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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Journal of Korean Institute of Electromagnetic Engineering and Science
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Journal DOI :
The Korean Institute of Electromagnetic Engineering and Science
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Volume & Issues
Volume 9, Issue 6 - Dec 1998
Volume 9, Issue 5 - Oct 1998
Volume 9, Issue 4 - Aug 1998
Volume 9, Issue 3 - Jun 1998
Volume 9, Issue 2 - Apr 1998
Volume 9, Issue 1 - Feb 1998
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An Analysis of the Unequal Wilkinson Power Divider Using the Finite-Difference Time-Domain (FDTD) Method
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 6, 1998, Pages 715~724
The FDTD(Finite-Difference Time-Domain) method is applied to analyze an unequal Wilkinson power divider. Unequal Wilkinson power divider has complex structures and the standard Yee Cell modeling method is not appropriate. In this paper, nonuniform gridding and subcell modeling are used to accurately analyze the characteristics of an unequal Wilkinson power divider. For comparison, the numerical results are presented with those from a commercial circuit simulator.
Analysis of Electromagnetic Radiation Hazard for Electro-explosive Device Using Fiber Optic Sensor
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 6, 1998, Pages 725~734
When the EED is exposed to the high power radiation, it is possible to verify systems survivability through measuring the induced current of EED. The usual method of performing a system level test is to replace the EED's with modified units from which the explosive charge has been removed and replaced with the fiber optic sensor. The thermal transient test was performed to obtain the temperature vs current characteristic curve for optical sensor installed in EED. The currents measured when the system is exposed to a known EME are compared to the proposed specfication about the EED and a decision is made on whether system is safe or not.
MLFMA for Computation of TM Scattering from Near Resonant Object
;W. C. Chew;
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 6, 1998, Pages 735~745
The method of moments has been widely used in the analysis of TM scattering problems. Recently, significant advances in the development of fast and efficient techniques for solving large problems have been reported. In such methods, iterative matrix solvers are preferred by virtue of their speed and low memory requirements. But for near resonant and strong multiple scattering problems, e.g., involving an aircraft engine inlet, a large number of iterations is required for convergence. In this paper, an efficient approximate inverse based preconditioner is used to reduce this number of iterations. By using the matrix partitioning method, the computational is used to reduce this number of iterations. By using the matrix partitioning method, the computational cost for obtaining the approximate inverse is reduced to O(N). We apply this preconditioner to an O(NlogN) algorithm, the multilevel fast multipole algorithm, for the aircraft engine inlet problem. The numerical results show the efficiency of this preconditioner.
An Adaptive Receiver Using Reduced-state Sequence Detection for the Trellis-coded CPFSK
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 6, 1998, Pages 746~760
In this paper, an adaptive RSSD(reduced-state sequence detection) receiver is proposed for the purpose of reducing the complexity and decision delay of the adaptive MLSD(maximum-likelihood sequence detection) receiver in the mobile satellite channel. The RSSD receiver reconstructs the trellis with a reduced number of states. The performance degradation due to the reduced states is compensated by modifying the branch metric calculation which uses the symbols in each path memory to estimate the residual ISI(intersymbol interference) terms. The structure of the proposed adaptive RSSD is a modified RSSD utilizing a per-survivor processing as well as the symbol-aided method and a channel estimation using the tentative data sequences. The complexity and performance of the proposed adaptive RSSD are controlled by the number of system states and ISI cancelers and the inserting period of the known symbols. In spite of a suboptimal alternative receiver compared to the adaptive MLSD receiver, the proposed adaptive RSSD receiver is able to reduce the complexity significantly and track the time-varying channel fast and reliably.
