• Journal of Advanced Navigation Technology
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• 제18권4호
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• pp.371-375
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• 2014

In this paper, the solutions of TE(transverse electric) scattering problems by a resistive strip grating over a grounded dielectric layer are analyzed by applying the PMM(point matching method) known as a numerical method of electromagnetic fileld. The boundary conditions are applied to obtain the unknown field coefficients and the resistive boundary condition is used for the relationship between the tangential magnetic field and the induced surface current density on the resistive strip. The induced surface current density of resistive strip is obtained by difference of the up and down of the magnetic field in two boundary areas of the resistive strip. The numerical results for reflected power of zeroth order mode analyzed by according as the resistivity, the width and spacing of resistive strip, the relative permittivity and thickness of dielectric layer, and incident angles. The numerical results shown in good agreement compared to those of the existing papers using FGMM(fourier galerkin moment method).

• Journal of Electrical Engineering and Technology
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• 제7권4호
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• pp.564-569
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• 2012

This paper proposes a hybrid-excited linear synchronous motor (LSM) that has potential applications in a magnetically levitated vehicle. The levitation and thrust force characteristics of the LSM are investigated by means of three-dimensional (3-D) numerical electromagnetic FEM calculations and experimental verification. Compared to a conventional LSM with electromagnets, a hybrid-excited LSM can improve levitation force/weight ratios, and reduce the power consumption of the vehicle. Because the two-dimensional (2-D) FE analysis model describes only the center section of the physical device, it cannot express the complex behavior of leakage flux, which this study is able to predicts along with levitation and thrust force characteristics by 3-D FEM calculations. A static force tester for a hybrid-excited LSM has been manufactured and tested in order to verify these predictions. The experimental results confirm the validity of the 3-D FEM calculation scheme for the description of a hybrid-excited LSM.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.647-652
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• 2015

A fully coupled finite element analysis (FEA) technique was developed for analyzing the discharge phenomena and dielectric liquid flow while considering surface charge density effects in dielectric flow guidance. In addition, the simulated speed of surface charge propagation was compared and verified with the experimental results shown in the literature. Recently, electrohydrodynamics (EHD) techniques have been widely applied to enhance the cooling performance of electromagnetic systems by utilizing gaseous or liquid media. The main advantage of EHD techniques is the non-contact and low-noise nature of smart control using an electric field. In some cases, flow can be achieved using only a main electric field source. The driving sources in EHD flow are ionization in the breakdown region and ionic dissociation in the sub-breakdown region. Dielectric guidance can be used to enhance the speed of discharge propagation and fluidic flow along the direction of the electric field. To analyze this EHD phenomenon, in this study, the fully coupled FEA was composed of Poisson's equation for an electric field, charge continuity equations in the form of the Nernst-Planck equation for ions, and the Navier-Stokes equation for an incompressible fluidic flow. To develop a generalized numerical technique for various EHD phenomena that considers fluidic flow effects including dielectric flow guidance, we examined the surface charge accumulation on a dielectric surface and ionization, dissociation, and recombination effects.

• Proceedings of the KSME Conference
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1058-1063
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• 2004

This paper presents a new approach regarding thermal characteristics associated with a design of the high efficiency motor. Electrical conduction materials, such as coil and aluminum embedded in the core generate high heat exerting negative influence on both lifetime and performance of machine. Thus, it is necessary to design high efficiency motor considering heat transfer in order to improve motor performance and to be protected against overheating. In this paper, firstly, numerical analysis of electromagnetic field is carried out by the nonlinear transient finite element method (FEM). Secondly, the linear static FEA of magneto-thermal field is implemented by applying source current computed by the nonlinear transient analysis. FE results are validated in terms of electromagnetics and heat transfer by experiments. And then, the pseudo-transient topology optimization using a multi-objective function is performed. The proposed method is applied to a squirrel cage single-phase induction motor of the scroll compressor.

