• Journal of Internet Computing and Services
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• v.7 no.6
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• pp.113-121
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• 2006

To reduce switch cost, the optimum numbers of tunable wavelength converters (TWCs) and internal wavelengths required for contention resolution of asynchronous and variable length packets like internet traffics, is presented in the optical packet switch (OPS) with the shared fiber delay line (FDL) buffer. To optimize TWCs and internal wavelength related to on OPS design cost, we proposed a scheduling algorithm for the limited TWCs and internal wavelengths. For three TWC alternatives (not shared, partially shared, and fully shared cases), the optimum numbers of TWCs and internal wavelengths to guarantee minimum pocket loss are evaluated to prevent resource waste. Under o given load, TWCs and internal wavelengths could be significantly reduced, guaranteeing the same pocket loss probability as the performance of on OPS with full TWCs and internal wavelengths.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.1
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• pp.75-83
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• 1989

In this paper, applying the REC model which characterizes the coupling between the radiating edges to two coupled rectangular microstrip patch antenna, we obtain scattering parameters $\mid$ $S_{11}$ $\mid$ and $\mid$ $S_{12}$ $\mid$for the various coupling separations, Se=0.5mm, 1.0mm, 1.5mm, and 2.0mm, The calculated values are compared with the measured values. For the rectangular microstrip patch antenna with a parasitic element which is gap-coupled to the radiating edges of the rectangular patch, calculated return losses using the REC model are compared with measrued values. Here, the each microstrip antenna is fed by a 50 microstrip line. The purpose of the paper is to compare a 50$\Omega$ microstrip line fed case with a coaxial fed case treated in Ref.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.4
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• pp.610-618
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• 2000

A T-shaped microstripline -fed printed slot antenna is anlayzed by using the transmission line model(TLM) in this paper. Microstrip-slotline junction is modeled by employing a transformer and the transformer turn ratio is derived empirically. The method is extended to the case of $1\times2,l\times4$array antennas. Return loss results obtained by using the transmission line model. The maximum measured results and demonstrated the usefulness of the transmission line model. The maximum bandwidths of a single antenna, $1\times2,l\times4$ array antennas are 28.5%, 47.8%, and 50.9%, respectively, for the VSWR$\leq2$. The gain of $1\times4$ array antenna is 7.97dBi and the beamwidth is about $27^{\circ}$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.7
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• pp.1182-1190
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• 2001

In this paper, microstrip photonic bandgap (PBG) structure with special perforation patterns etched on the line itself is analyzed and optimized in shape, then used for harmonic tuning of power amplifier. This PBG has an advantage in being fabricated and grounded. The dimension of unit lattice is enlarged vertically, but its input and output line maintain 50 Ω using tapered line. This modification from original structure can lessen possible error in etching PCB. The analysis and design of PBG structure are acquired from using EM simulation. The measured insertion loss of the final structure is 0.3 ∼0.4 dB, and its bandwidth of stopband is 6∼7 GHz. Measured results of improved characteristics by using PBG structure at the output of the power amplifier are 0.72∼0.99 dB in output power, 1.14∼7.8 % in PAE, and 1 dBc in the third IMD.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.3
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• pp.230-239
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• 2009

In this paper, we propose a novel on-glass antenna for FM radio reception in a recreation vehicle(RV). We use a multi-loop structure that takes advantage of a broad matching bandwidth and a high vertical radiation gain by efficiently utilizing a given space of a quarter glass in spite of the simple planar structure. Transparency of the antenna is also improved by adjusting the stripline widths based on the induced current distributions. The proposed antenna is printed on a quarter glass of a commercial vehicle and antenna performances such as the return loss and the gain are measured in a semi-anechoic chamber. The result shows the average gain of -9.67 dBi along the bore-sight direction($\theta=90^{\circ}$, $\phi=270^{\circ}$) in the FM radio band(80$\sim$l10 MHz), which is higher than a commercial monopole typed on-glass antenna($G_{ave}$=-12.49 dBi) and micro-antenna($G_{ave}$=-19.24 dBi) mounted on the roof of the RV.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.3
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• pp.417-422
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• 2022