1-D Modal PML for Analysis of Waveguide Discontinuities Using the FDTD Method
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 6, 1998, Pages 761~767
The Perfectly Matched Layer(PML) provide good performance in absorption over a wide frequency range and is an appropriate ABC for waveguides with high dispersion. In this paper, a novel algorithm is proposed to improve the computational efficiency of the PML. In the input and output ports, the fields are decomposed into a series of modes, and then an appropriate ABC is applied to each mode. CPU time and memory storage requirements are greatly reduced, since the computational region is analyzed in one dimension. A WG-90 rectangular waveguide with a thick asymmetric iris is analyzed by Finite-Difference Time-Domain(FDTD) simulations with the conventional PML and the proposed one-dimensional (1-D) PML. Numerical results show that the computational efficiency is significantly improved by the proposed method.
A Channel Estimation Using the Sliding Window and an Adaptive Receiver in the Mobile Communication Channels
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 6, 1998, Pages 768~775
The equalizer is the central part of the receiver and its performance significantly affects the overall performance of the system in the mobile communication. A proposed equalizer is composed of the channel estimator, MLSE based on the Viterbi algorithm and GMSK decoder. The approximation of GMSK with QPSK has great impact on the equalizer design, because it allows us to use the existing simple and efficient algorithms for designing optimal QPSK equalizer. In order to estimate efficiently channel, we use a sliding window algorithm based on energy calculation and cross-correlator. And also a tuning scheme is presented in order to improve the equalizer performance. Simulation results indicate that a proposed equalizer meets the GSM standards easily in terms of performance.
Analysis of SAR in a Human Head for a Cellular Phone
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 6, 1998, Pages 776~787
This paper analyzes the local specific absorption rates (SAR's) averaged over 1 g and 10 g in a human head model in contact with a mobile phone operating at 835 MHz. The used numerical method is a total field finite-difference time-domain (FDTD) technique. The phone was simulated with a conducting box, a plastic case, and a whip antennal composed of a monopole and a helix. The discrete human model of the spatial resolution 3 mm is based on Magnetic Resonance Imaging (MRI), computerized tomography (CT) and anatomical images. The near field and far field and far field patterns were analyzed for extended and retracted phone. The two methods to take the volumes of the weights, 1 g or 10 g in tissue are proposed and compared to offer a reproductive technique for SAR estimations.
Improvement of Short Range Performance of Meteor Burst Path with Buried Antenna
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 6, 1998, Pages 788~801
Meteor Burst Communication can provide effective and economical means of communication where long distance VHF NLOS data transmission is needed ; often ranges more than 1000 km. It has been, however, so far considered unsuitable for short distance application because of phenomenal decrease in burst durations, which leads to decreation of total duty rate of the system. This paper extensively analyzes characteristics of shot distance MB(Meteor Burst) path and shows the low duty rate may be improved by increasing burst rate through adapting antennal beam width to cover entire hot-spot region in the space and, by compensating effective burst length throughcutting down man-made noises introduced by antennal. Based on the analysis, we are developed a small-opening-cavity antennal, especially designed for short distance MB path. In operation, the antenna is to be buried under ground surface so as to improve directivity and reduces noise introduction. The antennal exhibits power gain of 3 dB with 90 degree beam width and thus enables to illuminate entire hot-spot regions with the elevation angle of 8-90 degree which is the case of transmission less than 100 km. Directivity horizontal to earth surface is suppressed to minimum which enables to cut man-made noises from near-by sources down to more than 3 dB from the level reported with conventional 4 element Yagi. A series of experiments performed on 100km MB paths have conformed that, with the antenna installed at receiving site, the burst rate and duration time have been noticed to increase by 10 and 20 percent respectively from the values obtained by conventional 4-element Yagi antennal under same testing condition.
Calculation of Induced Current in the Human Body around 765 kV Transmission Lines
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 6, 1998, Pages 802~812
Safety related to electric field exposure for the personnel of high voltage power plant and substation is of importance. To analyze the induced current influencing on human body in this paper, we calculate directly capacitance in three dimension which is complex and time consuming, as not to separate the voltage source and the induced object using a effective modeling technique. The proposed algorithm in this paper has been applied to 765 kV high voltage transmission line to evaluate human hazard for the induced current through the case study. As the results, the short circuit current of human body has been identified in the range of 0.3 mA to 6.8 mA. Closing to transmission line, this range of short current can exceed 5 mA that ANSI recommended let-go current. Therefore, it is necessary to countermeasure such as putting on conductive clothing in live-line maintenance of transmission line.
