• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.943-953
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• 2007

In this paper, we propose a Cassegrain antenna with a scalar feed horn opt rating in Ka-band. For an effective EM simulation of the Cassegrain antenna, the near-field of the feed hone is used ai the equivalent source of the Cassegrain antenna using the surface equivalent theorem. A corrugated circular horn operating with $HE_{11}$ mode is used as the feed horn. The angle and feed center of the main and sub reflectors are optimized to achieve maximum antenna efficiency. The designed feed horn shows the gain of 19dBi, the side-lobe level of less than -25dB and the half power beam width of $20^{\circ}$ at 33 GHz. The Cassegrain antenna shows the gain of 41dBi, the efficiency of 60%, the side-lobe level of less than -20dB and the half power beam width of $1.2^{\circ}$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.5
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• pp.502-507
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• 2013

In this paper, a circular dual mode horn with modified aperture is proposed to improve a E/H-plane radiation pattern symmetry of a conventional oversized circular dual mode horn. The proposed antenna consists of a feeding section, a mode generation section and a phase matching section which has aperture shape transition from circle to ellipse or rectangle to improve a E/H-plane radiation pattern symmetry. To compare the performances between the proposed antenna and the convenional circular dual mode horn, the conventional circular dual mode horn and the proposed circular dual mode horn with rectangular aperture are fabricated and researched at 15 GHz. The measured results show that the conventional circular dual mode horn has 3.394 dB difference while the proposed antenna has only 0.539 dB difference between E and H-plane radiation patterns within the -11 dB beamwidth($53^{\circ}$) which is required beamwidth of the feed horn for the maximum aperture efficiency where f/d ratio of reflector antenna is 1.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.10
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• pp.1096-1103
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• 2008

This paper proposes an individual order predistortion linearizer using intermodulation distortion(IMD) generator for cancellation the third and the fifth IMD of power amplifier. The IMD generator for controlling the third and the fifth IMD consist of common Emitter amplifier and Schottky diode. These signals are generated by series feedback of Schottky diode to obtain the inverse AM/AM and AM/PM characteristics of power amplifier. The individual order predistorters are consisted of individual IMD generator, power splitter and combiner. The test results show that the third and the fifth IMD can be improved by a maximum 13.5 dB and 0.9 dB in case of CW 2-tone signals. Also, the Adjacent Channel Leakage Ratio(ACLR) can be improved 2.3 dB, 2.5 dB at ${\pm}0.885$ MHz, ${\pm}1.23$ MHz offset frequency for CD-MA IS-95 2FA signals.

• Industry Promotion Research
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• v.8 no.1
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• pp.119-134
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• 2023

An Analysis of the Choice of Wedding Time Based on the Gimundungap Theory. The purpose of this study is to research the utility and validity of wedding time selection based on the principles of Ungokgimun, a recent development of Gimundungap theory. Unlike the conventional way of choosing from common auspicious hours and days deemed available for important ceremonial occasions, Ungokgimun determines the propitious heavenly wedding time catered for a particular couple based on the birth table consisting of the four pillars of the bride- and groom-to-be. Using the Hong Guk-soo numbers which are drawn from the basic principles of oriental philosophy, it utilizes a deductive approach to wedding time choice, which is considered decisive and logical. Wedding time selection for a bride and a bridegroom is determined by auspicious combinations of matching and supporting HongGuk-soo numbers. Some relevant determining factors for the time choice are three number combination of samhap, two number combination of half-hap, latitudinal combination of yuk-hap, support and control relationships between related elements, two number punishment of hyung-sal, and three number punishment of samhyung-sal, etc. The specific auspicious palace of the spouse-to-be's luck is selected on the basis of supporting or brotherly combination of numbers which are manifested on the baseline earthly plate of the bride- and groom-to-be. This is followed by the selection of the ten-year luck, and year and month luck, and finally by the selection of auspicious day and hours. The validity of this study was verified through theoretical consideration of the Ungokgimun and practical analysis of a variety of marriage cases. It was found that the way of wedding time selection using Ungok Gimundungap was relatively more effective than other conventional methods.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.5 s.108
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• pp.476-482
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• 2006

