• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5B
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• pp.842-849
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• 2000

In this paper, We analyzed the protocol to improve the performance of the multicast traffic processing in WDM networks. In the protocol, control channels are devided into contention-less minislots and contention minislots. And the packets which fail to have successful reservation in the present time slot have priority to have successful reservation in the contention-less minislots of the next time slot. Therefore, control channel contentions and destination conflicts can be reduced with the use of contention-less minislots. For the multicast traffic processing, the theoretical analysis and computer simulation are important to estimate the network performance and to calculate the optimized number of contention-less minislots. In this paper, the state transition probability of the number of contention-less minislots and arrival packets are calculated using 4-dimension matrix. The maximum number of contention-less minislots is equal to the number of channels for maximum performance improvement of the system. It is theoretical analysis and prove to computer simulation the performance of the protocol.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.84-94
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• 2006

In this paper, we propose the algorithm to reduce guard time of UWB MAC time slot for throughput gain. In the proposed draft by multiband ofdm alliance (MBOA), Guard time of each medium access slot (MAS) is composed of shortest inter-frame space (SIFS) and MaxDrift which is the time caused by maximum frequency offset among devices. In this paper, to reduceguard time means that we nearly eliminate MaxDrift term from guard time. Each device of a piconet computes relative frequency offset from the device initiating piconet using periodically consecutive transferred beacon frames. Each device add or subtract the calculated relative frequency offset to the estimated each MAS starting point in order to synchronize with calculated MAS starting point of the device initiating piconet. According to verification of simulations, if the frequency offset estimator is implemented with 8 decimal bit, the ratio of the wasted time to Superframe is always less than 0.0001.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.1
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• pp.103-107
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• 2024

This paper is a study on a triangle patch antenna using a rectangle slot and strip conductor. The length and spacing of the slot were adjusted to confirm the characteristics of the triangle patch antenna with rectangle slot, and the area and shape of the radiation patch were changed to triangle, rectangle, and hexagon for impedance matching. The HFSS simulator was used to check the antenna parameter characteristics, and the antenna size was 26 mm ×26 mm. In this proposed antenna, the simulation frequency range with VSWR of 2 or less was 5.27 to 6.24 GHz. The bandwidth was 970 MHz. The frequency range of the fabricated antenna was 5.24 to 6.38 GHz, and the bandwidth 1140 MHz. The maximum radiation gain is 5.01 dBi. It was confirmed that all radiation patterns had directional characteristics.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.11
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• pp.1668-1670
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• 2012

In this paper, a satellite array antenna operates at 12.2GHz~12.75GHz was designed and fabricated. The lowest height and high gain electrical beam tilt was obtained by applying backed slot and sub-reflector widening the distance between the patch and the GND. The simulation and measurement showed good agreements, the electrical beam tilt was $10^{\circ}$, the gain was 26.5dBi, the VSWR was less than 3:1 and the return loss was less than -15dB.

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1362-1369
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• 2018

A method aimed at improving the beam-wave interaction efficiency by changing the coupling slot configuration has been proposed in the study of extended interaction oscillators (EIOs). The dispersion characteristics, coupling coefficient and interaction impedance of the high-frequency structure based on different types of coupling slots have been investigated. Four types of coupled cavity structures with different layouts of the coupling slots have been compared to improve the beam-wave interaction efficiency, so as to analyze the beam-wave interaction and practical applications. In order to determine the improvement of the coupling slot to a coupled cavity circuit in an EIO, we designed four nine-gap EIOs based on the coupled cavity structure with different coupling slot configurations. With different operating frequencies and voltages takes into consideration, beam voltages from 27 to 33 kV have been simulated to achieve the best beam-wave interaction efficiency so that the EIOs are able to work in the $2{\pi}$ mode. The influence of the Rb and the ds on the output power is also taken into consideration. The Rb is the radius of the electron beam, and the ds is the width of the coupling slot. The simulation results indicate that a single-slot-type EIO has the best beam-wave interaction efficiency. Its maximum output power is 2.8 kW and the efficiency is 18% when the operating voltage is 31 kV and electric current is 0.5 A. The output powers of these four EIOs that were designed for comparison are not less than 1.7 kW. The improved coupling-slot configurations enables the extended interaction oscillator to meet the different engineering requirements better.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.1
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• pp.36-43
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• 2004

In this paper, we proposed a novel compact microstrip lowpass filter with an ultra-wide stopband and prominent cutoff sharpness using slot on the ground plane and microstrip shunt open stub. The microstrip shunt open stub and slot exhibit the different stopband response. The combined characteristics of these structures gives the ultra-wide stopband characteristics and the coupling effect between slots on the ground plane makes the prominent cutoff sharpness. The fabricated microstrip lowpass filter with the size of 20.1 mm ${\times}$ 18.7 mm has -3 ㏈ cutoff frequency at 1.187 ㎓ and -20 ㏈ stopband from 1.33 ㎓ to over 20 ㎓ and the insertion loss in the passband is less than -0.4 ㏈ form DC to 1 ㎓.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.4
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• pp.105-111
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• 2019

In this paper, a performance analysis of waveguide broad-wall slot array antenna for millimeter-wave seeker in Ka-band was performed as using near-field measurement. The measurement of slot array antenna was conducted in both far-field and near-field. And the validation of near-field test in millimeter band was confirmed. It was confirmed that the beam pattern characteristics including beam width and side lobe level of the slot array antenna that performed the verification were the same. Differenced in the side lobe level of azimuth and elevation beam pattern were verified to be less than 1dB. Additionally, the new antenna aperture distribution was extracted as using back-projection method modifying the near-field data and then introduced the method conducting performance analysis of array antenna.

• Journal of the Korean Operations Research and Management Science Society
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• v.28 no.4
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• pp.21-29
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• 2003

The traffic scheduling problem for a satellite cluster with an arbitrary number of satellites is considered. which is one of the most interesting problems in the satellite communication scheduling area. This problem is to find a time slot assignment maximizing the transponder utilization for a satellite cluster This problem is known to be NP-complete, and several heuristic algorithms have been proposed. In this paper, we suggest new efficient algorithms for this problem, which have less time complexity than the best existing one and provide much better solution quality. Extensive simulation results are reported.

• Journal of information and communication convergence engineering
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• v.6 no.2
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• pp.172-176
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• 2008

This paper presents a novel feeding structure of the triple-band internal antenna which covers CELLVLAR/DCS/US-PCS bands. The proposed antenna consists of a U-slot patch radiator with a shorting post connected with ground plane and symmetric feeding lines with respective a feeding and shorting posts on both faces of the fixed FR-4 substrate. Through the simulation and experimental results, the proposed antenna is confirmed to have the features of less interference with a human head/body, broad bandwidth, desirable radiation patterns and efficiency for triple-band applications.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.709-712
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• 2003

Recently, high noise problem was experienced during the development of 2-pole squirrel cage motor for industrial compressor. In order to firstly identify the noise characteristics, a variety of measurements were carried out. It was found out that high noise was dominated by linear and nonlinear slot noise components. For the development of low noise indusrial motor, the air gap between rotor and stator in the motor was firstly enlarged. Secondly, it was also modified for the cooling housing to have high absorption features. Consequencely, low noise 2-pole motor having the noise level of less 80㏈(A) was developed. In this paper, a series of noise identification and control process for this motor are introduced.