It is always desirable that the continuation of power flow through the lines should not be interrupted for a long time. The optimized guideline of reclosers on distribution lines is known to improve the reliability of power systems, the protection functions on distribution systems heavily rely on the number and placement of such reclosers. This study reviewed the effect of using protection settings methodology with the number of reclosing operations to reduce the damage sustained during faults on distribution networks. The aim of the study is to determine the number of reclosing operations and fault current conditions based on simulation data of PSCAD/EMTDC for standard distribution networks. It is found that the determination of the number of operations on reclosers, which are the protection function of feeders, helped to optimize the operation and reliability of distribution networks.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.4
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• pp.323-332
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• 2009

In this paper, we introduce a modified short-circuited stub bandpass filter suitable for ultra-wideband(UWB) applications utilizing low temperature co-fired ceramic(LTCC) technology. By modifying the conventional short-circuited stub bandpass filter structure with stubs and connecting lines of lower characteristic impedances, the number of stubs has been reduced from 5 to 2 on a high dielectric constant substrate($\varepsilon_r$ = 40). A wireless local area network (WLAN) stopband in the frequency range of 5.15 to 5.825 GHz has been inserted into the filter characteristic using three short-circuited coupled lines. The filter has been measured with an insertion loss less than 1.0 dB and return loss better than 10 dB in the pass bands. A bandwidth ratio of 109.49 % has been achieved. Measurement results agree well with simulation results. The dimensions of the filter are $4{\times}8{\times}0.57\;mm^3$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.4
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• pp.369-376
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• 2003

In this paper, Ka-Band NRD guide band pass filter with newly designed inductive post structure is proposed and analyzed with its test results. Generally, millimeter-wave filters are very sensitive in their physical dimensions, hence, it is requires extreme precisions of several micron so as to get the designed performance. In case of common NRD Guide filter with air gap coupled structure, it is fabricated with dielectric blocks coupled via air gap. In these structures, however, it was not easy to fabricate and to process of each NRD guide dielectric resonator blocks using PTFE, so it was almost impossible to assemble with several microns in precision. In this our research, however, each dielectric resonators are coupled with a pair of inductive metal post, so all resonators are located in a single NRD Guide. The dielectric parts between two pairs of posts are operated as resonators of each stage, and the positions of the post decide the couplings between resonators. The structure we suggested is suitable fur mass production, because it is very simple and easy to process. As a result of measurements, designed NRD guide inductive post filter has a superior performance. The center frequency is 39.475 GHz with 350 MHz bandwidth, insertion loss is less than 1.8 dB, and the return loss is below than -18 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.8
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• pp.754-763
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• 2002

This paper discusses the improved power performances of the size-reduced amplifier using defected ground structure (DGS). The slow-wave effect and enlarged electrical length occur due to the additional equivalent circuit elements of DGS. Using these properties, it is possible to reduce the length of transmission lines in order to keep the same original electrical lengths by inserting DGS on the ground plane. The matching and performances of the amplifier are preserved even after DGS patterns have been inserted. While there is no loss in the size-reduced transmission lines at the operating frequency, but there exists loss to some extent at harmonic frequencies. This leads to the more excellent inherent capability of harmonic rejection of the size-reduced amplifier. Therefore, it is expected tile harmonics of the size-reduced amplifier are smaller than those of the original amplifier. The measured second harmonic, third order intermodulation distortion (IMD3), and adjacent channel power ratio (ACPR) of the size-reduced amplifier are smaller than those of the original amplifier by 5 dB, 2~6 dB, and 1~4 dB, respectively, as expectation.

• Journal of Internet Computing and Services
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• v.10 no.2
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• pp.171-177
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• 2009

Optical packet switching(OPS) is a strong candidate for the next-generation internet, since it has a fine switching granularity at the packet level for providing flexible bandwidth, and provides seamless integration between WDM layer and IP layer. Optical packet switching have been studied in two categories: OPS in synchronous and OPS in asynchronous networks. In this article we are focused on contention resolution of OPS in asynchronous networks. The hybrid buffer have been addressed, to reduce packet loss further as one of the alternative buffer structures for contention resolution of asynchronous and variable length packets, which consists of the FDL buffer and the electronic buffer. The OPS design issue for the limited number of TWCs and internal wavelengths is important in the aspect of switch cost and resource efficiency. Therefore, an hybrid buffer structured optical packet switch and its scheduling algorithm is presented for considering the limited number of TWCs and internal wavelengths, for contention resolution of asynchronous and variable length packets. The proposed algorithm could lead to the packet loss improvement compared to the legacy LAUC-VF algorithm with only the FDL buffer.