In this paper, a multimode feed horn antenna is suggested for a high power microwave(HPM) antenna system. The proposed HPM feed horn antenna which is connected with a mode converter is located between source and reflector antenna. A multimode feed horn antenna which has reduced -25 dB beamwidth is designed and fabricated for miniaturization of reflector antenna because -25 dB beamwidth which is determined by considering spillover of feed horn antenna decides a size of reflector in case of HPM. As a result, feed system which uses the multimode feed horn antenna has high gain about 27 dBi and return loss is less than -22 dB at 10 GHz. The measured -25 dB beamwidths of the radiation pattern at vertical, horizontal-plane equal to $20.24^{\circ},\;28.92^{\circ}$ which is less than about $10^{\circ}$ beamwidth of conventional feed system. Thus the suggested feed hem antenna is suitable to feed horn for miniaturization of HPM antenna system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.1-7
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• 2016

In this paper, the design methodology of a corrugated conical horn antenna is proposed to be obtain wide-band properties over the full range of frequencies in the Ku-band. In order to improve the properties of the corrugated conical horn antenna, such as its gain, VSWR, co-polarization to cross-polarization ratio and wide-bandwidth, two types of mode matching converters are implemented within it. One is located at the end of the circular waveguide, while the other is positioned in front of the horn-flare section. The properties of the antenna are analyzed and compared according to the position of the proposed converters through simulations. In the comparison of the antenna performance in the case where the VSWR, co-polarization to cross-polarization ratio and antenna gain over the Ku band of 12-18 GHz are less than 2, greater than 30dB and 20dB respectively, the former antenna exhibits greater stability and a wider frequency band than the latter from the viewpoint of transmitting and receiving signals simultaneously. Therefore, considering the gain, VSWR, radiation pattern and bandwidth, the horn antenna structure in which the mode matching converter is implemented inside the circular waveguide has better performance than the other.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.14 no.2
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• pp.72-78
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• 1981

The purpose of this study is to find directivity characteristics and relative gain of directivity of the wedge horn in conjunction with a projector with varing horn length, horn angle and frequency. The horns are constructed with aluminum plate covered with styrofoam. By using hinges the horn angle could be varied with wide range. Measurements were made over the frequency range of 25 KHz-100 KHz by varing the horn lengths from 5cm to 21cm and the horn angles up to 90 degrees. The followings were the results obtained from the study, 1. As the horn angle increased, the beam width for tile major lobe initially decreased and then increased. At 80 KHz with horn length 21cm the minimum beam widths were obtained with 16 degrees in horizontal plane and 36 degrees in vertical plane. 2. The maximum relative gains of directivity were 4.4 dB in horizontal plane and 3.4 dB in vertical plane when the horn length was 21cm. 3. Beam width was decreased with increasing of frequency. 4. When the mouth apertures were small the major lobes obtained by the experiment agreed with the computed ones, and when the mouth apertures were wide the major lobes by the observed were wide than the computed ones.

• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.970-976
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• 2002

In this paper, the slump flow of the concrete, suspension, pH, corrosion effect, bleeding and the characteristics of coompressive strength were analyzed using antiwashout underwater admixture and antiwashout underwater agent+corrosion inhibitor mixed admixtures(1type). The results showed that there were no rare difference in physical properties but in the results of rapid corrosion tests there were lots of corrosion inhibitor ratio differences between concrete using only antiwashout underwater admixture and the corrosion inhibitor mixed(1type). In the case of only antiwashout underwater admixture 5.4%, the case corrosion inhibitor mixed(1type) 0.07%, the Antiseawater of the concrete which uses the Corrosion Inibitor Mixed(1type) appeared highly.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.5
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• pp.389-392
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• 2018

Herein, a horn antenna that has the maximum back lobe reduction characteristic using a corrugated structure at 1.57 GHz for a high-power microwave system is proposed. The back-lobe characteristics of the proposed antenna was optimized using simulation as the number of corrugated structures increase, and the three-staged corrugated structure was designed. Consequently, the front-to-back ratio(FBR) of the fabricated antenna is 47.2 dB, which is improved by 23.7 dB based on that of the basic horn antenna, i.e., 23.47 dB.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.2
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• pp.118-126
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• 2011

The characteristics of the responses obtained in thermosonic tests are investigated in this study to improve the performance of a thermosonic test system. Thermosonic tests are conducted with an acoustic horn with high power capability to investigate the characteristics of the vibration produced in turbine blades with complex geometry. The influences of the excitation signal that is input to the horn and the coupling methods between a clamp and the acoustic horn on the characteristics of the vibration excited in a component are presented. As a result, an excitation method with a fast narrow band chirp test (sweep test) and a stud coupling is proposed as an excitation method for thermosonic testing. This method can be applied to different types of turbine blades and also to other components.