• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.2 no.3
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• pp.32-40
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• 1991

A modified transmission line model is proposed for input impedance analysis of a square microstip antenna with single-circularly-polarized. Alog-periodic arrangement with microstrip antenna (LPMA) which consists of 3 resonant element ($3\times1$) is designed for broadband operation ranging from 11.2 GHz to 12.4 GHz, based on this pro- posed model from transmission line model. Aplanar array ($3\times4$array), in which 4sets of the above LPMA are in the same plane, is fabricated for high gain X-band satellite communication antennas. The optimum spacing between each LPMA is determined using computer simulation for the minimum bariation of far field pattern and null. This $3\times4$array has a measured values of gain greater than 8dBi, VSWR les then 2.3, and bandwidth greater than 7% respectively.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.411-414
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• 2002

The CdTe semiconductor detector has a higher detection efficiency for x-rays and $\square$amma rays and a wider energy band gap compared with Si and Ge semiconductor detectors. Therefore, the size of the detector element can be made small, and can be operated at room temperature. The interaction between a CdTe detector and incident x-rays is mainly photoelectric absorption in the photon energy range of up to 100 keV. In this energy range, Compton effects are almost negligible. We have developed a 256 channel CdTe array detector system for monochromatic x-ray CT using synchrotron radiation. The CdTe array detector system, the element size of which is 1.98 mm (h) x 1.98 mm (w) x 0.5 mm (t), was operated in photon counting mode. In order to improve the spatial resolution, we tilted the CdTe array detector against the incident parallel monochromatic x-ray beam. The experiments were performed at the BL20B2 experimental hutch in SPring-8. The energy of incident monochromatic x-rays was set at 55 keV. Phantom measurements were performed at the detector angle of 0, 30 and 45 degrees against the incident parallel monochromatic x-rays. The linear attenuation coefficients were calculated from the reconstructed CT images. By increasing the detector angle, the spatial resolutions were improved. There was no significant difference between the linear attenuation coefficients which were corrected by the detector angle. It was found that this method was useful for improving the spatial resolution in a parallel monochromatic x-ray CT system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1413-1419
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• 2015

Monopulse RADAR is the radar which detects the range of the target using a single transmitted signal. In this paper, using 9.41GHz X-band radar, the research for the phase comparison monopulse algorithm used in the marine environment is conducted. In addition, by applying the phase comparison monopulse algorithm, we calculate the RMSE for the various antenna spacings and the positions of the target. Based on that result, we compare the performance of the phase comparison monopulse algorithm in the uniform linear array with that in the non-uniform linear array. Finally, the differences in performance among the MUSIC algorithm, Bartlett method and the proposed phase comparison monopulse algorithm are analyzed.

• Journal of Educational Research in Mathematics
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• v.20 no.3
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• pp.305-322
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• 2010

The epistemological obstacles in the area learning of plane figure can be categorized into two types that is closely related to an attribute of measurement and is strongly connected with unit square. First, reasons for the obstacle related to an attribute of measurement are that 'area' is in conflict. with 'length' and the definition of 'plane figure' is not accordance with that of 'measurement'. Second, the causes of epistemological obstacles related to unit square are that unit square is not a basic unit to students and students have little understanding of the conception of the two dimensions. Thus, To overcome the obstacle related to an attribute of measurement, students must be able to distinguish between 'area' and 'length' through a variety of measurement activities. And, the definition of area needs to be redefined with the conception of measurement. Also, the textbook should make it possible to help students to induce the formula with the conception of 'array' and facilitate the application of formula in an integrated way. Meanwhile, To overcome obstacles related to unit square, authentic subject matter of real life and the various shapes of area need to be introduced in order for students to practice sufficient activities of each measure stage. Furthermore, teachers should seek for the pedagogical ways such as concrete manipulable activities to help them to grasp the continuous feature of the conception of area. Finally, it must be study on epistemological obstacles for good understanding. As present the cause and the teaching implication of epistemological obstacles through the research of epistemological obstacles, it must be solved.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.5
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• pp.504-514
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• 2014

An MMIC multi-function chip with a low DC power consumption for an X-band active phased array radar system has been designed and fabricated using a 0.5 ${\mu}m$ GaAs p-HEMT commercial process. The multi-function chip provides several functions: 6-bit phase shifting, 6-bit attenuation, transmit/receive switching, and signal amplification. The fabricated multi-function chip with a compact size of $16mm^2(4mm{\times}4mm)$ exhibits a gain of 10 dB and a P1dB of 14 dBm from 7 GHz to 11 GHz with a DC low power consumption of only 0.6 W. The RMS(Root Mean Square) errors for the 64 states of the 6-bit phase shift and attenuation were measured to $3^{\circ}$ and 0.6 dB, respectively over the frequency.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.5
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• pp.558-565
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• 2017

Accurate prediction of wave-structure interactions is important in the safety and design cost effectiveness of fixed and floating offshore structures exposed to extreme environmental conditions. In this study, regular waves and circular column structure interactions for four circular columns in regular waves are analyzed. To simulate 3D two-phase flow, open source computational fluid dynamics libraries, called OpenFOAM, were used. When the four circular columns are arranged in a square array, the interactions according to the incident slopes of the regular waves are analyzed. The wave run-up in the circular column surface was compared according to the slope of the incident wave. It was confirmed that high amplitude waves are generated between the circular columns due to the interaction between the circular column and the incident wave. It is expected that this analytical result will be used as the basic data of the study on the air gap due to the interaction between the structure and incident wave.

