• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.11
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• pp.9-16
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• 1995

In this paper, an ultrasonic phased array transducer with spherical liquid lens, which utilizes both electronic focusing by linear phased array and variable geometric focusing by spherical lens. is investigated. This system reduces the elevational beamwidth which is disadvantage of the 1-dimensional linear phased array, and adds real-time dynamic focusing capability by controlling the volume of liquid in the lens. A prototype of this transducer is constructed and tested. The experimental results are compared with those of computer simulations. The range of applications are in the hyperthermia applicators or ultrasonic image system with narrow beam and rapid scanning characterisitcs.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.5 no.1
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• pp.14-19
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• 2009

NDE(Nondestructive examination) detects a flaw or discontinuity in materials. Flaws detected by the examination shall be evaluated for the decision basis of the integrity. The internal flaws of forging products can be detected by UT. However, UT has detection limits because of its reflected signal weakness. Normally, a 1mm or less flaw is known as the limit. If a flaw was detected, the size of flaw would be evaluated by AVG(or DGS) technique. To verify the evaluation data, alternative examination methods are needed. But there is no alternative examination methods until now. In this study, Phased array ultrasonic technique can be used to size the flaws in the generator rotor with focused beam of ultrasonic wave as a supplement method of AVG. Also, the phased array ultrasonic technique described enables the shape of flaw to be depicted exactly.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.541-547
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• 1992

The phased array antenna has the ability to perform adaptive sampling by directing the radar beam without inertia in any direction. The adaptive sampling capability of the phased array antenna allows each sampling time interval to be varied for each target, depending on the acceleration of each target at any time. In this paper we design a three-dimensional adaptive tracking algorithm for the phased array radar system with a given set of measurement parameters. The tracking algorithm avoids taking unnecessarily frequent samples, while keeping the angular prediction error within a fraction of antenna beamwidth so that the probability of detection will not be degraded during a track update illuminations. In our algorithm, the target model and the sampling rate are selected depending on the target range and the target maneuver status which is determined by a maneuver detector. A detailed simulation is conducted to test the validity of our tracking algorithm for encounter geometries under various conditions of maneuver.

• Journal of the Optical Society of Korea
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• v.18 no.4
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• pp.406-413
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• 2014

An optical true-time delay beam-forming system using a tunable dispersion compensating module (DCM) for dense-wavelength division modulation (DWDM) and a multiwavelength fiber ring laser for a phased array antenna is proposed. The multiwavelength fiber ring laser has one output that includes four wavelengths; and four outputs that include only single-wavelength. The advantage of such a multiwavelength fiber ring laser is that it minimizes the number of devices in the phased array antenna system. The time delays according to wavelengths, which are assigned for each antenna element, are obtained from the tunable DCM. The tunable DCM based on a temperature adjustable Fabry-Perot etalon is used. As an experimental result, a DCM could be used to obtain the change of the beam angle by adjusting the dispersion value of the DCM at the fixed lasing wavelengths of the fiber ring laser in the proposed optical true-time delay.

• ETRI Journal
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• v.27 no.6
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• pp.677-684
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• 2005

A phased array antenna was fabricated using four-element ferroelectric phase shifters with a coplanar waveguide (CPW) transmission line structure based on a $Ba_{0.6}Sr_{0.4}TiO_3(BST)/MgO$ structure. Epitaxial BST films were deposited on MgO (001) substrates by pulsed laser deposition. To attain the large differential phase shift and small losses for a ferroelectric CPW phase shifter, an impedance-matching-part adding technique between the effective transmission line and connecting cable was used. The return loss and insertion loss for this techniqueadapted BST CPW device were improved with respect to those for a normal BST CPW device. For an X-band phased array antenna system consisting of ferroelectric BST CPW phase shifters, power divider, dc block, patch antenna, and programmed dc power, the steering beam could be tilted by $15^{\circ}$ in either direction.

