• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.2
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• pp.192-198
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• 1992

The electrical properties of the ultrasonic probes and the piezoelectric composite materials with 1-3 connectivity by the extrusion method have been studied. The relative permittivity and piezoelectric coefficient increase linearly as PZT volume% increases and resonance frequency moves to low frequency as the sample thickness increases. The acoustic impedance matching with body and water is better than PZT ceramics' and the reception sensitivity is fine as the thickness thins down.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.195-198
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• 1999

Complex resonant frequency of on a uniaxial substrate with a superstrate-loaded microstrip structure is investigate. The study is performed by Galerkin’s method. The numerical convergence using sinusoidal basis function. Numerical results for the effects of anisotropy in the substrate, superstrate permittivity, in the complex resonant frequency of the rectangular microstrip structure are also presented. Half-power bandwidth are increased due to the positive uniaxial an isotropy and superstrate.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.3
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• pp.252-261
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• 1988

Employed the new invese scattering scheme based on the moment mehtod, which was presented in the Part I of these companion papers, numerical simulations are performed to investigate the effect of measurement errors and noise contaminating the field scattered from dielectric objects. In order to reduce those effects on the reconstructed permittivity profiles, some techniques such as regularization, iterative matrix inversion, and multiple incidence are applied to this problem.

• Journal of Electrical Engineering and information Science
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• v.2 no.5
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• pp.40-44
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• 1997

This paper presents the results of studies made for measuring the relative complex permittivity of PCB sheet material in he frequency a range of 100MHz∼1GHz using vector network analyzer. A measurement cell was developed for this purpose using broad-band impedance method and the dielectric constant and loss tangent of two PCBV sheet materials, glass-epoxy and teflon, were measured. The effect of copper cladding was studied.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.1
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• pp.16-22
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• 2003

This paper presents an application of an impedance boundary condition to 3D vector finite element analysis of a multi-port cylidrical microwave cavity using Snell's law. Computing memory benefits and computing time reduction are obtained from this method compared with the conventional finite element method(FEM). To verify the method, a high permittivity scatterer in free space is analyzed and compared with the results of conventional (FEM). In addition, this method has been analyzed several types of cavities, including water load, to demonstrate the validity and accuracy of the program.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.6
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• pp.334-338
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• 2006

The finite volume time domain(FVTD) method gives accurate results for the calculation of electromagnetic wave propagation but it should be noted that the number of sampling points per wavelength should be increased when more accurate numerical results are required. Moreover it requires large amount of computer memory resources. In this paper we propose a modified FVTD that employs a time subdivision. The local time-subdivided FVTD(FVTD-LTS) method is enough to divide the space domain grid with a large step size. This method can reduce computation time and memory resources. To validate the proposed method, sever numerical examples are presented. We have then shown that the proposed method yields a reasonable solution.

• KIEE International Transactions on Electrophysics and Applications
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• v.2C no.5
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• pp.268-272
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• 2002

In this paper, we proposed a procedure to analyze a shielded-microstrip step discontinuity using the mode matching method (MMM) combined with the vector finite element method (VFEM), which is used to find the equivalent waveguide-model for a microstrip. In order to calculate the effective-widths and -dielectric permittivity of the equivalent waveguide-model corresponding shielded-microstrip, the propagation constant and characteristic impedance are calculated from the VFEM. MMM is then applied to find the scattering parameter in the planar waveguide. This technique makes it possible to take advantage of the high accuracy of the VFEM as well as the high efficiency of the MMM.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.7
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• pp.22-27
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• 2001

In this paper, the complex permittivity of various dielectrics such as powder(sugar and flour) and solid(teflon and acrvl) are measured by using an open ended coaxial-line probe, which is self designed and manufactured, The probe is connected to a vector network analyzer(VNA) through a coaxial cable, The end of the cable is corrected by using an OSL(open, short, and load) calibration kit, The phase difference, which is produced by inserting the probe at the end of the line. is compensated by using the numerically calculated reflection coefficient of distilled water, The complex permittivity is reconstructed by inserting the measured reflection coefficient, which is produced at the interface between the probe and measuring material, into ,an virtual conical cable conversion model. Over a wide frequency range from 30 MHz to 3 GHz, the measured complex permittivitis of various powder and solid using the our method are compared with the results, which are measured by using an transmission-line method of the Korea Research Institute of Standards and Science(KRISS).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.1
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• pp.42-48
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• 2017

Characteristics of ground-penetrating radar(GPR) signals for detecting buried pipes are investigated numerically. Transmitting and receiving parts of a GPR system, a subsurface soil and a plastic pipe filled with a dielectric material are modeled by using the finite-difference time-domain(FDTD) method. FDTD simulations for observing aspects of GPR signals are performed as a function of the diameter of the pipe and the permittivity of the filling material in the pipe. GPR signals scattered by a dielectric filled pipe appear as a superposition of two waves, such as the specular wave from the front convex surface of the pipe and the axial wave from the rear concave surface of the pipe. We show that the amplitude, the polarity, the delay time of two waves depend on the size of the pipe and the permittivity of the filling material in the pipe.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.1
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• pp.161-167
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• 2014

This paper presents the results of permittivities of various materials by measurements of the dielectric properties for the materials in millimeter-wave band. Since the advantages of millimeter wave band include the miniaturization, weight reduction of component and a lot of information transfer, its study has received increasing attention of researches. Also, because of the characteristics of the band have the superior straightness and the small diffractive, in the band, the analysis for the reflection and transmission characteristics of the materials will be very important. Moreover, a low interference is one of characteristics of the band due to the fact that the millimeter wave is absorbed in the materials. Therefore, in this paper, the reflection and transmission characteristics of materials are measured in the band by using the free space method. Based on the presented result, the permittivities of the materials are derived by the calculation of Nicolson-Ross Weir method.