• The Journal of the Acoustical Society of Korea
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• v.29 no.7
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• pp.431-438
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• 2010

The radiation pattern of conformal transducers installed on a curved surface is likely to be complicated depending on the array pattern on the curved surface. In this research, the acoustic sources constituting a conformal transducer are arrayed in equi-angle, equi-interval, and geodesic dome forms, and the radiation pattern function of each of the array geometries has been derived, and therewith the radiation pattern has been analyzed for each array geometry. Based on the analysis result, we have determined the equi-interval array geometry that provides the widest beam width with the lowest side lobe level among the three array geometries. Results of the present work are expected to be utilized to the design of conformal transducer structures.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.3
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• pp.196-213
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• 2001

A split beam ultrasonic transducer operating at a frequency of 70 kHz to use in the fish sizing echo sounder was developed and the acoustic radiation characteristics were experimentally analyzed. The amplitude shading method utilizing the properties of the Chebyshev polynomials was used to obtain side lobe levels below -20 dB and to optimize the relationship between main beam width and side lobe level of the transducer, and the amplitude shading coefficient to each of the elements was achieved by changing the amplitude contribution of elements with 4 weighting transformers embodied in the planar array transducer assembly. The planar array split beam transducer assembly was composed of 36 piezoelectric ceramics (NEPEC N-21, Tokin) of rod type of 10 mm in diameter and 18.7 mm in length of 70 kHz arranged in the rectangular configuration, and the 4 electrical inputs were supplied to the beamformer. A series of impedance measurements were conducted to check the uniformity of the individual quadrants, and also in the configurations of reception and transmission, resonant frequency, and the transmitting and receiving characteristics were measured in the water tank and analyzed, respectively. The results obtained are summarized as follows : 1. Average resonant and antiresonant frequencies of electrical impedance for four quadrants of the split beam transducer in water were 69.8 kHz and 83.0 kHz, respectively. Average electrical impedance for each individual transducer quadrant was 49.2$\Omega$ at resonant frequency and 704.7$\Omega$ at antiresonant frequency. 2. The resonance peak in the transmitting voltage response (TVR) for four quadrants of the split beam transducer was observed all at 70.0 kHz and the value of TVR was all about 165.5 dB re 1 $\mu$Pa/V at 1 m at 70.0 kHz with bandwidth of 10.0 kHz between -3 dB down points. The resonance peak in the receiving sensitivity (SRT) for four combined quadrants (quad LU+LL, quad RU+RL, quad LU+RU, quad LL+RL) of the split beam transducer was observed all at 75.0 kHz and the value of SRT was all about -177.7 dB re 1 V/$\mu$Pa at 75.0 kHz with bandwidth of 10.0 kHz between -3 dB down points. The sum beam transmitting voltage response and receiving senstivity was 175.0 dB re 1$\mu$Pa/V at 1 m at 75.0 kHz with bandwidth of 10.0 kHz, respectively. 3. The sum beam of split beam transducer was approximately circular with a half beam angle of $9.0^\circ$ at -3 dB points all in both axis of the horizontal plane and the vertical plane. The first measured side lobe levels for the sum beam of split beam transducer were -19.7 dB at $22^\circ$ and -19.4 dB at $-26^\circ$ in the horizontal plane, respectively and -20.1 dB at $22^\circ$ and -22.0 dB at $-26^\circ$ in the vertical plane, respectively. 4. The developed split beam transducer was tested to estimate the angular position of the target in the beam through split beam phase measurements, and the beam pattern loss for target strength corrections was measured and analyzed.

• Journal of Oral Medicine and Pain
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• v.24 no.2
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• pp.171-179
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• 1999

The authors experienced a oral carcinoma involving the medial cortex of the right ramus of mandible and the left side of the maxilla which was metastasized from primary rectal adenocarcinoma based on the comprehensive evaluation of data obtained from (1) the past medical history of primary rectal adenocarcinoma, (2) the computerized tomographic views of the homogeneous mass on the anteromedial region of the right ramus of mandible destructing the medial cortex of the right ramus of mandible, and the irregular mass around the clivus spreading into the sphenoid sinus and destructing the left side of the maxilla ; the bone scanning of hot spots on the nasal region and the left side of maxilla ; the posteroanterior chest radiographic view of multiple nodular radiopacities on the lung, (3) the retrospective review of the sonographic view of a hypoechoic, well-demarcated, target-like mass with central hyperechoic focus on right lobe of liver in a Korean female of 49-year-old who complained the ptosis of left eyelid, the swelling on left zygomatic area, the left facial paralysis, the facial asymmetry and a round-shaped, elevated lesion with a hematoma on the mucosa covering the right ramus of mandible.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.21 no.6
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• pp.241-249
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• 2022

