• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.1
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• pp.52-60
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• 1997

A 23GHz 2-stage LNA was designed using MPIE numerical analysis and microwave CAD EEsof softwares. The basic circuit was designed by EEsof tools but analyzed more precisely using numerical MPIE tools and modified. The matching sections of the input and output terminals were designed with paralledl coupled filter-type lines, these matching sections perform impedance matching and DC blocking, more over have the advantages of small discontinuities and small errors in the design process. The FET chip is directly attached to the ground metal. The designed LNA gives 15.2dB gain and 2.7dB noise figure. without considering 1.8dB loss of connectors. These results validate our design process and matching schemes and fabrication technologies over the 20GHz frequency range.

• Journal of Ocean Engineering and Technology
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• v.15 no.1
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• pp.7-11
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• 2001

In this paper, trapezoid sections and prominence sections were examined to improve the performance of floating breakwater in long waves. The linear potential theory is used and the boundary element method with a matching boundary is employed for numerical computation. The effects of the side slope of the trapezoid section and the geometry ratio of the prominence section on the floating breakwater were examined. It was found that trapezoid sections show lower transmission coefficients than the rectangular sections in the long wave range. In prominence sections the size of the sides are more important than the size of the top. Proper choices of the pontoon type geometry may move the local minimum point of the wave transmission coefficient toward the longer wave ranges and improve the performance of the floating breakwater in the long wave range for a given wave period.

• Korean Journal of Remote Sensing
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• v.40 no.2
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• pp.219-228
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• 2024

Vessels can operate with their Automatic Identification System (AIS) turned off, prompting the development of strategies to identify them. Among these, utilizing satellites to collect radio frequency (RF) data in the absence of AIS has emerged as the most effective and practical approach. The purpose of this study is to develop a matching algorithm for RF with AIS data and find the RF's applicability to classify a suspected ship. Thus, a matching procedure utilizing three RF datasets and AIS data was employed to identify ships in the Yellow Sea and the Korea Strait. The matching procedure was conducted based on the proximity to AIS points, ensuring accuracy through various distance-based sections, including 2 km, 3 km, and 6 km from the AIS-based estimated points. Within the RF coverage, the matching results from the first RF dataset and AIS data identified a total of 798 ships, with an overall matching rate of 78%. In the cases of the second and third RF datasets, 803 and 825 ships were matched, resulting in an overall matching rate of 84.3% and 74.5%, respectively. The observed results were partially influenced by differences in RF and AIS coverage. Within the overlapped region of RF and AIS data, the matching rate ranged from 80.2% to 98.7%, with an average of 89.3%, with no duplicate matches to the same ship.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.343-346
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• 2005

Radiation properties of flush mounted circular patch antenna are investigated. The patch is fed axis-symmetrically by a coaxial cable. Rigorous analysis is given using integral transform and mode matching techniques. The presented method accommodates radiating patch, and integrated matching sections and band pass filter.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.8
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• pp.862-877
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• 2008

In this paper, two types of wideband 3-dB ring hybrids are compared and discussed to show the ring hybrid with a set of coupled-line sections better. However, the better one still has a realization problem that perfect matching can be achieved only with -3 dB coupling power. To solve the problem, a set of coupled-line sections with two shorts is synthesized using one- and two-port equivalent circuits and design equations are derived to have perfect matching, regardless of the coupling power. Based on the design equations, a modified ${\Pi}-type$ of transmission-line equivalent circuit is newly suggested. It consists of coupled-line sections with two shorts and two open stubs and can be used to reduce a transmission-line section, especially when its electrical length is greater than ${\pi}$. Therefore, the $3\;{\lambda}/4$ transmission-line section of a conventional ring hybrid can be reduced to less than ${\pi}/2$. To verify the modified ${\Pi}-type$ of transmission- line equivalent circuit, two kinds of simulations are carried out; one is fixing the electrical length of the coupled-line sections and the other fixing its coupling coefficient. The simulation results show that the bandwidths of resulting small transmission lines are strongly dependent on the coupling power. Using modified and conventional ${\Pi}-types$ of transmission-line equivalent circuits, a small ring hybrid is built and named a compact wideband coupled-line ring hybrid, due to the fact that a set of coupled-line sections is included. One of compact ring hybrids is compared with a conventional ring hybrid and the compared results demonstrate that the bandwidth of a proposed compact ring hybrid is much wider, in spite of being more than three times smaller in size. To test the compact ring hybrids, a microstrip compact ring hybrid, whose total transmission-line length is $220^{\circ}$, is fabricated and measured. The measured power divisions($S_{21}$, $S_{41}$, $S_{23}$ and $S_{43}$) are -2.78 dB, -3.34 dB, -2.8 dB and -3.2 dB, respectively at a design center frequency of 2 GHz, matching and isolation less than -20 dB in more than 20 % fractional bandwidth.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.3
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• pp.9-16
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• 1997

A 23GHz 1-stage LNA was designed by using new topology of coupled line type with EEsof softwares and modified by using MPIE numerical analysis. The parallel coupled filter-type matching sections give impedance matching and DC blocking simultaneously, and have small discontinuities. This matching scheme has simple structure in the design process and give small error. The EFT chip was directly attached to the ground metal. The designed LAN gives 6.2dB gain and 2.5dB noise figure without considering the loss of connectors. Through these results, it was verified that our design process, matching schemes and fabrication technologies was valied for developing 20GHz-band LNA.

