• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.59-60
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• 2017

In this paper, we studied a design method for obtaining broadband property by loading a chip capacitor on a coplanar waveguide(CPW)-fed compact quasi-Yagi antenna(QYA). The proposed antenna is a three-element QYA with dipole, reflector, and director. To reduce the size, the ends of both dipole and reflector are bent, and balun is incorporated in the antenna. To improve impedance matching, the loading position and capacitance value of chip capacitor were determined. From some simulations, the proposed antenna using an FR4 substrate with a size of 90 mm by 90 mm was designed for the operation in a broadband covering the UHF RFID and GPS systems. The antenna showed a good performance with a broadband of 850-1,626 MHz(62.7%) for a VSWR ${\leq}2$, a gain ${\geq}3dBi$, and a frong-to-back ratio ${\geq}4.6dB$.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.1
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• pp.153-161
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• 2022

This paper analyzes the economic effects when platform provider including CP contributes to broadband universal service and uses broadband bandwidth providing high quality network service. In this model, the contribution rate of broadband universal service is determined by ISP and platform provider sets its price of contents. The main results are as follows. First, the traffic usages is less than social optimum when the market of contents is monopoly. The sum of contribution fee and network usage rate must be less than marginal cost of network operation to get social optimum traffic. Second, the rate set by ISP is equal to social optimum when the market of contents is competitive. Third, when platform provider does not charge contents provided, ISP sets social optimum prices and the network usage rate for contents user is decreasing as advertisement revenue becomes larger. These results suggest that the platform provider should contribute to universal service funding to encourage the network investment of ISP.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.475-476
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• 2015

In this paper, we introduce a novel feeding method for a broadband planar quasi-Yagi antenna (QYA) for terrestrial digital television (DTV) receiving. The balun between the balanced coplanar strip (CPS) line feeding the driver dipole and the unblanaced microstrip line is a rectangular patch inserted into the CPS line along the center of the CPS. The end of the balun is connected to the CPS line through a shorting pin. The effects of various geometrical parameters and balun on the antenna characteristics are examined. An antenna, as an design example for the proposed antenna, is designed for the operation in the frequency band of 470-806 MHz for terrestrial DTV.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.74-75
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• 2016

Various types of microstrip antennas can be used for many applications in wireless communication systems. In this paper, we studied a design method for a broadband dual-fed stacked microstrip patch antenna. The impedance bandwidth is improved by adjusting the sizes of main radiating patch and parasitic patch, the distance between the patches, the length of inset feed line, etc. The antenna is designed by simulation for an operation in the frequency range of 2.3-2.7 GHz, and the antenna characteristics such as return loss, gain, radiation patterns are examined.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.10
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• pp.1103-1108
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• 2010

This paper proposes a new type of PIFA with a capacitor structure inserted into the feeding loop. It operates in GSM900, DCS, PCS, and W-CDMA frequency bands. By inserting the capacitor, it shows the effect of lowering the return loss from -2.73 dB to -6.26 dB at the parallel frequency, 2.01 GHz. The improvement of the poor radiation property near the parallel resonance frequency leads to a broadband operation in the upper band, DCS, PCS, and W-CDMA.

• Journal of the Optical Society of Korea
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• v.19 no.5
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• pp.449-455
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• 2015

In this study we propose a new photonic crystal fiber (PCF) design that simultaneously offers broadband single-mode operation, high birefringence, and large normal dispersion in the optical-communication wavelength regime. The waveguide is based on a hybrid square-lattice PCF (HS-PCF) that has circular air holes of two different diameters alternating in the cladding, plus a pure silica defect at the center. The optical properties of the guided modes are analyzed numerically by the finite-element method (FEM) with a perfectly matched layer as the boundary condition. The optimized HS-PCF has a dispersion coefficient of $-601.67\;ps\;nm^{-1}\;km^{-1}$ and a high birefringence of $1.025{\times}10^{-2}$ at $1.55{\mu}m$. In addition, over the S+C+L+U wavelength bands the proposed HS-PCF with ultraflat birefringence with a slope on the order of $10^{-5}$.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1846-1848
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• 1999

A technique is investigated for achieving broadband properties by controlling the operation frequency of microstrip antennas. The control is achieved by applying DC and AC bias to the microstrip antenna. Air gap antenna with pzt post and microstrip antenna with simple rectangular patch on the $LiNbO_3$ substrate were fabricated. In the case of Air gap antenna, the variation of operating frequency was 11Mhz and $LiNbO_3$ antennas was 11Mhz. Also, frequency scanning was achieved by appling AC bias.

• Korean Management Science Review
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• v.11 no.3
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• pp.103-128
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• 1994

Due to the trend of evolution toward a broadband communication network with fiber-optics, the design and operation of fiber-optic network have been received a great deal of research attention recently. Furthermore, even a single fiber link failure in the network may result in severe service loss. Thus, the network survivability becomes an importantissue in planning and designing the network. This survey is on modelling of various fiber-optic subscriber loop network(FSLN) design problems, which are essential ones for providing broadband communication services and B-ISDN services. Models are classified and investigated as either conventional decomposition-iteration approach or integrated design method. To build survivable networks, SHR models are also suggested by ring control schemes. The result of this study will be effectively applied to build a design model for FSLN in the practical applications.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1576_1576
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• 2009

We present the design of an EMI filter to mitigate the electrical noise from the power supply over a broadband of a few tens of KHz to 18GHz. Admitting that our approach is not apart from the standard technology of EMI filter, it is worth checking out how we can implement the filter that meets the challenging spec. on band of operation. The function of the EMI filter is well-depicted by its performance on the CE(Conducted Emission) and RE(Radiated Emission) suppression through tests which convince us of its application to power supplies of land, water and flying vehicles.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.12
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• pp.573-577
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• 2002

We designed wideband HTS antennas which consists of two triangle -radiation patches using a $YBa_2Cu_3O_{7-X}$ (YBCO) superconducting thin film. The major limitation of high-Tc superconducting (HTS) microstrip antennas is the narrow bandwidth due to the high Q and thin substrate. Defining bandwidth as the frequency range over which standing wave ratio (SWR) 2:1 or less, HTS antenna bandwidths are typically 0.85 % to 1.1 %. Thus considerable effort has been focused on developing antennas for broadband operation. To calculate input impedance and design of the broadband HTS antennas a moment method technique was used. The HTS antenna fabricated in this work was designed for K-band, which is useful band for satellite to satellite communications. The bandwidth obtained was a significant 6.7 % and the other measured performance of our HTS antenna, including the bandwidth, radiation Pattern, efficiency, standing wave ratio (SWR) and return losses was reported.