• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.13 no.5
• /
• pp.444-452
• /
• 1988

The LP(Log-periodic) type antenna composed of the cross fed and parasitic loop elements has been proposed for a high gain and broadband characteristics. This antenna has been analyzed by using moment method, and current distribution, input impedence, power gain, and radiation patterns has been calculated and compared with LPDA. It was found to have high gain, broadband characteristics, and similiar patterns for E and H plane against LPDA.

• Proceedings of the KIPE Conference
• /
• 2012.07a
• /
• pp.592-593
• /
• 2012

Buck converter must operate at fairly high switching frequency for miniaturizing a whole circuit and achieving a fast response. However, at the conditions of low output voltage, high output current, and high switching frequency, the influence of parasitic elements to circuit operation will become extremely obvious. In this paper, it has been shown that these parasitic elements of output capacitor link the ripple of the output voltage. The MCP capacitors and aluminum electrolytic capacitors are applied to the buck converter and observed characteristics and the experimental results were reported.

• Structural Engineering and Mechanics
• /
• v.87 no.3
• /
• pp.283-296
• /
• 2023

Free-vibration and buckling analyses of plate problems are investigated with the aid of the strain gradient notation finite element method (SGN-FEM). As SGN-FEM employs physically interpretable polynomials in developing finite elements, parasitic shear sources, which are the cause of shear locking, can be precisely identified and subsequently eliminated. This allows two mutually complementary objectives to be defined in this work, namely, evaluate the efficiency of free-vibration and buckling results provided by corrected models, and study the severity of parasitic shear effects on plate models performance. Parasitic shear are flexural terms erroneously present in shear strain polynomials. It is reviewed here that six parasitic shear terms arise during the formulation of the four-node Mindlin plate element. Two parasitic shear terms have been identified in the in-plane shear strain polynomial while other two have been identified in each of the transverse shear strain polynomials. The element is corrected a-priori, i.e., during development, by simply removing the spurious terms from the shear strain polynomials. The computational implementation of the element in its two versions, namely, containing the parasitic shear terms (PS) and corrected for parasitic shear (SG), allows for assessments of the accuracy of results and of the deleterious effects of parasitic shear in free vibration and buckling analyses. This assessment of the parasitic shear effects is a novelty of this work. Validation of the SG model is done comparing its results with analytical results and results provided by other numerical procedures. Analyses are performed for square plates with different thickness-to-length ratios and boundary conditions. Results for thin plates provided by the PS model do not converge to the correct solutions, which indicates that parasitic shear must be eliminated. That is, analysts should not rely on refinement alone. For thick plates, PS model results can be considered acceptable as deleterious effects are really critical in thin plates. On the other hand, results provided by the SG model converge well for both thin and thick plates. The effectiveness of the SG model is established via high-accuracy results obtained in several examples. It is concluded that corrected SGN-FEM models are efficient alternatives for free-vibration and buckling analysis of Mindlin plate problems, and that precise elimination of parasitic shear is a requirement for sound analyses.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.26 no.8
• /
• pp.710-717
• /
• 2015

In this paper, we design an array antenna structure based on a patch ESPAR(Electronically Steerable Parasitic Array Radiator) antenna with three elements for reliable communication in high-speed railway wireless communication. The ESPAR antenna consists of the active element with a single RF-chain and the parasitic elements surrounding an active element. The ESPAR antenna is capable of beamforming by adjusting the reactance of the parasitic element. We propose a vertical array antenna structure based on the patch ESPAR antenna and simulate it according to the change of the number of antennas and the distance between antenna rows. The simulation results show that we can get the maximum beam gain and highest directivity when the distance between antenna rows is ${\lambda}$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.2
• /
• pp.167-173
• /
• 2009

