• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.18 no.3 s.118
• /
• pp.305-314
• /
• 2007

In this paper, we suggested a CPW-fed UWB antenna with uni-planar sectoral structure. The area where radiation device face ground is designed to have the shape of tapered slot based on exponential function. We modified a rectangular bow-tie dipole structure antenna and thus formed a multi-resonant mode. From this, we expanded the impedance bandwidth and made a feature satisfying VSWR of less than 2 between $3.1\sim10.6GHz$. The test result showed that the return loss less than -10 dB was met in the full-band UWB system and maximum gain of $0.9\sim3.1dB$ was made with the half-power beamwidth of $40.1\sim89.9^{\circ}$ on XY plane(Theta, $Phi=90^{\circ}$) and the full band. By using CPW-fed structure with no ground on the back of the substrate, the suggested antenna is easy to design and its miniaturization is also possible.

• The Journal of the Acoustical Society of Korea
• /
• v.33 no.3
• /
• pp.163-173
• /
• 2014

Sound propagation algorithm for a sonar simulator is required to run in real-time and should be able to model the range and depth dependence of the Korean ocean environments. Ray model satisfies these requirements and we developed an algorithm for range-dependent ocean environments. In this algorithm, we considered depth-dependence of sound speed through rays based on a rectangular cell method and layer method. Range-dependence of sound speed was implemented based on a split-step method in the range direction. Eigen-ray is calculated through an interpolation of ray bundles and Gaussian interpolation function was used. The received time signal of sonar was simulated by Fourier transform of eigen-ray solution in the frequency domain. Finally, for the verification of proposed algorithm, we compared the results of transmission loss with other validated models such as BELLHOP, SNUPE, KRAKEN and OASES, for the Pekeris waveguide, wedge, and deep ocean environments. As a result, we obtained satisfactory agreements among them.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.9 no.3
• /
• pp.296-304
• /
• 1998

A design method of an electromagnetic wave absorber with ferrite fins in the second layer, which has very wide band frequency characteristics and is used for single-polarized wave absorption such as TV wave etc, has been designed. To examine the effectiveness of the Equivalent Material Constants Method$(EMCM)^{[1]}$ which is approximate method, the effective complex permittivity calculated by the Hashin-Strikman formulas and the EMCM are compared. Since, furthermore, the reflectivities by the EMCM in space and the FDTD method in an rectangular waveguide agreed well each other, it has been confirmed that the proposed electromagnetic wave absorber has excellent absorption characteristics in the frequency range of 30 MHz to 5830 MHz. Thus, it can be concluded that the EMCM is usefull to design and analyze the electro-magnetic wave absorber proposed here.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.6 no.3
• /
• pp.80-90
• /
• 1995

The scattering parameters of a microstrip single line, a right-angle bend and a coupled line are calculated using the multiport network model for the frequency range from 1 to 18 GHz. The single line is analyzed using the planar waveguide model. The right-angle bend is broken into two rectangular segments, and each segment is analyzed in a similar fashion as the single line. Impedance matrices corresponding to the two segments are combined by the segmentation method. In the analysis of elec- tromagnetic coupling of the coupled line, a new method is employed resulting in much less computation time than those previous methods involving Green's functions. A good agreement between the numerical results for the three structures and those from SuperCompact reveals the usefulness of the multiport network medel in analyzing complicated mirostrip single and coupled line discontinuities.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.19 no.3
• /
• pp.173-179
• /
• 1999

The defects on the metal surface. such as the ended circular pressed hole. the penetrated circular drilled hole, and the linear hollow lanes have been investigated by means of the microwave. In this experiment, frequency was set at 9.2GHz with 3kHz modulation, and the methods of reflection, transmission, fixed carrier frequency, and mod-demodulated technique have been used for investigating defects. The magnitudes of the microwave signals have been changed at the ended circular pressed hole and the penetrated circular drilled hole. The defect sizes that were estimated from the reflected microwave signals had the dimensions enlarged by twice the original size of the penetrated circular drilled hole and 2.5 times the original size of the ended circular pressed hole. The magnitudes of the reflected microwave signals from the linear hollow lane have increased with expansion of the width of the notch. In the linear hollow lane with the depth of 2.4mm, the reflected microwave signals versus the defect widths had a maximum value at the defect width of 50mm, and in the linear hollow lanes with the depths of 1.2mm and 0.45mm, the reflected microwave signals versus the defects widths had the maximum values each at the defect depths of 55mm.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.7
• /
• pp.3140-3145
• /
• 2012

In this paper, a design method for a compact slot antenna fed by a coplanar waveguide (CPW) is studied. A T-shaped tuning stub is inserted inside a narrow rectangular slot and the slot is impedance matched to the CPW feedline by adjusting the width, length, and position of the stub. The resonance frequency is adjustable by the slot length and the antenna size can be reduced by bending the slot. The resonance frequency and impedance matching property of the compact slot antenna are similar to those of the half-wavelength slot antenna, which enables one to design compact antenna of this type with ease. A compact slot antenna for 2.45-GHz ISM band is designed, fabricated on an FR4 substrate (dielectric constant of 4.4 and thickness of 0.8 mm), and experimentally tested. The measured results agree well with the simulations, which confirms the validity of this study. The fabricated compact slot antenna shows an impedance bandwidth of 200 MHz(2.32-2.52 GHz) for a VSWR < 2, which is suitable for 2.45-GHz ISM band (2.4-2.48 GHz). The measured radiation patterns show ${\infty}$-shaped directional pattern in the E-plane and nearly omni-directional pattern in the H-plane with a peak gain of 2.0 dBi, which are similar to those of a monopole antenna. The proposed antenna is expected to be suitable for the applications as antennas for WLAN, RFID, and mobile handset.

• Journal of the Korean Magnetics Society
• /
• v.19 no.6
• /
• pp.203-208
• /
• 2009

Magnetic and Ka-band absorbing properties have been investigated in Ti-Co substituted M-type barium hexaferrites with $BaTi_{0.5}Co_{0.5}Fe_{11}O_{19}$ composition. The ferrite powders were prepared by conventional ceramic processing technique and used as absorbent fillers in ferrite-rubber composites. The magnetic properties were measured by vibrating sample magnetometer. The complex permeability and dielectric constant were measured by using the WR-28 rectangular waveguide and network analyzer in the frequency range 26.5~40 GHz. For the Ti-Co substituted M-hexaferrites, the ferromagnetic resonance is observed at Ka-band (29.4 GHz). The matching frequency and matching thickness are determined by using the solution map of impedance matching. A wide band microwave absorbance is predicted with controlled ferrite volume fraction and absorber thickness.