• Journal of Sensor Science and Technology
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• v.27 no.4
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• pp.232-236
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• 2018

A radiation detection sensor was developed and characterized by combining three types of CsI(Tl) scintillators and an array-type SiPM to detect the radioactive contamination of discharged water in real time. The characterization results showed that type 3 exhibited the most desirable characteristics in response linearity (R-square: 0.97889) according to detection sensitivity and incident radiation dose. Furthermore, in terms of spectral characteristics, type 3 exhibited 16.54% at 0.356 MeV (the emission gamma ray energy of $^{133}Ba$), 10.28% at 0.511 MeV (the emission gamma ray energy of $^{22}Na$), 9.68% at 0.356 MeV (the emission gamma ray energy of $^{137}Cs$), and 2.55% and 4.80% at 1.173 MeV and 1.332 MeV (the emission gamma ray energies of $^{60}Co$), respectively. These measurements confirmed the good energy characteristics. The results were used to evaluate the spectral characteristics and energy linearity in a mixed source using type 3 with the best detection characteristics. It was confirmed that the gamma ray peaks of $^{133}Ba$, $^{22}Na$, $^{137}Cs$, and $^{60}Co$ were well resolved. Moreover, it was confirmed that R-square, which is an indicator of energy linearity, was 0.99986. This indicates a good linearity characteristic. Based on this study, further commercialization studies will contribute to measurements in real time and to the management of the contamination caused by radioactive wastewater or radioactive material leakage, which originate from facilities that use radioactive isotopes or care facilities.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.2 s.117
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• pp.158-165
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• 2007

In this paper, the circularly polarized $4{\times}4$ array antenna is proposed for the X-band. A single antenna consists of square patch and unequal cross-aperture coupled feeding. The RHCP(Right Handed Circularly Polarization) is generated by unequal cross-aperture coupled feeding. By reducing space among elements of way antenna from 0.8 ${\lambda}_0$ to 0.45 ${\lambda}_0$, the mounting area of array antenna is miniaturized. The $2{\times}2$ array antenna is designed using sequential rotation feeding network. The good level of gain, axial ratio, and impedance bandwidth are achieved. The $4{\times}4$ array antenna is extended by ${\lambda}/4$ transformer and T-junction power divider. The simulated maximum radiation gain is 15.09 dBi at 10 GHz. The simulated 3 dB Axial Ratio bandwidth is from 9.05 to 10.4 GHz(13.5%). Also the measured impedance bandwidth($VSWR{\leq}2$) of manufactured $4{\times}4$ array antenna is from 8.45 to 11.84 GHz(33.9%). The measured maximum radiation gain is 11.10 dBi at 10 GHz. The measured 3 dB Axial Ratio bandwidth is from 9.42 to 10.47 GHz(10.5%).

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.2
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• pp.227-236
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• 2001

This paper proposes a frequency-domain partially adaptive algorithm, called a censoring algorithm, to reduce the computational complexity of the frequency domain adaptive array. The proposed censoring algorithm determines the existence of interferences in the frequency-domain at each frequency bin using a constant false alarm rate (CFAR) processor. The censoring algorithm adapts only those parts of the weights that correspond to the frequency bins expected to contain interferences. The censoring algorithm is also expanded to overcome the signal cancellation phenomenon caused by smart jammers. Accordingly, a censoring spatial smoothing, which combines the censoring algorithm with spatial smoothing, is proposed. Simulation results show that the proposed algorithms are effective in removing interferences with only part of the computational complexity of conventional algorithms yet with the same level of performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.7
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• pp.1282-1290
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• 2000

The LHCP circularly polarized antenna operating at the satellite broadcast receiving band is developed by employing the sequential-rotation technique in which each truncated-corner patch square element is arranged in the triangular lattice type. Antenna designed with sequentially rotated technique of triangular lattice type has the effect of improved axial-ratio bandwidth, cross-polarization etc., and the degradation of radiation pattern can be reduced significantly by minimizing the radiation loss of feeding line structure. Characteristics of antenna designed is satisfied with specifications of array antenna for DBS that is -27 dB of side lobe level and -20 dB of cross-polarized level at $\Phi$=45$^{\circ}$ plane.