This paper discusses the design of a ground clutter prevention fence for a radar wind profiler (RWP). The design point of the clutter fence is to improve the quality of the received signal by removing the non-weather clutter coming from the side. In this paper, a clutter prevention fence composed of a metallash mesh around the RWP is proposed, and the phase center of the antenna, the length, and height of the down fence, and the height and slop of the top fence through M&S are designed. The designed ground clutter prevention fence and 256 active phase array antennas were used as basic data. The effectiveness of the design was confirmed by a simulation. The side lobe in the ±90° direction was reduced by more than 30dB depending on the presence or absence of the designed ground clutter prevention fence. The fence was manufactured by 3D modeling, and the clutter shielding performance of approximately 20dB or more on the side of the antenna (±90°) was confirmed by applying it to the currently operated RWP.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.7
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• pp.1369-1375
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• 2016

In this paper, we present a depth extraction method of integral imaging using correlation between elemental images with phase only filter. Integral imaging is a passive three-dimensional (3D) imaging system records ray information of 3D objects through lenslet array by 2D image sensor, and displays 3D images by using the similar lenslet array. 2D images by lenslet array have different perspectives. These images are referred to as elemental images. Since the correlation can be calculated between elemental images, the depth information of 3D objects can be extracted. To obtain high correaltion between elemental images effectively, in this paper, we use phase only filter. Using this high correlation, the corresponding pixels between elemental images can be found so that depth information can be extracted by computational reconstruction technique. In this paper, to prove our method, we carry out optical experiment and calculate Peak Sidelobe Ratio (PSR) as a correlation metric.

• Tuberculosis and Respiratory Diseases
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• v.58 no.2
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• pp.179-184
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• 2005

Epithelioid hemangioendothelioma (EH) is a rare borderline malignant tumor which originating from vascular endothelial cells and occurs in many organs such as soft tissues, lung, liver and bone. But, pulmonary EH which simultaneously involves pleura and liver is very rare. In the present report, we describe an uncommon case of EH involving the lung, pleura and liver in a 26-year-old woman. Chest CT showed single nodule in right upper lobe with large amount of pleural effusion at ipsilateral side and abdominal CT multiple round low densities in liver. The EH was confirmed by microscopic analysis and immunohistochemical staining of CD34+ from open lung biopsy specimen.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.2 no.4
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• pp.5-16
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• 2003

We have analyzed the performance of optical matched filters in the fiber-optic code division multiple access (FO-CDMA) system based on optical parallel coupler access encoder (PCAE) and parallel coupler access decoder (PCAD) by experiment. In previous studies, the performance evaluation of the FO-CDMA system using SCAE and SCAD was not sufficiently accurate because they analyzed system performance only considering the first order signals. Since optical SCAE and SCAD intrinsically have high order signals of various patterns as the number of coupler increases, they change auto- and cross-correlation intensities. Thus, it is necessary to investigate properties of the PCAE and PCAD so that we may analyze the exact performance of system. In this paper, it is found that the peak to sidelobe ratio using the PCAE and PCAD increases as $\alpha$ (coupling coefficient) value increases. Also, we found that the proposed PCAE and PCAD are superior to SCAE and SCAD in performance improvement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.3
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• pp.261-268
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• 2016

In this paper, dual-polarized monopulse cassegrain antenna for W-band millimeter-wave seeker was proposed and the performances were verified by the measured results of the fabricated antenna. Dual-polarized monopulse Cassegrain antenna consists of main/subreflector, dual-polarized feed horn and monopulse comparator. The proposed feed horn has $2{\times}2$ array square waveguide feeding structure to make monopulse signals and it was designed using 90 degree rotational symmetric structure to receive dual-polarized signals. At the sum and difference channel, the measured vertical and horizontal polarization radiation pattern were similar. Measurement gains are 35.1 dBi for v-pol. and 35.6 dBi for h-pol. at the center frequency with 0.5dBi difference between each polarization and the side lobe level is below -21.6 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.7
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• pp.571-575
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• 2017

This paper presents a C-band bi-directional T/R chipset in $0.13{\mu}m$ TSMC CMOS technology for phased array antenna. The T/R chipset, which is a key component of phased array antenna, consists of a 6 bit phase shifter, a 6 bit step attenuator, and three bi-directional gain amplifiers. The phase shifter is controlled up to $354^{\circ}$ with $5.625^{\circ}$ phase step for precise beam steering. The step attenuator is also controlled up to 31.5 dB with 0.5 dB attenuation step for the side lobe level rejection. The LDO(Low Drop Output) regulator for stable 1.2 V DC power and the SPI(Serial Peripheral Interface) for digital control are integrated in the chipset. The chip size is $2.5{\times}1.5mm^2$ including pads.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.6
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• pp.1031-1036
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• 2019

This study describes the technique of the beam pattern measurement of array antenna for VHF band radar using drone and active beam pattern measuring device. There is no anechoic chamber for measuring the beam pattern of a large size antenna in the country. In this study, to test the antenna beam pattern characteristics of the developed VHF band radar, the antenna beam pattern characteristics were tested by Drone mounting an Active Beam Pattern Measuring Device. By comparing the results of the pre-simulation analysis with the measured results for the antenna, we could confirm that the beamwidth and side-lobe characteristics are satisfactory. Through the antenna beam pattern measurement technology using Drone and Active Beam Pattern Measuring Device, the beam pattern measurement technology of array antenna of low frequency band and large antenna for low band radar will be used.