• Journal of information and communication convergence engineering
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• v.18 no.4
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• pp.254-259
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• 2020

Phased-array antennas comprise a demanding antenna design methodology for commercial wireless communication systems or military radar systems. In addition to these two important applications, the phased-array antennas can be used in beamforming for wireless charging. In this study, a four-way analog beamforming front-end module (FEM) for a hybrid beamforming system is developed for 2.4 GHz operation. In a hybrid beamforming scheme, an analog beamforming FEM in which the phase and amplitude of RF signal can be adjusted between the RF chain and phased-array antenna is required. With the beamforming and beam steering capability of the phased-array antennas, wireless RF power can be transmitted with high directivity to a designated receiver for wireless charging. The four-way analog beamforming FEM has a 32 dB gain dynamic range and a phase shifting range greater than 360°. The maximum output RF power of the four-way analog beamforming FEM is 40 dBm (=10 W) when combined the four individual RF paths are combined.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.735-741
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• 2003

A simplified view of array design and application process was introduced. Array design is critical to achieve a successful phased array measurements. A planar microphone array is designed to produce optimum performance and also to fit economic requirement in integrating data acquisition system. Certain performance characteristics are of primary concern when designing arrays. These characteristics include array resolution, spatial aliasing and array sidelobe suppression. Every array has its directional pattern that shows such characteristics. Assuming that a monopole source is located in center, beam-patterns have been simulated varying measurement conditions such as number of sensors. array aperture size, distance between array and source, frequency of interest and so on. Sensor correction was conducted on very channel using magnitudes and phased of FRF with respect to a reference microphone channel. Then with a spiral type array, measurements have been made with two point sources of same frequency in order to investigate array resolving abilities. It is observed that higher frequency source achieves better resolution than lower one does.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.12
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• pp.1155-1164
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• 2011

In this paper, we proposed the transmit beam measurement method of active phased array antenna, which is installed in Korea's first developed naval medium range radar, using near-field measurement facility. The pulse-mode high power characteristics of active phased array antenna's trasmit-beam make it difficult to measure with general near-field measurement facilities where low power continuous RF signals are used. Thus, in this paper, the measurement method of active phased array antenna's transmit beam in conjunction with the near-field measurement facility, which is suitable for the high-power transmit beam measurement, and PNA-X network analyzer(Agilent Technologies), which can support pulse-mode measurement, was proposed and measured by near-field measurement techniques. And the EIRP(Effective Isotropic Radiated Power), the transmit characteristic of active phased array antenna, was measured by the near field measurement techniques and compared to numerical estimation which was nearly equal with small difference of 0.1 dB.

• Journal of Applied Reliability
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• v.16 no.4
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• pp.338-346
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• 2016

Purpose: The purpose of this research is to improve the reliability of the composite material blades used for the wind power generator, by applying the phased array ultrasonic testing technique out of the many nondestructive test into the blades. Method: The wind power generation composite blades are used, as a case study, in order to evaluate the reliability of the phased array ultrasonic testing technique. Defects that are most likely occurred in the field are injected into the different locations of the three different types of artificial test pieces and then phased array ultrasonic testing technique are applied to evaluate the reliability of its effectiveness. Result: As a result of the analysis of the defect signals by applying the A scan and B scan simultaneously, depth and width of the defect could be obtained. An area of defect was proportional to the amount of energy by color in B scan image. The larger amount of energy, reflected amount of energy was appeared in the order of red, orange, yellow, blue color. Conclusion: The most reliable testing method to detect the defect in composite blades for wind power generation is considered to be the combination of the other destructive testing technique with the phased array ultrasonic testing since the PAUT alone could not detect all range of the defects in the blades.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.4 no.2
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• pp.40-45
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• 2008

There exist many types of pipe and component fatigue through vibrations, thermal fatigues or shifting. In some cases of thermal stratification/thermal fatigue, pipes & components are receiving thermal stress by means of material expansion and shrinkage by continuous thermal repetitive variation. Small cracks initially occur on the inside surface by thermal stress. These cracks grow in depth the pipe wall and finally come to a rupture. Pipe parts of susceptibility to thermal stratification and thermal fatigue are now being examined by conventional UT(ultrasonic test) as volumetric examination. It is difficult to fully satisfy the code & standards requirements because 3" weldolet weldments of RCS 16" pipe to 3" branch connection lines have complex structural shape. To solve the problems of conventional UT examination, we made a realistic mock-up and UT calibration block. We performed a simulation of phased array UT utilizing CIVA as NDE(Non-Destructive Examination) simulation software. Also we designed phased array UT transducer and wedge, optimal frequency by using simulation data. We performed phased array UT experiment through mock-up including artificial flaws(notch). The phased array UT technique is finally developed to improve the reliability of ultrasonic test at RCS 16" pipe to 3" branch connection weld.