• Journal of electromagnetic engineering and science
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• v.9 no.2
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• pp.85-97
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• 2009

As operating frequency is raised and as more integration with active and passive elements is required, it becomes difficult to fabricate more than 120 ${\Omega}$ characteristic impedance of a mierostrip line. To solve this problem, an equivalent high impedance transmission-line section is suggested, which consists mainly of a pair of coupled-line sections with two shorts. However, it becomes a transmission-line section only when its electrical length is fixed and its coupling power is more than half. To have transmission-line characteristics(perfect matching), independently of coupling power and electrical length, two identical open stubs are added and conventional design equations of evenand odd-mode impedances are modified, based on the fact that the modified design equations have the linear combinations of conventional ones. The high impedance transmission-line section is a passive component and therefore should be perfectly matched, at least at a design center frequency. For this, two different solutions are derived for the added open stub and two types of high impedance transmission-line sections with 160 ${\Omega}$ characteristic impedance are simulated as the electrical lengths of the coupled-line sections are varied. The simulation results show that the determination of the available bandwidth location depends on which solution is chosen. As an application, branch-line hybrids with very weak coupling power are investigated, depending on where an isolated port is located, and two types of branch-line hybrids are derived for each case. To verify the derived branch-line hybrids, a microstrip branch-line hybrid with -15 dB coupling power, composed of two 90$^{\circ}$ and two 270$^{\circ}$ transmission-line sections, is fabricated on a substrate of ${\varepsilon}_r$= 3.4 and h=0.76 mm and measured. In this case, 276.7 ${\Omega}$ characteristic impedance is fabricated using the suggested high impedance transmission-line sections. The measured coupling power is -14.5 dB, isolation and matching is almost perfect at a design center frequency of 2 GHz, showing good agreement with the prediction.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2118-2126
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• 2017

The large-scale power system blackouts have indicated that conventional protection relays that based on local signals cannot fit for modern power grids with complicated setting or heavily loaded-flow transfer. In order to accurately detect various faulted lines and improve the fault-tolerance of wide-area protection, a novel multi-section weighed fault matching and detecting algorithm is proposed. The real protection vector (RPV) and expected section protection vectors (ESPVs) for five fault sections are constructed respectively. The function of multi-section weighed fault matching is established to calculate the section fault matching degrees between RPV and five ESPVs. Then the fault degree of protected line based on five section fault degrees can be obtained. Two fault detecting criterions are given to support the higher accuracy rate of detecting fault. With the enumerating method, the simulation tests illustrate the correctness and fault-tolerance of proposed algorithm. It can reach the target of 100% accuracy rate under 5 bits error of wide-area protections. The influence factors of fault-tolerance are analyzed, which include the choosing of wide-area protections, as well as the topological structures of power grid and fault threshold.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.5
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• pp.974-980
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• 1997

The 23GHz 1-state LNA was designed by using MPIE numerical analysis and conventional design EEsof softwares. The circuit was designed using conventional tools but analyzed and modified by using numerical MPIE tools. he matching sections was designed with parallel coupled filter-type, which gives impedance matching and DC blocking and has small discontinuities. THe FET chip is directly attached to the graound metal. The designed LNA gives 5.8dB gain and 2.5dB noise figure withoug considering the loss and impedance shift of connectors that degenerate the gain and noise figure considerably. this results gives very promising characteristics for our design process and matching schemes and fabrication technologies.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.7
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• pp.190-198
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• 1994

In this paper, we propose the cross-section processing method which is simple in describing the SHGC of objects in a range image and which can describe the SHGC of occluded objects for the recognition of 3D objects. This method produces the cross-sections of an object along the assumed axis of the SHGC and describes the SHGC of the object by processing the produced cross-sections of the object using $\psi$ -S curves with invariant properties in position and size. Our method is simple in a process and can descirbe the SHGC of partially occluded objects because it uses range images with 3-D informations of objects without matching contours of objects with a model base. Thus it is a useful description method of a range image for the recognition of 3D objects shaped in SHGC form and we proved the usefulness of it in experiments.