar: MIMO Radar, Phased Array Radar, Directional MIMO Radar (비동기식 레이더의 검출 성능 비교: MIMO 레이더, 위상 배열 레이더, 지향성 MIMO 레이더)

  • An, Chan-Ho;Yang, Jang-Hoon;Pak, Ui-Young;Ryu, Young-Jae;Han, Duk-Chan;Kim, Dong-Ku
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.12B
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    • pp.1752-1757
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    • 2011
  • In a traditional phased array radar, closely spaced antenna elements transmit a scaled version of single waveform to maximize the signal energy. On the contrary, a multiple-input multiple-output (MIMO) radar consists of widely separated antennas and transmits an arbitrary waveform from each antenna element. These waveforms and spatial diversity enable superior capabilities compared with phased array radar. At high signal-to-noise ratio (SNR), the detection performance of the MIMO radar is better than the phased array radar due to the diversity gains. However, the phased array radar outperforms the MIMO radar at low SNR, due to the energy maximization. In this paper, we investigate the compromised scheme between the MIMO radar and the phased array radar. Employing the MIMO radar equipped with phased array elements, the compromised scheme achieves both array gain and diversity gain. Also, we compare the performance degradation when the steering direction is incorrect.

4×4 Broadband Phased Array Antenna Using LHTL Based Phase Shifter (LHTL 위상변위기를 이용한 4×4 광대역 위상배열안테나)

  • Park, Soonwoo;Kim, Hongjoon
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.2
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    • pp.379-382
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    • 2017
  • This paper proposes a $4{\times}4$ broadband phased array antenna using a Left-Handed Transmission Line (LHTL) based phase shifter. The phased array is constructed with sixteen quasi-Yagi antenna elements and the phase shifters, as well as four power dividers. A key component of the system, the LHTL based phase shifter is able to control a phase delay of incident waves linearly and continuously. The fabricated phased array antenna operate for a frequency range of 800 MHz (1.6 GHz~2.4 GHz). The beam scanning range of the $4{\times}4$ array antenna is ${\pm}27^{\circ}$ horizontally and vertically while the antenna gain is maintained with a variation of ${\pm}1.4dBi$.