• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.184-185
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• 2003

Unlike the conventional waveguide such as optical fiber using total internal reflection, photonic crystal waveguide(PCW), a waveguide made of a line defect in a photonic crystal(PC) structure, does not admit an analytic approach due to its complexity but requires a direct numerical approach. Here, we present numerical results of computer simulation for PCW by using the three-dimensional(3D) Finite-Difference Time -Domain(FDTD) algorithm. (omitted)

• Journal of the Korean Ceramic Society
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• v.31 no.1
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• pp.11-16
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• 1994

The impedance matching solution map is not a sufficient method for designing the broad-band absorber because of its difficulty to get numerical data about practical band-width. Therefore, we develope a new method to design the broad-band absorber. The complex permeability limits, which is necessary for designing the broad-band absorber in C-X band (4 GHz~12.4 GHz) were investigated and application was also examined. The complex permeability limits represent the frequency dependence of the complex permeability at a practical frequency band. These complex permeability limits can be used effectively to design broad-band single-layered absorber because they offer numerical data about the band-width in the case of various dielectric loss tangent, practical frequency bands and permitted reflection losses of an absorber.

• Bulletin of the Korean Chemical Society
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• v.25 no.9
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• pp.1403-1407
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• 2004

Dielectric relaxation measurements on 3-nitrotoluene (3-NT) mixture of dimethylacetamide (DMA), dimethylformamide (DMF) and dimethysulphoxide (DMSO) have been carried out across the entire concentration range using Time domain reflectometry technique at 15, 25, 35 and $45^{\circ}C$ over the frequency range from 10 MHz to 20 GHz. For all the mixtures, only one dielectric loss peak was observed in this frequency range and the relaxation in these mixtures can be well described by a single relaxation time using Debye model. Bilinear calibration method is used to obtain complex permittivity ${\varepsilon}^{*}({\omega})$ from complex reflection coefficient ${\rho}^{*}({\omega})$ over frequency range 10 MHz to 20 GHz. The excess permittivity, excess inverse relaxation time, Kirkwood correlation factor, molar energy of activation are also calculated for these mixtures to study the solute-solvent interaction.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.12 no.1
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• pp.27-34
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• 1999

We investigated the effect of mechanical back side damage in viewpoint of electrical and surface morphological characteristics in Czochralski silicon wafer. The intensity of mechanical damage was evaluated by minority carrier recombination lifetime by laser excitation/microwave reflection photoconductance decay technique, atomic force microscope, optical microscope, wet oxidation/preferential etching methods. The data indicate that the higher the mechanical damage degree, the lower the minority carrier lifetime, and surface roughness, damage depth and density of oxidation induced stacking fault increased proportionally.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05a
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• pp.45-49
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• 2002

In this paper, we have studied about electromagnetic wave absorbing properties of ferrite-rubber composite with a variation of ferrite. Amounts of ferrite in a composite absorber were changed from 52 wt.% to 62 wt.%. As a result, it has been shown that the electromagnetic wave absorbing properties of ferrite-rubber composite are related to the amount of ferrite in composite absorber. As a summary, it could be controled the electromagnetic wave absorbing property of ferrite-rubber composite by changing some kinds of annex A and amount of ferrite.

• Journal of information and communication convergence engineering
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• v.16 no.4
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• pp.203-212
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• 2018

In this article, a novel design of patch antenna with wide band characteristics is presented. The proposed antenna is having electrical dimensions of $0.14{\lambda}{\times}0.11{\lambda}$ (at lower initial frequency) and footprints of $150mm^2$. Structural parameters optimization shows 3.1-23.5 GHz frequency range for a (reflection coefficient) $S_{11}{\leq}-10dB$ and simulated gain 6.8 dB is obtained. An equivalent circuit model is proposed to get an insight view of antenna. Advanced Systems Design (ADS) simulation results are obtain which confirm the validity of proposed model. Degenerated foster canonical form has been used to explain the reactance and capacitive behavior idea of simulated proposed antenna's input impedance later on an equivalent circuit model and smith chart is also suggested. HFSS and CST have been used to analyze antenna behavior. The proposed antenna can be further used for microwave image detection applications.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.3
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• pp.408-412
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• 1987

The designing method of the reflection and the loaded-line phase shifter is presented. Its phase shift is variable with changing of the stub parameters. In this paper, we design the 2-bit phase shifter which have 10\ulcornerand 90\ulcornerbit phase shift and analysi its characteristics. The experiments show 2d B max.insertion loss, 2.0max. input VSWR and 6\ulcornerphase error on 2.9-3.1GHz frequency range. They agree well with the theoretical results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.8
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• pp.1169-1175
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• 1993

Plasma spraying method was used to fabricated the microwave absorbing ferrite-silicon carbide on the aluminum-alloy of the fuselage of an aircraft to protect it from RADAR detection. In this paper 15[rm] instead of 34[rm], the mean size of SIC-powder for ferrite-silicon carbide surface films(I) was used. 50(Kg/h) Instead of 70(Kg/h), the powder feed and 100[mm] Instead of 80(mm), spray distance of spray parameters was used. This M/W absorbers were designed experimentally and fabricated trially, as a result of which the relative frequency bandwidth of 2.8% were obtained under the tolerance limits of the reflection coefficients lower than-10[dB], and the maximum absorption thickness becomes 0.5[mm], which is much thinner than that of the conventional ones.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.10 s.101
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• pp.989-994
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• 2005

A MMIC(Monolithic Microwave Integrated Circuit) switch chip using InGaAs/GaAs p-HEMT process has been designed for MSM(Microwave Switch Matrix) of satellite communication system. An absorptive type MMIC switch is adopted for good reflection coefficients performances of input and output ports at both on and off states. And, a quarter wavelength impedance transformer is realized with lumped elements of MIM capacitor and spiral inductor for 3 GHz band to reduce the chip size. This MMIC switch covers the frequency range of $3.2\~3.6\;GHz$. According to the on-wafer measurement, the fabricated MMIC switch with miniature size of $1.6\;mm{\times}1.3\;mm$ demonstrates insertion loss below 2 dB and isolation above 56.8 dB, and the performance coincides with simulation results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1621-1628
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• 2003

Packaging structures to block the propagation of higher­order modes in the shielded microstrip lines are designed. Packaging for microwave circuits is necessary, basically, to isolate and protect circuits from outside environments both physically and electrically. The drawback of packaging is the possibility of higher­order mode propagation, similar to waveguide modes, as the operating frequency increases. One of Possible choices for the higher­order mode suppression is to insert diaphragms to the housing structure. The shielding effects of diaphragms are analyzed using an FEM code. Several parameters such as dispersion, mode conversion, and higher­order mode transmission and reflection are analyzed. The effect of higher­order mode suppression is eminent as the depth or width of a diaphragm is increased in the air region of the microstrip line. It is shown that inductive diaphragm structure can lower ${S_21}$ for the second­order mode incidence by 30㏈, comparing with the conventional capacitive diaphragm structure. Packaging structure analyzed in this paper can be applied usefully to the design of the microwave system in a package such as transmit/receive modules.