• Journal of the Korea Institute of Military Science and Technology
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• 제23권4호
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• pp.328-336
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• 2020

This paper presents an asymptotic analysis method using the PO(physical optics) approximation technique to analyze the scattering contribution of an electrically large object partially coated with a radar absorbing material(RAM). By using the feature of the PO technique that can calculate the equivalent current value for each mesh independently, instead of analyzing the entire structure, scattering analysis was performed only by calculating the current on the area where the RAM coating is applied. By the numerical examples, the accuracy and the computation time of the proposed method were verified, and the computational efficiency of inverse synthetic aperture radar(ISAR) of the electrically large objects that require enormous resources is improved.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• 제5권1호
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• pp.3-12
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• 1994

We have proposed the optimum threshold detection(OTD) technique of 16 QAM signal in the Rician fading channel and analyzed its error performance with and without the selective combining(SC) diversity technique. And we compared the error performance of OTD with that of conventional threshold detection(CTD). Having the SC diveresity reception, optimum threshold detection(OTD) technique proposed in this paper provides the performance improvement of 1.8~3.2 [dB] in CNR for fading depth K values ranging from 5 to 30 over CTD when the error rate is $10_5$. From the result of numerical analysis, we know that the proposed OTD technique is superior to CTD technique in the Rician fading channel and adoption of the SC diversity technique with the proposed OTD can be considered as a good countermeasure for the Rician fading.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제16권5호
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• pp.488-493
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• 2005

In this study, waveguide-to-CPW transitions were developed for integrating waveguide and MMIC at V-band. The finite element method for numerical analysis and repeated experiments were performed to propose two types of waveguide-to-CPW transition. Using quartz substrate, proposed structures were designed for low loss as well as broadband characteristics. These waveguide-to-CPW transitions showed a good reliability and insensitivity to matching precision, and they could be fabricated with lower cost than that of the conventional connectors. Proposed two types of the structure showed insertion loss less than 1.9 dB and return loss better than 14 dB from 53 GHz to 60 GHz except unwanted resonance region, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제7권5호
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• pp.384-394
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• 1996

The propagation properties of square and Gaussian pulse signals on the microstrip line are investigated by using proper conventional models to meet the frequency range of a pulse, accuracy, and geometrical requirements of the microstrip line. Numerical integration technique which has its accuracy and is easily simulated, is used to obtain the time domain response of pulse signals. The dispersion of pulse signals is analyzed regarding to the relative permittivity $\varepsilon_r$, substrate height h, strip width w of the microstrip line and pulse width $\tau$ of signal pulse. The simulation results show that small relative permittivity and small rationale of w/h are advantageous for the dispersion of the pulse signals, and that pulse signals with small bandwidth cause smaller dispersion. The results of this paper are compatible to the trade-off determination of relative permittivity, substrate height, strip width and pulse width of signal pulse when a design of MIC and MMIC is necessary.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제19권4호
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• pp.418-426
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• 2008

In this paper, investigations on the impedance characteristics of a DGS(Defected Ground Structure) slot in the groud plane of microstripline are presented in spectral domain and applied to the characteristic improvement of stepped impedance microstrip low pass filter(LPF). In this method, expressions for the impedance of a DGS slot are derived from self-reaction of the angular spectrum of plane waves and the discontinuity in the modal voltage. The numerical results are compared with those of the rigorous full-wave method and are shown to produce reasonably accurate data. And the stepped impedance microstrip low pass filter is designed and fabricated with the uniform and nonuniform DGS slots for improving the frequency responses. The experiments show that the proposed filter with slots in the ground plane has a wider stopband and sharper cutoff response.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제19권4호
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• pp.427-435
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• 2008

In this paper, a stable marching-on in time(MOT) method with a time domain combined field integral equation(CFIE) is presented to obtain the transient scattering response from arbitrarily shaped three-dimensional conducting bodies. This formulation is based on a linear combination of the time domain electric field integral equation(EFIE) with the magnetic field integral equation(MFIE). The time derivatives in the EFIE and MFIE are approximated using a central finite difference scheme and other terms are averaged over time. This time domain CFIE approach produces results that are accurate and stable when solving for transient scattering responses from conducting objects. Numerical results with the proposed MOT scheme are presented and compared with those obtained from the conventional method and the inverse discrete Fourier transform(IDFT) of the frequency domain CFIE solution.