This paper proposes an electronically beam steering array antenna, consisting of single fed active element and 4 parasitic elements, operating in 5.8 GHz ISM band. Beam steering can be achieved by controlling the reactance of the variable reactance control circuit connected to the load of the parasitic elements without using the high cost phase shifters. The proposed antenna realizes ${\pm}30^{\circ}$ beam scanning of E-plane and H-plane with the below -10 dB return loss in ISM band. The gain of the $6.18{\sim}7.53\;dBi$ in E-plane and $7.022{\sim}7.779\;dBi$ in H-plane is shown in the scanning range.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.7
• /
• pp.719-725
• /
• 2008

In this paper, we have proposed a printed monopole antenna using parasitic elements. The broadband characteristics of the antenna is obtained by using the printed monopole and parasitic elements. To confirm the broadband characteristics of the antenna, of have designed and fabricated the proposed antenna. The return loss and radiation patterns are measured in the frequency range of$0.8{\sim}1.2\;GHz$. The measured results show that the proposed antenna has return loss less than -10 dB in the operating frequency band and the radiation pattern is the dipole-like patterns. The antenna gain varies from 1.7 to 4.6 dBi in the operating frequency band. Thus, the proposed antenna can be used for the broadband repeater antenna $0.806{\sim}0.960\;GHz$(TRS-800, CDMA and GSM-900).

• KIEE International Transactions on Electrophysics and Applications
• /
• v.5C no.2
• /
• pp.49-53
• /
• 2005

The current drive in a MOSFET is limited by the intrinsic channel resistance. All other parasitic elements in a device structure perform significant functions leading to degradation in the device performance. These other resistances must be less than 10$\%$-20$\%$ of the channel resistance. To meet the necessary requirements, the methodology of separation and quantification of those resistances should be investigated. In this paper, we developed an extraction method for the resistances using calibrated TCAD simulation. The resistance of the extension region is also partially determined by the formation of a surface accumulation region that gathers below the gate in the tail region of the extension profile. This resistance is strongly affected by the abruptness of the extension profile because the steeper the profile is, the shorter this accumulation region will be.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.2
• /
• pp.115-123
• /
• 2009

In this paper, we extract the parasitic elements of the transmission line with the defected ground structure(DGS) and the short-circuited comb line section using the Short-Open Calibration(SOC). The scattering matrixes of short, open and the distributed elements in microstrip line are measured by full electro-magnetic(EM) simulator and Vector Network Analyser(VNA). The electro-magnetic effects of the proposed structures are considered by the II and T equivalent circuits with frequency independent elements, and the relations between the measured scattering parameters and the elements in the circuits are shown by performing 2 port network analysis. Moreover, to design the 2.4 GHz bandpass filter with second order butterworth prototype, the proposed methods are applied. As results, the measured $S_{11}$ and $S_{21}$ indicate -20 dB and -1.3 dB at center frequency, and these are shown within 5 % error compare to the predicted results at $0.5{\sim}5\;GHz$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.12
• /
• pp.1410-1415
• /
• 2008

This paper proposes an small electronically steerable parasitic array radiator composed of a uniplanar dipole as a feeding element and two dipoles as parasitic elements. The fabricated antenna shows by measurement the $3.3{\sim}4.3\;dB$ gain between $-100{\sim}1000$ azimuth range in the dipole vertical plane and -10 dB return loss within $5.4{\sim}5.9\;GHz$, which includes $5.725{\sim}5.825\;GHz$ UNII band.

• Journal of Korea Society of Industrial Information Systems
• /
• v.15 no.2
• /
• pp.11-16
• /
• 2010

In this papar, we have proposed a small electronically steerable parasitic array radiator with 180 degree azimuth beam coverage and high gain characteristics. The proposed antenna is composed of a uniplanar Yagi dipole as a feeding element and two dipoles as parasitic elements. The fabricated antenna is tested by electronically changing the reactance loaded on the parasitic dipoles and the results show that it has 5.2dB~6.7dB gain in $-90^{\circ}{\sim}90^{\circ}$wide azimuth range and -10dB return loss characteristics within 5.725GHz~5.825GHz UNII band.