An Analysis of A Circularly Polarized Conformal Microstrip Parch Antenna Using The Unsplit Anisotropic Perfectly Matched Layer(UAPML)
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 6, 1998, Pages 813~823
This paper analyzed the circularly polarized conformal microstrip patch antennal using the unsplit anisotropic perfectly matched layer(UAPML) method. Also, this paper are treated effectively the edge and corner parts on the 3 dimensional UAPML. Especially, to analyze microstrip patch antennas with the coaxial feeder line, it was applied to mixed the UAPML with Mur's first order absorbing boundary condition. Therefore this paper suggest the new the method to mix the UAPML with Mur's first order absorbing boundary condition. The results show the time responses of electromagnetics
, input impedances of coaxial cable and radiation patterns of strip parchs on the single and the array patchs with central frequencies 1.575 GHz, 1.778 GHz and 4.8 GHz in L-band and C-band for mobile communication. The results of this paper shows that its results was compared the Mur's first order abc and mixed the second order dispersion boundary condition(SDBC) with the Mur's first order absorbing boundary condition. In accordance with, the validity of the method is confirmed.
Field Strength Prediction Program Using Terrain and Land Usage Data for Cheju
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 6, 1998, Pages 824~832
The significant additional path loss is caused by scattering, diffraction, and attenuation of propagation. Most of the wave propagation models for rural areas mainly have considered the influence of topography but ignored the effects due to land usage. The goal of this paper is development of the field strength prediction program for Cheju which is used the contour map and the effects due to land usage. In oder to classify the propagation path and divide the environment of land, data of the terrain and the land-cover are formed into a pixel. Two-ray model is transformed into equivalent model by the predicted reflection coefficient and the slope of terrain. For non line of sight, the additional loss is determined by quantitative analysis. The result show good accord and the wave propagation model program can be applied to predicted the service region in rural area of Cheju.
A K-band Hair-pin Oscillator Using a Frequency Doubler
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 6, 1998, Pages 833~842
In this paper, a K-band oscillator which is composed of a hair-pin resonator, a GaAs MESFET, and a frequency doubler, is suggested, implemented by HMIC(Hybrid Microwave Integrated Circuits) form, and characterized for its microwave performance. A
/4 open stub is used in frequency doubler to suppress the fundamental frequency of 9 GHz which is the output of the hair-pin resonator oscillator and output matching network is optimized for its second harmonic freuency of 18 HGz. For the oscillator, the output power of -0.83 dBm, the fundamental frequency suppression of -23 dBc, and phase noise of -86 dBc/Hz at 18.20 GHz are obtained.
Voltage-controlled Oscillator Using Dielectric Resonator for WLL System
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 6, 1998, Pages 843~849
A voltage controlled oscillator using dielectric resonator for 2.4 GHz WLL System is designed and fabricated. To improve the phase noise characteristic resonator is used as an inductor of VCO. At the bias condition of 5 V and 10 mA, the output power and phase noise in the operating frequency range of 2210~2240 MHz are 0 dBm and 100 dBc/Hz 10 kHz offset from the carrier, respectively. The phase noise and harmonic response of fabricated VCO are suitable for WLL system.
Frequency Characteristic Analysis of Noise Cut Transformer for the Power Line Noise Reduction
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 6, 1998, Pages 850~859
Broadband noise with frequency components in the range from several kHz up to tens of MHz is widespread in the AC power line. Noise filter or surge suppressor, often used to suppress the conducted noise, have a poor performance in reducing the common-mode. In this paper, we proposed a lumped-circuit analysis model for Noise Cut Transformer(NCT) which can be used to suppress both the common mode and normal-mode noise. The simulations with our model show a good agreement with experimental results. It has been also shown that our NCT is superior to noise filter and general isolation transformer in reducing the conducted noise.